The Stay-at-home Scientist

Friday Favourites

thestayathomescientist — Fri, 03 Aug 2012 21:56:15 +0000

Since the new post on non-vascular plants and ferns has been delayed, I thought I’d put together a brief collection of the most interesting science news that has come across my desk this week.

“Predatory beetles eavesdrop on ants’ chemical conversations to find best egg-laying sites“

There is a complicated relationship between ants (Azteca instabilis), scale insects (Coccus viridis), lady beetles (Azya orbigera), and phorid flies (Pseudacteon laciniosus) on the coffee plants in Mexico. The ants protect the scale insects from predators so that they can ‘farm’ their honeydew (the sugar dense liquid that aphids and some scale insects produce when they feed on plant sap). Because the ants are protective, large quantities of scale insects can be found in these ant run farms on coffee plants. Scale eating coccinellids, or lady beetles, would be killed by the ants as adults, but their larvae, who also appreciate a scale meal, are covered in sticky, waxy, filaments that protect them from ants. Finding oneself born in a scale farm would mean an important, and easy, first meal for a lady beetle larva.

An ant having a sticky encounter with a lady beetle larvae. Photo by Ivette Perfecto from the University of Michigan press release.

Even though the larvae may be protected, the female lady beetle still has to arrive in ant guarded territory to lay her eggs somewhere the ants won’t immediately find them (sometimes she’ll even lay them underneath scale insects). As seen in the video above, getting around the ants is a challenge, but worth it, if it means giving her offspring the best start to life (an open buffet).

Enter the phorid flies. The ants themselves are not immune to predation, and for them, the parasitic phorid flies are the stuff of nightmares. Phorid flies attack ants and lay their eggs in them, while the ants are still alive. The larvae develop within the ant until eventually the ant is decapitated when the fly is ready to emerge. It seems that phorid flies require a moving target though, in order to know that their future ‘baby sitters’ are alive and ready to be hosts. Because of this, the ants have developed a simple strategy – they freeze when phorid flies are around.

When a fly attack begins, the ants release a very specific pheromone that tells the entire colony to stop moving. In turns out, female lady beetles have learned to recognize this fly attack pheromone so when they smell it, they know they have a clear window to come in and lay their eggs. This is especially interesting because it is one of the first examples of a non-ant picking up on those ant specific pheromones.

Hsun-Yi Hsieh, Heidi Liere, Estelí J. Soto, Ivette Perfecto1, “Cascading trait-mediated interactions induced by ant pheromones”, Ecology and Evolution, published online: 27 JUL 2012. DOI: 10.1002/ece3.322

“Birds that live with varying weather sing more versatile songs“

Cardinalis sinuatus, the Desert Cardinal, one of the song birds studied. Their songs change in volume and tempo with changing seasonal precipitation averages. Photo © by Motorrad67 Source: Wikimedia commons, Uploader: Motorrad-67 [link]

Current research seems to suggest that for birds, variation in songs has something to do with variation in habitat. Looking at 44 species of North American song bird, a study published this week found that variation in precipitation changed the complexity of bird songs. Why might this be? One idea, put forth by the study’s authors is that precipitation levels affect plant growth (in terms of sheer amount as well as diversity of vegetation types), and plant growth affects acoustics.

Co-author, Clinton D. Francis, said:

Sound transmits differently through different vegetation types. Often when birds arrive at their breeding grounds in the spring, for example, there are hardly any leaves on the trees. Over the course of just a couple of weeks, the sound transmission changes drastically as the leaves come in.

Iliana Medina, the other co-author of the study, added:

Birds that have more flexibility in their songs may be better able to cope with the different acoustic environments they experience throughout the year.

And this would make sense, given that a song that would be ‘successful’ (reproductively speaking) at one time of the year, say in the winter or during drought times in a bare field, might sound quite different being sung during a lush spring.

Iliana Medina and Clinton D. Francis, “Environmental variability and acoustic signals: a multi-level approach in songbirds”, Biology Letters, Published online August 1, 2012, doi: 10.1098/rsbl.2012.0522

Wasps and Hornets Start the Wine Making Process (Seriously)

Vespa crabro, the European Hornet, plays an important role in wine making as an early yeast bringer. Source: Wikimedia Commons, User: PiccoloNamek. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

NPR has an interesting read about a study published online this week in the Proceedings of the National Academy of Sciences. The process of wine making is an ancient and commercially significant one that is all about fermentation. Traditionally, we think about wine making as a process westart – after the grapes are picked and crushed, we either add yeast or make due with the ambient yeasts in the air. It turns out, we’re not as in-control of when the process starts as we thought we were.

Paper wasps and European hornets feed on grapes - Vespa crabro, common in the Mediterranean and Southern Europe, apparently has a mouth particularly well designed for breaking the skin of grapes. When they feed, they leave behind Saccharomyces cerevisiae from their gut, otherwise known as brewer’s yeast. Since wasp and hornet mouth parts are so small, a little bite doesn’t stop the grape from being harvestable, but it does start the fermentation process, ever so slightly, while the grape is still on the vine. Wine from different regions tastes differently, not just because grape varieties and growing conditions are different, but because the local yeast strains are different. Now it seems that not only ambient and added yeast affect the flavour, but the gut flora of the local insects play a role too. Wine made from grapes that have had fermentation begin while still on the wine will taste differently than wine made from grapes where fermentation begins later. Wasps and hornets, as much as we sometimes try to keep them out of our spaces, help give wine their flavour.

Anyone growing their own grapes from home wine making might not want to discourage wasp activity in their yard.

Irene Stefanini, Leonardo Dapporto, Jean-Luc Legras, Antonio Calabretta, Monica Di Paola, Carlotta De Filippo, Roberto Viola, Paolo Capretti, Mario Polsinelli, Stefano Turillazzi, and Duccio Cavalieri. “Role of social wasps in Saccharomyces cerevisiae ecology and evolution”, PNAS, Published online July 30, 2012, doi: 10.1073/pnas.1208362109.

A Brief History of Floral Design, or, How Angiosperms Ended Up in Our Vases

thestayathomescientist — Mon, 16 Jul 2012 22:08:29 +0000

Floral design is an art form like any other. It takes into account a full range of artistic principles, where compositions are thought of in terms of balance, proportion, harmony, and even rhythm. Color, texture, lines and space are all aspects one can contemplate when viewing or creating an arrangement, and like all art, personal taste and school of thought determine its success.

Ikebana arrangement.

Source: Wikimedia Commons, User: Ellywa. Creative Commons Attribution-Share Alike 3.0 Unported [link]

Instead of starting our journey into floral design with the Europeans or the Japanese, we will begin with an interesting, and perhaps unexpected, cast of characters – the ancient “fern allies”. To meet them, we have to go back in time, back to before flowering plants even existed, to the Carboniferous period.

The Carboniferous period (359.2 ± 2.5 to 299.0 ± 0.8 million years ago).

Source: Wikimedia Commons, User: Nonenmac. Original Source: “Carboniferous Pteridophyta (After Dana)” from a the 1896 edition of Underwood’s Native Ferns and their Allies. Public Domain. [link]

The Carboniferous period was the geological time on Earth that spanned from roughly 360 million years ago to 300 million years ago. Great spore-bearing forests dominated the forming super-continent Pangaea during this time that, as the name carboniferous suggests, would eventually become great coal fields. Land animals were limited to amphibians, reptiles, and predatory and sap sucking insects[33-35].

Left: A 360 to 300 million years ago Calamite fossil. Right: Modern Equisetum myriochaetum.

Left Source: Wikimedia Commons, User: Verisimilus. Sedgwick Museum’s collection. Creative Commons Attribution 3.0 Unported. [link] Right Source: Wikimedia Commons, User: MPF. Original Source: alexlomas on Flickr. Royal Botanic Gardens, Edinburgh. Creative Commons Attribution 2.0 Generic. [link]

Ferns, horsetails, and club mosses were probably the most familiar flora of the Carboniferous period, although some took on a larger stature. Calamites, an extinct cousin of our modern Equisetum, were tree-like horsetails reaching 30 meters tall.

Left: 360 to 300 million year old Lepidostrobus variabilis fossil. Right: Modern Lycopodiale Huperzia selago.

Left Source: Wikimedia Commons, User: Smith609. Sedgwick museum, Cambridge. Attribution: Smith609 at en.wikipedia. Creative Commons Attribution 3.0 Unported. [link] Right Source: Wikimedia Commons, User: Ghislain118. Creative Commons Attribution-Share Alike 3.0. [link]

Lepidodendrons, an extinct cousin of our club moss Lycopodium, were no ‘ground pines’, but were towering scale trees, stretching 30 meters above ground with trunks a meter wide.

Left: 310-290 million year old Walchia piniformis fossil (an early cypress-like conifer). Right: Modern Cupressus sempervirens.

Left Source: Wikimedia Commons, User: Woudloper. Naturhistorisches Museum, Bern, Switzerland. Public Domain. [link] Right Source: Wikimedia Commons, User: MPF. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

The late Carboniferous period also saw the rise of the gymnosperms (think conifers). Gymnosperms differed from much of the plant life of the earlier Carboniferous period in that they produced seeds instead of spores. Unlike the angiosperms (the flowering plants) that also produce seeds, gymnosperm seeds are “naked” (gymnospermosis “naked seeds” in Greek), meaning that they are not produced within an ovary but instead on the surface of an ovule-bearing scale. Ovaries (fruit) and flowers come a little later in our story. It was also this time period that saw the first beetles appear[33-35].

A 270 to 250 million year old Glossopteris fossil, a gymnosperm with a modified leaf structure resembling a carpel (similar to what is found in flowering plants).

