As a kid I used to get a kick out of a couple trees without ever giving any thought towards what it was. My friend's neighbor had a some Osage orange trees (Maclura pomifera) growing at the end of his driveway. Their houses were situated atop a large hill and the road was pretty much a straight drop down into a small river valley. After school on fall afternoons, we would hang out in my friends front yard and watch as the large "hedge apples" would fall from the tree, bounce off the hood of his neighbor's car (why he insisted on parking there is beyond me) and go rolling down the hill. I never would have guessed that almost two decades later the Osage orange would bring intrigue into my life yet again. This time, however, it would be because of the evolutionary conundrum it presents to those interested in a paleontological mystery...
The fruit of this tree are strange. They are about the size of a softball, they are green and wrinkly, and their insides are filled with small seeds encased in a rather fibrous pulp that oozes with slightly toxic white sap. No wild animal alive today regularly nibbles on these fruits besides the occasional squirrel and certainly none can swallow one whole. Why then would the tree go through so much energy to produce them when all they do anymore is fall off and rot on the ground? The answer lies in the recently extinct Pleistocene megafauna.
The tree is named after the Osage tribe who used to travel great distances to the only known natural range of this tree in order to gather wood from it for making arrows. It only grew in a small range within the Red River region of Texas. When settlers made it to this continent, they too utilized this tree for things like hedgerows and natural fences.
What is even stranger is that recent fossil evidence shows that Maclura once had a much greater distribution. Fossils have been found all the way up into Ontario, Canada. In fact, it is believed that there were once 7 different species of Maclura. It was quickly realized that this tree did quite well far outside of its current natural range. Why then was it so limited in distribution? Without the Pleistocene megafauna to distribute seeds, the tree had to rely on flood events to carry the large fruit any great distance. With a little luck, a few seeds would be able to germinate out of the rotting pulp. Botanists agree that the Red River region was a the last stronghold for this once wide ranging species until modern man came on the scene.
Another clue comes from the toxicity of the fruits. Small animals cannot eat much of it without being poisoned. This makes sense if you are a Maclura relying on large animals as dispersers. You would want to arm your fruit just enough to discourage little, inefficient fruit thieves from making a wasteful meal out of your reproductive effort. However, by limiting the amount of toxins produced in the fruit, Maclura was still able to rely on large bodied animals that can eat a lot more fruit without getting poisoned. Today, with the introduction of domesticated megafauna such as horses and cows, we can once again observe how well these fruits perform in the presence of large mammals.
Finally, for anyone familiar with Maclura, you will notice that the tree is armed with large spines. Why the heck does a large tree need to arm itself so extravagantly all the way to the top? Again, if you need things like mammoths or giant ground sloths to disperse your seeds, you may want to take some extra precautions to make sure they aren't snacking on you as well. It takes energy to produce spines so it is reasonable to assume that the tree would not go through so much trouble to protect even its crown if there once wasn't animals large enough to reach that high. The Pleistocene megafauna went extinct in what is evolutionarily speaking only the blink of an eye. Trees like the Osage orange have not had time to adapt accordingly. As such, without the helping hand of humans, this tree would still be hanging on to a mere fraction of its former range down in the Red River region of Texas.
Further Reading:
http://plants.usda.gov/core/profile?symbol=MAPO
http://www.americanforests.org/magazine/article/trees-that-miss-the-mammoths/
http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0001745
Green Islands
Autumn is here and all across the northern hemisphere deciduous trees are putting on a show unlike anything else in the natural world. The range of colors are spectacular both from afar and up close. If you're like me then every single leaf is worth investigation. The trees are shedding their leaves in preparation for dormancy. The leaves aren't dying outright. Instead, the trees are reabsorbing the chemicals involved in photosynthesis as a way of getting back some of the energy investment that went in to producing them in the first place.
If you look closely at some leaves, however, you may notice green spots in an otherwise senescent leaf. Why is it that certain parts of these leaves are still photosynthetically active despite the rest of the photosynthetic machinery shutting down around them? The answer to this question is way cooler than I ever expected.
These "green islands" as they are called are almost always associated with an insect. If you look closely towards the base of these spots you will usually find a tiny leaf mining larvae of a moth busy munching away at the remaining photosynthetic tissue. The most obvious conclusion at this point would be to say that the moth larvae are the cause of the green islands. However, it is not that simple.
When researchers raised the moth larvae under sterile conditions, they did not produce the green island effect. This proved to be a bit of a conundrum. Why would this happen in the wild but not under sterile conditions in a lab? The answer is bacteria.
It would appear that the moth larvae have a symbiotic relationship with bacteria living on their bodies. These bacteria interact with the tissues of the leaf and alter the production of cytokinins. In the leaf, cytokinins inhibit leaf senescence. When the plant switches into dormancy mode, cytokinin production is shut down. The bacteria, however, actually ramp up cytokinin production throughout the tissues surrounding the larva. The result of which is a small region or "island" of tissue with prolonged photosynthetic life.
Because of this, the larvae are able to go on feeding well into the fall when food would otherwise become nonexistent. By harboring these bacteria, the moths are able to get more out of each seasons reproductive efforts instead of simply stopping once fall hits. This is the first ever evidence of insect bacterial endosymbionts have been shown to manipulate plant physiology, though it most certainly will not be the last.
