The Fuzziest of Flowers

Describing plants can be quite a task for taxonomists. When a new species is discovered, the honor of naming it often goes to the discoverer. At the very least, they have some input. Some folks go for the more traditional rout and give the plant a descriptive name rooted in either Latin or Greek. Others decide to name the plant in honor of a botanist of the past or perhaps a loved one. Still others take a stranger approach in order to immortalize a famous celebrity. However, in doing so they risk taking something away from the species in question.

Instead of a descriptive name that clues you in on specific features of the plant, instead you hit an etymological dead end in which you are stuck with nothing more than a last name. This became quite apparent to University of Alabama botanist John Clark when it was time to name a newly discovered plant species from South America. 

Had things been slightly different, the recently discovered Kohleria hypertrichosa would have been named after Chewbacca. One look at the flowers of this species and you can understand why. The long tubular petals of this gesneriad are covered in dense, fuzzy hair. This is unlike any other plant known to science. The appearance of these odd fuzz balls may seem puzzling at first but considering where this plant was found growing, it quickly becomes apparent that these flowers are a marvelous adaptation in response to climate. 

Kohleria hypertrichosa is only known to grow in a very narrow swath of mountainous cloud forest in the Ecuadorian Andes. At home between elevations of 3,600 and 6,600 feet above sea level, this wonderful gesneriad experiences some pretty low temperatures for a tropical region. It is likely that the thick layer of hairs keeps the flowers a bit warmer than the surrounding air, offering a welcoming microclimate for pollinators. This could potentially make them much more likely to be pollinated in a habitat where pollinators may be in short supply. 

At the end of the day, Clark decided to stick with a more traditional name for this new species. Its scientific name is no less interesting as a result. The specific epithet 'hypertrichosa' is derived from a condition in humans known as hypertrichosis, or werewolf syndrome, in which a person grows excessive amounts of body hair. 

Photo Credit: Andreas Kay [1]

Further Reading: [1]

The Curious Case of a Dancing Plant

Plants aren't generally known for their speed. They tend to move at rates we simply can't perceive. The few species that exhibit rapid movements such as the sensitive plant (Mimosa pudica) and the Venus fly trap (Dionaea muscipula) have become quite famous as a result. Such movements happen in fits and bursts. These plants certainly cannot maintain such activity. However, there is another plant out there whose activity puts these other plants to shame.

Meet the telegraph plant. It has gone by a handful of scientific names since its discovery (Desmodium motorium, D. gyrans, Hedysarum gyrans, Codariocalyx motorius) but that's not why its famous. This Asian legume is renown for its maneuvers. Its compound leaves are quite active. The larger terminal leaflets move up and down throughout the course of a day but its smaller lateral leaflets exhibit rhythmic movements on the scale of minutes.

Perhaps most famously, the leaflets show an increase in movement when exposed to music. Search the web and you will find lots of videos of the telegraph plant "dancing" to a variety of musical styles. Though entertaining, music is not why this plant moves. Having evolved long before music was ever invented, its movement must have its roots in something a bit more natural. Despite how popular such motion has made this species over the past few centuries, their its function has remained a bit of a mystery.

Before we get into the theories, let's take a closer look at exactly how this plant moves. At the base of its leaflets there sits a ring of cells called the "pulvinus." They act a bit like water balloons and thanks to some dedicated work, it has been found that, when stimulated, these cells can quickly move water in and out via osmosis. This causes the cells to either swell or deflate and this is where the movement originates. Now, onto the why...

A relatively recent opinion piece puts forth some of the most interesting theories on telegraph plant movement yet. The author suggests that leaflet movements are defensive in nature. They believe that the leaves could be mimicking butterfly (or some other winged arthropod movements). In doing so, it may convince gravid female insects that this individual plant is already occupied. Such strategies do indeed exist in some plant species, though via physical adornments rather than movements. Another theory this author puts forth is that this could also attract potential predators. By mimicking the movement of a tasty insect, it could entice birds to come in to take a closer look. Once there, they could easily find other herbivores hiding on the plant.

Another possibility related to defense is that the movements are meant to deter herbivory altogether. Studies on other plants have shown that some species can actually detect the sound of an insect chewing on leaves. This causes an uptick in the production of defense compounds. Perhaps the telegraph plant, when sensing sound waves, increases its movements in order to knock away a hungry insect. Certainly a moving meal is less appealing than a stationary one. This is also thought to be the reason for rapid leaflet closure in sensitive plants. Hungry insects have a hard time hanging on to a plant when the leaf suddenly collapses from underneath it.

Another hypothesis is that these movements are meant to increase sun exposure. It has been discovered that far from only responding to music, the leaflets move throughout the day depending on temperature. When temperatures are low, leaflet movements are more vigorous. They eventually slow down if temperatures are high enough. This hypothesis is bolstered by the fact that movements cease once the sun goes down. In a sense, the leaflets seem to be using temperature as a means of detecting whether or not they are getting as much sun on them as possible.

In reality, it very well could be a mix of these ideas. Natural selection works like that. In the end, movement of the leaflets has certainly benefited the telegraph plant whether it be fore defense or just to take advantage of as much sun as possible. Despite centuries of popularity, this awesome little legume still has some secrets tucked away and I kind of like that about it.

Photo Credit: [1]

Further Reading: [1] [2] [3] [4]

Wasabi

15288589_1565701140123412_5342557884822718000_o.jpg

Whether you like wasabi or hate it, there is a very high probability that you have never actually tasted it. It is estimated that only about 5% of Japanese restaurants around the world actually offer the real stuff. Instead, the wasabi we most often indulge in is a mix of mustard, European horseradish (Armoracia rusticana), and green food coloring. This begs the question, why is real wasabi so hard to come by?

