The Sexual Ruse of the Bee Orchids

There are flowers out there that offer rewards far more enticing than any amount of pollen or nectar - they offer sex. Sexual deception is a rather tricky way of achieving pollination. By duping sex-crazed male insects into thinking they have found a female rather than a flower, such plants have tapped into an irresistible force of nature. Nowhere is this more beautifully illustrated than the orchids belonging to the genus Ophrys

Collectively referred to as the bee orchids, Ophrys grow native throughout much of Europe, North Africa, the Canary Islands, and parts of the Middle East. Phylogenetically speaking, they are a bit of a mess. Estimates of the number of species range from as few as 20 to as many as 130. The range of variation in floral color is staggering and has everything to do with the evolution of this genus. 

The reason they are called bee orchids is because that is exactly what they have entered into an evolutionary syndrome with. And what an evolutionary relationship it is! The bee orchids have evolved to trick male bees into thinking their flowers are receptive females. 

The most obvious aspect of this ruse is their appearance. Though there is quite a lot of variation, the overall theme is that the labellum acts as a female dummy complete with hairy abdomens and, in some species, iridescent wing marks. The ruse does not end there. Far more convincing than their appearance is the odor released by each flower. 

Ophrys produce chemical compounds called "allomones." These allomones closely mimic the pheromones released by female bees. What's more, each species of bee orchid produces allomones specific to the species of bee they are trying to attract. For some this can be very specific, attracting males of only a single species. For others it would seem that a small handful of different species have fallen for the orchid's trick. 

Regardless, male bees find these flowers irresistible at first, often preferring flowers to actual females. However, the males soon learn to avoid flowers, which results in consistently low pollination rates. This doesn't seem to be much of an issue for these orchids as a single plant can produce tens of thousands of seeds. 

This pollination syndrome has obviously worked for this genus. Slight mutations on the allomones produced have led to the massive radiation of Ophrys species we see today. Even more amazing is that research suggests that most of this radiation has occurred since the Pleistocene. 

Photo Credit: http://bit.ly/23pJWe0

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

Paleo Pinus

What you are looking at here is the oldest fossil evidence of the genus Pinus. Now, conifers have been around a long time. I mean really long. Recognizable members of this group first came onto the scene sometime during the late Triassic, some 235 million years ago. Today, one of the most species-rich genera of conifers are those in the genus Pinus. They dominate northern hemisphere forests and can be found growing in dry soils throughout the globe. For such a commonly encountered group, their origins have remained a bit of a mystery. 

The fossil was discovered in Nova Scotia, Canada. Unlike the rocky fossils we normally think of, this fossil was preserved as charcoal, undoubtedly thanks to a forest fire. The degree of preservation in this charcoal specimen is astounding and provides ample opportunity for close investigation. 

I mentioned that this fossil is old. Indeed it is. It dates back roughly 133 –140 million years, which places it in the lower Cretaceous. What is remarkable is that it predates the previous record holder by something like 11 million years. Even more remarkable, however, is what this tiny fossil can tell us about the ecology of Pinus at that time. 

Firstly, the leaf scars indicate that this tree had two needles per fascicle. This implies that the genus Pinus had already undergone quite the adaptive radiation by this time. If this is the case, it pushes back the clock on pine evolution even earlier. Another interesting feature are the presence of resin ducts. In extant species, these ducts secrete highly flammable terpenes, which would have potentially promoted fire. 

Species that exhibit this morphology today often utilize an ecology that promotes devastating crown fires that clear the land of competition for their seedlings. Although more evidence is needed to confirm this, it nonetheless suggests that such fire adaptations in pines were already shaping the landscape of the Cretaceous period. All in all, this fossil is a reminder that big things often come in small packages. 

Photo Credit: Howard Falcon-Lang, Royal Holloway University of London

Further Reading:

http://bit.ly/1QP85zm

Bowerbirds - Accidental Gardeners

To look upon the bower of a male bowerbird is to see something bizarrely familiar. These are not elaborate nests but rather architectural monuments whose sole purpose is to serve as a staging ground for mating displays. Males build and adorn these structures with precision and a sense of aesthetics. Because of this behavior, at least one species of bowerbird, the spotted bowerbird, can add another occupation to its resume - accidental gardener.

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When a male finds a certain color he likes, he scours the landscape in search of these treasures. For many male bowerbirds, fruits offer a wide array of colors and textures of which they can add to their menagerie. Male spotted bowerbirds seem to have a fondness for the fruits of the potato bush (Solanum ellipticum). Their stark green hue contrasts nicely with the bower architecture.

When the fruits start to decompose, they no longer serve any purpose for the male bowerbird and he tosses them aside. Seeds begin to accumulate around the bower and after some time they will germinate. Researchers decided to investigate this relationship a bit further. What they found was pretty astounding.

They discovered that bush potato plants grew in higher numbers around bowers than they do at random locations throughout the forest. What's more, the fruits produced by bush potatoes growing near bowers were much greener than those of plants elsewhere. In effect, male spotted bowerbirds are not only cultivating the bush potato, they are also artificially selecting for improved coloration of its fruits.