Source: Wikimedia Commons, User: High Contrast. Original Source: Peter Rejcek, National Science Foundation [link]. Researchers Edith and Tom Taylor, University of Kansas. Public Domain. [link]

At the end of the Carboniferous period, the Glossopteridales appear in the fossil record. As far back as 299 million years ago, at the start of the Permian period, we find Glossopterids all over what is now the Southern Hemisphere. Originally placed with the ferns, Glossopteris had no spores, and was in fact a seed-bearing gymnosperm. What makes the Glossopterids special from the gymnosperms of the Carboniferous period, is that they had modified leaves that resembled a carpel, the seed producing organ in flowering plants. While not true carpels, the fused leaf structure perhaps provided the forming seed protection against the new beetle threat. Glossopteris was not flowering, and while it may be an evolutionarily distant cousin of flowering plants, it was no angiosperm “Eve”, despite a passing resemblance[5][7][33-35].

As far back as 280 million years ago, in the Permian period, time of Pangaea and the ancestors of the dinosaurs, something interesting appeared in the fossil record, not flowers but an organic compound called oleanane[16].

Left: Sketch of a 260 to 250 million years old Gigantopterid fossil. Right: Oleanane, an insect suppressant used by angiosperms and Gigantopterids.

Source: Me. Public Domain. [5][7]

The gigantopterids were a family of Permian period plants whose origin is still a little unclear. What makes them of particular importance though, is that unlike the other seed producing plants of the time, the fossil record indicates that they contained oleanane. Oleanane is special because it is produced by many flowering plants today to help protect from fungal and insect invaders, but it doesn’t commonly exist outside of angiosperms[15]. Were gigantopterids the ancestors of flowering plants? Unfortunately, we don’t know, because they disappear from the fossil record after the Permian–Triassic extinction(252.28 million years ago), but that doesn’t mean they vanished, they could have just adapted to the post new, post extinction, conditions on Earth[5][7].

In the Permian period, we see many rather familiar forms, but no flowers. The Gnetophytes were another early division of Plantae, now considered to be gymnosperms, that possessed angiosperm-like xylem (water-nutrient transport tissue) very similar to that found in modern flowering plants. Gnetophyta still exists today, including modern members like the well known Ephedra genus, but genetic testing shows that Gnetophytes are not close kin to flowering plants[18][19][20].

Whether the direct ancestors of angiosperms appeared during the Permian period is still debated, but things were clearly moving in that direction. As the climate and animal life of the Earth changed, new niches needed to be filled and new methods of protecting, and creating, offspring needed to be established.

Left: Sketch of 250 million year old Caytonia nathorstii. Right: Close up of Caytonia “cupule”, a protective seed casing (like those found in flowering plants)

Source: Me. Public Domain[7].

At the start of the Mesozoic era, the period from 250 to 70 million years ago, we meet another possible angiosperm ancestor, a gymnospermic order known as the Caytoniales. Fossils of Caytoniales show that they contained a modified leaf cupule- cupules are the protective casing around the seeds of some angiosperms, like oaks. This interesting angiosperm characteristic isn’t enough to remove the Caytoniales from the gymnosperms, but the seeds were not as ‘naked‘ as the other gymnosperms. While not a ‘flowering plant’, the emergence of Caytoniales suggest that flowering plant traits could have been beneficial in light of the changing Earth (a protected seed has a better chance of survival once seed eaters come along)[7].

A 250-200 million year old Bennettitales cycadeoidaceae fossil, with reproductive organs surrounded by bracts

Source: Wikimedia Commons, User: Smith609. Sedgwick Museum’s collection. Creative Commons Attribution 3.0 Unported. [link]

The bennettitales, another early Mesozoic gymnosperm, possessed the most flower-like form yet, with their reproductive organs surrounded by bracts (almost like a bromeliad). While genetically, the bennettitales are more closely related to the cycads than the angiosperms, they, like the Gigantopteridales, contained oleanane, which hints at an evolutionary link to flowers. Protecting seeds was clearly becoming more and more important[5][7][17].

The first dinosaurs and the earliest mammals shared the Earth with these flower-like bennettitales. 220 million years ago saw enormous gymnosperm forests dominate the land, a move away from the spore-bearing forests of the Carboniferous period. The Earth was warmer and far more rich in carbon dioxide than both present day and the Carboniferous climate, which was perfect for the changing flora and large herbivores[33-35].

It wasn’t until 140 million years ago, during the Cretaceous period, that the fossil record definitively shows ‘flowers’. The Cretaceous period was a time of warm air, high seas, dinosaurs, mammals, bees and angiosperms.

The phylogeny of angiosperms.

Source: Me, Public Domain. Data from the APG III system (Angiosperm Phylogeny Group III system), 2009[26]

Typically, three early angiosperm families stand out, they are thus labelled the ‘basal angiosperms’ because as far as we know, they were the first. What is exciting is that all three basal angiosperm families still have members that are alive today[25][26].

Basal angiosperm Amborella (140 to 130 million years old). Shown: modern Amborella trichopoda, the only living species of the Amborellaceae family.

Source: Wikimedia Commons, User: Bff. Original Source: Scott Zona on Flickr. Amborella trichopoda. Wertheim Conservatory, Florida International University, Miami, Florida, USA. Creative Commons Attribution 2.0 Generic. [link]

There is only one species from Amorella still alive today, Amborella trichopoda. A. trichopoda is a rare, understory, evergreen tree, found only on the Pacific island of New Caledonia. The urbanization of New Caledonia is threatening the home of the last Amborella. Green houses and botanical gardens may be the only way for future generations to see this ‘dinosaur flower’.

Basal angiosperm Nymphaeales (140 to 130 million years old). Shown: Modern Nymphaea nouchali.

Source: Wikimedia Commons, User: uleli. Original Source: 香水蓮花 on Flickr. Creative Commons Attribution 2.0 Generic. [link]

The Nymphaeales are a well known order of flowering plants because they contain the water lilies (the Nymphaeaceae family). In total, there are three living families within the Nymphaeales order, and perhaps 80 extant species total.

Basal angiosperm Austrobaileyales (140 to 130 million years old). Shown: modern Austrobaileya scandense.

Source: Wikimedia Commons, User: Art Poskanzer. Original Source: Art Poskanzer on Flickr. Creative Commons Attribution 2.0 Generic.[link]

The Austrobaileyales order contains possibly three families of woody plants, and perhaps 100 species in all. There is still much debate on the identities of some members here. The most well known Austrobaileyales is Illicium verum, the plant we get the spice ‘star anise‘ from.

Next came the mesangiosperms. Shortly after the basal angiosperms appeared in the fossil record, another large grouping of flowering plants diverged, roughly 135 million years ago. Today, the mesangiosperms make up roughly 99.95% of all flowering plants – that’s around 350,000 known species.

The Magnoliids were one of the earliest groupings of flowering plants, appearing 130 million years ago. Pictured: modern Magnolia denudata

Source: Wikimedia Commons, User: KENPEI. Osaka-fu Japan. Creative Commons Attribution-Share Alike 3.0 Unported [link]

The Magnoliids are currently a group of approximately 9000 extant flowering plants. The magnoliids contain the well known order Magnoliales (with the Magnolia genus, of course), the familiar order Laurales – with its culinary members like Bay Laurel (Laurus nobilis), cinnamon (the Cinnamomum genus), and Persea americana (Avacado)-, the order Piperales (think Piper nigrum, otherwise known as Black Pepper), and the order Canellales. Fossil record of their distinctive pollen particles – with only one pore – indicate the Magnoliids were around 130 million years ago[5][7][8].

Chloranthaceae, another one of the earliest diverging angiosperm orders, appearing 120 million years ago. Shown: modern Sarcandra glabra.

Source: Wikimedia Commons, User: KENPEI. Creative Commons Attribution-Share Alike 3.0 Unported [link]

Chloranthaceae is another one of the early angiosperm orders from 120 million years ago with one living family today. The flowers are without petals and sometimes even without sepals. There are four extant genera with roughly 75 species between them[5][7].

Monocots appeared roughly 120 million years ago. Pictured is a modern Monstera in flower, relative to the 120 to 110 million year old Mayoa portugallica.

Source: Wikimedia Commons, User: A9l8e7n. Public Domain. [link]

The monocots contain approximately 60,000 distinct species alive today. When people think about flowers in cultivation, especially in regards to floral design, they often think of monocots. Amaryllis, bromeliads, daffodils, irises, lilies, orchids (orchids make up more than one third of all monocots), and tulips are all monocots, and so are corn, wheat, palm trees, rice, and sugar cane. The earliest fossil monocots seem to appear roughly 120 million years ago in the early Cretaceous period[23].

A 125 million year old Archaefructus liaoningensis fossil.

Altered from Source: Wikimedia Commons, User: Shizhao. Creative Commons Attribution-Share Alike 2.5 Generic. [link]

125 million years ago, we meet Archaefructus liaoningensis, another one of the earliest known flowering plants. Three extinct species within the now lost Archaefrutus genus have been discovered although where this genus should be placed in our above tree is a bit of a mystery still. It has been proposed that Archaefructaceae should be a fourth basal angiosperm order, although this isn’t widely supported. Some suggest that Archaefructus could actually be a member of the Nymphaeales, or perhaps a basal eudicot[28].

Eudicots are a well known modern collection of flowering plants that are dicots, meanings their seeds typically contain two embryonic leaves (separating them from monocots, that have one embryonic leaf). Now, the Eudicots, Magnoliids, Amborella, Nymphaeales, Austrobaileyales, Chloranthales, and Ceratophyllum are all dicots, but the eudicots are distinguished by having three parallel groves along their pollen grains that run along the polar axis of the pollen (plus, they’re seen to be far more genetically related to each other than to any of the other basal angiosperms). Eudicots may make up to 70% of all flowering plants, from Taraxacum (dandelions) to Acer (maple trees).