The answer to this lies in the plant. Real wasabi comes from a species of mustard native to the mountains of Japan. Flowering for this group consists of an inflorescence packed with small, white, 4-petaled flowers shoots up above the leaves. There exists two species within the genus - the uncultivated Wasabia tenuis and the cultivated Wasabia japonica. It has been suggested that these plants be moved out of the genus Wasabia and into the genus Eutrema. Regardless of their taxonomic affiliation, these are beautiful and interesting plants. 

Whereas W. tenuis tends to grow on mesic mountainsides, W. japonica prefers to grow in and around streams. In fact, it can often be found growing right out of the gravelly stream bed. Its strict riparian habit has made it hard for this plant to catch on commercially. Although it doesn't grow submerged like an aquatic plant, it nonetheless needs running water. Without it, the plant will languish and die. Although methods of soil growing W. japonica are sometimes used, these are very labor intensive and require a lot of inputs in order for the plants to thrive. The plant also seems to be highly susceptible to disease if planted in high densities. Overall this has made finding real wasabi a difficult, and not to mention expensive, venture. 

Photo Credit: Qwert1234 (Wikimedia Commons)

Further Reading: [1]

Staying Warm: An Alpine Plant Approach to Reproduction

Things are beginning to cool down throughout the northern hemisphere. As winter approaches, most plant species begin to enter their dormancy period. Very few plants risk wasting their reproductive efforts in the chill of late fall, having gotten most of it out of the way during the warm summer months. This is easy enough for low elevation (and low latitude) plants but what about species living in the high arctic or alpine habitats. Such habitats are faced with cold, harsh conditions year round. How do plants living in these zones deal with reproduction?

These limitations are overcome via physiology. For starters, plants living in such extreme habitats often self pollinate. Insects and other pollinators are too few and far between to rely solely upon them as a means of reproduction. Also, the flowers of most cold weather plants are heliocentric. This means that, as the sun moves across the sky, the flowers track its path so that they are constantly perpendicular to its rays. This maintains maximum exposure to this precious heat source. 

Additionally, many arctic and alpine plants have parabolically shaped flowers. This amplifies the incoming radiation being absorbed by the flower. Experiments have shown that flowers that have been shaded from the heat of the sun had a dismal seed set of only 8% whereas plants exposed to the sun had an elevated seed set of 60%. 

For plants in these habitats, its all about persistence. Low reproductive rates are often offset by extremes in longevity. This is one of the many reasons why hikers must remember to tread lightly in these habitats. Damages incurred by even a single careless hiker can take decades, if not centuries, to recover. 

Photo Credit: [1]

Further Reading: [1]

Plants and Music

Turn up the music! My plants can't hear it! Okay, there goes a cheap attempt at humor... In all seriousness, I was always told as a child that plants respond to music. I have since heard many variations on the theme but basically the ideas is that plants, when exposed to music, respond with increased growth. To take things one step further, it would seem that plants have something akin to musical tastes, preferring classical to rock music.

Is there any real scientific evidence to this or is it all just a bunch of silly pseudoscience? Also, if it is true, what could possibly be going on within the plant that causes a response to music, something we thought was reserved to lifeforms with the proper sensory equipment?

The truth is, there is not much real science to base these assumptions on. The internet is full of anecdotal tales and "experiments" that hinge themselves on new age belief systems. In fact, the first "experiments" on how music influences plant growth was done by a woman named Dorothy Retallack. 

Retallack claimed that plants exposed to classical music grew vigorously whereas plants exposed to rock music languished. Considering how much heavy metal my houseplants are exposed to, I think I have more than enough evidence to say otherwise. Besides her poor experimental design, Retallack was heavily motived by quite a conservative, religious agenda. She had it out for mean old rock n' roll and was damned if she couldn't prove her point. What work has been done since Rettalack's time is tantalizing at best but from this point on, keep in mind that the jury is still out on this topic.

So, why would plants respond to music? They don't have ears or anything in their biology that would function as an auditory device, right? Let's re-frame the question in a more basic sense. What is music? Music is nothing more than organized sounds and sounds are nothing more than pressure waves, that is, disturbances in the atmosphere, a process akin to wind. Plants do, in fact, respond to wind, however, wind is a far more physical force than music. Wind can blow over entire swaths of forest whereas music cannot. What mechanism exists that could possibly explain a plant having any kind of response to music? 

Plants respond to heavy wind by growing smaller or by hugging the ground (think alpine vegetation). High winds could generally be seen as a taxing force in the plant world so why would music make plants grow taller and more vigorous? In my opinion, this idea is not a satisfying explanation. As stated above, music doesn't come close to the raw physical power of wind so there could be something else at work. 

In a study done by Margaret E. Collins and John E.K. Foreman out of the University of Western Ontario in London, Canada, they demonstrated that plants responded to different kinds of tones. The tones were either pure (without variation) or random. The results did not show any sort of negative responses from the plants, but rather the plants showed different rates of growth. Plants exposed to pure tones grew better than those exposed to random tones. 

The mechanism they hypothesized for the increased growth in pure tone plants was that the pure tones were able to move air, however slightly, around the leaf. Plants don't like stagnant air and thus, slight air movement is likely to be more beneficial. The random tones did not produce as vigorous of a response, but the plants still grew. It is possible that the random tones caused less air movement around the plants and, because of this, they did not grow as quickly.