To date, this is the only example of something other than a human cultivating a plant for reasons other than food. The similarities between human cultivation and bowerbird cultivation are mind blowing. Similar to human farmers, male bowerbirds clear the site of competing vegetation and remove the fuel load so as to minimize the risk of fire, all of which provides ideal habitat for germination. Though the male bowerbirds are not intentionally cultivating the bush potato, they have nonetheless entered into a mutualistic relationship in which the males get ready access to beautiful fruits and in return, the bush potato gets a nice, safe place to grow.

Photo Credit: University of Exeter and bit.ly/1T29wjN

Further Reading:

http://www.sciencedirect.com/science/article/pii/S0960982212002084

Shhhh... Let Him Finish

Sexual deception is rampant in the orchid family. Orchid genera all over the world produce flowers that trick sexually charged male insects into failed mating attempts. The orchids go to great lengths to resemble females both in appearance and smell. Indeed, many sexually deceptive orchid species emit odors that precisely mimic the pheromones of specific insect species. 

In many instances, the orchids ruse is so powerful that male insects will often preferentially visit the flower over an actual female. For many of the sexually deceptive orchids, all that is required is the male to pay a visit. No attempt at copulation is necessary, though that doesn't stop vigorous attempts. Because of this, it is easy to see how the minute cost incurred to the insects is not enough to drive evolution away from deception. However, there is a group of tongue orchids (genus Cryptostylis) from Australia that seem to throw a wrench into this finely tuned system.... or do they?

The tongue orchids rely on deceiving male wasps in the genus Lissopimpla into mating with their flowers. As mentioned above, the males simply cannot resist the attempt. However, unlike many other reported cases, the male wasps actually mate to completion, depositing their sperm onto the flower. This should be disastrous for the wasps since males not only prefer flowers to wasp females, but they also waste their precious few mating attempts. How could this have evolved?

Most sexually deceptive orchids rely on bees and wasps (family Hymenoptera) for their pollination. Thus, the answer to this evolutionary conundrum lies in the mating system of these insects. Queens are genetically haplodiploid. I will spare you the details on that but basically what it means for Hymenoptera is that female offspring are produced via fertilized eggs whereas male offspring are produced via unfertilized eggs. 

The orchids have (unknowingly of course) tapped into this system to their benefit. If by mating with the flower and not a female wasp meant that no offspring were produced, this system surely would not have evolved to the level that it has. Instead, female wasps that have not been mated with or received less sperm than usual end up producing a higher amount of male offspring.

The orchids are effectively skewing the sex ratio of their pollinators! "How is this a sustainable system?" you may be asking. Well, by causing female wasps to produce more males, the orchids are ensuring that there will be more naive males in the population the next time they are in bloom. Also, by skewing the sex ratio towards males, there are now fewer females to mate with so that males become less choosy and more readily mate with orchids. Finally, with more sexually charged males flying around, each female has a greater chance of being fertilized. Because of the unique mating system that has evolved in Hymenoptera, the orchids have thus been able to evolve this pollination strategy with little harm to the pollinators.

Photo Credit: photobitz

Further Reading:
http://instructional1.calstatela.edu/kfisher2/BIOL360/classroom.activities/species_interact._casestudies/orchid.sex.pseudo.II.pdf

Orchid Ant Farms

I am beginning to think that there is no strategy for survival that is off-limits to the orchid family. Yes, as you may have figured out by now, I am a bit obsessed with these plants. Can you really blame me though? Take for instance Schomburgkia tibicinis (though you may also see it listed under the genera Laelia or more accurately, Myrmecophila). These North, Central, and South American orchids are more commonly referred to as cow-horn orchids because they possess hollow pseudobulbs that have been said to been used by children as toy horns. What is the point of these hollow pseudobulbs?

A paper published back in 1989 in the American Journal of Botany found the answer to that question. As it turns out, ants are quite closely associated with orchids in this genus. They crawl all over the flowers, feeding on nectar. The relationship goes much deeper though. If you were to cut open one of these hollow pseudobulbs, you would find ant colonies living within them. The ants nest inside and often pile up great stores of food and eventually waste within these chambers. The walls of the chambers are lined with a dark tissue that was suspect to researchers.

Using radioactively labeled ants, the researchers found that the orchids were actually taking up nutrients from the ant middens! What's more, nutrients weren't found solely in adjacent tissues but also far away, in the actively growing parts of the roots. These orchids are not only absorbing nutrients from the ants but also translocating it to growing tissues.

While orchids without a resident ant colony seem to do okay, it is believed that orchids with a resident ant colony do ever so slightly better. This makes sense. These orchids grow as epiphytes on trees, a niche that is not high in nutrients. Any additional sources of nutrients these plants can get will undoubtedly aid in their long-term survival. Also, because the ants use the orchids as a food source and a nest site, they are likely defending them from herbivores.

