The Other Balsaminaceae

hydrocera.JPG

Have you heard of Hydrocera triflora? I hadn't until just recently. To my surprise, Hydocera is one of only two genera that make up the family Balsaminaceae. What's more, it is a monotypic genus, with this lovely species being the single representative. There is no question that H. triflora has been completely overshadowed by its cousins, the Impatiens. In fact, literature on this species is quite scant across the board.

The first question you may be asking is what differentiates Hydrocera from the Impatiens? The differences are rather subtle. I don't know if I would have considered this plant unique enough to warrant its own genus, however, closer botanical observations tell a more nuanced story. The biggest differences between Hydrocera and Impatiens has to do with flower and fruit morphology.

5363624290_f9ab68a2a6_o.jpg

For starters, the flowers of Hydrocera consist of a full compliment of 5 sepals and 5 petals. The petals themselves are all free from one another. Contrast this with Impatiens, whose flowers mostly consist of 3 sepals and 4 petals that are fused into pairs. The second major difference lies in the fruits. Many of us will be familiar with the explosive capsules of the various Impatiens species, each of which contains many seeds. Hydrocera on the other hand, produces berries that contain 5 seeds. Such vastly different developmental pathways in reproductive structures appear to be enough to warrant the taxonomic separation between the two genera.

The next question one might asking is why are Impatiens so diverse while Hydrocera contains only a single species? This is anyone's guess, really, but there has been at least a few hypotheses put forward that sound plausible. One has to do with habitat preference. Impatiens are largely plants of upland forests and montane environments. Such habitats may offer more potential for diversification due to high heterogeneity in resources and lots of potential for isolation of various populations. Contrast this with the habitat of H. triflora. Though it occurs throughout a wide swath of lowland Asia and India, it is semi-aquatic and these types of habitats may be more restrictive for diversification.

hydro dist.JPG

Another possibility has to do with seed dispersal. As mentioned above, Impatiens produce lots of seeds per capsule and, with their explosive habit, can disperse them over relatively large distances. Contrast this with Hydrocera. When the berries mature, they fall into the water and sink. They remain submerged until rot or various aquatic organisms eat away at the fleshy coating. Once the seeds have been freed, air sacs cause them to float on the currents until seasonal drying brings them back into contact with the mud. Though this is certainly an effective method for dispersal, the lower seed production rate coupled with being at the mercy of the currents means that Hydrocera is probably considerably less likely to find itself in new habitats.

Again, this is largely speculation at this point. We simply don't know enough about this oddball of the balsam world to make any serious conclusions. Luckily H. triflora is not a species under immediate threat. It seems to do quite well throughout its range, frequently occurring in flooded ditches and rice patties. Still, such stories underlie the importance of fostering and funding organism-focused research.

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

Further Reading: [1] [2]

Dipterocarp Forests

32040724474_46958f58d8_b.jpg

Spend any amount of time reading about tropical forests around the world and you are destined to come across mention of dipterocarp forests. If you're anything like me, your initial thought might have been something along the lines of "what the heck does that mean?" Does it describe some sort of structural aspect of the forest, or perhaps a climatic component? To my surprise, dipterocarp forests refer to any forest in which the dominant species of trees are members of the family Dipterocarpaceae. Thus, I was introduced to a group of plants entirely new to me!

The family Dipterocarpaceae is comprised of 16 genera and roughly 700 species. Its members can be found throughout the tropical regions of the world, though they hit their greatest numbers in the forests of southeast Asia and specifically Borneo. As far as habit is concerned, the dipterocarps are largely arborescent, ranging in size from intermediate shrubs to towering emergent canopy trees. If you have watched a documentary on or been to a tropical forest, it is very likely that you have seen at least one species of dipterocarp.

14100164413_52c69bc260_b.jpg

The dipterocarps have a long evolutionary history that stretches back to the early Triassic on the supercontinent of Gondwana. As this massive landmass proceeded to break apart, the early ancestors of this group were carried along with them. Today we can find members of this family in tropical regions of South America, Africa, and Asia. Taxonomically speaking, the family is further divided into three sub families that, to some degree, reflect this distribution.  The subfamily Monotoideae is found in Africa and Colombia, the subfamily Pakaraimoideae is found in Guyana, and the subfamily Dipterocarpoideae is found in Asia.