I would like to thank Charley Eiseman for the use of this photo as well as inspiring this post. Charley is the man behind one of my all time favorite blogs Bug Tracks so make sure to visit and like Northern Naturalists.
Further Reading: [1] [2] [3] [4] [5]
Kin Selection in Plants
Apparently some plants can recognize their relatives...
The plant world is highly competitive. Since they can't move around, plant have gotten quite creative in terms of defense and competition. From brute force to chemical warfare, plants are not the static entities that most write them off as. And, while most of what we see is going on above ground, underground, things get even more crazy.
Recent evidence shows that the sea rocket (Cakile edentula) seems to be able to distinguish between plants that it shares DNA with and plants that it doesn't. According to a study done by researchers at McMaster University in Hamilton, Canada, plants that grow around genetic relatives allocated less to root growth than those around non-relatives. Basically, when planted near a non-relative, the sea rocket will expand its root system to try and get the most out of its surroundings. When planted near a relative, the plant limits this expansion. So what does this mean? Well, they believe that the plants are recognizing their relation to other plants and attempting to limit the amount of competition for nutrients and water to genetically related individuals.
So, is this altruism? Not exactly. According to evolutionary geneticist John Kelly, its more along the lines of reduced antagonism. Sea rockets tend to grow in high disturbance beach habitats and because of their short lifespan they frequently self-pollinate. Their seed capsules also tend to stay on the mother plant and because of this, groups of clones tend to be found within close proximity to each other.
If they were to be as aggressive to their relatives as they would be with non-relatives, then they would be essentially competing with copies of their own DNA. From an evolutionary standpoint, preserving copies of your DNA, even in individuals other than yourself, is a boost to overall fitness. The researchers make it a point to note that, in this study, they were not looking at overall lifetime fitness of the plants in question. They do not know if reduced root mass, in this situation, incurs any positive or negative fitness to individuals overall. It should be noted that studies have shown that, at least in some plant species, reduced root mass seems to incur greater reproductive efforts. It is possible that sea rocket, in the presence of related individuals, can produce more seed.
How do the plants recognize their relation to their neighbors? The mechanism is not known at this point. My guess is that there is some form of chemical signature that the plants can recognize. How this information is processed is another story entirely. More and more we are discovering how complex the botanical world really is. According to the researchers, they feel that this type of relationship is not unique to this species alone. Research like this is opening new doors into uncharted and exciting territory.
Further Reading:
http://plants.usda.gov/java/profile?symbol=caed
Fiery Peppers - Evolution of the Burn
Photo by Ryan Bushby licensed under CC BY 2.5
Love them or hate them, one must respect the fiery chili pepper. If you're like me then the addition of these spicy fruits can greatly enhance the culinary experience. For others, spice can be a nightmare. Peppers are so commonplace throughout many cultures of the world that it is easy to overlook them. As a plant fanatic, even the simple act of cooking dinner opens the door to so many interesting questions. What is a pepper? Where do they come from? And why are some so spicy?
Peppers evolved in the Americas. The genus to which they belong, Capsicum, is comprised of somewhere around 27 species. Of these, five have been domesticated. They have no relation whatsoever to black pepper (Piper nigrum). Instead, the chili peppers are relatives of tomatoes, potatoes, and eggplants - family Solanaceae.
The fruit that they produce is actually a type of berry. In the wild, Capsicum fruits are much smaller than the ones we buy at the farmers market or grocery store. Centuries of domestication has created such gaudy monsters. The spicy effect one experiences when biting into a pepper is the result of a chemical called capsaicin. It is mainly produced in the placental tissues and the internal membranes. It is in its highest concentrations in the white pith that surrounds the seeds.
As with any fruit, the main goal is seed dispersal. Why then would the plant arm its fruits with fiery capsaicin? The answer to this riddle lies in their wild relatives. As mentioned, the fruits of wild peppers are much smaller in nature. When ripe, they turn bright shades of reds, yellows, and oranges. Their small size and bright coloration are vivid sign posts for their main seed dispersersal agents - birds.
As it turns out, birds are not sensitive to capsaicin. Mammals and insects are, however, and that is a fact not lost on the plants. Capsaicin is there to deter such critters from feeding on the fruits and wasting hard earned reproductive efforts. As such, the well defended fruits can sit on the plant until they are ripe enough for birds to take them away, spreading seeds via their nutrient rich droppings.
It may be obvious at this point that the mammal-deterring properties of Capsicum have been no use on humans. Many of us enjoy a dash of spice in our meals and some people even see it as a challenge. We have bred peppers that are walking a thin line between spicy and dangerous. All of this has been done to the benefit of the five domesticated species, which today enjoy a nearly global distribution. Take this as some food for thought the next time you are prepping a spicy meal.