Another explanation that seems plausible was put forth by USCB via their science line. They feel that one possible explanation is that the plants aren't the ones responding to the music, but rather the gardener. If you are listening to music while caring for your plants, then chances are it is music you enjoy. If you are like me, then music really has the power to put you in a good mood. If you are in a good mood then chances are you are more likely to take better care of your plants.

All in all, this is an interesting idea. As I said above, the results are mostly controversial and new agey. There are some tantalizing papers that have been published but their methods have been heavily scrutinized. It seems like this is one of the more popular science fair projects for kids to explore and really, anything that gets kids thinking about science and plants is a cool idea in my book. Until more hard science is done on the subject, we can't say for certain. Either way, I will continue to rock out to my favorite tunes and maybe, just maybe, my plants are benefiting from it too.

Further Reading: [1] [2] [3] [4]

Bacteria Help the Cobra Lily Subdue Prey

The aptly named cobra lily (Darlingtonia californica) is one of North America's most stunning pitcher plants. Native to a small region between northern California and southwestern Oregon, this bizarrely beautiful carnivore lives out its life in nutrient poor, cold water bogs and seeps. Although it resides in the same family as our other North American pitcher plants, Sarraceniaceae, the cobra lily has a unique taxonomic position as the only member of its genus.

It doesn't take much familiarity with this plant to guess that it is carnivorous. Its highly modified leaves function has superb insect traps. Lured in by the brightly colored, tongue-like protrusions near the front tip of the hood, insects find a sweet surprise. These tongue-like structures secrete nectar. As insects gradually make their way up the tongue, they inevitably find themselves within the downward pointing mouth of the pitcher. This is where those translucent spots on the top of the hood come in.

These translucent spots trick the insects into flying upwards into the light. Instead of a clean getaway, insects crash into the inside of the hood and fall down within the trap. The slippery walls of the pitchers interior make escape nearly impossible but that isn't the only thing keeping insects inside. Research has shown that the cobra lily gets a helping hand from bacteria living within the pitcher fluid.

Unlike other pitcher plants, the cobra lily does not fill its traps with rain water. The downward pointing mouth prevents that from happening. Instead, the pitchers secrete their own fluid by pumping water up from the roots. Although there is evidence that the cobra lily does produce at least some of its own digestive enzymes, it is largely believed that this species relies heavily on a robust microbial community living within its pitchers to do most of the digesting for it. This mutualistic community of microbes save the plant a lot of energy while also providing it with essential nutrients like nitrogen in return for a safe place to live.

That isn't all the bacteria are doing for this pitcher plant either. As it turns out, the pitchers' microbial community may also be helping the plant capture and subdue its prey. A recent study based out of UC Berkeley demonstrated that the presence of these microbes helps lower the surface tension of the water, effectively drowning any insect almost immediately.

The microbes release certain compounds called biosurfactants. Through an interesting chemical/physical process that I won't go into here, this keeps insects from using the surface tension of the water's surface to keep them afloat, not unlike a water strider on a pond. Instead, as soon as insects hit the bacteria infested waters, they break the surface tension and sink down to the bottom of the pitcher where they quickly drown. There is little chance of escape for a hapless insect unlucky enough to fall into a cobra lily trap.

Although plant-microbe interactions are nothing new to science, this example is the first of its kind. Although this prey capture role is very likely a secondary benefit of the microbial community within the pitchers, it very likely makes a big difference for these carnivores living in such nutrient poor conditions.

Photo Credit: Wikimedia Commons

Further Reading: [1]

The Explosive Dwarf Mistletoes

I used to think mistletoes were largely a southern phenomenon, preferring regions with mild or even no winters. Then I was introduced to the dwarf mistletoes in the genus Arceuthobium. These odd parasites can be found growing throughout the northern hemisphere. Their affinity for conifers has landed them on the watch list of many a forester yet, despite their economic implications, the dwarf mistletoes are fascinating parasitic plants. 

First and foremost, these are aggressive little plants. They vary in their host specificity. Some species can grow on a wide variety of conifer species from Abies balsamea (balsam fir), Larix laricina (American larch), to Pinus strobus (eastern white pine), whereas others are more specialized, preferring only spruces (Picea spp.). Regardless, infestations of these parasites can do some interesting things to conifer stands. 

Similar to other mistletoes, the dwarfs are stem parasites. They penetrate into their hosts vascular tissues and set up shop, sucking up water and photosynthates and giving nothing in return. Because of this, large infestations can seriously drain their host trees as they themselves have reduced or even no photosynthetic capacity. Additionally, they interfere with nutrient and hormone flows throughout the branches of their host. Such disruptions can result in the formation of dense clusters of branches called "witches brooms." Some dwarf mistletoe infestations can become so intense that they effectively girdle their host tree.

In natural settings, this serves an ecological function. By weakening their hosts, dwarf mistletoes can leave room for other plant species to take root. They also keep one species from becoming too dominant. As such, mistletoe infestations can actually increase plant diversity in the long run. Dwarf mistletoe infestations only become an issue once humans get involved. They can cause serious financial issues for foresters as well as damage important or valued specimen trees. In our highly fragmented forests, their natural behavior can get in the way of human ideals. 

All of this talk of damage can distract us from just how amazing some of these species really are from an organismal standpoint. For instance, the lodgepole pine dwarf mistletoe, Arceuthobium americanum, is capable of thermogenesis. Unlike the other examples of thermogenesis in the plant world, this has nothing to do with flowers. Instead, thermogenesis in A. americanum is used as a seed dispersal agent. 