122.6–125.8 million year old Leefructus gen., an early eudicot, on the March 31st, 2011 cover of Nature.

Source: March 31st, 2011 cover of Nature. Volume 471 Number 7340 pp547-672. [link] Photograph by C. T. Li. [link]

122.6–125.8 million years ago we meet Leefructus, a basal eudicot.

The diversity of angiosperm fossils we find from 130 to 120 million years ago tells us something important – flowering plants had probably been there for awhile, we just haven’t found older fossils yet. There are many factors that affect whether fossilization can occur instead of say, compost. Leaves and flowers have to die in exactly the right spot, under exactly the right conditions for them to leave an imprint behind that will be able to last hundreds of millions of years. The variety of early angiosperms we see in the Cretaceous period makes us suspect a longer history of angiosperms than we have yet to uncover [1].

An early angiosperm order, Ceratophyllum, from 120 to 100 million years ago. Here, modern Ceratophyllum demersum with male flowers.

Source: Wikimedia Commons, User: Christian Fischer. Attribution: Christian Fischer. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

The Ceratophyllales are an interesting, and unassuming, early order of aquatic angiosperm, most commonly known as hornworts. They were first found in the fossil record roughly 120 to 100 million years ago. Today, there is only one genera of Ceratophyllales with perhaps 30 species that can be seen all over the world. The fact that they actually are flowering plants, can take one by surprise, but flowers and fruit of the Ceratophyte Donlesia dakotensis have been found in sediment from the early Cretaceous period[22].

Roughly 125 million year old Lepidoptera (moth) fossil from the Yixian Formation, Chao Yang, Liaoning Province of China.

Source: The Virtual Fossil Museum. See VFM for permissions.

The Cretaceous period also saw the rise of pollinators. Perhaps unsurprisingly, pollinators and flowers evolved together, giving angiosperms the edge they needed over other plant life. Giving credit where credit is due, when in comes to floral design, is a bit of a tricky task. Do we credit the plants themselves for their variation in floral arrangement and inflorescence displays? Or do we credit the pollinators involved in exerting the selective pressure with creating that variation?

Plants that are wind pollinated have to expend much more energy than plants that are animal pollinated, because they have to produce more pollen (or spores) in a hope that it will end up at an appropriate receptacle.

Early insects discovered this pollen to be a good source of food and slowly over time became dependent on it, carrying pollen from flower to flower as they fed. Eventually, mutations arose that caused the creation of nectar, which lured pollinators all the more. Bright colors and shaped petals developed and were even more eye-catching for insects. Those without a protected ovule (ie. anyone with a ‘naked seed’) could be eaten by visiting pollinators, and were less likely to survive as a species. This is how the angiosperm became so successful.

Plants developed more specialized flowers as insects developed more specialized forms, as it was beneficial for both parties to be ‘monogamous’, so to speak. For the pollinator, having a food source that you and you alone can eat means less competition, and a greater chance of survival. For the plant, having a dedicated pollinator means less wasted pollen on casual passersby and if your pollinator is dependent on you, you’ll have a much better chance of being visited and pollinated [6].

65 million years ago, the Cretaceous–Paleogene extinction occurred, and roughly half of all animal species were wiped out. Dinosaurs disappeared, leaving only a few bird ancestors behind, and mammals rapidly filled the void on land. 65 to 35 million years ago, we also find bees and butterflies in the fossil record, and we find flowers fit for a bouquet, as angiosperms replaced gymnosperms as the most plentiful and more diverse terrestrial plant life.

Here is a sampling of the Paleogene (65.5 ± 0.3 to 23.03 ± 0.05 million years ago) angiosperm fossil record:

49 million years old fossil, unidentified angiosperm, possibly Gordonia sp..

Source: Wikimedia Commons, User: Kevmin. Stonerose Interpretive Center Collection. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

49.5 million years old Corylus johnsonii.

Source Wikimedia Commons, User: Kevmin. Stonerose Interpretive Center Collection # SR 99-05-05. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

48.5 million years old Eucommia montana seeds.

Source: Wikimedia Commons, Users: Kevmin. Stonerose Interpretive Center Collections # SR 95-05-05. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

49 million years old Florissantia quilchenensis.

Source: Wikimedia Commons, User: Kevmin. Stonerose Interpretive Center Collection. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

49 million years old Florissantia sp.

Source: Wikimedia Commons, User: Kevmin. Stonerose Interpretive Center Collection. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

35 million years old unidentified fossilized flower.

Source: Wikimedia Commons, User: Slade Winstone (Sladew). Clare Family Florissant Fossil Quary, Florissant, Colorado, USA.. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

The Earth’s climate changed significantly over the course of the Paleogene. The world was less tropical than it had been during the Cretaceous period – deciduous plants and the newly evolved grasses became better competitors than the old tropical forest dwellers now that seasonal climate variation was more significant. Separating continents, cooler temperatures, dryer weather, and new pollinators put pressure on plants to change.

Yucca whipplei flowers that have a dedicated pollinator, the moth Tegeticula maculata.

Source: Wikimedia Commons, User: Noah Elhardt. Public Domain. [link]

An important example of pollination leading floral design is the yucca plant (example: Yucca whipplei) and its exclusive pollinator, the yucca moth (example: Tegeticula maculata). Yuccas began to flourish roughly 40 million years ago with the Yucca moths appearing soon afterwards. Today, Yucca moths generally only visit one species of yucca with a flower specifically aligned with their needs. The moths arrive at sheltered flowers for a snack and to lay their eggs, while getting pollen on themselves in the process, before moving on to a new flower. The flowers must be shaped in such a way to allow the eggs to stay safe, and allow the yucca moth to become covered in pollen during their visit. When the eggs hatch, the larvae feed on the Yucca seeds, but leave enough untouched so that the some seeds still mature. Despite the somewhat parasitic actions of the Yucca moth, the relationship still ends up being beneficial for both parties[13].

Babiana ringens has developed a special perch for its pollinator, the Malachite sunbird, to sit while drinking nectar. Adaptions like this, that make visits from pollinators easier make pollination more likely.

Source: American Journal of Botany. Photo credit: C. E. Smith. 21 May 2012, doi: 10.3732/ajb.1100295 Am. J. Bot. June 2012. (press release) [link]

Hummingbirds and the flowers they feed on are another classical example of coevolution. The first hummingbird fossils are 30 million years old[33-35], which is likely when bird pollination became an important force in floral design. Elongated nectar cavities, shades of red, and sucrose (instead of the typical fructose and glucose) concentrated nectar make certain flowers more appealing to birds rather than to insects. As flowers diversified, beaks slowly adapted to find their lowest competition niche. Bloom time of certain bird-pollinated flowers even lines up with specific hummingbird mating seasons. Hummingbirds aren’t the only bird pollinator though, and flowers have adapted to meet the needs of others. More than just colour and shape, recent research (on the cover of this June’s issue of the American Journal of Botany no less) suggests that certain flowers, Babiana ringens above, developed a special perch, to make visits from their prime pollinator easier. By developing flowers lower to the ground, damage from mammalian herbivores is decreased, but birds may have a harder time stopping for nectar. The modified, flowerless inflorescence axis that Babiana ringens has developed compensates for the lower blooms, but creating a perfectly placed perch for their Malachite sunbird pollinator[3]. Brightly coloured, floral scented, eye-catchingly shaped flowers evolved for, and in some cases with, pollinators. A successful floral design for a sunbird is one that catches the eye and is easy to stop and have drink from – not exactly what one aims for with Ikebana arrangements.

In May of 1862, Charles Darwin published a book called “On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing“, known more concisely as Darwin’s “Fertilisation of Orchids“[27]. In it, he discussed the evolutionary connection between plants and the insects that fertilized them while setting up a discussion of natural selection. Many scientists, especially botanists, actually consider this to be Darwin’s most significant work, as it emphasized the importance of pollinators and cross-pollination for plants, which wasn’t fully appreciated at the time.

Angraecum sesquipedale, an orchid with a nectar spur 35 cm long.

Source: Wikimedia Commons, User: Michael Wolf. Botanischen Garten Köln Creative Commons Attribution-Share Alike 3.0 Unported, 2.5 Generic, 2.0 Generic and 1.0 Generic license. [link]

After detailed study of many distinctly moth pollinated orchids, Darwin came across Angraecum sesquipedale. The shape of the spur (the elongated spike where nectar would be sucked from during pollen collection) told Darwin that A. sesquipedale would need to be pollinated by a moth with a 20 to 35 cm long proboscis. At the time of this assessment, no such moth was known to exist. Everything Darwin had seen up until that point suggested that orchids and pollinators must have evolved together, to be a unique fit, so it wasn’t that A. sesquipedaledidn’t fit the pattern, it was that the pattern predicted the existence of a moth, with a 35 cm long proboscis, that had yet to be seen.

Xanthopan morgani, an orchid pollinating moth with a 35 cm long proboscis.

Source: Wikimedia Commons, User: Esculapio. Natural History Museum of London. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

In 1903, the sphinx moth Xanthopan morgani was discovered, absurdly long proboscis and all, and has been seen feeding from the orchids.

Proplebeia dominicanacarrying 20-15 million year old orchid pollinarium on the August 31st, 2007 Nature cover.

Source: August 31st, 2007 cover of Nature. Santiago R. Ramírez, Barbara Gravendeel, Rodrigo B. Singer, Charles R. Marshall & Naomi E. Pierce. Nature 448, 1042-1045(30 August 2007) doi:10.1038/nature06039. [link]

Orchids and moths are a must in any conversation on coevolution, although moths are not the only orchid pollinator. Meliorchis caribea was a Miocene orchid, alive at least 20 to 15 million years ago. While Meliorchis is extinct, it appears to be a close relative of the modern orchid genus Ligeophila. We know about Meliorchis caribea because scientists have found the above preserved bee, Proplebeia dominicana, seen on a 2007 cover of Nature, covered in orchid pollen[2]. Fossils like the above provide an exciting and rare window into the lives of extinct plants and animals.