Photo Credit: Scott.Zona (http://bit.ly/1hvWiGX)

Further Reading:
http://www.jstor.org/stable/2444355

Devil's Claws

Proboscidea louisianica

Proboscidea louisianica

I would like to introduce you to the genus Proboscidea. These lovely, albeit sticky plants are collectively referred to as the Devil's claw plants. The common name comes from the nasty looking seed pods which likely evolved in response to large mammals that once roamed this continent. The genus Proboscidea has traditionally been placed into the sesame family (Pedaliaceae) due to superficial similarities in flower and seed morphology, but more recent work has moved it into the unicorn plant family, Martyniaceae. That's right... unicorn plants.

The entire family is found in the New World, with two species (P. lousianica P. althaeifolia) hailing from arid parts of the southern portions of North America. At least two other species are readily naturalizing in this region as well. There are some aspects of these species that make them quite interesting to botanists. For starters, the apt name of Devil's claw was bestowed upon this genus because of the bizarre seed pods they produce. Similar to burs, they can become entangled in fur quite readily. The odd thing about this seed dispersal mechanism for some Devil's claws is how big those seed pods are. Until cattle were introduced to this continent, animals large enough to effectively disperse these massive seed pods seemed to be missing, having gone extinct at the end of the last ice age. It is believed that these plants may be an anachronism of this era.

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The flora we are familiar with today spent millennia co-evolving with ice age megafauna like mammoths and giant ground sloths. There is a growing school of thought that many close relationships probably developed over this time and have not yet been lost due to the relatively limited amount of time since the extinction of these large mammals. There are some people who will tell you that the seed pods are "designed" to ensnare small mammals like mice, causing them to die, which then provides the seeds a nutrient-rich, rotting corpses on which to germinate. I have never been able to find any evidence in support of these claims.

Another intriguing anatomical feature of this species are the countless sticky glands that cover the entire plant. These readily ensnare insects that land on or try to climb up the plant. Analysis of the fluids secreted by these glands show evidence of digestive enzymes but the jury still seems to be out on whether or not Devil's claws are undergoing any active carnivorous behavior.

Proboscidea althaeifolia

Proboscidea althaeifolia

It is more likely that these glands are a form of defense against insect herbivores and indeed they work quite well. Even a brief run-in with this plant leaves you quite sticky and slimy. It is possible that by ensnaring herbivorous insects, the plant can attract carnivorous insects that will eat the herbivores and then "repay" the devil's claw with nutrient-rich feces. Another possibility is that the glands cause the plant to become covered in sand grains over time. Such sandy armor would get in the way of hungry herbivores. To ad insult to injury, the plant kind of smells. It has been likened to old gym clothes.

These are neat plants. I have had fun growing them in the past. They are an annual but may reseed if care is not taken to removing the seed pods before they pop open. Because of their lively appearance and the unique look of their seed pods, these plants are often grown as horticultural oddities. Be careful though, as they have escaped cultivation outside of their native range and can be considered a noxious weed!

Photo Credit: [1] [2] [3]

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

Aquatic Angiosperm: A Cretaceous Origin?

It would seem that yet another piece of the evolutionary puzzle that are flowering plants has been found. I have discussed the paleontological debate centered around the angiosperm lineage in the past (http://bit.ly/1S6WLkf), and I don't think the recent news will put any of it to rest. However, I do think it serves to expand our limited view into the history of flowering plant evolution.

Meet Montsechia vidalii, an extinct species that offers tantalizing evidence that flowering plants were kicking around some 130–125 million years ago, during the early days of the Cretaceous. It is by no means showy and I myself would have a hard time distinguishing its reproductive structures as flowers yet that is indeed what they are thought to be. Detailed (and I mean detailed) analyses of over 1,000 fossilized specimens reveals that the seeds are enclosed in tissue, a true hallmark of the angiosperm lineage.

On top of this feature, the fossils also offer clues to the kind of habitat Montsechia would have been found in. As it turns out, this was an aquatic species. The flowers, instead of poking above the water, would have remained submerged. An opening at the top of each flower would have allowed pollen to float inside for fertilization. Another interesting feature of Montsechia is that it had no roots. Instead, it likely floated around in shallow water.

This is all very similar to another group of extant aquatic flowering plants in the genus Ceratophyllum (often called hornworts or coon's tail). Based on such morphological evidence, it has been agreed that these two groups represent early stem lineages of the angiosperm tree. Coupled with what we now know about the habitat of Archaefructus (http://bit.ly/1S6WLkf), it is becoming evident that the evolution of flowers may have happened in and around water. This in turn brings up many more questions regarding the selective pressures that led to flowers.

What is even more amazing is that these fossils are by no means recent discoveries. They were part of a collection that was excavated in Spain over 100 years ago. Discoveries like this happen all the time. Someone finds a interesting set of fossils that are then stored away on a dark shelf in the bowels of a museum only to be rediscovered decades or even centuries later.

All in all I think this discovery lends credence to the idea that flowering plants are a bit older than we like to think. Also, one should be wary of anyone claiming to have found "the first flower." The idea that there could be a fossil out there that depicts the first anything is flawed a leads to a lot of confusion. Instead, fossils like these represent snapshots in the continuum that is evolution. Each new discovery reveals a little bit more about the evolution of that lineage. We will never find the first flower but we will continue to refine our understanding of life on this planet.