Photo Credits: Ryan Bushby, André Karwath, and Eric Hunt - Wikimedia Commons
Further Reading:
http://link.springer.com/article/10.1007%2FBF00994601
http://www.jstor.org/stable/4163197…
http://www.press.uchicago.edu/ucp/journals/journal/ijps.html
Mighty Mighty Squash Bees
Photo by MJI Photos (Mary J. I.) licensed under CC BY-NC-ND 2.0
It's decorative gourd season, ladies and gentlemen. If you are anything like me then you should be reveling in the tastes, smells, and overall pleasing aesthetics of the fruit of the family Cucurbitaceae. If so, then you must pay your respects to a hard working bee that is responsible for the sexual efforts of these vining plants. I'm not talking about the honeybee, no no. I am talking about the squash bees.
If we're being technical, the squash bees are comprised of two genera, Peponapis and Xenoglossa. They are not the hive forming bees we generally think of. Instead, these bees are solitary in nature. After mating (which usually occurs inside squash flowers) the females will dig a tunnel into the ground. Inside that tunnel she places balls of squash pollen upon which she will lay an egg. The larvae consume the protein-rich pollen as they develop.
The story of squash bees and Cucurbitaceae is a North American story. Long before squash was domesticated, these bees were busy pollinating their wild relatives. As a result, this bee/plant relationship is quite strong. Female squash bees absolutely rely on squash flowers for the pollen and nectar needs of their offspring. In fact, they often dig their brood tunnels directly beneath the plants.
Because of this long standing evolutionary relationship, squash bees are the best pollinators of this plant family. The flowers open in the morning just as the squash bees are at their most active. Also, because they are so specific to squash, the squash bees ensure that pollen from one squash flower will make it to another squash flower instead of an unrelated plant species. Honeybees can't hold a candle to these native bees. What's more, crowds of eager honeybees may even chase off the solitary squash bees. For these reasons, it is often recommended that squash farmers forgo purchasing honeybee hives for their crops. If left up to nature, the squash bees will do what they are evolutionarily made to do.
Photo Credit: MJI Photos (https://www.flickr.com/photos/capturingwonder/4962652272/)
Further Reading:
http://www.researchgate.net/profile/Victor_Parra-Tabla2/publication/226134213_Importance_of_Conserving_Alternative_Pollinators_Assessing_the_Pollination_Efficiency_of_the_Squash_Bee_Peponapis_limitaris_in_Cucurbita_moschata_(Cucurbitaceae)/links/549471010cf20f487d2a95b8.pdf
http://www.jstor.org/stable/25084168?seq=1#page_scan_tab_contents
http://extension.psu.edu/plants/sustainable/news/2011/jan-2011/1-squash-bees
Why We See Color
Photo by Francisco Anzola licensed under CC BY 2.0
Seeing the world in trichromatic color is a wonderful thing. I truly feel for those who can't. Humans, by and large, have pretty decent color vision. We have three different kinds of opsins on our cones which allows us to see the variety in hues that we do. It is a trait we share with apes and most Old World monkeys. Why do we possess such a wonderful adaptation? As it turns out, plants were likely the driving factor.
Whereas most mammals tend to have only two different kinds of opsins (dichromacy), the primate lineage from which we evolved developed trichromacy at some point in the past. Why did this happen? The answer may lie in the diet of our common ancestors. As climates changed over time, the common ancestors of Old World monkeys, apes and humans had to constantly adapt to new food sources. A majority of primate diets consist of fruits and leaves. Being able to distinguish between ripe and unripe fruit would be a valuable advantage to have. For our ancestors, dichromacy would have made this quite difficult. Thus the evolution of trichromacy would have incurred quite a selective advantage to our ancestors.
The advantage doesn't end with ripe vs. unripe either. Trichromacy would have also made finding colorful fruits against a backdrop of green much easier as well. Even for the majority of primates that eat leaves, color vision would have been quite useful. Leaves can vary in edibility and even toxicity with age. Being able to tell younger from older leaves could easily make the difference between life and death for these primates. Leaf color is often the only way this can be done. Again, selection for color vision would have quickly spread through these populations. So, the next time you stop to admire a flower or any of the wonderful colors of the world around you, take a moment to think about the fact that plants just might be the reason you can enjoy that wonderful sense.
Further Reading:
http://anthro.palomar.edu/primate/color.htm
http://rspb.royalsocietypublishing.org/content/263/1370/593
http://www.sciencedirect.com/science/article/pii/S0047248402001677
On Orchids and Fungi
It is no secret that orchids absolutely need fungi. Fungi not only initiate germination of their nearly microscopic seeds, the mycorrhizal relationships they form supplies the fuel needed for seedling development. These mycorrhizal fungi also continue to keep adult orchids alive throughout their lifetime. In other words, without mycorrhizal fungi there are no orchids. Preserving orchids goes far beyond preserving the plant. Despite the importance of these below-ground partners, the requirements of many mycorrhizal fungi are poorly understood.
Researchers from the Smithsonian Environmental Research Center have recently shone some light on the needs of these fungi. Their findings highlight an important concept in ecology - conservation of the system, not just the organism. Their results clearly indicate that orchid conservation requires old, intact forests.
Their experiment was beautifully designed. They added seeds and host fungi to dozens of plots in both young (50 - 70 years old) and old (120-150 years old) forests. They continued to monitor the progress of the seeds over a period of 4 years. Orchid seeds only germinated in plots where their host fungi were added. This, of course, was not very surprising.