An interesting study last month in the Proceedings of the Royal Society B [10] looked at flowering plants in Australia and their pollinators. It’s not new knowledge that flower colour and shape are lures for bees[11][12], but how that relationship came about hasn’t always been well understood. Looking at the colour spectrum of 111 Australian native flowers and comparing that data to the visual abilities of a variety of important pollinators, the scientists noticed that flower colours were predominately those viewed best by bees, as opposed to butterflies or birds. This is important because it’s believed that the visual system of hymenoptera (bees) predates angiosperms. This means that bees and flower colouring didn’t evolve together, but that flowers independently evolved to be optimally viewed by bees. North American flower colours align with the Australian results[10].

10 million years ago, the grasslands were well established and insects were diverse and numerous. Not long after, the first hominids (the great apes, like us) are found in the fossil record. Millions of years go by, and it’s not until 200,000 years ago that we find anatomically modern humans.

Entrance to Shanidar Cave, Kurdistan Region, Iraq. 60,000-80,000 year old Neanderthal burial site.

Altered from Source: Wikimedia Commons, User: JosephV. View of the exterior of Shanidar Cave, taken during the summer of 2005. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

The earliest possible evidence for flowers being used for ceremonial or esthetic purposes comes not from humans, but from a related hominid, the Neanderthals. There is a burial site known as the Shanidar Cave, in the Kurdistan Region of Iraq, dating back 80,000 to 60,000 years ago. A site known as Shanidar 4, also called the “flower burial” contained an unusual amount of pollen, that some speculate is evidence of flowers being used as part of a ceremonial burial. Some speculate that non-hominid animals buried plant matter there for storage and that there was no ceremony intended, but at this point in time, we can’t know one way or the other.[24].

Angiosperms have been an important food source for animals as long as there have been angiosperms, but it has only been recently, relatively speaking, that they have been actively cultivated for these purposes. More than 12,500 years ago, humans were selecting grains, like rye, for larger seeds and better yields[36]. When the esthetic history of floral cultivation began is a little less clear.

Left: An image of Nymphaea caerulea (the Egyptian Blue Water-lily) from the 18th Dynasty, Ancient Egypt (1550 – 1292 BCE). Right: Nymphaea caeruleaflower.

Left Source: Wikimedia Commons, User: BrokenSphere. © BrokenSphere / Wikimedia Commons. Rosicrucian Egyptian Museum in San Jose, California. RC 1842, 444. Creative Commons Attribution-Share Alike 3.0. No Public Domain, contact author outside of approved uses. [link] Right altered from Source: Wikimedia Commons, User: Peripitus. Botanic Garden, Adelaide, South Australia. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

The ancient Egyptians used images of flowers, with particular attention to the water lily, in all manners of artistry and story telling creations. Egyptian art shows evidence of formal gardens around important sites. Even a 3000 year old burial in the Valley of the Kings had garlands of preserved flowers, strung together with gold, left behind as relics. While flowers had not been cultivated, at least by today’s standards, formal arrangements and bouquets were assembled from poppy, cornflower, water lily, and papyrus[30].

An example of a classical Chinese garden: the Yuyuan Garden in Shanghai (created in 1559).

Source: Wikimedia Commons, User: Jakub Hałun. Yuyuan Gardens in Shanghai. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

The earliest record of formal Chinese gardens appear during the Shang Dynasty(1600-1046 BCE). Gardens were created to not only house fruits and vegetables, but also birds and animals, some of which were hunted for sport by nobles. It is possible that the cultivation of roses began in China as far back as 5000 years ago[31].

A 19th century imaging of the ‘Hanging Gardens of Babylon’, 605-562 BCE.

Source: Wikimedia Commons, User: Rex. Photograph of 19th century work ‘Hanging Gardens of Babylon’. Public Domain . [link]

Possibly created by the Neo-Babylonian king, Nebuchadnezzar II, between 605 and 562 BCE, the Hanging Gardens of Babylon was a wonder of the ancient world. Interestingly, there is debate over whether these gardens actually existed, as despite mention of them appearing in the writings of a great many ancient scholars, they were not written about by the Babylonians themselves, nor has any archeological evidence ever been unearthed to suggest their construction. Whether they were real gardens or poetic fantasy, at least the concept of a formal garden existed and flowers appeared symbolically and esthetically in art from the period.

510–500 BCE Greek pottery of Eros holding a flower as a gift of love.

Source: Wikimedia Commons, User: sailko. Attribution: I, Sailko. Kachrylion (potter), ca. 510–500 B.C. Archaeological Museum of Florence, Inv. 91456. Beazley, ARV² 108/27. From Orvieto. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

Religion for the ancient Greeks was centred around colourful characters who personified natural phenomena. Above we see Eros, the god of love, as a creation of the famous Greek potter Kachrylion, holding a flower as a ‘gift of love’. While there were no private gardens in ancient Greece, gardens were planted around temples and floral imagery used heavily in art.

4th century CE floral Roman mosaic.

Source: Wikimedia Commons, User:Zaqarbal. Original Source: Larry Wentzel on Flickr. Depositado en 1947 por la Institución Príncipe de Viana. National Archaeological Museum of Spain. Creative Commons Attribution 2.0 Generic [link]

Flowers were an important design element in many early mosaics. Above, we see a portion of a design from the Villa del Ramalete, an ancient Roman site, located in what is now Navarre, Spain. The Roman empire, from 100 BCE – 500 CE was very interested in horticulture and botany, more so than the earlier Greeks. There is evidence to suggest Romans cultivated roses[31], shaped topiary, and shared their best seeds. The ruins of Pompeii even showed that gardens were not just for the wealthy or elite, but something that average Romans had in whatever space around their home was available. Paintings from Pompeii show that window box gardens and potted plants were used by would-be-gardeners whose space was in short supply[29] (some of us might be able to relate).

260 CE, Persian-Roman floor mosaic detail with flowers from the palace of Shapur I at Bishapur.

Source: Wikimedia Commons, User: Cordanrad. Palace of Shapur I at Bishapur, Iran. Public Domain. [link]

Here we see a close up of a mosaic from from the palace of Shapur I the Great, the king of the Second Persian Empire ( from 240 to 270 CE). The Persians have a long history with gardens, especially formal gardens. The great Pasargad Persian Garden was built in 500 BCE, although it has been suggested that Persian gardens existed as far back as 4000 BCE. One of the most iconic styles of Persian gardens was the Charbagh, which originated during the first Persian Empire, at the time that the Pasargad Garden was built. Overall geometric form was emphasized more than floral cultivation[32].

Images of flowers appear throughout modern human history – like our incredibly distant pollinating cousins, something about flowers draws our eye.

Here we see a modern monocot, the Tulip, in cultivation in South Holland.

Source: Wikimedia Commons, User: Alessandro Vecchi. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

The modern floral trade took off in Europe in the 1500s after tulips arrived in Vienna from the Ottoman Empire in 1554. This lead to the famous Tulip Mania during the Dutch Golden Age and the first economic ‘bubble’ to burst. Despite the hardships to the Dutch floral trade in the 1600s, the Netherlands remains one of the most productive centres for the floral market to this day.

Instead of relying on pressure from pollinators, predators, and the weather, we now select for larger blooms and brighter colours artificially. Mutations that might not have survived in the wild, if they produce variegated foliage or double petals, are now cultivated in a multi-billion dollar industry. Nature is still doing her thing though, and new species can still come along without us.

For hobbyists looking to get into plant breeding, the University of Illinois has great resources to get you started.

References:

[1] Ge Sun, David L. Dilcher, Hongshan Wang & Zhiduan Chen “A eudicot from the Early Cretaceous of China”, Nature 471, 625–628 (31 March 2011) doi:10.1038/nature09811 (Paywall)

[2] Santiago R. Ramírez, Barbara Gravendeel, Rodrigo B. Singer, Charles R. Marshall, & Naomi E. Pierce. “Dating the origin of the Orchidaceae from a fossil orchid with its pollinator” Nature 448, 1042-1045 (30 August 2007) doi:10.1038/nature06039 (Paywall) (Press release)

[3] Caroli de Waal, Spencer C. H. Barrett, and Bruce Anderson, “The effect of mammalian herbivory on inflorescence architecture in ornithophilous Babiana (Iridaceae): Implications for the evolution of a bird perch” Am. J. Bot. June 2012. doi: 10.3732/ajb.1100295 (Paywall) (Press release)

[4] Else Marie Friis, Kaj Raunsgaard Pedersen, and Peter R. Crane, “Diversity in obscurity: fossil flowers and the early history of angiosperms” Philos Trans R Soc Lond B Biol Sci. 2010 February 12; 365(1539): 369–382. doi: 10.1098/rstb.2009.0227 (Open access)

[5] Gerhard Leubner, “The Seed Biology Place”, Gerhard Leubner Lab, Royal Holloway, University of London, 2000. Website

[6] J. Stein Carter, “Coevolution and Pollination”, Clermont College, Bio303 Course Notes, 1999,2005. Website

[7] John M. Miller, “Origin of Angiosperms” & “Research”, University of California, Berkeley, November 2011. Website & Research

[8] Crepet WL, Nixon KC. “Two new fossil flowers of magnoliid affinity from the Late Cretaceous of New Jersey.” Am J Bot. 1998 Sep;85(9):1273-88. (Open access)