The dwarf mistletoes don't rely on fleshy fruits to get their seeds from one tree to another. Instead, they utilize ballistic means. As their seed pods mature, they gradually swell. Once pressure is great enough, the seed pods erupt, sending their sticky seeds flying through the canopy at speeds of up to 62 mph (100 km/h)! If lucky, the seeds will stick to the branches of a viable host or be transported there in the fur or feathers of an animal. For A. americanum, the eruption of its seed pods is triggered by heat. Using specialized metabolic pathways at the cellular level, A. americanum is able to heat its seed pods up to ~2 °C warmer than its surroundings, thus triggering its pods to explode. 

Pretty incredible for a species so often labelled as a pest. 

Photo Credit: [1]

Further Reading: [1] [2] [3] [4]

A Green Daffodil From Spain

There are some plants that are so ubiquitous in horticulture that I almost forget that they have wild constituents. Every plant in our gardens can trace its lineage back to the wild. As is often the case, I find the wild congeners of our most beloved horticultural curiosities to be far more fascinating. Take, for instance, the genus Narcissus. Who doesn't recognize a daffodil? The same cannot be said for their wild cousins. In fact, there exists some pretty fantastic species within this genus including a small handful of species that flower in autumn. 

One of the most unique among the fall flowering daffodils is a species known scientifically as Narcissus viridiflorus. This lovely little plant is quite restricted in its range. You will only find it growing naturally in a small region around Gibraltar where it is restricted to rich, clay and/or rocky soils. During years when it is not in flower, N. viridiflorus produces spindly, rush-like leaves. As such, it can be hard to find. 

When Narcissus viridiflorus does decide to flower, it forgoes leaf production. From the bulb arises a single green scape. From that scape emerges the flower. The flowers of this bizarre daffodil are decidedly not very daffodil-like. They are rather reduced in form, with long, slender green petals and a nearly nonexistent daffodil cone. Also, they are green. Though I have not seen this investigated directly, it has been suggested that the green scape and flowers contain enough chlorophyll that they plant can recoup at least some of the energy involved in producing flowers and eventually seed. 

The flowers themselves open at night and are said to be very fragrant. Again, no data exists on who exactly pollinates this species but the timing, color, and smell all suggest nocturnal insects like moths. Like the other daffodils of this region, Narcissus viridiflorus is poorly understood. Taken in combination with its limited distribution one can easily see how such a species may be quite vulnerable to human disturbance. As it stands now, this species and many of its cousins are no more than horticultural curiosities for more niche bulb societies. In other words, Narcissus viridiflorus is in need of some real attention. 

Photo Credit: [1]

Further Reading: [1]

The Gas Plant

Meet the gas plant, Dictamnus albus. This lovely herbaceous species is native to southern Europe, north Africa, and Asia. The gas plant is a member of the citrus family, Rutaceae, and like many members of this group, it has very showy blossoms. Its affiliation with the citrus fruits on your counter isn't the only interesting thing about this species. As the common name might suggest, this plant does something quite strange. 

During the heat of summer, parts of the gas plant exude an oily substance that smells much like the fruits of its cousin, the lemon. These oils have been known to cause contact dermatitis not unlike the sap of giant hogweed. However, this is not the strangest aspect of the gas plants oily nature. One of the properties of these oils is that they are highly volatile. So volatile in fact that they can ignite. 

Another common name for this species is burning bush (though not the one of biblical lore). If air temperatures get high enough or if someone takes a match to this plant on a hot day, the oils covering its tissues will ignite in a flash. The oils burn off so quickly that it is of no consequence to the plant. It goes on growing like nothing ever happened. If you're like me then you have one burning question after reading this - why?!

Despite how incredible this phenomenon may seem, it doesn't appear that too many people have looked into its function. Research has identified a highly flammable organic compound within the oils called isoprene. In plants, isoprenes are thought to protect against heat stress. This is bolstered by the fact that the gas plant produces these compounds during the heat of summer. 

Another possibility is that spontaneous ignition of these compounds could create small wildfires that clear the surrounding area of competition. I have not seen any evidence suggesting this. Yet another possibility is that this is simply an unrelated side effect of oil production. Since the plant is not hurt by the quick burst of flames, it simply hasn't had any reason to evolve a less flammable alternative. Evolution is funny like that. 

Still don't believe what you are reading? Check out this video:

Photo Credit: Jörg Hempel (Wikimedia Commons)

Further Reading: [1]

 

Lizard Helpers

The beauty of Tasmania's honeybush, Richea scoparia, is equally matched by its hardiness. At home across alpine areas of this island, this stout Ericaceous shrub has to contend with cold temperatures and turbulent winds. The honeybush is superbly adapted to these conditions with its compact growth, and tough, pointy leaves. Even its flowers are primed for its environment. They emerge in dense spikes and are covered by a protective casing comprised of fused petals called a "calyptra." Such adaptations are great for protecting the plant and its valuable flowers from such brutal conditions but how does this plant manage pollination if its flowers are closed off to the rest of the world? The answer lies in a wonderful little lizard known as the snow skink (Niveoscincus microlepidotus).

The snow skink is not a pollinator. Far from it. All the snow skink wants is access to the energy rich nectar contained within the calyptra. In reality, the snow skink is a facilitator. You see, the calyptra may be very good at shielding the developing flower parts from harsh conditions, but it tends to get in the way of pollination. That is where the snow skink comes in. Attracted by the bright coloration and the nectar inside, the snow skink climbs up to the flower spike and starts eating the calyptra. In doing so, the plants reproductive structures are liberated from their protective sheath. 