The most interesting data they collected was data on fungal performance. As it turns out, the host fungi displayed a marked preference for older forests. In fact, the fungi were 12 times more abundant in these plots. They were even growing in areas where the researchers had not added them. What's more, fungal species were more diverse in older forests.
The researchers also noted that host fungi grew better and were more diverse in plots where rotting wood was added. This is because many mycorrhizal fungi are primarily wood decomposers. Nutrients from the decomposition of this wood are then channeled to growing orchids (as well as countless other plant species) in return for carbohydrates from photosynthesis. It is a wonderful system that functions at its best in mature forests.
This research highlights the need to protect and preserve old growth forests more than ever. Replanting forests is wonderful but it may be centuries before these forests can ever support such a diversity of life. Also, this stands as a stark reminder of the importance of soil conservation. Less obvious to most is the importance of decomposition. Without dead plant material, such fungal communities would have nothing to eat. Clearing a forest of dead wood can be just as detrimental in the long run as clearing it of living trees.
Research like this is made possible by the support of organizations such as the Native North American Orchid Conservation Center. Head on over to www.indefenseofplants.com/shop and pick up an In Defense of Plants sticker. Part of the proceeds are donated to this wonderful organization, which helps support research such as this! As this research highlights: What is good for orchids is good for the ecosystem.
Further Reading:
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2012.05468.x/abstract;jsessionid=3385C965FF5BA4CB83290005DFD47FD1.f01t02
Mossive Disjunctions are from the Birds
Photo by barloventomagico licensed under CC BY-NC-ND 2.0
Though we may not think about it, plants have migratory capacity. Their migrations are not like those of a wildebeest or neotropical warblers. Instead of moving as individuals, plants migrate via seeds, spores, or pieces of the parent plant that can then grow into a new, albeit genetically identical individual. Either way, long distance dispersal events have long puzzled ecologists. It has been demonstrated time and again that even modest barriers can inhibit propagule movement. Still, it would seem that over the course of time, plants have managed to overcome such boundaries. One way or another, plants have made some impressive migrations.
Some species have really managed to confuse ecologists. Certain mosses and lichens have very curious distributions. There are species that are found only in the Arctic and the very southern tip of South America. Nowhere in between. Why is this? There have been hypotheses regarding wind currents but the genera to which these plants belong originated in the Miocene and Pleistocene, while the Intertropical Convergence Zone (a major barrier between northern and southern wind currents) was already in place.
Recently, researchers have looked towards long-distance fliers like plovers to explain these distributions. These birds breed in the Arctic and overwinter in South America. Could these be the vessels by which these plants migrate? It has long been known that seeds passing through the gut of a bird often have high germination rates. Many plant species gear their fruit specifically for this reason. Birds travel great distances in their search for food and breeding territory, much greater than the average plant can. But birds aren't necessarily eating mosses and lichens. However, they do use them in their nests. Spores and bits of vegetative material can then get stuck in their feathers. After breeding, the birds migrate to South America and begin their molt. The feathers containing spores and plant material are now shed into the wild where they can germinate and grow.
Considering the size of these migrations, it is likely that these migratory shore birds, and possibly many other species of migratory birds, play a significant role in the dispersal of these plant species.
Photo Credit: barloventomagico (http://bit.ly/1p1X2WC)
Further Reading:
https://peerj.com/articles/424/
The Deciduous Conifer Conundrum
Broad leaf trees get all the glory come fall. Their dazzling colors put on a display for a few weeks every year that is unrivaled. However, it isn't just broad leaf trees that are preparing for winter in this manner. There are some conifers doing the same. The handful that have evolved this deciduous strategy are just as dazzling as their broad leaf neighbors.
The most famous of these are the larches (genus Larix), however, there are others such as baldcypress (genus Taxodium) and the dawn redwoods (genus Metasequoia). So, why have these conifers evolved to be deciduous? There are likely many reasons these genera utilize this strategy but it most likely comes down to cost versus benefit. Needles that last for years are costly to make despite their advantages. They are no guarantee of success either, especially for the larches, which often grow in areas that experience some of the harshest winters on the planet. Heavy snow pack and deep winter chills can take their toll on conifers and many evergreen species show signs of frost damage and broken limbs from snow loads. The habitats in which deciduous conifers are found can be tough places to eek out a living.
By shedding their needles, the larches can get around these issues a bit. They also tend to grow in swampy areas where getting the nutrients needed for survival can be extra difficult. By producing relatively weak needles that are easily replaced from year to year, trees like larches and cypress may get around having to waste resources on more robust needles. Finally, it should be noted that this strategy is by no means less efficient. These genera do quite fine with their deciduous nature. For the most part, these trees are nonetheless successful and can live for centuries. It is mysteries like these that keep the wonderful world of botany interesting.
Further Reading:
http://www.metla.fi/silvafennica/full/sf36/sf363703.pdf
The Plight of the Venus Fly Trap
Photo by NC Orchid licensed under CC BY-NC 2.0
The fact that endangered plants do not receive the same protection as animals speaks volumes towards our perception of their importance. If one were to gun down an endangered bird, regardless of where it happened, they would likely face jail time. This is a good thing. However, regardless of how endangered a plant may be, as long as it is on private property and written consent is given by the land owner, one can harvest to their hearts content. It could be the last population in existence. The point of the matter is, endangered plants only receive protection on federal lands. Even then, enforcement is difficult at best.