Photo Credits: Bernard Gomeza, Véronique Daviero-Gomeza, Clément Coiffardb, Carles Martín-Closasc, David L. Dilcherd, and O. Sanisidro,

Further Reading:
http://www.pnas.org/content/112/35/10985.abstract

Is it a Fungus? Is it a Forb? No, it's a Tree!

Botanical gardens are winter sanctuaries for a northerner like myself. Winter tree ID can only do so much for me during these times. As such, I try my best to make regular trips to tropical houses wherever and whenever I can. On a recent excursion to the Missouri Botanical Garden, I came across something completely unexpected.

I was perusing their tropical house aptly named "The Climatron." As I rounded a corner I happened to look down and saw what looked like something only a member of the birthwort family (Aristolochiaceae) could produce. There, lying near the ground were a cluster of some of the coolest flowers I have personally laid eyes on.

I began searching for the plant that produced them. Up until this point, I have only encountered members of this family in the form of low-lying understory herbs and scrambling vines dangling from the canopy. There were no apparent leaves associated with these flowers and the part of my brain responsible for search images became confused. I traced the flower stems to their place of origin and realized they were attached to the nearest trunk. I followed the trunk upwards and realized that what I had found was in fact a small tree!

The species I was looking at was none other than Aristolochia arborea, a small tree native to the tropical forests of Central America. Needless to say I was floored. There is something to be said about any plant family than can vary this much in size and habit. The coolest aspect about this tree is that, similar to the more herbaceous members of this family, the flowers are produced close to or directly on the forest floor.

A closer inspection of these strange blooms reveals an interesting morphology. It would appear that they are mimicking fungi in the genus Marasimus. Now this could simply be a manifestation of apophenia. Was I seeing patterns where there are none? Of course, this was a job for scientific literature.

It seems I may have been on to something. Botanists agree that in the wild this plant is pollinated by fungus gnats and flies. However, no direct observations of this have ever been made. That being said, the flowers do emit a rather musty smell that could very well be described as "fungal." Regardless, this is an excellent choice of tree to showcase in a botanical garden because stumbling into it like I did led me down an curious path of discovery.

Tree photo credit: Cymothoa exigua (Wikimedia Commons)

Further Reading: [1] [2]

Why We See Color

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.

Photo Credit: Jay Neitz Laboratory (http://www.neitzvision.com/content/people.html)

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

CAM Photosynthesis

 

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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. 

Photo Credit: C T Johansson (Wikimedia Commons)

Further Viewing: https://www.khanacademy.org/science/biology/cellular-molecular-biology/photosynthesis/v/cam-plants

There's Water In Them There Rocks!

 

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Plants go to great lengths to obtain the necessities of survival. Nowhere is this more apparent than in the desert regions around the world. Amazingly, myriads of plants have adapted to the harsh conditions that deserts offer up. Needless to say, water is a major limiting resource in these climates and many of the adaptations we see in desert plant species have to do with obtaining and holding on to as much water as possible. Some species get around the issue by going dormant whereas others stick it out using deep taproots that plug into the groundwater. A select few others hit the rocks.

Rocks? Well, gypsum to be precise. This interesting mineral is quite common in arid regions throughout the world. What is more interesting is that 20.8% of a gypsum crystal is water. Because of this, it has been suspected that gypsum in the soil could be a potential source of water for plants growing in these regions and a team of researchers out of Spain may have found just that.

Meet Helianthemum squamatum. This distant relative of hibiscus grows throughout the gypsum hills of the Mediterranean region. Unlike other desert plants, it is shallowly rooted. Unlike other shallowly rooted species, H. squamatum doesn't go dormant during the dry summer months. The physiology of this species in the context of the dry environments that it grows offers up quite a conundrum. How does this plant get the water it needs to grow through the hottest, driest months of the year?

By analyzing the isotopic composition of the water within the plant and comparing it to background sources, the team found that 90% of the plants water intake during the dry summer months comes from the crystallization water in gypsum! How is this possible? How does a plant get water from a mineral?

The actual physiological processes involved are not yet understood but there are some running hypotheses. The first has to do with temperature. When gypsum is exposed to temperatures above 40 degrees C, water can be released from the crystalline matrix. It would then be available to the plants via passive uptake. 40 degrees C is not unheard of in these environments. Any water that isn't taken up by the plants could be reincorporated back into gypsum when things cool down at night. Another possibility is that H. squamatum grows its roots into and around the gypsum. Using root exudates, it is possible that the plant is able to dissolve gypsum to some degree, thus unleashing the water within. This may rely on the microbial community associated with the roots. Until further research can be done on this, the jury is still out.

The most exciting aspect of this research is the doors it has now opened in our search for extraterrestrial life. Life as we know it depends on water. Our search for this molecule has us looking for planets in a sweet spot where water can be found in a liquid state. Knowing now that at least some life on our planet is able to obtain water from gypsum broadens the kinds of places we can look. Mars is chock full of gypsum. Just sayin'.