[9] Jules Janick, “History of Horticulture”, Purdue University, HORT 303, 2002. Website

[10] Adrian G. Dyer1, Skye Boyd-Gerny, Stephen McLoughlin, Marcello G. P. Rosa, Vera Simonov, and Bob B. M. Wong. “Parallel evolution of angiosperm colour signals: common evolutionary pressures linked to hymenopteran vision”. The Proceedings of the Royal Society B. June 6, 2012, doi: 10.1098/rspb.2012.0827. (Paywall) (News article)

[11] Lars Chittka and Randolf Menzel. “The evolutionary adaptation of flower colours and the insect pollinators’ colour vision”. Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology. Volume 171, Number 2 (1992), 171-181, DOI: 10.1007/BF00188925. (Paywall)

[12] Yosuke Yoshioka, Kazuharu Ohashi, Akihiro Konuma, Hiroyoshi Iwata, Ryo Ohsawa and Seishi Ninomiya. “Ability of Bumblebees to Discriminate Differences in the Shape of Artificial Flowers of Primula sieboldii(Primulaceae) “. Ann Bot (2007) 99 (6): 1175-1182. doi: 10.1093/aob/mcm059. (Open Access)

[13] Olle Pellmyr and James Leebens-Mack. “Forty million years of mutualism: Evidence for Eocene origin of the yucca-yucca moth association” PNAS August 3, 1999 vol. 96 no. 16 9178-9183. doi: 10.1073/pnas.96.16.9178 . (Open Access)

[14] Else Marie Friis, Kaj Raunsgaard Pedersen, and Peter R. Crane. “Diversity in obscurity: fossil flowers and the early history of angiosperms”. Philos Trans R Soc Lond B Biol Sci. 2010 February 12; 365(1539): 369–382. doi: 10.1098/rstb.2009.0227. (Open Access)

[15] Taylor, D.W.; Li, H.; Dahl, J.; Fago, F.J.; Zinniker, D.; Moldowan, J.M. “Biogeochemical evidence for the presence of the angiosperm molecular fossil oleanane in Paleozoic and Mesozoic non-angiospermous fossils.” Paleobiology 32(2), 179-190. doi: 10.1666/0094-8373(2006) (Paywall) (earlier press release from April 2001 American Chemical Society Biogeochemistry of Terrestrial Organic Matter”symposium)

[16] J. Michael Moldowan, Jeremy Dahl, Bradley J. Huizinga, Frederick J. Fago, Leo J. Hickey, Torren M. Peakman, David Winship Taylor. “The Molecular Fossil Record of Oleanane and Its Relation to Angiosperms”. Science 5 August 1994: Vol. 265 no. 5173 pp. 768-771 DOI: 10.1126/science.265.5173.768. (Paywall)

[17] Daniel L. Nickrent,”Elements of Plant Systematics”, Plant Biology 304, Southern Illinois University Carbondale. February 2012. Website

[18] Peter R. Crane, “The Fossil History of the Gnetales”, International Journal of Plant Sciences, Vol. 157, No. 6, Supplement: Biology and Evolution of the Gnetales (Nov., 1996), pp. S50-S57. (Paywall)

[19] Catarina Rydin and Else M Friis, “A new Early Cretaceous relative of Gnetales: Siphonospermum simplex gen. et sp. nov. from the Yixian Formation of Northeast China”. BMC Evolutionary Biology 2010, 10:183 doi:10.1186/1471-2148-10-183. (Open Access)

[20] Michael W. Frohlich, “MADS about Gnetales”, Proceedings of the National Academy of Sciences, PNAS August 3, 1999 vol. 96 no. 16 8811-8813. doi: 10.1073/pnas.96.16.8811. (Open Access)

[21] David Grimaldi, “The Co-Radiations of Pollinating Insects and Angiosperms in the Cretaceous”, Annals of the Missouri Botanical Garden , Vol. 86, No. 2 (Spring, 1999), pp. 373-406. (Paywall)

[22] David L. Dilcher and Hongshan Wang, “An Early Cretaceous fruit with affinities to Ceratophyllaceae”. American Journal of Botany 96(12): 2256–2269. 2009. doi: 10.3732/ajb.0900049. (Open Access)

[23] Else Marie Friis, Kaj Raunsgaard Pedersen, and Peter R. Crane, “Araceae from the Early Cretaceous of Portugal: Evidence on the emergence of monocotyledons”, PNAS November 23, 2004 vol. 101 no. 47 16565-16570, doi: 10.1073/pnas.0407174101. (Open Access)

[24] Owen Edwards, “The Skeletons of Shanidar Cave”, Smithsonian magazine, March 2010. (Open Access, journalism).

[25] Yin-Long Qiu, Jungho Lee, Fabiana Bernasconi-Quadroni, Douglas E. Soltis, Pamela S. Soltis, Michael Zanis, Elizabeth A. Zimmer, Zhiduan Chen, Vincent Savolainen & Mark W. Chase, “The earliest angiosperms: evidence from mitochondrial, plastid and nuclear genomes” Nature 402, 404-407 (25 November 1999) | doi:10.1038/46536. (Open Access)

[26] THE ANGIOSPERM PHYLOGENY GROUP, “An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III”, Botanical Journal of the Linnean Society, Volume 161, Issue 2, pages 105–121, October 2009. DOI: 10.1111/j.1095-8339.2009.00996.x (Open Access)

[27] Charles Darwin, “On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing“. London, John Murray, Albermarle Street, 1862. (Wikipedia)

[28] Else Marie Friis, James A. Doyle, Peter K. Endress, and Qin Leng, “”Archaefructus – angiosperm precursor or specialized early angiosperm?”, Trends in Plant Science, Volume 8, Issue 8, 369-373, 1 August 2003, doi:10.1016/S1360-1385(03)00161-4. (Paywall) (News)

[29] Tanya Kane, “Garden Paintings of Pompeii: Context and
Meaning”, Master’s Thesis, McMaster University, 5-1-1998. (Open Access)

[30] Robert McDuffie, “Outline of notes from class on Ancient gardens”, Virginia Tech, Hort3524. (Open Access pdf)

[31] “The History of Roses”, University of Illinois Extension Services. Website

[32] D. Fairchild Ruggles, Islamic Gardens and Landscapes, University of Pennsylvania Press, 2008, p.39.

[33] “Plant Evolution Timeline”, University of Cambridge, Centre for Applied Research in Educational Technology. (Downloadable tool)

[34] “History of life through time”, University of California Museum of Paleontology. Website

[35] “Plant and Animal Evolution” The University of Waikato, School of Science and Engineering. Animal Evolution Website Plant Evolution Website

[36] Ehud Weiss, Mordechai E. Kislev, Anat Hartmann, “Autonomous Cultivation Before Domestication”, Science 16 June 2006: Vol. 312 no. 5780 pp. 1608-1610 DOI: 10.1126/science.1127235 (Paywall)

Because of the length of this post, I would not be surprised at all to find errors in the above, especially if I grabbed an out of date reference. If you see any mistakes, or out of date material, please let me know. Hopefully I didn’t violate any copyright laws in the images used above (the Nature covers may not acceptable use), so if I’ve used an image without appropriate permission, please let me know so I can remove it. Apologies to those who started reading expecting an actual history of flower arrangement (I’ll try to write one at some point).

Update on December 6th, 2012: Since writing this an interesting new paper has come out that those ending up here might enjoy: Clément Coiffard, Bernard Gomez, Véronique Daviero-Gomez, and David L. Dilcher, Rise to dominance of angiosperm pioneers in European Cretaceous environments, PNAS 2012, doi: 10.1073/pnas.1218633110. (Paywall). A press release on the paper is available here: “Research yields understanding of Darwin’s ‘abominable mystery’” from Indiana University.

‘Clean Air Plants’ or Sansevieria trifasciata in bloom

thestayathomescientist — Fri, 06 Jul 2012 12:32:37 +0000

Sansevieria trifasciata in flower in my living room. The pungent, sweet citrus smelling, flowers open at night, where in the wild they would be pollinated by moths.

Sansevieria trifasciata, otherwise known as the ‘snake plant’ or ‘mother-in-law’s tongue’, is a common ornamental plant, for a few very good reasons. Like all easy houseplants, it thrives on neglect. Low light and infrequent, irregular, waterings serve this plant well, which is great for those who want the tropical look, without the bright light and humidity to support it. Many people who have grown Sansevieria for years have never seen it flower because they are ‘too good’ to it. A rough repotting (or conversely, letting it get too root bound) is often enough to trick Sansevieria trifasciata into flowering (because if it thinks it might die, making offspring is a good idea), although once flowered, new leaves will not grow from that particular rhizome. While the care is easy and the flowers beautiful, one of its main draws for me originally was its reputation as an “air cleaner”.

Most people, especially plant people, are familiar with the important role that plants (and other photosynthetic organisms) play in our lives by taking in carbon dioxide from the air and producing oxygen. Air quality is about more than just carbon dioxide and oxygen levels though, but thankfully plants play an important role in helping us with air pollution too.

Indoor air quality is often a lot worse than people expect it to be. Second hand smoke, mold, dust mites, radon (from rocks below the foundation or even granite countertops), and volatile organic compounds (like benzene and formaldehyde, from paints and plastics) all can negatively impact our health. Starting in the 1970s, NASA became interested in this issue, and how it might effect astronauts who would have to live in small, poorly ventilated spaces for long stretches of time (hello, city apartments). They found that certain common houseplants could actually remove pollutants like formaldehyde, benzene, and ammonia from a room rather efficiently.

A little Golden pothos (Epipremnum aureum) and Snake Plant (Sansevieria trifasciata) combo I put together for my husband’s office.