Plant poaching is serious business. The victims are usually pretty species like orchids or valuable species like American ginseng. The rarer something is, the higher the price. Someone will always be willing to pay top dollar to add something rare to their collection. This story is repeated time and time again throughout the world but one particularly interesting example centers on a plant that most people are familiar with and have probably attempted to grow at one point in their lives - the Venus fly trap (Dionaea muscipula).
It may be counter intuitive to believe that a plant so often sold in grocery stores could be in trouble but the Venus flytrap truly is. In the wild, Venus fly traps are what we call endemics. They are native to a small portion of land in the Carolinas and nowhere else. Sadly, the long leaf pine savannahs and Carolina bays that they call home are being gobbled up by golf courses, pine plantations, and housing developments. The Venus fly trap (as well as over 100 other endangered species) are quickly losing the only habitat in the world that they exist.
Of the 107 Venus fly trap populations that remain, only 65 of them are located on protected land. If habitat destruction wasn't enough, plant collectors, both legal and illegal, descend upon this region to get their hands on wild fly traps. This, my friends, is the definition of stupidity and greed. A simple internet search will turn up countless hobbyists and nurseries alike that culture these plants in captivity. It isn't very hard to do and it can be done on a massive scale.
There is simply no reason to have to harvest Venus fly traps from the wild. None. Despite the plight of this unique species, legal protection of the Venus fly trap is almost non existent. It is listed as a "species of special concern" in North Carolina, which basically means nothing. For poachers, this really doesn't matter. Thousands of plants are stolen from the wild on protected and unprotected lands alike. Recent felony charges against Venus fly trap poachers offer some hope that the situation may be changing but that still does nothing to protect plants that, through senseless loopholes, are collected legally.
This circles back to those plants we often see for sale in grocery stores. If they are in a red pot with a clear plastic cup on top, you can almost guarantee they came from the Fly-Trap Farm. This company openly admits to buying and selling plants collected from the wild. Despite the afore mentioned fact that culturing them in captivity is done with relative ease, the demand for these carnivorous curiosities coupled with their perceived disposability means that wild populations of this already threatened plant are growing smaller and smaller.
Venus fly traps are endemics. They grow nowhere else in the world. If their habitat is destroyed and demand for wild plants continues, there is no Plan B. This species will be lost to the world forever. Again, there is no reason to buy wild collected plants. Plenty of hobbyists and nurseries such as The Carnivore Girl, Meadowview Biological Research Station, and California Carnivores (just to name a few) offer reasonably priced cultivated Venus fly traps. Whereas it is difficult or even impossible to squash poaching for good, we as consumers can always vote with our wallets.
It is tough to say whether or not there is hope for the Venus fly trap and its neighbors. This region of the Carolinas is growing in its human population. So many Venus fly trap populations have already been lost forever and more are likely to disappear in the near future. There may be hope, however, and it comes in the form of land protection. Recent acquisitions of large tracts of Venus fly trap habitat are promising. Regardless, unless the public speaks up about the plight of these long leaf pine savannahs and Carolina bays, no one is going to listen. Plants deserve the same protection as animals. Heck, we wouldn't have any cute and fuzzy megafauna if it were not for healthy plant populations. Protecting plants needs to be a priority.
Photo Credit: NC Orchid (http://bit.ly/1MUlE0x)
Further Reading:
http://archive.audubonmagazine.org/features0803/carnivorousplants.html
http://www.iucnredlist.org/details/39636/0
http://wunc.org/post/north-carolina-enacts-venus-flytrap-theft-laws-how-big-problem-really#stream/0
Blue
Blue is a strange color. This may seem like an odd statement yet, when you think about it, so few things in nature are truly blue. It is estimated that, of all the colors plants utilize to attract pollinators, blue occurs in less than 10% of species. This isn't a pattern restricted to plants either. Blue is an infrequent occurrence throughout the biological world.
When it does appear, the color blue is usually the result of structure rather than pigment. The feathers of a bluejay, the wings of a morpho butterfly, and the sheen of a beetles elytra - these blues owe their vibrancy to refracted light, not pigment. Without light, the crystalline cells responsible for the blue hue would appear dull brown. As light enters their structure, it is bent in a way that gives off blue wavelengths.
The metalic blue hue of these Pollia condensata are the result of refracted light, not pigment. Photo by Juliano Costa licensed under CC BY-SA 3.0
Plants have adopted this strategy as well. The berries of Pollia condensata use a similar crystalline structure that results in blue. However, there are true blue flowers out there. How have species with blue flowers managed to overcome the rarity of blue pigments?
The simple answer is that they haven't. There are no blue pigments in the floral world. Instead, plants utilize what can only be described as an evolutionary hack. Blue flowers obtain their color by doing something we all did in art class, blending pigments (similar to the one true black flower). By producing varying amounts of anthocyanins (the pigments responsible for reds) floral cells are able to make blue flowers.