Photo Credit: José María Escolano (http://bit.ly/ZeSVzB)

Further Reading:

http://www.nature.com/ncomms/2014/140818/ncomms5660/full/ncomms5660.html

Primitive Orchids

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The genera Neuwiedia and Apostasia represent something quite interesting. What you are looking at here are believed to be two of the most primitive extant orchid lineages. Unlike most orchids, which have a single fertile stamen fused with a single pistil, these genera have 3 and 2 fertile stamens respectively. Though botanists hesitate to consider these genera ancestral to all other orchid lineages, they nonetheless feel that they represent a very primitive sister-group to other basal orchid lineages such as the cypripediads. They can be found in parts of China, India, Sri Lanka, Southeast Asia, New Guinea, and Queensland, with Neuwiedia having the smallest distribution. 

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Photo Credit: Rachmat Setiawan Saleh (http://bit.ly/Zuy37j), Johannes Lundberg (http://bit.ly/1ydRIah), and chipmunk1 (http://bit.ly/1sjMJTh)

Further Reading: 

http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8339.1993.tb00331.x/abstract

Cleistogamy

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In the wild, plants are not always found growing under ideal conditions. Often, many plant species find themselves on the fringe of their habitable range. Other times, pressures like trampling or grazing cause a plant to expend a lot of energy trying to recoup for lost resources. If a plant growing under these conditions is to successfully reproduce, it has to sometimes stake its bets on self-fertilization. 

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The evolution of special flowers that never open has arisen in many different plant families. These permanently closed flowers are known as cleistogamous flowers. These are not always produced as a result of a direct environmental stress, however, and their persistence throughout so many different plant families is a bit of a puzzle to evolutionary biologists. How and why are these mixed mating systems maintained in a plant population? There must be selective advantages to both.

It has long been thought that plant populations should only stably exist as either fully opened, chasmogamous flowers, or fully closed, cleistogamous flowers. The existence of many species in which both forms exist on the same plant really threw a wrench into that hypothesis. Some examples of plants that possess such mixed mechanisms can be seen in genera such as Impatiens, Viola, and Utricularia. 

In the cases that have been studied, it was shown that cleistogamous flowers produce healthier seed with higher germination success than those of an openly pollinated chasmogamous flowers. It has also been shown that the production of cleistogamous flowers is much more economical for the plant. If flowers never open and never have to attract pollinators, then the plant doesn't need to waste energy on the production of petals, color, nectar, etc. This way, more energy can be pumped into seed production. 

The flip side to this mating system is that cleistogamy produces no genetic diversity. The plant is more or less cloning itself with every seed. This is okay if the plant is growing under challenging conditions. If the parent was able to survive long enough to reproduce then it obviously has the genetic make-up that is fit enough to survive such conditions and now, all of the cloned offspring do as well and thus all copies of its genes made it into the next generation. It is neat to think that plants kind of have this insurance policy built in to their reproductive strategy.

PHOTO NOTE: I found the picture of cleistogamous violet flowers on the following blog. It is not my picture! Please check out the blog for more!

source: http://blog.chestnutherbs.com/even-violets-need-a-plan-b

Further Reading: 

http://www.amjbot.org/content/96/11/2074.full.pdf+html?sid=41c1503d-23a8-40f8-93bf-8d849be7edec

http://www.jstor.org/discover/10.2307/1936588?uid=3739256&sid=21102186350373

http://onlinelibrary.wiley.com/doi/10.1046/j.1095-8312.2002.00039.x/abstract

Deaf Plants

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As we continue to make advances in the field of genetics, the cost of genome sequencing is getting cheaper and cheaper. We are sequencing entire genomes seemingly overnight. As we learn more about this code that programs every living thing on this planet, the more surprises we uncover. One such surprise came when researchers sequenced the genome of a little mustard known as Arabidopsis thaliana. As it turns out, this lowly little plant has more in common with our own genetic lineage than we ever thought possible. 

One interesting thing that turned up in the genome of Arabidopsis were a handful of genes associated with hearing in humans. For all intents and purposes, plants can't hear. They don't have ears nor do they have a nervous system capable of translating vibrations into what we know as sound. Why, then, were these genes present in a plant? 

Humans contain over 50 genes associated with hearing. A mutation in any of these can cause hearing loss. Arabidopsis shares at least 10 of these genes with us. In humans, one of these shared genes codes for proteins that are involved in forming the microscopic hairs within our inner ear that pick up sound waves. Again, why would a plant need this? When researchers mutated this gene within Arabidopsis, a surprising thing happened. 

Plants produce hair-like structures from their roots. These root hairs vastly increase the amount of surface area the root has for soaking up water and nutrients in the soil. A mutation in one of these hearing genes causes the root hairs to fail to elongate. As a result, the plant then has trouble absorbing things. 

Hearing genes are by no means the only genes we share with plants either. Within the genome of Arabidopsis, researchers have discovered over 100 genes involved in human diseases including breast cancer and cystic fibrosis. Though the differences between humans and plants seem insurmountable, we nonetheless share a common ancestor. The genes that control the development of an organism were laid down long before our lineages became distinct. It would appear that many genes don't change but are simply adopted for different purposes. It is discoveries like these that stand as a stark reminder that so-called "science for the sake of science" is incredibly important. 