Once removed, the flowers are visited by a wide array of insect pollinators. In fact, research shows that this is the only mechanism by which these plants can successfully outcross with their neighbors. Not only does the removal of the calyptra increase pollination for the honeybush, it also aids in seed dispersal. Experiments have shown that leaving the calyptra on resulted in no seed dispersal. The dried covering kept the seed capsules from opening. When calyptras are removed, upwards of 87% of seeds were released successfully. 

Although several lizard species have been identified as pollinators and seed dispersers, this is some of the first evidence of a reptilian pollination syndrome that doesn't actually involve a lizard in the act of pollination. It is kind of bizarre when you think about it. As if pollination wasn't strange enough in requiring a third party for sexual reproduction to occur, here is evidence of a fourth party required to facilitate the action in the first place. It may not be just snow skinks that are involved either. Evidence of birds removing the calyptra have also been documented. Whether its bird or lizard, this is nonetheless a fascinating coevolutionary relationship in response to cold alpine conditions. 

Photo Credits: [1] [2]

Further Reading: [1]

Rare African Plant Gets A Boost

The reappearance of the silver tree (Leucadendron argeteum) to the slopes of the Tokai Arboretum is so exciting. A member of the family Proteaceae, this beautifully bizarre plant was once common around Cape Town, South Africa. Sadly, their populations have declined by 74%. The cause of this decline is not surprising - deforestation, urbanization, fire sequestration, disease, and invasive species have all taken their toll on this species. With this recent discovery, however, there may be hope yet.

The plants were discovered by a team of volunteers while they were clearing the land of invasive tree cover. The seedlings were small but this species grows fast, up to 500 mm per year. A seedling today can quickly become a mature tree in only a few years. The key to their resurgence are their seeds. Silver tree seeds will not germinate under a closed canopy. Instead, they lie and wait in the soil for decades until fire clears the area of competing vegetation. Without fire, no new trees were growing in to replace dying adults. Hence the situation was looking bleak. 

The discovery of juvenile trees is worth celebrating. After a century of functioning as a pine plantation, this area just might be recovering some of its lost diversity. This species is not out of the woods yet. Experts estimate that it could take another 100 years of seed sowing and proper land management before this area can bolster a thriving silver tree population. Still, it stands as an important reminder that there is hope. Even the most degraded patches of land can hold on to their legacies. There are countless other species out there that, like the silver tree, are teetering on the edge of extinction just waiting for a dedicated group of experts and volunteers to invest time and energy.

Photo Credits: [1] [2]

Further Reading: [1]

The Benefits of Houseplants

I don't know about you, but I find indoor gardening to be just as satisfying and intellectually stimulating as any amount of outdoor gardening. Coming from a temperate climate, I don't think I would be able to survive the long winters if it were not for my houseplants. The benefits to keeping plants in the home as well as the office are numerous and range the spectrum from improving air quality to diminishing stress and aiding in healing.

Few would probably argue that a room with plants in it feels far more lived in and hospitable than an empty, sterile room. It makes sense. We evolved, like everything else on this planet, in a natural setting filled with seemingly endless varieties of different plant species. It should be no surprise that our minds would be more at ease the more natural any environment seems. Studies have shown that in an indoor work environment, offices that contained plants had statistically significant reductions in employee discomfort, stress, and an increase in their overall well being. It doesn't end at work either. Hospitals and other medical facilities also showed that overall well being improved both physically and mentally with their residents. In patients suffering from dementia, indoor plants are said to "stimulate residents’ senses, created positive emotions, and offered opportunity for rewarding activity."

Plants do so much more than just improve our moods and reduce stress, they also clean the air we breath. Many every-day household items off-gas some pretty nasty chemicals. Insulation, particle board, PVC and vinyl, carpets, flooring, even our own clothing, all of these things come with their own gaseous and particulate chemical cocktails. It has been shown time and time again that many species of commonly kept house plants help to remove these molecules from the home environment. Some species are better than others. For instance, spider plants (genus Chlorophytum), are exceptionally good at removing formaldehyde compounds in the air. A room full of plants also exhibits statistically significant reductions in particulate matter as well as a measurable increase in humidity levels.

Whether they make you feel at ease or because they clean the air you breath, having house plants is a good thing. There are many species that are available both in nurseries as well as online. Some of the best plants for the home are also the most sensibly priced. Get online and do some research. There are a lot of easy plants to care for out there if you don't necessarily have a green thumb.

Further Reading: [1] [2] [3] [4] [5] [6] [7]

Some Trees Can Tell When Deer Are Browsing Them

Not being able to escape form your predators makes for an interesting challenge. Plants, being the static organisms that they are, have risen to this challenge in some interesting ways. From thorns, to hairs, and even chemical warfare, there is no end to the strategies plants have evolved to discourage herbivores. However, these adaptations come at a cost. Whether its physical or chemical, defenses are costly to produce. That is why so many plant species have evolved induced defense mechanisms. They don't bother producing their chemical cocktails until they sense that herbivores are munching on their tissues. Whereas the literature is rife with examples of insect induced defenses in plants, few studies have ever investigated whether plants can sense mammalian herbivory. 