The anthocyanins can also be tweaked to appear blue. One way of doing this is through changes in pH. The famous blue poppies (Meconopsis grandis), for example, have a defect in the proton pumps found inside their flower cells. This causes the cells to become more basic than acidic, which manifests in blue, rather than purple, flowers. Blue petunias do this as well.
Despite the lack of blue in the floral world, it nonetheless seems to work well when it comes to pollinators. I watched multiple different species of bee visit the flowers of this downy gentian (Gentiana puberulenta). Hummingbirds often visit the amazing floral display produced by the great blue lobelias (Lobelia siphilitica) in my garden. Anyone that has looked over a patch of blue lupine or delphiniums can attest to the success of this color.
Photo Credits: [1]
Itty Bitty Bartonia
Every plant enthusiast has a handful of species that they search high and low for any time they find themselves out and about. It may be a species you have seen a bunch of times or one your have only read about in the literature. Either way, the search image burns strong in your mind so that when you finally come across the species in question, it is like seeing a celebrity. For me, one of those species is Bartonia virginica.
It may not look like much. Indeed, it is a rather diminutive plant, barely poking its flowers out of the shadows cast by pretty much every other plant near by. However, when conditions are just right, this little gentian seems to flourish. With leaves that have been reduced to small scales that sheath the dainty stem in a couple places, all that really stands out are the tiny, cream colored flowers that cluster near the top. A close inspection of the flowers with a hand lens reveals the unmistakable morphology that runs true throughout the gentian family.
Whereas the stem of the plant does contain chlorophyll, it has long been suspected that this plant must rely on other means of obtaining carbon due to its highly reduced leaves. A paper published in 2009 by Cameron et al., was able to shed some light on this matter. As it turns out, there is strong evidence in support of B. virginica being partially mycoheterotrophic.
This is such a cool little gentian. I was so happy to have come across some. Sometimes it's not always the biggest or the showiest that make our day, but rather the subtle and unique.
Further Reading:
http://plants.usda.gov/core/profile?symbol=bavi3
http://www.amjbot.org/content/97/8/1272.short
Southern Tundra
One would hardly consider the southern half of North America to be a tundra-like environment but even so, some tundra plants exist there today...
Up until about 11,000 years ago, much of North America was covered in massive glaciers that were, in some places, upwards of a mile thick. These colossal ice sheets scoured the land over millennia as they advanced and retreated throughout the Pleistocene. Where they covered the land, nothing except some mosses survived. A vast majority of plants were either wiped out or were forced to survive in what are referred to as glacial refugia.
Refugia are ice free areas either within the range of the ice sheets, such as mountain tops, or areas just outside of the ice sheets. Many of North America's plant species took refuge to the south of the glaciers in what is now the Appalachian Mountains. Echos of these plant communities still exist in the southern US today. Some of which are quite isolated from the current distribution of their species. These plant communities are considered disjunct and coming across them is like seeing back in time.
One such plant is the three-toothed cinquefoil (Sibbaldiopsis tridentata). This species is mainly found in northern Canada and Greenland and is considered a tundra species. It needs cold temperatures and is easily out competed in all but the most hostile environments. Why then can you find this lovely cinquefoil growing as far south as Georgia?
The answer are mountains. A combination of high elevation, punishing winds, and lower than average temperatures, means that the peaks of the Appalachian Mountains have more in common with the tundras found much farther north on the continent. As a result of these conditions, plants like S. tridentata have been able to survive into the present while the majority of their tundra associates migrated north with the retreat of the glaciers.
Because of their isolated existence in the Appalachians, S. tridentata is considered endangered in many southern states. Being able to see this plant without having to visit the tundra is quite a unique and humbling experience. It is amazing to consider the series of events that, over thousands of years, have caused this species to end up living on top of these mountains. It is one of those things that one must really stop and mull over for a bit in order to fully appreciate.
Further Reading:
http://plants.usda.gov/core/profile?symbol=sitr3
http://onlinelibrary.wiley.com/…/j.1365-2699.1998.…/abstract
http://www.castaneajournal.org/doi/abs/10.2179/10-039.1
http://instaar.colorado.edu/AW/abstract_details.php?abstract_id=16
Pearly Everlasting
Photo by Pendragon39 licensed under Public Domain
I have gardened with a lot of native plants over the years but pearly everlasting (Anaphalis margaritacea) may be one of my favorites. Not only is it easy to grow, this tough little plant can handle some pretty harsh soil conditions. In the wild, I often find it growing along gravelly roadsides where it puts on quite a show. Let's be honest with each other, who doesn't love a fuzzy plant.
Pearly everlasting is a member of the largest dicot family on the planet, the asters. As such, what appears to be single flowers doing their best imitation of a sunny side up egg is actually a collection of many tiny flowers clustered together to look like one big one. In a sense, this is a form of floral mimicry.
What is most unique about pearly everlasting is that it is dioecious. Individual plants produce disks that are either male or female. I can't really think of other asters that adopt this strategy. And what an awesome strategy it is. Being dioecious means cross-pollination. The reproductive disk flowers are those yellow ones in the center. The pearly white outer ring of each inflorescence is actually made up of a dense cluster of involucre.