Photo Credit: virken (http://bit.ly/1DI50Qz)

Further Reading:

http://www.plantphysiol.org/content/146/3/1109.short

http://nar.oxfordjournals.org/content/31/4/1148.short

The Vernal Dam Hypothesis

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I have already established that spring ephemerals are badasses (http://bit.ly/1CsEtj1) but what I am about to tell you is really going to kick it up a notch...

While offering our native pollinators some much needed food resources along with giving us humans a much needed jolt of life after a long and dreary winter, spring ephemerals like these trout lilies (Erythronium americanum), are important nutrient sinks for forests.

Back in 1978, a guy by the name of Robert Muller put forth a very intriguing idea known as the vernal-dam hypothesis. Basically, he proposed the idea that soil nutrients are heavily leached into waterways during the spring melt and subsequent rains. Where spring ephemerals are present, they act as nutrient sinks, taking up much of the nutrients that would otherwise be lost. The idea was well liked but unfortunately, the important assumptions of this hypothesis were not tested until the last decade or so. Recently, more attention is being paid to this concept and some research is being published that do indeed support his claims!

Though the research does not address whether or not the nutrients really would be lost from the system in the absence of spring ephemerals, it is showing that some species really do serve as nutrient sinks. Trout lily, for instance, is a massive sink for nitrogen and potassium. As they grow they take in more and more. When the warmer summer weather hits and the leaves die back, they then release a lot of nutrients back into soil where vigorously growing plants are ready to take it up. It should be noted that trees will still take in nutrients even before leafing out for the summer. One study even showed that net uptake of nitrogen and potassium by a variety of spring ephemeral species is nearly equal to the net annual losses. I must admit that I did not quite understand what the "losses" are in this particular study but the evidence is tantalizing nonetheless. In one example, nitrogen uptake by ephemerals was 12% of the nitrogen in annual tree litter!

Whether or not it is shown that nutrients taken up by ephemerals would otherwise be loss is, in my opinion, beyond the point. What has been demonstrated in the ability of spring ephemeral species to uptake and store vital forest nutrients suggests major ecosystem benefit! Furthermore, when you consider the fact that mycorrhizal fungi are non-specific in most cases and will bond with many different plant species and then go as far as sharing nutrients among the forest flora, you really start to see a big picture story that has been playing out all over the world for millennia. 

Further Reading:

http://www.jstor.org/discover/10.2307/2937357?uid=3739256&sid=21102213017237

http://iub.edu/~preserve/docs/library/BlankJL_1980.pdf

http://www.jstor.org/discover/10.2307/2425383?uid=3739256&sid=21102213017237

http://link.springer.com/article/10.1007/s00442-002-0958-9#page-1

The Badass Spring Ephemerals

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Spring ephemerals and the word "badass" are probably not frequent associates but I am here to argue that they should be.

Spring ephemeral season is here for some and just around the corner for the rest of us. It's my favorite wildflower season and I often go missing in the woods for those first few weeks of spring. It is easy to look at their diminutive size and their ephemeral nature as signs of delicacy but these plants are anything but. In fact, when one examines the intricacies of their lifestyle, they can see that spring ephemerals make most other plants look like total softies.

Spring ephemerals, the designation of which gets blurred depending on who you ask, have to complete most of their life cycle in the early spring before the trees and understory shrubs leaf out and completely take over most of the available light. This is an incredibly tough time to be a plant. Soil temperatures are low, which makes nutrient and water uptake a difficult task, all but the most robust pollinators are still sound asleep, and there is the ever present danger of a hard frost or freak snow storm. These factors have led to some incredible adaptations in all of the species that emerge around this time. Whereas each species has its own methods, there are some generalities that are common throughout.

For the most part, spring ephemerals have two distinct growth phases; epigeous (above ground) and hypogeous (below ground). The hypogeous phase of growth takes place throughout fall and winter. Yes, winter. This is the phase in which the plants put out more roots and develop next season’s buds. This goes on at the expense of nutrients that were stored the previous spring. Once spring arrives and soils begin to warm, the plants enter the epigeous phase of growth where leaves and flowers are produced and reproduction occurs. This is an incredibly short period of time and spring ephemerals are well suited for the task.

Typical growth cycle of many spring ephemerals  [Source}

Typical growth cycle of many spring ephemerals [Source}

For starters, photosynthetic activity for these species is at its best around 20 °C. Photosynthetic proteins activate very early on so that by the time the leaf is fully expanded, the plant is a powerhouse of carbohydrate production. Photosynthesizing in cool temperatures comes at a cost. Water stress in at this time of year is high. Low soil temperatures make uptake of water difficult and it is strange to note that many species of spring ephemeral have very little root surface area in the form of root hairs. These species, however, have extensive mycorrhizal associations which help assuage this issue.

Nutrient availability is also very limited by low soil temperatures. Chemical reactions that would unlock such nutrients are not efficient at low temperatures. Again, spring ephemerals get around this via their increased mycorrhizal associations. It should be noted that some species such as those belonging to the genus Dicentra, do not have these associations. In this situation, these species do in fact develop extensive root hairs as a coping mechanism. Despite specific adaptations for nutrient uptake, you will rarely find spring ephemerals not growing in deep, nutrient-rich soils.