So this big NASA push, and the follow up studies in the ’80s and ’90s, give us a list of good house plant choices that are both easy to care for indoors and act as air cleaners. The usual list you see recommends Mother-in-law’s tongue (Sansevieria trifasciata), Chrysanthemum (Chrysanthemum morifolium), English Ivy (Hedera helix), Spider plant (Chlorophytum comosum), Boston fern (Nephrolepis exaltata ‘Bostoniensis’), a few good palms, a handful of Dracaena, and Golden pothos (Epipremnum aureum) and many other similar members of the Araceae family (for Araceae think pothos, peace lily, and philodendron). Are these the only good air cleaners? No, NASA actually looked at a wide range of houseplants, of which I’ve compiled some of my favorites from their data into a chart below. If English Ivy and Golden Pothos aren’t your thing, there is no reason you can’t have a house of orchids, bromeliads, and ferns. Not all plants were tested in the same situations so a ‘-’ doesn’t necessarily mean that ‘Plant X doesn’t remove Y’, in some cases it just means that we don’t know.

I took data from the two main studies quoted, the first from 1989 from NASA on “Interior Landscape Plants for Indoor Air Pollution Abatement”[1] and the second from 1993 in the Journal of the Mississippi Academy of Sciences by B.C. Wolverton and John D. Wolverton[2] (B.C. Wolverton was the principle investigator on the 1989 NASA study). While these are “new” compared to the original work from the 1970s[3], they are still outdated and the methods not “the best” scientifically, as repeatability is a bit of an issue here, but the data is still worth looking at in context.

In the 1989 study, all “plants tested were obtained from nurseries in [the] local area. They were kept in their original pots and potting soil, just as they were received from the nursery”. Because plant size was so variable, pollutant removal measurements are normalized against “total plant leaf surface area”. Tests were preformed in climate controlled Plexiglass chambers for a period of 24 hours only. In the 1993 study, plants were all “standard nursery stock” in various sized pots (which is why I used pot diameter to normalize the data a bit, as leaf surface area wasn’t available in this study) and the μg/hour particulate removal measurements were averaged over a five month period inside a sealed plastic chamber (with 12 hours of grow lights a day, fans, and temperature and humidity settings). All tests were repeated “three or more times” (although if that was with the same individual plants each time, I don’t know). In both studies, the chambers had artificially high levels (higher than normal room levels) of the pollutants in questions pumped in. Only for formaldehyde do I have an overlap in numbers, but because the tests were so different and specimens so few, you can’t compare numbers between the two studies meaningfully.

Now some data:

	Ammonia Removed (μg/hour/pot diameter in cm)[2]	Benzene Removed (μg/hour/leaf surface area in cm²)[1]	Formaldehyde Removed (μg/hour/leaf surface area in cm²)[1] (μg/hour/pot diameter in cm)[2]	Xylene Removed (μg/hour/pot diameter in cm)[2]
Silver-Vase Bromeliad/”Urn Plant” (Aechmea fasciata)	-	-	15.395 μg/hour/cm[2]	-
Chinese evergreen (Aglaonema modestum)	-	.196 μg/hour/cm²	.096μg/hour/cm²[1] 37.11μg/hour/cm[2]	-
Flamingo lily (Anthurium andraeanum)	162.165μg/hour/cm	-	13.228μg/hour/cm[2]	10.866μg/hour/cm
Spider plant (Chlorophytum comosum ‘Vittatum’)	-	-	0.175 μg/hour/cm²[1] 27.586 μg/hour/cm[2]	12.167 μg/hour/cm
Garden Mum (Chrysanthemum morifolium)	239.539 μg/hour/cm	.758 μg/hour/cm²	95.395 μg/hour/cm[2]	13.224 μg/hour/cm
Dendrobium Orchid (Dendrobium sp.)	-	-	-	25.000 μg/hour/cm
Cornstalk Dracaena ‘Janet Craig’ (Dracaena fragrans ‘Janet Craig’)	-	.071 μg/hour/cm²	.133 μg/hour/cm²[1] 53.583 μg/hour/cm[2]	6.063 μg/hour/cm
Striped Dracaena (Dracaena fragrans ‘Warneckei’)	-	.225 μg/hour/cm²	29.921 μg/hour/cm[2]	11.614 μg/hour/cm
Fragrant Dracaena (Dracaena fragrans var. ?)	-	-	46.207 μg/hour/cm[2]	13.498 μg/hour/cm
Dracaena marginata (Dracaena reflexa v. augustifolia)	-	.167 μg/hour/cm²	.113 μg/hour/cm²[1] 38.030 μg/hour/cm[2]	-
Golden Pothos (Epipremnum aureum)	-	-	.138 μg/hour/cm²[1]	-
Banyan Ficus (Ficus benghalensis)	97.368 μg/hour/cm	-	61.842 μg/hour/cm[2]	17.829 μg/hour/cm
Guzmania “Cherry” Bromeliad (Guzmania lingulata × wittmackii)	-	-	-	11.496 μg/hour/cm
English Ivy (Hedera helix)	-	0.301 μg/hour/cm²	0.408 μg/hour/cm²[1] 55.172 μg/hour/cm[2]	6.453 μg/hour/cm
Neoregelia Bromeliad (Neoregelia sp.)	-	-	-	3.701 μg/hour/cm
Boston Fern (Nephrolepis exaltata v. Bostoniensis)	-	-	91.773 μg/hour/cm[2]	10.246 μg/hour/cm
Kimberly Queen Fern (Nephrolepis obliterata)	-	-	52.283 μg/hour/cm[2]	12.717 μg/hour/cm
“Moth Orchid” (Phalaenopsis sp.)	-	-	15.789 μg/hour/cm[2]	-
Snake plant/mother-in-law’s tongue (Sansevieria trifasciata)	-	.417 μg/hour/cm²	.454 μg/hour/cm²[1] 12.434 μg/hour/cm[2]	10.329 μg/hour/cm
Peace Lily (Spathiphyllum sp.)	83.487 μg/hour/cm	0.217 μg/hour/cm²	0.079 μg/hour/cm²[1] 61.776μg/hour/cm[2]	17.632 μg/hour/cm

An interesting quirk of taxonomy is that plant species move around quite a bit, naming wise, and it can sometimes be confusing knowing what is what. Sometimes genetic testing reveals two plants to be more or less related than they were thought to be, and other times people just realise the exact same thing has been named more than once. Dracaena fragrans received its named from the famous 18th century English botanist John Bellenden Ker Gawler. Later, the famous 19th century German botanist, Adolf Engler, named it again, Dracaena deremensis. Unfortunately for Engler, Ker Gawler got there first, so officially D. fragrans is the name. In the above study, three Dracaena fragrans cultivars were used in the 1993 study, although they were named as Dracaena deremensis ‘Warneckei’, Dracaena deremensis ‘Janet Craig’, and Dracaena fragrans. Which cultivar the later was, is anyone’s guess. What is nice though is that now we have three test subjects, within a single species, so we can compare a little data.

For our three Dracaena fragrans, looking at formaldehyde, we see removal levels of 53.583 μg/hour/cm, 29.921 μg/hour/cm, and 46.207 μg/hour/cm. Does this mean that one cultivar is better than another at removing formaldehyde? No, not necessarily. Without 100s, if not 1000s, of tests on unique plants, we can’t say one variant of Dracaena fragrans is strictly better than another. We can probably say that, in general, Dracaena fragrans is better at removing formaldehyde than Sansevieria trifasciata and, in general, worse at removing formaldehyde than Chrysanthemum morifolium or Nephrolepis exaltata v. Bostoniensis, but without a larger sample size, we can’t say with certainty.

What we can say, though, is that clearly some houseplants remove volatile organic compounds from the air, and that’s a good thing.

A good question to ask at this point is how are these plants filtering this stuff out of the air? The answer isn’t actually all that straightforward.

In the 1993 study, the scientists decided to play with a few variables, and repeated the test with a few plants where the potting soil was covered in sterile sand. Looking at the Boston fern (Nephrolepis exaltata v. Bostoniensis) they found that, averaged over five months, 1027 μg/hour of formaldehyde and 208 μg/hour of xylene were removed when the soil was exposed and only 409 μg/hour of formaldehyde and 103 μg/hour of xylene were removed when the soil was covered in sterile sand. By looking closely at the soil, they determined that, for the Boston fern, 60% of formaldehyde was actually being removed by the microbes in the soil and the other 40% taken in by the leaves (50.5% of xylene was taken in by microbes in the soil and the other 49.5% went to the leaves). In 1989, when the tests were repeated without plants at all, and just open containers of soil, the results weren’t nearly as good. 20.1% of benzene in a sealed container was removed over a 24 hour period with just soil, while 89.8% of benzene was removed when that soil also contained English ivy (Hedera helix)( 77.6% for Dracaena fragrans ‘Janet Craig’, 70.0% for Dracaena fragrans ‘Warneckei’, 73.2% for Epipremnum aureum, and 52.6% for Sansevieria trifasciata (hey, it’s better than a pot of dirt)). The combination of these two results suggests that microbes in the soil, in connection with the roots of the plants, not in isolation, take in the majority of pollutants.

So, to remove pollutants, plants need leaves, roots, and microbe rich soil. Pretty basic stuff, actually.

The next big question I think one should ask is, “Okay, so the microbes+roots take in the lions share of pollutants, what are they doing with it?” Again, that’s a question that doesn’t have an easy answer. Bacteria like Dechloromonas can anaerobically metabolize benzene into carbon dioxide, but that’s not one of the bacteria that we expect to find in potting soil. How and why each particular microbe-root system is taking in and using these pollutants depends entirely on the system and in some cases, we honestly don’t know.