Biologically, the dipterocarps are quite fascinating. Some species can grow quite large. Three genera - Dryobalanops, Hopea, and Shorea - regularly produce trees of over 80 meters (260 feet) in height. The world record for dipterocarps belongs to an individual of Shorea faguetiana, which stands a whopping 93 meters (305 feet) tall! That's not to say all species are giants. Many dipterocarps live out their entire lives in the forest understory.

Dipterocarpus_retusus_-_Köhler–s_Medizinal-Pflanzen-054.jpg

For species growing in seasonal environments, flowering occurs annually or nearly so. Also, for dipterocarps that experience regular dry seasons, deciduousness is a common trait. For those growing in non-seasonal environments, however, flowering is more irregular and leaves are largely evergreen. Some species will flower once every 3 to 5 years whereas others will flower once every decade or so. In such cases, flowering occurs en masse, with entire swaths of forest bursting into bloom all at once. These mast years often lead to similar aged trees that all established in the same year. Though more work needs to be done on this, it is thought that various bee species comprise the bulk of the dipterocarp pollinator guild. 

Ecologically speaking, one simply cannot understate the importance of this family. Wherever they occur, dipterocarps often form the backbone of the forest ecosystem. Their number and biomass alone is worth noting, however, these trees also provide fruits, pollen, nectar, and habitat for myriad forms of life. The larger dipterocarps are often considered climax species, meaning that they dominate in regions comprised of mostly primary forest. For the most part, these trees are able to take advantage of more successional habitats, however, this has been shown to be severely limited by the availability of localized seed sources. 

5663117269_7afdcf4948_b.jpg

Since we are on the topic of regeneration, a conversation about dipterocarps would not be complete if we didn't touch on logging. These trees are massive components of tropical economies. Their wood is highly coveted for a a variety of uses I won't go into here. The point is that, on a global scale, dipterocarp forests have taken a huge hit. Many species within this family are now threatened with extinction. Logging, both legal and illegal, specifically aimed at dipterocarps has seen the destruction of millions of acres of old growth dipterocarp forests. With them goes all of the life that they support.

It's not enough to protect individual species. We need to rally behind whole ecosystem protection. Without it, we literally have nothing. Luckily there are groups like the Center For International Forestry Research and the Forest Research Institute of Malaysia that are working hard on research, conservation, and improved forestry standards in an effort to ease up on the detrimental practices currently in place. Still, these efforts are not enough either. Without the care, concern, and most important, the funding from folks like us, little can be done to stop the tide. That is why supporting land conservation agencies is one of the most powerful things we can do for this planet and for each other. 

Some great land conservation organizations worth supporting:

The Rainforest Trust - https://www.rainforesttrust.org/

The Nature Conservancy - http://bit.ly/2B0hFm

The Rainforest Alliance - https://www.rainforest-alliance.org/

Photo Credits: [1] [2] [3] [4]

urther Reading: [1]

Everlasting or Seven Years Little

Syncarpha_vestita_flowers.JPG

Common names are a funny thing. Depending on the region, the use, and the culture, one plant can take on many names. In other situations, many different plants can take on a single name. Though it isn't always obvious to those unfamiliar with them, the use of scientific names alleviates these issues by standardizing the naming of things so that anyone, regardless of where they are, knows what they are referring to. That being said, sometimes common names can be entertaining.

Take for instance, plants in the genus Syncarpha. These stunning members of the family Asteraceae are endemic to the fynbos region of the Eastern and Western Cape of South Africa. In appearance they are impossible to miss. In growth habit they have been described as "woody shrublets," forming dense clusters of woody stems covered in a coat of woolly hairs. Sitting atop their meter-high stems are the flower heads.

Each flower head consists of rings of colorful paper-like bracts surrounding a dense cluster of disk flowers. The flowering period of the various species can last for weeks and spans from October, well into January. Numerous beetles can be observed visiting the flowers and often times mating as they feed on pollen. Some of the beetles can be hard to spot as they camouflage quite well atop the central disk. Some authors feel that such beetles are the main pollinators for many species within this genus.

Syncarpha_species_in_flower_visited_by_Hopliini_Monkey_beetle_1084.jpg

Their mesmerizing floral displays are where their English common name of "everlasting" comes from. Due to the fact that they maintain their shape and color for quite a long time after being cut and dried, various Syncarpha species have been used quite a bit in the cut flower industry. A name that suggests everlasting longevity stands in stark contrast to their other common name. 