Again, we must keep in mind that all of this is happening so that the plant can quickly complete what it needs to do in the few weeks before the canopy closes and things heat up. It has been observed that high temperatures are associated with slowed growth in most of these species. As temperatures increase, the plants begin to die back. Another adaptation to this ephemeral lifestyle is an increased ability to recycle nutrients in the leaves. As spring temperatures rise, the plants begin to pull in nutrients and store them in their perennial organs. They also show specific compartmentalization of energy stores. In many species, seed production is fueled solely by energy reserves in the stem. Some underground storage structures then receive nutrients to fuel autumn and winter growth while others receive nutrients to fuel leaf and stem growth in the early spring.

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Despite all of these amazing adaptations, life is still no cake walk and growth is painstakingly slow. Many species, like trout lilies (Erythronium spp.), can take upwards of 8 years to flower! 8 years!! Think about that next time you are thinking of harvesting or picking some. Even worse in some areas are white tailed deer. East of the Mississippi their populations have grown to a point in which their foraging threatens the long term survival of many different plant species. Especially hard hit are spring ephemerals as they are the first plants to emerge after a long winter of near starvation. 

I hope this post wakes people up to how truly badass these species really are. As our climate warms, we can only speculate how things are going to change for many of them. Some research suggests that things may get easier whereas others suggest that conditions are going to get harsher. It's anyone's guess at this point. As populations are wiped out due to development or invasive species, we are losing much needed genetic diversity and corridors for gene transfer. This is yet another reason why land conservation efforts are so vital to resilient ecosystems. Support your local land conservancy today!

Spring is here and things are getting underway. Get out there and enjoy the heck out of the spring ephemerals! In a few short weeks they will be back underground, awaiting the next cold, damp spring.

Further Reading: [1] [2]

Plant "Sight"

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As the sun rises higher into the sky and our days get incrementally longer, I am thinking about plant sight. I'm not talking sight as you or I know it but rather their own unique brand of knowing where the light is and how to respond to it. Anyone that has ever grown plants will have undoubtedly recognized the way in which houseplants lean towards the nearest window or sunflowers track the sun's path through the sky each day with their blooms. Plants need the light and know how to respond to it but how do they do this without eyes, nerves, or a brain to process the world around them?

One of the first tantalizing pieces of evidence to this puzzle came from none other than Darwin himself. With the help of his son he carried out a series of experiments on seedlings using a candle lit room and rather ingenious methodology. They knew that seedlings naturally bent towards candle light so they were curious as to which part of the plant was responsible for this response. They cut off some of the seedling tips, covered the tips of some with light-proof caps, and covered others with transparent glass caps. There were also control seedlings as well as seedlings in which they only covered the stems, leaving the tips exposed. What they found was that only the seedlings with their tips cut off as well as those with light-proof caps didn't bend. 

So, it appeared that the tip of the plant was where "sight" occurs, at least when plants are trying to figure out where the light source is emanating, however, this is not the full picture. Plants can also measure the length of day. Known as photoperiodism, many species of plants will regulate growth and flowering based on day length. Long-day plants will only flower when days are at their longest. The opposite is true for short-day plants. But the question remains, how do they know? Scientists quickly figured out that they could mess with this photoperiodism in the greenhouse by turning lights on in the middle of the night, a technique that is a boon to the horticulture industry. 

Research into this revealed that different wavelengths of light have different effects. Blue or green light, for instance, does not do anything to upset a plants flowering schedule whereas red light does. Even stranger, the relative shade of the red light also has an effect. Shining a bright red light on a long-day plant in the middle of the night will cause it to flower while you can cancel this effect by shining dark red light right after. This may seem weird but it makes sense when you consider how these plants evolved.

It is not actually the length of day that plants measure, but rather the length of night. Shorter nights mean longer days, an excellent cue that the environment is favorable for flowering. By turning on lights in the middle of the night, you are effectively simulating short nights. In nature, plants receive bright red light when the sun is rising in the sky and dark red light as it sets. Bright red light activates chemical cues for flowering and dark red light turns them off. Only when the bright red signal is turned on longer than the dark red signal will the plants actually flower. 

The chemical responsible for this "color vision" in plants is known as "phytochrome." Unlike Darwin's experiments, shining light on the tip of the plant has no effect on phytochrome. However, shining light on even a single leaf will elicit a response. Plants in which the leaves have been pruned will not react to red light at all. Though I can't speak for leafless plants like cacti, I am sure the concept remains the same, albeit more adapted to their lifestyle. 

In total, roughly 11 photoreceptive compounds have been identified in plants. Though they do not perceive images as you and I do, their sense of "sight" is nonetheless quite sophisticated. Plants feed on light so it is no wonder that they have quite the chemical arsenal for responding to it. 