© 2009 Walter Siegmund licensed under GNU Free Documentation License, Version 1.2
Did I mention this plant is fuzzy? Dense trichomes cover the stem and underside of each leaf. Hairs like this are adaptations to reduce water loss and overheating. However, there is evidence that in pearly everlasting, these hairs can also reduce feeding by spittlebugs. Nymphs looking for a tasty plant to drill into cannot seem to penetrate the dense growth of trichomes, which means each pearly everlasting gets to hold on to its sap.
Again, I can't speak highly enough about this species. It is native to much of North America and, in this writers opinion, should be in the drier portions of every native garden. All you need are a handful of seeds and a small population of pearly everlasting will soon be keeping you company.
Photo Credit: Wikimedia Commons
Aquarium Banana
One of my first true passions in life was maintaining freshwater aquariums. There is something about being able to observe a world totally foreign to our own that drew me in. It wasn't long before I discovered the splendor of planted aquascapes. I would have to say that my first foray into this realm probably planted the botanical seed that would later explode into the obsession it is today.
I was always rather perplexed by a plant that I would see for sale at the local aquarium shop. They were labelled as "banana plants" because of their peculiar root structures. They never seemed to fit my aesthetic in those early days so I largely passed them by. Recently I have gotten back into aquariums, only this time it is very plant centric. While perusing the plants offered here in town, I again came across the peculiar banana plant.
This time around, I am a bit more versed in taxonomy and this plant made more sense. I realized that the banana plants we see for sale for aquariums are small, immature specimens of some sort of "lily pad." A deeper investigation would prove me correct. Though not a true water lily (family Nymphaeaceae), the banana plants nonetheless take on a similar growth form with large, floating leaves emerging from an underwater rootstock.
Banana plants are known scientifically as Nymphoides aquatica. Their generic name comes from their striking similarity to the afore mentioned water lilies. However, this resemblance is merely superficial. Banana plants belong to the family Menyanthaceae, making it a relative of plants like buckbean (Menyanthes trifoliata). They grow native in calm bodies of water throughout southeastern North America. Whereas the young leaves grow immersed, larger adult leaves eventually make their way to the surface where they float.
From time to time, small white flowers are produced. This is when its familiar affiliation makes the most sense. This species is dioecious, though seed set is apparently sporadic. Regardless, banana plants readily reproduce vegetatively, either by fragmentation of their roots or by broken leaves settling in a spot and forming roots themselves.
So far this is an interesting aquarium specimen. It seems to have adjusted to my aquarium rather well and it grows pretty quickly. In time I hope it performs more like it does in the wild than as a sad, stunted specimen doomed to a slow death. Only time will tell.
Flower Pic: Show_ryu (Wikimedia Commons)
Further Reading: [1]
CAM Photosynthesis
I was in a lecture the other day and I heard something that made the plant nut inside of me chuckle. The professor was trying to make the point that C3 photosynthesis is the most common photosynthetic pathway on the planet. To do this he said "it is the vanilla pathway." In this context, he was using vanilla as an adjective meaning "plain or ordinary." Of course, this was all very facetious, however, I thought it interesting and funny how, if taken literally, that statement was just plain wrong.
I have written before about the reproductive ecology of Vanilla orchids (http://bit.ly/1LcC857). They are anything but vanilla the adjective. The other part of the statement that was wrong (again, if taken literally) is that C3 is the photosynthetic pathway of the vanilla orchid. In reality, vanillas are CAM photosynthesizers.
Last week I wrote about the C4 pathway and how it has helped plants in hot, dry places, but the CAM pathway is yet another adaptation to such climates. The interesting thing about CAM photosynthesis is that it separates out the different reactions in the photosynthetic pathway on a temporal basis.
CAM is short for Crassulacean acid metabolism. It was first described in succulents in the family Crassulaceae. Hence the name. Similar to the C4 pathway, CO2 is taken into the leaves of the plant and stored as an organic acid. This is where the process differs. For starters, having acid hanging around inside your leaves is not necessarily a good thing. CAM plants deal with this by storing it in large vacuoles. That is one reason for the succulent appearance of many CAM species.
Because these plants so often grow in hot, dry climates, they need to minimize water loss. Water evaporates from holes in the leaves called stomata so to avoid this, these holes must be closed. However, closing the stomata means not letting in any CO2 either. Whereas C4 plants get around this by only opening their stomata during the cooler hours of the day, CAM plants forgo opening their stomata entirely when the sun is up.
Instead, CAM plants open their stomata at night when the vapor pressure is minimal. This ensures that water loss is also minimal. Like camels storing water for lean times, CAM plants store CO2 as organic acid to use when the sun rises the next day. In this way, CAM plants can close their stomata all the while the hot sun is baking the surrounding landscape yet still undergo ample photosynthesis for survival.
Not all orchids do this. In fact, some can switch photosynthetic pathways in different tissues. However, there are many other CAM plants out there including some very familiar species like pineapples, cycads, peperomias, and cacti. If you're like me and prone to talking to your plants, it is probably best to talk to your CAM plants after the sun has set. Not only does it confuse neighbors and friends, it provides them with CO2 when they are actively absorbing it.