These plants are referred to as "sewejaartjie" in Afrikaans, which roughly translates to "seven years little." Why would these plants be referred to as everlasting by some and relatively ephemeral by others? It turns out, sewejaartjie is a name that has more to do with their ecology than it does their use in the floral industry.

As a whole, the 29 described species of Syncarpha are considered fire ephemerals. The fynbos is known for its fire regime and the plants that call this region home have evolved in response to this fact. Syncarpha are no exception. They flower regularly and produce copious amounts of seed but rarely live for more than 7 years after germination. Also, they do not compete well with any vegetation that is capable of shading them out.

Syncarpha_vestita_Cape_snow.JPG

Instead, Syncarpha invest heavily in seed banking. Seeds can lie dormant in the soil for many years until fires clear the landscape of competing vegetation and release valuable nutrients into the soil. Only then will the seeds germinate. As such, the mature plants don't bother trying to survive intense ground fires. They burn up along with their neighbors, leaving copious amounts of seeds to usher in the next generation.

Research has shown that its not the heat so much as the smoke that breaks seed dormancy in these plants. In fact, numerous experiments using liquid smoke have demonstrated that the seeds are likely triggered by some bio-active chemical within the smoke itself.

So, there you have it. Roughly 29 plants with two common names, each referring back to an interesting aspect of the biology of these plants. Despite their familiarity and relative ease of committing to memory, the common names of various species only get us so far. That's not to say we should abolish the use of common names altogether. Learning about any plant should be an all encompassing endeavor provided know which plant you are referring to.

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

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

 

The Incredible Feat of a Resurrection Plant

4Pa9zdN.gif

It is understandable why one would look at the crispy brown bundle of a Selaginella lepidophylla and think that it was dead. No wonder then why this hardy spikemoss has become such a novelty item for those looking for a unique gift. Indeed, even the common name of "resurrection plant" suggests that this species miraculously returns from the dead with the simple addition of water. A dormant resurrection plant is far from dead, however. It is in a state of dormancy that we are still struggling to understand.

Selaginella lepidophylla is native to the Chihuahuan desert, spanning the border between the US and Mexico. This is a harsh habitat for most plants, let alone a Lycophyte. However, this lineage has not survived hundreds of millions of years by being overly sensitive to environmental change and S. lepidophylla is a wonderful reminder of that.

As you can probably imagine, tolerating near-complete desiccation can be pretty beneficial when your habitat receives an average of only 235 mm (9.3 in) of rain each year. A plant can either store water for those lean times or go dormant until the rains return. The latter is exactly what S. lepidophylla does. As its water supply dwindles, the whole body of the plant curls up into a tight ball and waits. No roots anchor it to the ground. It is at the mercy of the winds as it blows around like a tiny tumbleweed until it winds up wedged into a crack or crevice.

3759099369_48777f4494_z.jpg

When the rains return, S. lepidophylla needs to be ready. Wet this crispy bundle and watch as over the course of about a day, the dormant ball unfurls to reveal the stunning body of a photosynthetic spikemoss ready to take advantage of moist conditions. Such conditions are short lived, of course, so after a few days drying out, the plant shrivels up and returns to its dormant, ball-like state. How does the plant manage to do this? Why doesn't it simply die? The answer to these questions has been the subject of quite a bit of debate and investigation. 

What we do know is that part of its success has to do with curling up into a ball. Without water in its tissues, its sensitive photosynthetic machinery would easily become damaged by punishing UV rays. By curling up, the plant essentially shelters these tissues from the sun. Indeed, plants that were kept from curling up experienced irreversible damage to their photo systems and were not as healthy as plants that did curl up. To this, the plant owes its success to rather flexible cell walls. Unlike other plants that snap when folded, the cells of S. lepidophylla are able to fold and unfold without any major structural damage.

As far as metabolism and chemistry is concerned, however, we are still trying to figure out how S. lepidophylla survives such drastic shifts. For a while it was thought that, similar to other organisms that undergo such dramatic desiccation, the plant relies on a special sugar called trehalose. Trehalose is known to bind to important proteins and membranes in other desiccation-tolerant organisms, thus protecting them from damage and allowing them to quickly return to their normal function as soon as water returns.

An analysis of non-desiccating Selaginella species, however, showed that S. lepidophylla doesn't produce a lot of trehalose. Though it is certainly present in its tissues, more wet-loving species of Selaginella contain much higher amounts of this sugar. Instead, it has been found that other sugars may actually be playing a bigger role in protecting the inner workings of this plant. Sorbitol and xylitol are found in much higher concentrations within the tissues of S. lepidophylla, suggesting that they may be playing a bigger role than we ever realized. More work is needed to say for sure.