Further Reading:

http://www.plantphysiol.org/content/125/1/85.full

Cyclamen

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There is something about flowers with reflexed petals that I find quite appealing. That is probably why I have always had a soft spot for Cyclamen. These interesting little plants are quite popular as horticultural specimens due to their relative hardiness. A lush individual can really brighten up a room. As with any common house plant, I am always eager to learn about their ecology. A quick search for Cyclamen in the literature turns up some interesting facts. 

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Cyclamen are native to Europe, the Mediterranean Basin, Iran, with a single species native to Somalia. There are approximately 23 different species and a decent amount of revisions regarding where they fit taxonomically. The latest that I am aware of has placed this genus in a subfamily within Primulaceae. Though they seem to grow well in a lot of different habitats, most species appear to be at home growing along mountainsides in stable scree slopes. Each plant grows from a true tuber, which allows them energy stores for re-sprouting after a dry season dormancy. 

The flowers are adapted for buzz pollination, not unlike tomatoes and their relatives. However, some researchers have noted that for some species, buzz pollination is a rare event. Instead, many non-specialist pollinators are the most frequent visitors. Some have taken this as a sign that certain species of Cyclamen have lost their original pollinator for an unknown reason. 

Throughout their range, many species have been severely depleted due to over-collection for the horticulture trade. As such, a handful of species are considered quite endangered. Luckily, there are many organizations out there that are cultivating these species on a large scale to take pressure off of wild populations. There may be hope after all. However, some climate change projections put other species at risk of loosing the habitats that sustain them. This is especially true for montane species. Only time will tell. 

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Photo Credit: Wikimedia Commons

Further Reading:

http://www.sciencedirect.com/science/article/pii/S0367253006000211

http://www.biomedcentral.com/1471-2148/6/72

http://www.amjbot.org/content/87/9/1325.full

http://www.cyclamen.org/indexCS.html

Sweet Nectar

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Plants produce some serious chemical cocktails. Any compound that a plant produces that isn't involved in growth or reproduction is coined a secondary metabolite. These compounds often function as herbivore deterrents. We humans are well aware of this fact and have been utilizing plants as medicine for millennia. Though the human animal may appear unique in this aspect, self-medicating has nonetheless been discovered in many other animals. Everything from monkeys to birds and even elephants seek out specific plants for things like parasite control and birthing. A study published in 2015 suggests that using plants as medication may even extend to insects. 

It has been documented that for a multitude of plant lineages, secondary metabolites are not restricted to vegetative structures. Many species produce secondary metabolites in their nectar. One interesting example of this can be found in coffee trees (Coffea sp.). These plants produce caffeinated nectar that has shown to keep bees coming back for more, not unlike we humans frequent our coffee pots. Plenty of other plants are doing this as well. Everything from amino acids, alkaloids, phenolics, glycosides, terpenoids, and even microRNA have turned up in the nectar of different plant species.

Researchers wanted to know if these chemicals may be benefiting pollinators. By isolating the different compounds, researchers found that bumblebees drinking from these flowers had drastically reduced parasite loads, specifically the gut parasite Crithidia. About half of the compounds tested were implicated in reducing parasite load but one group in particular stood out - the tobacco alkaloids. 

Alkaloids such anabasine are not limited to tobacco plants. They can be found in the nectar of trees like the basswoods (Tilia sp.) and forbs like the turtle heads (Chelone sp.). Bees that drank nectar containing these alkaloids saw parasite reductions of upwards of 80%. However, like any viable medicine, there were side effects. The eggs of bees that drank these compounds took considerably longer to develop and hatch. This cost may be well worth the lower parasite transmission rates and likely do not pose considerable selective pressures.

Whether or not bees are specifically targeting these plants for their anti-parasite properties remains to be seen. More recent work has found that we must be tentative in our conclusions at this point. Tests on other nectar compounds have shown no benefit to pollinators. Either way, these findings have opened up a whole new door into the interactions between plants and their pollinators. 

Further Reading: [1]  [2]

Amber Fossils of Grain

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In what may be one of the most interesting fossil discoveries in recent years, scientists from Oregon State University have described the earliest fossil evidence of grasses. Encased in 100 million year old amber this ancient grass spikelet suggests grasses were already around in the early to mid Cretaceous period. This is some 20 to 30 million years earlier than previous estimates for grass evolution. If that isn't cool enough, the grass appears to have been infected by a fungus related to ergot (the darker portion at the top), showing that this parasitism may be as old as grasses themselves. 

We humans have a long history with ergot's fondness for grasses. It is best known for producing the chemical precursors of LSD (as well as many other useful drugs) and has been implicated in some major historical events throughout our short time on this planet. However, suggesting that dinosaurs were getting high off the stuff is pushing it. Ergot likely evolved its chemical cocktail to deter herbivores from eating the grasses that it parasitizes. It has a bitter taste and cattle are said to avoid grasses that have been infected by it. It is quite possible that dinosaurs probably did the same thing. 

Either way, this finding represents a major milestone in the understanding of one of the most important plant families on the planet. Following the mass extinction at the end of the Cretaceous, grasses quickly rose to dominate roughly 20% of global vegetation. This little piece of amber now suggests that dinosaurs and their neighbors likely had a role in shaping this plant family. 

Photo Credit: Oregon State University

Further Reading: [1]