Now, houseplants may take in ammonia, benzene, formaldeyhe, xylene, toluene, tricloroethyne, and likely others (I didn’t include everything in the chart above for brevity), but they also give back. A 2009 study in the American Society for Horticultural Science‘s journal looked at the reversal of the above studies. They closed plants into controlled glass container, and they monitored what came out (not including emissions from the plastic pots). Nicely, this study had an overlap with some of the plants we looked at above (and a final tie-back to my Sansevieria trifasciata flowers).

Table 1 from “Volatile Organic Compounds Emanating from Indoor Ornamental Plants” by Dong Sik Yang, Ki-Cheol Son, and Stanley J. Kays. HortScience April 2009 vol. 44 no. 2 396-400. Click to expand and read.

Looking at Spathiphyllum wallisii, Sansevieria trifasciata, and Ficus benjamina we see all sorts of volatile organics being emitted day and night. While Sansevieria trifasciata may not have been the best at cleaning the air, it also doesn’t make nearly as big of a mess as others. What are all the chemicals? Some of these compounds help attract pollinators, some deter pests, some are flavors, some are odors, some help regulate temperature, and some are still kind of a mystery at this point.

One interesting feature of the data is that day time emission of volatile organic compounds is much greater than night time emission. Most plants require their stomata (the pores on the leaves that allow gases in and out) to be open during the day to facilitate photosynthesis and carbon dioxide exchange. An open stomata means water loss however, so at night, when photosynthesis doesn’t occur, the stomata close, to conserve resources. A closed stomata doesn’t just mean less water vapour escaping, it almost means fewer volatile organics escaping.

Now here is my favourite aspect of this study: their Peace Lily (Spathiphyllum wallisii) was flowering at the time. Because of the flowers being open (and most people like Peace Lilies for the flowers after all), a lot more was being released than in the other cases. The biggest contributor was α-farnesene, both an insect pheromone and a distinct floral scent. Spathiphyllum wallisii was producing 100 times more α-farnesene than everything Sansevieria trifasciata was producing.

Are the farnesene compounds harmful? Probably if you’re in an enclosed space with a lot of them. From the Material Safety Data Sheet for a mixture of Farnesene isomers:

Inhalation of vapours may cause drowsiness and dizziness. This may be accompanied by narcosis, reduced alertness, loss of reflexes, lack
of coordination and vertigo.

Basically, if your Peace Lily is in flower, open a window. Is this unique to Peace Lilies? No, there just aren’t studies on floral emissions from all flowering houseplants. If it has a strong smell, it likely is producing a large quantity of some volatile organic, whether you want to be in a room with it entirely depends on what it is.

While I couldn’t find on a study on volatile emissions from Sansevieria trifasciata flowers, I know that the smell, however sweet, was strong enough for me to chop the flower stalk off after a few days.

Beautiful, but the headache wasn’t worth it for me.

References:

[1] B.C. Wolverton, Anne Johnson, Keith Bounds. “Interior Landscape Plants for Indoor Air Pollution Abatement”. NASA, September 15th, 1989. [Open Access PDF]

[2]B. C. Wolverton and J.D. Wolverton. “Plants and Soil Microorganisms: Removal of Formaldehyde, Xylene, Ammonia From the Indoor Environment”, Journal of the Mississippi Academy of Sciences. 1993 [Open Access PDF]

[3] National Aeronautics Sciences and Space Administration. 1974. Proceedings August Symposium, TM-X-58154. 27-29, 1974. NASA of the Skylab Johnson Life Space Center. 161-68.

[4] Dong Sik Yang, Ki-Cheol Son, and Stanley J. Kays. “Volatile Organic Compounds Emanating from Indoor Ornamental Plants” American Society for Horticultural Science. HortSci. April 2009 vol. 44 no. 2 396-400. [Open Access HTML]

Container Grown Chamomile Tea (Matricaria chamomilla in the city)

thestayathomescientist — Wed, 27 Jun 2012 00:39:12 +0000

My Matricaria chamomilla grows on the edge of a pot overlooking a city street.

Chamomile is actually a catch-all term for several plants within the Asteraceae family (the aster family). The most common two ‘chamomiles’ in cultivation are Matricaria chamomilla (German chamomile) and Chamaemelum nobile (Roman camomile). Chemically, Matricaria and Chamaemelum are quite different, unsurprising given that they are in different genera, however they both contain chamazulene, an aromatic compound sought after in the essential oils trade[1].

Chamomile has been used medicinally since the time of the Ancient Egyptians, where it was found to help alleviate the pain associated with malarial fevers[2]. While Matricaria chamomilla is currently the most cultivated version of chamomile in the United States[3], the Chamaemelum genus, until recently grouped within the Anthemis genus, has had a long history of significance.

The Anthemis genus. John Hill, “Virtues of British Herbs. With the history, description, and figures of the several kinds”, London, M.DCC.LXX. [1770].

In 1770, John Hill wrote in his book[4] the following about Chamaemelum nobile, then Anthemis nobilis:

All parts of this excellent Plant are full of virtue. The Leaves, given in infusion, cure Colics; and dispel wind from the Stomach; and are excellent against Indigestion.

The Flowers are a fine and noble bitter. Few things are equal to them in strengthening the Stomach, and creating an appetite, as well as assisting digestions. But more than this, they will cure Agues. I have known them do it after the Bark has failed.

He may have given chamomile a little too much credit, but many studies have shown potential medical benefits, as least in non-human trials[5][6][7][8]. Plus, it’s just nice to sit with a fresh cup of homegrown chamomile tea.

Thankfully, chamomile is easy to grow and doesn’t need much space or care. To brew your own herbal infusion, you simply harvest the flowers at their peak and then you can use them fresh or dry. During chamomile ‘season’ (when the flowers are ready), I don’t bother with drying, and just use the flowers fresh.

All you need is a few flowers in an infuser or sieve, some boiling water, and a little patience and you’ll have yourself a wonderful pot of homegrown chamomile tea*. You can also steep the chamomile with a few slices of apple for something a little different.

Recipe

Ingredients

1 tbsp fresh chamomile flowers (rinsed) per 1 cup of boiling water (approximately)
Optional: anything else you might want for additional flavour, like apple slices, lemon, peppermint, honey, etc.

Directions

Place rinsed chamomile flowers into an infuser and place the infuser into the teapot
If you want to add additional flavourings do so
Pour boiling water over the infuser into the teapot and cover
Let infusion steep five minutes, longer if you’ve used less flowers
Take the infuser out, pour and enjoy**

*Other easy “Tea Garden” plants to grow for herbal infusions are peppermint and lavender. If you have the climate, or a nice indoor space, you can grow Camellia sinensis, the plant we harvest actual tea from.
**Make sure you’re medically able to drink chamomile tea first. While it is considered generally safe, there are people who might want to avoid it (WebMD).

References

[1] “German chamomile production”, Department of Agriculture, Forestry, Republic of South Africa, June 2009. Open Access PDF
[2] “RELEVANCE AND USE OF CHAMOMILE (MATRICARIA RECUTITA L.)”, R. Franke, H. Schilcher, 2006, ISHS Acta Horticulturae 749: I International Symposium on Chamomile Research, Development and Production. Pay-wall
[3] “German Chamomile”, Nancy W. Callan, Mal P. Westcott, Susan Wall-MacLane, James B. Miller, Leon Welty and Louise Strang. Montana State University, College of Agriculture. 2000. Open Access
[4] John Hill, “With the History, Description, and Figures, of the Several Kinds; an Account of the Diseases They Will Cure; the Family Methods of Giving Them; and the Management of the Patients in Each Disease”, London, M.DCC.LXX. [1770].
[5] “A Review of the bioactivity and potential health benefits of chamomile tea (Matricaria recutita L.)”, Diane L. McKay, Jeffrey B. Blumberg, Phytotherapy Research, Volume 20, Issue 7, pages 519–530, July 2006. Pay-wall
[6] “Antiproliferative and Apoptotic Effects of Chamomile Extract in Various Human Cancer Cells”, Janmejai K. Srivastava† and Sanjay Gupta, J. Agric. Food Chem., 2007, 55 (23), pp 9470–9478. Pay-wall
[7] “An experimental study of the effects of Matricaria chamomilla extract on cutaneous burn wound healing in albino rats”, Morteza Jarrahi, Natural Product Research: Formerly Natural Product Letters, Volume 22, Issue 5, 2008, pages 422-427. Pay-wall
[8] “Wound healing activity of Matricaria recutita L. extract.”, Nayak BS, Raju SS, Rao AV, J Wound Care. 2007 Jul;16(7):298-302. Pay-wall

Basic care instructions for Matricaria chamomilla

(synonym Matricaria recutita)
Light: Full sun to partial shade
Water: Basic watering needs, water regularly, but don’t keep moist
Soil pH: 5.6-7.5
Hardiness: Annual, preferred temperature range of 7-26 degrees centigrade, although can survive hotter and near freezing temperatures for a period. Grows easily in much of North America.
Flowering Time: Early to mid summer
Seeds can be sowed directly outside before the last frost. Prefers well draining soil with some organic matter, but doesn’t need to be “well fed”.
References: USDA Natural Resources Conservation Services, Dave’s Garden, Purdue Agriculture Department.

As Shakespeare wrote in Henry the IV,

For though the camomile, the more it is trodden on, the faster it grows, yet youth, the more it is wasted, the sooner it wears.

The ‘Pixie Grape’, a dwarf Pinot Meunier

thestayathomescientist — Fri, 22 Jun 2012 21:33:02 +0000

Pixie Grape, nearly ripe

A new, and interesting, addition to my container grape collection this year was a small one, the newly marketed Pixie Grape. The Pixie, a dwarf version of the Pinot meunier, is a creation of Dr. Peter Cousins that is now being marketed in Canada by Sunrise Greenhouses.