Finally, it would appear that S. lepidophylla is able to maintain enzyme activities within its cells at much higher levels during desiccation periods than was initially thought possible. When dried, some enzymes were found to be working at upwards of 75% efficiency of those found in hydrated tissues. This is really important for a plant that needs to respond quickly to take advantage of fleeting conditions. Along with quick production of new enzymes, this "idling" of enzymatic activity during dormancy is thought to not only protect the plant from too much respiration, but also allows it to hit the ground running as soon as favorable conditions return. 

Despite our lack of understanding of the process, it is amazing to watch this resurrection plant in action. To see something go from a death-like state to a living, photosynthetic organism over the course of a day is truly a marvel worth enjoying.

Photo Credits: [1] [2]

Further Reading: [1]

Cockroaches & Unexpected Partnerships

Say "cockroach" and most people will start to squirm. These indefatigable insects are maligned the world over because of a handful of species that have settled in quite nicely among human habitats. The world of cockroaches is far more diverse than most even care to realize, and where they occur naturally, these insects provide important ecological services. For instance, over the last decade or so, researchers have added pollination and seed dispersal to the list of cockroach activities. 

That's right, pollination and seed dispersal. It may seem odd to think of roaches partaking in such interactions but a study published in 2008 provides some of the first evidence that roaches are doing more with plants than eating their decaying tissues. After describing a new species of Clusia in French Guiana, researchers set out to investigate what, if anything, was pollinating it. The plant was named Clusia sellowiana and its flowers emitted a strange scent. 

Cockroach pollinating C. sellowiana

Cockroach pollinating C. sellowiana

The source of this scent was the chemical acetoin. It seemed to be a rather attractive scent as a small variety of insects were observed visiting the flowers. However, only one insect seemed to be performing the bulk of pollination services for this new species - a small cockroach called Amazonia platystylata. It turns out that the roaches are particularly sensitive to acetoin and although they don't have any specific anatomical features for transferring pollen, their rough exoskeleton nonetheless picks up and deposits ample amounts of the stuff. 

It would appear that C. sellowiana has entered into a rather specific relationship with this species of cockroach. Although this is only the second documentation of roach pollination, it certainly suggests that more attention is needed. This Clusia isn't alone in its interactions with cockroaches either. As I hinted above, roaches can now be added to the list of seed dispersers of a small parasitic plant native to Japan. 

 (A) M. humile fruit showing many minute seeds embedded in the less juicy pulp. (B) Fallen fruits. (C) Blattella nipponica feeding on the fruit. (D) Cockroach poop with seeds. (E) Stained cockroach-ingested seeds

Monotropastrum humile looks a lot like Monotropa found growing in North America. Indeed, these plants are close cousins, united under the family Ericaceae. Interestingly enough, it was only recently found that camel crickets are playing an important role in the seed dispersal of this species. However, it looks like they aren't the only game in town. Researchers have also found that a forest dwelling cockroach called Blattella nipponica serves as a seed disperser as well. 

The roaches were observed feeding on the fruits of this parasitic plant, consuming pulp and seed alike. What's more, careful observation of their poop revealed that seeds of M. humile passed through the digestive tract unharmed. Cockroaches can travel great distances and therefore may provide an important service in distributing the seeds of a rather obscure parasitic plant. To think that this is an isolated case seems a bit naive. It seems to me like we should pay a little more attention to what cockroaches are doing in forests around the world. 

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

Further Reading: [1] [2]

Are Crickets Dispersing Seeds of Parasitic Plants?

nph14859-fig-0001.png

Parasitic plants lead a rather unique lifestyle. Many have foregone photosynthesis entirely by living off fungi or their photosynthetic neighbors. Indeed, there are many anatomical and physiological adaptations that are associated with making a living parasitically. Whether they are full parasites or only partial, one thing that many parasitic plants have in common are tiny, dust-like seeds. Their reduced size and thin seed coats are generally associated with wind dispersal, however, there are always exceptions to the rule. Recent evidence has demonstrated that a handful of parasitic plants have evolved in response to a rather unique seed dispersal agent - camel crickets.