Further Viewing: https://www.khanacademy.org/science/biology/cellular-molecular-biology/photosynthesis/v/cam-plants
Invasive Beauty
The honeycomb ginger (Zingiber spectabile) produces one of the most stunning inflorescences I have ever seen. Sadly, it is this beauty that has led to its introduction far outside of its native range of Southeast Asia. As a result, it has become an aggressive invader in many tropical regions.
What a Dichaea
The orchid genus Dichaea includes some of the strangest orchids i have ever seen in person. Take this one for example. My sources tell me this is likely D. globosa. Right off the bat, the bristly seed pods are a tell for this genus. With this particular species, each stem juts off of the trunk of a tree at a near 90 degree angle. The stem itself is horizontally flattened and the subtle yet beautiful flowers emerge from between the leaves and are presented below the plant, facing the ground. I had seen this orchid out of flower in a few places in Costa Rica, however, I was lucky enough to stumble across these individuals in flower while hiking in Panama. An exciting find for this orchid fanatic!
Spikenard
There are times when you go looking for plants without any expectations. I really like those hikes because you never know what you're going to find. Inevitably you end up meeting a lot of old friends but every once in a while you meet a plant that completely throws you for a loop. Aralia racemosa is that plant.
More commonly referred to as spikenard, Aralia racemosa is both a large and stunningly beautiful member of the same family as ginseng. Growing upwards of 5 feet, its deep purple stem zigzags as it throws out some of the largest compound leaves on any native forb I have ever come across. Each leaf consists of multiple egg-shaped leaflets. Between the stem and each branch grows a long raceme packed full of circular flower bundles. In full bloom, the flowers are crawling with a myriad of insects.
Standing near this plant, you begin to pick up a rather pleasant odor. Somewhere between sweet and spicy, the entire plant seems to exude a scent that fills the surrounding air. Indeed, this plant is chocked full of different chemical compounds. The flowers eventually give way to dense clusters of green berries that gradually ripen to a deep purple. The contrast between ripe and unripe berries is rather stark and it is believed that the juxtaposition is to better attract birds, which are the main seed dispersers of this plant.
Genetic analysis has shown that Aralia racemosa is a sister species to Aralia californica in the west. This could be the result of disjunction and consequent speciation brought on by the glaciers. Either way, Aralia racemosa is easily one of the coolest plants I have ever met. I don't know why I don't see it more often. With its staggering beauty and robust growth, it is rather hard to miss. Aralia racemosa would be a great addition to a native shade garden as well.
Further Reading:
http://www.amjbot.org/content/85/6/866.short
http://www.nrcresearchpress.com/doi/abs/10.1139/b82-092#.U-eAc4BdW2s
http://plants.usda.gov/core/profile?symbol=ARRA
Vanilla Is Anything But Vanilla
Photo by H. Zell licensed under CC BY-SA 3.0
Vanilla companies seem to be lacking in their plant ID skills. You so rarely see any vanilla products with the correct flower on the label. While I can't speak for everyone, I think I may have a hunch as to why most companies slap a white Phalaenopsis, Dendrobium, or any of the other orchid flowers that could remotely pass for being Vanilla on their products. At the same time, it also explains the rather pricey nature of Vanilla "beans."
The answer, I believe, lies in the flowers themselves. Vanilla is a genus of orchids that contains roughly 110 species that span the tropical regions of the globe. They are vining orchids, climbing trunks of trees in an attempt to make their bid for the canopy. Some Vanilla orchids have lost their leaves entirely, relying solely on their green, photosynthetic stems and roots. The species that gives us the highly coveted vanilla flavor is Vanilla planifolia from Central America.
![[1]](https://commons.wikimedia.org/wiki/File:Pollia.jpg){kind=link}
Photo by Dinesh Valke licensed under CC BY-SA 2.0
Vanilla planifolia, like most other species of Vanilla, produce very short-lived, non-selfing flowers. They open up as the sun begins to rise and are mostly closed by afternoon. Vanilla are not self-fertile so if the flower has not been fertilized by afternoon, it will simply wither and fall off. Because of their ephemeral nature, it is probably hard for most vanilla companies to do the kind of photo shoot they would need to do their marketing. It is likely that they just fall back on orchids that kind of look like Vanilla and I am sure that outside of us botanical enthusiasts, no one really faults them for it.
The Vanilla reproductive strategy also lends to the pricey nature of real Vanilla "beans." In the wild, Vanilla relies on stingless bees for pollination. In most cases, Vanilla growers do not rely on the bees because, if they are present, fertilization rates are often extremely low. And, if the bees are not present, the plants will not reproduce on their own. Because of this, Vanilla growers must hand pollinate all of the flowers individually.
This is a labor intensive process that must be done at just the right time if it is to work. The resulting "bean" is not a bean at all but rather a large capsule filled with millions of dust-like seeds. The capsules themselves require about 6 weeks to fully mature and then sometimes as long as 9 months to properly cure and produce their characteristic vanilla flavor. So yes, I think it is safe to say that Vanilla is anything but vanilla.
Photo Credit: [1] [2]
Further Reading: [1]