Since it only made its debut in March at Canada Blooms, and the little plants were primed to fruit this year, I can’t say with any certainty how well this grape will do overtime or even what hardiness zone it is. However, while the standard grapes I grow, Flame (zone 4) and Interlaken (zone 5), do well in large containers, they still need space and ample trellising that Pixie doesn’t require. It’s clearly fast fruiting, and, in a six inch pot, has produced a plant .5ft x .5ft x 1.5ft in size with several full bunches of small grapes.

Despite the limited information out there on Pixie, it seems worth trying for those looking for a little viticulture in a small space, likely anywhere from a USDA zone 5 to a 9 (but don’t quote me on this). It also can be grown in greenhouses year round, and given its size, can be easily brought in for the winter.

My poorly trellised Flame and Interlaken grapes on the left and the Pixie Grape on the right. If space is in short supply, the Pixie is the way to go.

Update June 29th, 2012: The first bunch has been picked and they were delicious and sweet.

The first ripe bunch of Pixie grapes.

Basic care instructions

Light: Full sun
Water: Keep moderately moist (but grapes don’t like ‘wet feet’)
Fertilizer: Three times per growing season with a low nitrogen fertilizer, stop mid summer to slow vine growth.
Support: Vines require a small trellis for support
Winter: Keep plants in a cool, protected, location
Pruning: Standard for grapes

The Stay-at-home Scientist

Friday Favourites

“Predatory beetles eavesdrop on ants’ chemical conversations to find best egg-laying sites“

Hsun-Yi Hsieh, Heidi Liere, Estelí J. Soto, Ivette Perfecto1, “Cascading trait-mediated interactions induced by ant pheromones”, Ecology and Evolution, published online: 27 JUL 2012. DOI: 10.1002/ece3.322

“Birds that live with varying weather sing more versatile songs“

Iliana Medina and Clinton D. Francis, “Environmental variability and acoustic signals: a multi-level approach in songbirds”, Biology Letters, Published online August 1, 2012, doi: 10.1098/rsbl.2012.0522

Wasps and Hornets Start the Wine Making Process (Seriously)

A Brief History of Floral Design, or, How Angiosperms Ended Up in Our Vases

Source: Wikimedia Commons, User: Ellywa. Creative Commons Attribution-Share Alike 3.0 Unported [link]

Source: Wikimedia Commons, User: Nonenmac. Original Source: “Carboniferous Pteridophyta (After Dana)” from a the 1896 edition of Underwood’s Native Ferns and their Allies. Public Domain. [link]

Left Source: Wikimedia Commons, User: Verisimilus. Sedgwick Museum’s collection. Creative Commons Attribution 3.0 Unported. [link] Right Source: Wikimedia Commons, User: MPF. Original Source: alexlomas on Flickr. Royal Botanic Gardens, Edinburgh. Creative Commons Attribution 2.0 Generic. [link]

Left Source: Wikimedia Commons, User: Smith609. Sedgwick museum, Cambridge. Attribution: Smith609 at en.wikipedia. Creative Commons Attribution 3.0 Unported. [link] Right Source: Wikimedia Commons, User: Ghislain118. Creative Commons Attribution-Share Alike 3.0. [link]

Left Source: Wikimedia Commons, User: Woudloper. Naturhistorisches Museum, Bern, Switzerland. Public Domain. [link] Right Source: Wikimedia Commons, User: MPF. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

Source: Wikimedia Commons, User: High Contrast. Original Source: Peter Rejcek, National Science Foundation [link]. Researchers Edith and Tom Taylor, University of Kansas. Public Domain. [link]

Source: Me. Public Domain. [5][7]

Source: Me. Public Domain[7].

Source: Wikimedia Commons, User: Smith609. Sedgwick Museum’s collection. Creative Commons Attribution 3.0 Unported. [link]

Source: Me, Public Domain. Data from the APG III system (Angiosperm Phylogeny Group III system), 2009[26]

Source: Wikimedia Commons, User: Bff. Original Source: Scott Zona on Flickr. Amborella trichopoda. Wertheim Conservatory, Florida International University, Miami, Florida, USA. Creative Commons Attribution 2.0 Generic. [link]

Source: Wikimedia Commons, User: uleli. Original Source: 香水蓮花 on Flickr. Creative Commons Attribution 2.0 Generic. [link]

Source: Wikimedia Commons, User: Art Poskanzer. Original Source: Art Poskanzer on Flickr. Creative Commons Attribution 2.0 Generic.[link]

Source: Wikimedia Commons, User: KENPEI. Osaka-fu Japan. Creative Commons Attribution-Share Alike 3.0 Unported [link]

Source: Wikimedia Commons, User: KENPEI. Creative Commons Attribution-Share Alike 3.0 Unported [link]

Source: Wikimedia Commons, User: A9l8e7n. Public Domain. [link]

Altered from Source: Wikimedia Commons, User: Shizhao. Creative Commons Attribution-Share Alike 2.5 Generic. [link]

Source: March 31st, 2011 cover of Nature. Volume 471 Number 7340 pp547-672. [link] Photograph by C. T. Li. [link]

Source: Wikimedia Commons, User: Christian Fischer. Attribution: Christian Fischer. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

Source: The Virtual Fossil Museum. See VFM for permissions.

Source: Wikimedia Commons, User: Kevmin. Stonerose Interpretive Center Collection. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

Source Wikimedia Commons, User: Kevmin. Stonerose Interpretive Center Collection # SR 99-05-05. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

Source: Wikimedia Commons, Users: Kevmin. Stonerose Interpretive Center Collections # SR 95-05-05. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

Source: Wikimedia Commons, User: Kevmin. Stonerose Interpretive Center Collection. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

Source: Wikimedia Commons, User: Kevmin. Stonerose Interpretive Center Collection. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

Source: Wikimedia Commons, User: Slade Winstone (Sladew). Clare Family Florissant Fossil Quary, Florissant, Colorado, USA.. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

Source: Wikimedia Commons, User: Noah Elhardt. Public Domain. [link]

Source: American Journal of Botany. Photo credit: C. E. Smith. 21 May 2012, doi: 10.3732/ajb.1100295 Am. J. Bot. June 2012. (press release) [link]

Source: Wikimedia Commons, User: Michael Wolf. Botanischen Garten Köln Creative Commons Attribution-Share Alike 3.0 Unported, 2.5 Generic, 2.0 Generic and 1.0 Generic license. [link]

Source: Wikimedia Commons, User: Esculapio. Natural History Museum of London. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

Source: August 31st, 2007 cover of Nature. Santiago R. Ramírez, Barbara Gravendeel, Rodrigo B. Singer, Charles R. Marshall & Naomi E. Pierce. Nature 448, 1042-1045(30 August 2007) doi:10.1038/nature06039. [link]

Altered from Source: Wikimedia Commons, User: JosephV. View of the exterior of Shanidar Cave, taken during the summer of 2005. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

Source: Wikimedia Commons, User: Jakub Hałun. Yuyuan Gardens in Shanghai. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

Source: Wikimedia Commons, User: Rex. Photograph of 19th century work ‘Hanging Gardens of Babylon’. Public Domain . [link]

Source: Wikimedia Commons, User: sailko. Attribution: I, Sailko. Kachrylion (potter), ca. 510–500 B.C. Archaeological Museum of Florence, Inv. 91456. Beazley, ARV² 108/27. From Orvieto. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

Source: Wikimedia Commons, User:Zaqarbal. Original Source: Larry Wentzel on Flickr. Depositado en 1947 por la Institución Príncipe de Viana. National Archaeological Museum of Spain. Creative Commons Attribution 2.0 Generic [link]

Source: Wikimedia Commons, User: Cordanrad. Palace of Shapur I at Bishapur, Iran. Public Domain. [link]

Source: Wikimedia Commons, User: Alessandro Vecchi. Creative Commons Attribution-Share Alike 3.0 Unported. [link]

References:

‘Clean Air Plants’ or Sansevieria trifasciata in bloom

Ammonia Removed (μg/hour/pot diameter in cm)[2]

Benzene Removed (μg/hour/leaf surface area in cm²)[1]

Formaldehyde Removed (μg/hour/leaf surface area in cm²)[1] (μg/hour/pot diameter in cm)[2]

Xylene Removed (μg/hour/pot diameter in cm)[2]

Silver-Vase Bromeliad/”Urn Plant” (Aechmea fasciata)

-

Chinese evergreen (Aglaonema modestum)

Flamingo lily (Anthurium andraeanum)

Spider plant (Chlorophytum comosum ‘Vittatum’)

Garden Mum (Chrysanthemum morifolium)

Dendrobium Orchid (Dendrobium sp.)

Cornstalk Dracaena ‘Janet Craig’ (Dracaena fragrans ‘Janet Craig’)

Striped Dracaena (Dracaena fragrans ‘Warneckei’)

Fragrant Dracaena (Dracaena fragrans var. ?)

Dracaena marginata (Dracaena reflexa v. augustifolia)

Golden Pothos (Epipremnum aureum)

Banyan Ficus (Ficus benghalensis)

Guzmania “Cherry” Bromeliad (Guzmania lingulata × wittmackii)

English Ivy (Hedera helix)

Neoregelia Bromeliad (Neoregelia sp.)

Boston Fern (Nephrolepis exaltata v. Bostoniensis)

Kimberly Queen Fern (Nephrolepis obliterata)

“Moth Orchid” (Phalaenopsis sp.)

Snake plant/mother-in-law’s tongue (Sansevieria trifasciata)

Peace Lily (Spathiphyllum sp.)

References:

Container Grown Chamomile Tea (Matricaria chamomilla in the city)

Recipe

Ingredients

Directions

References

Basic care instructions for Matricaria chamomilla