A research team based out of Japan recently published a paper describing a rather intriguing seed dispersal situation involving three species of parasitic plants (Yoania amagiensis - Orchidaceae, Monotropastrum humile - Ericaceae, and Phacellanthus tubiflorus - Orobanchaceae). These are all small, achlorophyllous herbs that either parasitize trees directly through their roots or they parasitize the mycorrhizal fungi associated with said trees. What's more, each of these species are largely inhabitants of the dense, shaded understory of rich forests.

These sorts of habitats don't lend well to wind dispersal. The closed forest canopy and dense understory really limits wind flow. It would appear that these three plant species have found away around this issue. Each of these plants invest in surprisingly fleshy fruits for their parasitic lifestyle. Also, their seeds aren't as dusk-like as many of their relatives. They are actually quite fleshy. This is odd considering the thin margins many parasitic plants live on. Any sort of investment in costly tissues must have considerable benefits for the plants if they are to successfully get their genes into the next generation.

Fleshy fruits like this are usually associated with a form of animal dispersal called endozoochory. Anyone that has ever found seed-laden bird poop understands how this process works. Still, simply getting an animal to eat your seeds isn't necesarly enough for successful dispersal. Seeds must survive their trip through the gut and come out the other end relatively in tact for the process to work. That is where a bit of close observation came into play.

After hours of observation, the team found that the usual frugivorous suspects such as birds and small mammals showed little to no interest in the fruits of these parasites. Beetles were observed munching on the fruits a bit but the real attention was given by a group of stumpy-looking nocturnal insects collectively referred to as camel crickets. Again, eating the fruits is but one step in the process of successful seed dispersal. The real question was whether or not the seeds of these parasites survived their time inside either of these insect groups. To answer this question, the team employed feeding trials.

They compared seed viability by offering up fruits to beetles and crickets both in the field and back in the lab. Whereas both groups of insects readily consumed the fruits and seeds, only the crickets appeared to offer the greatest chances of a seed surviving the process. Beetles never pooped out viable seeds. The strong mandibles of the beetles fatally damaged the seeds. This was not the case for the camel crickets. Instead, these nocturnal insects frequently pooped out tens to hundreds of healthy, viable seeds. Considering the distances the crickets can travel as well as their propensity for enjoying similar habitats as the plants, this stacks up to potentially be quite a beneficial interaction. 

The authors are sure to note that these results do not suggest that camel crickets are the sole seed dispersal agents for these plants. Still, the fact that they are effective at moving large amounts of seeds is tantalizing to say the least. Taken together with other evidence such as the fact that the fruits of these plants often give off a fermented odor, which is known to attract camel crickets, the fleshy nature of their fruits and seeds, and the fact that these plants present ripe seed capsules at or near the soil surface suggests that crickets (and potentially other insects) may very well be important factors in the reproductive ecology of these plants.

Coupled with previous evidence of cricket seed dispersal, it would appear that this sort of relationship between plants and crickets is more widespread than we ever imagined. It is interesting to note that relatives of both the plants in this study and the camel crickets occur in both temperate and tropical habitats around the globe. We very well could be overlooking a considerable component of seed dispersal ecology via crickets. Certainly more work is needed.

Photo Credits: [1]

Further Reading: [1] [2]

Resin Midges, Basal Angiosperms, and a Strange Pollination Syndrome

kadsura.JPG

When we try to talk about clades that are "basal" or "sister" to large taxonomic groups, your average listener either consciously or unconsciously thinks "primitive." Primitive has connotations of something that under-developed or unfinished. This is simply not the case. Take, for instance, a family of basal angiosperms called Schisandraceae.

This family is nestled within the order Austrobaileyales, which, along with a small handful of other families, represent the earliest branches of the angiosperm family tree still alive today.  To call them primitive, however, would be a serious misnomer. Because they diverged so early on, these lineages represent serious success stories in flowering plant evolution, having survived for hundreds of millions of years. Instead, we must think of them as fruitful early experiments in angiosperm evolution.

Floral morphology of and interaction between midge and their larvae (white arrows) in Illicium dunnianum

Still, the proverbial proof is in the pudding and if there was any sort of physical evidence one could put forth to remove our hierarchical prejudices about the taxonomic position of these plants, it would have to be their bizarrely specific pollination syndromes.  Members of the family Schisandraceae have entered into intense relationships with a group of flies known as midges and their interactions are anything but primitive. 

We will start with two species of plant native throughout parts of Asia. Meet as Illicium dunnianum and Illicium tsangii. More will be familiar with this genus than they may realize as Illicium gives us the dreaded star anise flavor our grandparents liked to sneak into our cookies as kids (but I digress). These particular species, however, have more to offer the world than flavoring. They are also very important plants for a group of gall midges in the genus Clinodiplosis.