A 2016 paper published in Functional Ecology suggests that some trees certainly can. By looking at the responses of two different tree species, sycamore maple (Acer pseudoplantanus) and European beech (Fagus sylvatica), the research team found that trees seem to be able to distinguish between being clipped and being browsed. This experiment focused on deer browse. Deer populations are at historically high densities. This has had severe ramifications on forest composition. Tree saplings are especially vulnerable, so much so that we are witnessing an alarming decrease in tree replacement over time. 

The research team tested if trees could sense herbivory in a pretty ingenious way. They set out into the forest with pruners. Saplings were subjected to two different treatments - simple pruning and pruning followed by the addition of deer saliva. The team then took a molecular look at how each tree responded. What they found was quite startling. Trees that were subjected to pruning alone began producing a class of hormones called jasmonates. This was not surprising as jasmonates are involved in some generic plant defenses. The most interesting results came from the treatments in which deer saliva was added.

When saliva was added to pruned beech twigs, the researchers found that the trees increased their production of metabolites related to growth of buds and leaves. They also found that the addition of deer saliva caused an increase in the production of defense compounds, specifically tannins. Tannins bind to proteins in animal guts, making them harder to digest. In maples specifically, they also found an increase in certain types of flavanols, which have shown to have anti-herbivory properties in insects and humans, however, more work is needed to see if they do in fact deter other mammalian herbivores.

Although we still don't know what exactly the trees are responding to in deer saliva, these results nonetheless offer the first evidence of trees not only being able to perceive mammalian herbivores but also responding with an increase in defense compounds. Although they only looked at two tree species, it stands to reason that such responses are wide spread throughout many plant lineages. It also calls into question previous research that used simple pruning as a proxy for herbivory. Taken together, the picture of plants being unresponsive backdrops to more charismatic fauna is entirely erroneous. Plants are proving to be quite "aware" of their environment.

Photo Credit: [1]

Further Reading: [1]

 

 

The Termite-Eating Nepenthes

Plants and eusocial insects have some interesting ecological relationships with one another. A vast majority of these relationships are between a plant a members of the order Hymenoptera (ants, bees, and wasps), but what about those other eusocial insects, the termites?

Despite the social similarities they share with many ants, bees, and wasps, termites are actually distant relatives of the cockroaches. As many already know, termites also have a relationship with plants. Thanks to symbiotic bacteria residing in their gut, termites are able to make a living eating wood and building massive colonies, sometimes in undesirable locations like in the framework of your house. However, there is at least one species of plant out there that has evolved a different kind of relationship with termites.

Meet Nepenthes albomarginata. Native to Borneo, Malaysia, and Sumatra, this tropical carnivore seems to have a taste for termites. However, unlike flies or ants that are attracted to sweet nectar, termites have a different palate. Feeding on plant materials, termites don't necessarily seem like the kind of insect a plant would want to attract. N. albomarginata has seemingly found a way to attract tasty termites without becoming a meal itself.

As the specific epithet suggests, there is a white ring located around the margin of the pitchers' mouths. The ring is made up of a dense coat of hairs called trichomes. It was discovered that sometimes this white ring would disappear overnight. The pitchers without the white ring were also chock-full of partially digested termites. Just how the termites find these pitchers isn't quite certain. Researchers have not yet been able to isolate a scent compound.

Either way, the termites swarm the ring. While many termites make off with a free meal, plenty more of them slip and fall into the trap. It has been found that N. albomarginata obtains upwards of 50% of its nitrogen needs from termites in this way. What's more, all of this happens in a span of a single evening. Once the ring is picked clean, the pitchers are no longer attractive to the termites. They go their way and the plant has its meal. Because of the social structure of these peculiar insects, the loss of these individuals is never high enough to represent a serious selective pressure.

Further Reading: [1]

Plants May Be Piping Light to Their Roots

Plants just might be piping more than just carbohydrates down to their roots. A study published in Science Signalling offers the first evidence that plants may actually be piping light down underground. No this isn't a metaphor either.

The presence of photoreceptors in the roots has been a bit of a puzzle ever since they were identified. A handful of hypotheses have been put forth in attempt to explain their function. It has been suggested that these photoreceptors are able to sense minuscule amounts of light penetrating through the soil. However, this research suggests there is another mechanism.

A team of researchers based out of South Korea found that certain stem tissues efficiently conducted wavelengths of red light down to the roots. Now before we get too ahead of ourselves, it should be noted that these are minuscule amounts of light. It certainly isn't enough for photosynthesis. However, it is light. Detectors placed under the soil at the ends of roots confirmed that light was indeed being transmitted.

Light is conducted through the tissues in much the same way as fiber optic cables. It is likely that the affinity for red wavelengths in particular has to do with the fact that it can travel farther than other, more intense wavelengths.

By experimenting with gene expression and light exposure, the team was able to demonstrate that light being piped to the roots activates a transcription factor involved in root growth and response to gravity. When the researchers blocked the ability to transmit light they found that root growth was severely stunted. Taken together, these results suggest that not only do roots receive information regarding light conditions above ground, they also directly perceive it.

It should be noted that all of this research was done on a single species, Arabidopsis thaliana. The question remains how common this phenomenon is throughout the plant kingdom. Most plants have photoreceptors in their roots, suggesting this light-piping ability is widespread.