The midges cannot reproduce without I. dunnianum or I. tsangii. You see, these midges lay their eggs within the flowers of these plants and, in doing so, end up pollinating them in the process. At first glance it may seem like a very one-sided relationship. Female midges deposit their eggs all along the carpels packed away inside large, fleshy whorl of tepals. As the midges crawl all over the reproductive organs looking for a suitable place to lay, they inevitably pick up and deposit pollen. 

Floral morphology and interaction between midge larvae (white arrows) in  Illicium tsangii

This is not the end of this relationship though. After eggs have been deposited, something strange happens to the Illicium flowers. For starters, they develop nursery chambers around the midge larvae. Additionally, their tepals begin producing heat. Enough heat is produced to keep the nursery chamber temperature significantly warmer than the ambient air temperature. What's more flower heating intensifies throughout the duration of fruit development. It was originally hypothesized that this heating had something to do with floral odor volatilization and seed incubation, however, experiments have shown that at least seed development in these two shrubs is not influenced by floral heat in any major way. The same cannot be said for the midge larvae. 

As the flowers mature and give way to developing seeds, the midge larvae are hard at work feeding on tiny bits of the flowers themselves. When researchers looked at midge larvae development on these Illicium species, they found that they were completely dependent upon the floral heat for survival. Any significant drop in temperature caused them to die. Essentially, the plants appear to be producing heat more for the midges than for themselves. It may seem odd that these two plants would invest so much energy to heat their flowers so that midge larvae feeding on their tissues can survive but such face-value opinions rarely stand in ecology.

One must not forget that those larvae grow up to be adult midges that will go on to pollinate the Illicium flowers the following season. Although the plants are taking a bit of a hit by allowing the larvae to develop within their tissues, they are nonetheless ensuring that enough pollinators will be around to repeat the process again. If that wasn't cool enough, the relationship between each of these plants and their pollinators are rather specific and the authors of at least one paper believe that the midges that pollinate each species are new to science. 

Now, if I haven't managed to convince you that this angiosperm sister lineage is anything but primitive, then let's take a look at another genus within the family Schisandraceae that have taken this midge pollination syndrome to the next level. This story also takes place in Asia but instead involves a genus of woody vines known as Kadsura

Like the Illicium we mentioned earlier, a handful of Kadsura species rely on midges for pollination. The way in which they go about maintaining this relationship is a bit more involved. The midges that are attracted by Kadsura flowers are known as resin midges and their larvae live off of plant resins. The flowers of Kadsura are another story entirely. They are as odd as they are beautiful. 

Flowers, pollinators ,and their larvae (white arrows) in Kadsura heteroclita.

Flowers, pollinators ,and their larvae (white arrows) in Kadsura heteroclita.

In male flowers, stamens are arranged in dense, cone-like structures called androecia whereas the female flowers contain a compact shield-like structure with the uppermost part of the stigma barely emerging. This is called a gynoecium. Even weirder, the male flowers of one particularly strange species, Kadsura coccinea, produce large, swollen inner tepals. 

Once Kadsura flowers begin to open, visiting midges are not far behind. Male flowers seem to attract more midges than female flowers and it is thought that this has to do with varying amounts of special attractant chemicals produced by the flowers themselves. Regardless, midges set to work exploring the blooms with males looking for mates and females looking for a place to lay their eggs. 

When a suitable spot has been found, females will deposit their eggs into the floral tissues with their ovipositor. The wounded plant tissues immediately begin producing resin, not unlike a wounded pine tree. In the case of K. coccinea, it would appear that the oddly swollen tepals are specifically targeted by female midges for egg laying. They too produce resin upon having eggs laid within. 

The oddball flowers of Kadsura coccinea showing swollen tepals.

The function of plant resins in many cases are to fight off pathogens. From beetles to fungi, resin helps plug up and seal off wounds. This does not seem to be the case in the Kadsura-midge relationship though. The so-called "brood chambers" within the floral tissues go on producing resin for upwards of 6 days after the midge eggs were laid. Eventually the floral parts whither and drop off but the midge larvae seem to be quite happy in their resin-filled homes. 