Photo Credit: Dr John Runions/Science Photo Library

Further Reading: [1]

Underwater Pollinators

Modern day aquatic plants are highly derived organisms. Similar to dolphins and whales, today's aquatic plants did not originate in their watery environment. Instead, they gradually evolved from land plants living close to the water's edge. One of the biggest challenges for fully aquatic plants involves pollination. Many species overcome this hurdle by thrusting their flowers up and out of the water where there are far more pollen vectors. Others rely on water currents and a little bit of chance. For aquatic plants whose flowers open under water, water pollination, or "hydrophily", has long been the only proposed mechanism. Surely aquatic animals could not be involved in aquatic pollination. Well, a newly published study on a species of seagrass known scientifically as Thalassia testudinum suggests otherwise.

Seagrasses are ecological cornerstones in marine environments. They form vast underwater meadows and are considered one of the world's most productive ecosystems. Most seagrasses are clonal. Because of this, sexual reproduction in this group has mostly been overlooked. However, they do produce flowers that are tucked down in among their leaves. The production of flowers coupled with a surprising amount of genetic diversity have led some researchers to take a closer look at their reproduction.

A team of researchers based out of the National Autonomous University of Mexico decided to look at potential pollen vectors in Thalassia testudinum, a dominant seagrass species throughout the Caribbean and western Atlantic regions. T. tetidinum is dioecious, producing male and female flowers are separate plants. Flowers open for short periods of time and males produce pollen in sticky, mucilaginous strands. The research team had noticed that a wonderfully diverse group of aquatic animals visit these flowers during the night and began to wonder if it was possible that at least some of these could be effective pollinators.

The team was up against a bit of a challenge with this idea. A simple visit to a flower doesn't necessarily mean pollination has been achieved. To be an effective pollinator, an animal must a) visit both male and female flowers, b) carry pollen on their bodies, c) effectively transfer that pollen, and d) that pollen transfer must result in fertilization. To quantify all four steps, the team used a series of cameras, aquariums, and natural mesocosm experiments. What they discovered was truly remarkable.

Not only did a diverse array of marine invertebrates visit the flowers during the duration of the study, they also carried pollen, which stuck to their bodies thanks to the thick mucilage. What's more, that pollen was then deposited on the female flowers, which rake up these invertebrates with their tentacle-like stigmas. Finally, pollen deposited on female flowers did in fact result in fertilization. Taken together, these data clearly demonstrate that animal pollinators do in fact exist in aquatic environments. It is likely that these invertebrates are most effective during periods when water movement is minimized. Water currents likely still make up a significant portion of the pollen transfer between individual plants. Still, this evidence changes the paradigm of aquatic pollination in a big way.

Photo Credits: [1] [2] [3]

Further Reading: [1]

 

Shade Gives This Begonia the Iridescent Blues

Believe it or not, the blue iridescence of Begonia pavonina is an evolutionary adaptation to extracting the most amount of energy out of the dim light that makes it through the thick rainforest canopy above. Even more bizarre, it works thanks to an interesting property of quantum mechanics. 

Native to Malaysia, B. pavonina lives out its life in deep shade. Most of the sunlight that hits this region is absorbed by the thick canopy of trees above. As such, eking out an existence is a challenge for these understory herbs. That is where this fantastic blue iridescence comes in. To understand it better, researchers had to take a closer look at its cause. 

Inside any photosynthetic leaves resides the chloroplasts. Chloroplasts are filled with tiny stacks of membranous compartments called "thylakoids." This is where the light reactions of photosynthesis take place. Now, in most plants, these thylakoids are haphazardly distributed throughout the chloroplast. This is not the case for B. pavonina. For this species, the thylakoids are arranged in a very precise way.

It is this precision that gives the leaves their iridescent color. Their placement causes blue wavelengths of light to be reflected. This isn't a big loss for the plant as most of the blue light is absorbed by the canopy above anyway. What it does instead is quite fascinating. The stacked thylakoids act like a dense crystal. When light enters the chloroplasts of B. pavonina it is physically slowed down.

This effect is known to quantum physicists as "slow light." Whereas light traveling through a vacuum maintains a constant speed, light passing through different types of matter can actually be slowed down. By slowing light as it passes through the chloroplasts, the thylakoids are able to take advantage of what little light the leaves are able to intercept. For B. pavonina, this equates to a 10% increase in photosynthetic rates. Coupled with an increase in the absorbance of red-green light, one can understand why this is such an advantage. 

Another interesting aspect of its physiology is the fact that B. pavonina produces both "normal" and iridescent chloroplasts. It is thought that this is a form of backup for the plant. In instances where enough light actually does make it through to the forest floor, B. pavonina can use its normal chloroplasts instead. It should be noted that this is not the only case of blue iridescent leaves in the plant kingdom. Many other species including spike mosses, ferns, and even orchids exhibit this trait. Even leaves that don't appear iridescent to our eyes may be utilizing nanostructures such as those seen in B. pavonina to increase their photosynthetic efficiency in low light conditions. It is very likely that many different kinds of plants are physically manipulating light to their benefit.

Photo Credit: Michael Perry

Further Reading:

[1]

Evolving For City Life

Urban environments pose unique challenges to any plant. Cities are generally warmer, have significantly higher CO2 levels, and experience altered levels of disturbance and precipitation patterns than do rural areas nearby. Still, many plants have taken to these concrete jungles, popping up wherever they can eke out an existence. Although we are not reinventing ecological principals in urban areas, they nonetheless present distinct selective pressures on every living thing within their jurisdiction. Evidence now suggests that urban environments are actually shaping the evolution of at least some plant species. 

Motivated by a desire to better understand how urban conditions are influencing evolution, a team of researchers based out of the University of Minnesota decided to take a closer look at a common mustard called Virginia pepperweed (Lepidium virginicum). This hardy little annual is at home wherever disturbance occurs. As such, it can be found throughout most of North America and beyond. Because it self pollinates readily, researchers were able to quantify phenotypic differences between populations growing in dense urban centers and compare them to those growing in more rural areas. They collected seeds from numerous urban and rural populations and grew them together in a greenhouse experiment. By exposing each population to the same conditions in the greenhouse, the team were able to tease out the true phenotypic differences between these populations. 

What their data revealed were distinct differences between urban and rural populations. For starters, urban plants had larger rosettes but fewer leaves. They also bolted sooner than rural plants but then exhibited a much longer period of time between bolting and flowers. Previous studies have shown that the inflorescence of related species "accounted for 55% of a plants photosynthetic activity but only 25% of water loss." Coupled with the reduction in the number of leaves, these results suggest that urban plants are maximizing photosynthesis under drier conditions. 

Another interesting difference is that urban plants produced far more seed than their rural counterparts. This very well may be due to the fact that urban plants tended to be larger. This could also be due to reduced herbivory in urban environments, though such pressures may vary from city to city. Due to the urban heat island effect, it is likely that this could be a result of more stable temperature conditions than those experienced by their rural counterparts.Taken together, these results show that there is indeed selection for traits that allow plants to survive in an urban environment.

Photo Credit: Wikimedia Commons

Further Reading:

[1]

Newly Discovered Orchid Doesn't Bother With Photosynthesis or Opening Its Flowers

A new species of orchid has been discovered on the small Japanese island of Kuroshima. Though not readily recognized as an orchid, it nonetheless resides in the tribe Epidendroideae. Although the flowers of its cousins are often quite showy, this orchid produces small brown blooms that never open. What's more, it has evolved a completely parasitic lifestyle. 

The discovery of this species is quite exciting. The flora of Japan has long thought to be well picked over by botanists and ecologists alike. Finding something new is a special event. The discovery was made by Suetsugu Kenji, associate professor at the Kobe University Graduate School of Science. This discovery was made about a year after a previous parasitic plant discovery made on another Japanese island a mere stones throw from Kuroshima (http://bit.ly/2dYN12L).

Coined Gastrodia kuroshimensis, this interesting little parasite flies in the face of what we generally think of when we think of orchids. It is small, drab, and lives out its entire life on the shaded forest floor. Like the rest of its genus, G. kuroshimensis is mycoheterotrophic. It produces no leaves or chlorophyll, living its entire life as a parasite on mycorrhizal fungi underground. This is not necessarily bizarre behavior for orchids (and plants in general). Many different species have adopted this strategy. What was surprising about its discovery is the fact that its flowers never seem to open. 

In botany this is called "cleistogamy." It is largely believed that cleistogamy evolved as both an energy saving and survival strategy. Instead of dumping lots of energy into producing large, showy flowers to attract pollinators, that energy can instead be used for seed production and persistence. Additionally, since the flowers never open, cross pollination cannot occur. The resulting offspring share 100% of their genes with the parent plant. Although this can be seen as a disadvantage, it can also be an advantage when conditions are tough. If the parent plant is adapted to the specific conditions in which it grows, giving 100% of its genes to its offspring means that they too will be wonderfully adapted to the conditions they are born into. 

As you can probably imagine, pure cleistogamy can be quite risky if conditions rapidly change. In the face of continued human pressures and rapid climate change, cleistogamy as a strategy might not be so good. That is one reason why the discovery of this bizarre little orchid is so interesting. Whereas most species that produce cleistogamous flowers also produce "normal" flowesr that open, this species seems to have given up that ability. Thus, G. kuroshimensis offers researchers a window into how and why this reproductive strategy evolved. 

Photo Credit: Suetsugu Kenji

Further Reading:

[1]

How North America Lost Its Asters

It's that time of year in northern North America, where many of the most famous and easily recognized species come into flower, the asters. Some of my favorite species of plants once resided in this genus, but did you know that referring to our North American representatives as "asters" is no longer taxonomically accurate?

Since the time of Linnaeus, plants and animals have been categorized based on morphological similarities. With recent advances made in the understanding and sequencing of DNA, a new and more refined method of classifying the relationships of living organisms has come on to the scene. Much of what has been taken for granted for the last few decades is being changed. One group that has been drastically overhauled are the North American asters. At one time there were roughly 180 species of North American flowering plants that found themselves in the genus Aster. Today, there is only one, Aster alpinus, which enjoys a circumboreal distribution. 

Because the concept of "Aster" was developed using an Old World species (Aster amellus), New World asters were not granted that distinction. The other New World species have shown to have their own unique evolutionary history and thus new genera were either assigned or created. By far, the largest New World genus that came out of this revisions is Symphyotrichum. This houses many of our most familiar species including the New England aster (Symphyotrichum novae-angliae). Some of the other genera that absorbed New World aster include Baccharis, Archibaccharis, Ericameria, Solidago, and Machaeranthera, just to name a few.

Taxonomy is often a difficult concept to wrap your head around. It is constantly changing as we come up with better ways of defining organisms. Even the concept of a species is something biologists have a hard time agreeing on. Surely, genetic analysis is the best method we have to date, a fact that the Angiosperm Phylogeny Group is constantly refining. For some, this is all a bunch of silly name changes but for others this is the most important and dynamic form of natural science on the planet. One thing to consider is that, as species are split and regrouped, often times what was thought to be one species turns out to be many. In the case of an organism that is threatened or endangered, a split like that can unveil a disastrous elevation into a far more dismal ranking.

Further Reading: [1] [2]