As it turns out, the resin midge larvae feed on the viscous resin as their sole food source. Instead of trying to ward off these pesky little insects, the plants seem to be encouraging them to raise their offspring within! Just as we saw in the Asian Illicium, these Kadsura vines seem to be providing brood sites for their pollinators. Also, just as the Illicium-midge relationship thought to be species specific, each species of Kadsura appears to have its own specific species of resin midge pollinator! K. coccinea even goes as far as to produce tepals specifically geared towards raising midge larvae, thus keeping them away from their more valuable reproductive organs. In return for the nursery service, Kadsura have their pollinators all to themselves.

Pollination mutualisms in which plants trade raising larvae for pollen transfer are extremely derived and some of the most specialize plant/animal interactions on the planet. To find such relationships in these basal or sister lineages is living proof that these plants are anything but primitive. In the energy-reproductive investment trade-off, it appears that ensuring ample pollinator opportunities far outweighs the cost of providing them with nursery chambers. It is remarkable to think just how intertwined the relationships between these plants and there pollinators truly are. Take that, plant taxonomic prejudices! 

Photo Credits: [1] [2]

Further Reading: [1] [2] 

 

A Truly Bizarre Cactus From The Amazon

DN0Ia_SW4AIBjCB.jpg

When we think of cacti, we tend to think of dry deserts and sandy soils. Few of us would ever jump to the trunk of a tree, nestled in a humid rainforest, and experiencing periodic inundation. Yet, such a habitat is the hallmark of one of the world's most unique species of cactus - Selenicereus witii. In more ways than one, this species is truly aberrant.

Whereas epiphytic cacti aren't novel, the habits of S. witii surely push the limits of what we know about the entire cactus family. Despite having been discovered in 1899, little attention has been paid to this epiphytic cactus. What we do know comes from scant herbarium records and careful observation by a small handful of botanists.

S. witii is endemic to a region of central Amazonia and only grows in Igapó, or seasonally flooded, blackwater forests. It makes its living on the trunks of trees and its entire morphology seems particularly adapted to such a harsh lifestyle. Unlike most cacti, S. witii doesn't seem to bother with water storage. Instead, its stems grow completely appressed to the trunks of trees. Roots emerge from near the spine-bearing areoles and these help to anchor it in place. 

9714998740_596ee2ef55_b.jpg

Because they are often exposed to bright sunlight, the stems produce high amounts of chemical pigments called betalains. These act as sun block, protecting the sensitive photosynthetic machinery from too much radiation. These pigments also give the plant a deep red or purple color that really stands out against the trunks of trees. 

Like all members of this genus, S. witii produces absolutely stunning flowers. However, to see them, your best bet is to venture out at night. Flowers usually begin to open just after sundown and will be closed by morning. And my, what flowers they are! Individual blooms can be upwards of 27 cm long and 12.5 cm wide (10 in by 5 in)! They are also said to produce an intense fragrance. Much of their incredible length is a nectar tube that seems to be catered to a specific group of sphinx moths, whose proboscis is long enough to reach the nectar at the bottom.

Neococytius_cluentius_sjh.JPG

The seeds of S. witii are just as aberrant as the rest of the cactus. They are rather large and shaped like a kidney. Cross sections reveal that most of their size is devoted to hollow air chambers. Indeed, the seeds float like tiny pieces of cork when placed in water. This is likely an adaptation resulting from their preferred habitat.

As mentioned above, S. witii has only been found growing in seasonally flooded forests. What's more, plants only occur on the trunks of large trees right at the high water line. In fact, the highly appressed nature of its stems seems to suggest that this species can withstand periodic submergence in fast flowing water. The seeds must also cope with flooding and it is likely that their buoyant nature aids in seed dispersal during these periods. 

cactus seeds.JPG

All in all, this is one weird cactus. Although it isn't alone in its tropical epiphytic habit, it certainly takes the cake for being one of the most derived. Aside from a few publications, little attention has been given to this oddball. It would appear that the seasonal flooding of its preferred habitat has simply chased this cactus up into the trees, the environmental demands of which coaxed out strange but ingenious adaptations from its genome. The good news is that where it does occur, S. witii seems to grow in high numbers.

Photo Credit: [1] [2] [3] [4] [5]

Further Reading: [1]

Devil's Gardens

Tococa_leaves.jpg

Imagine, if you will, walking through the dense understory somewhere in the Amazon basin. Diversity reigns supreme here and it would seem that every few steps reveals myriad new plant species. As you walk along, something in the vegetation changes. You stumble into a clearing in the middle of the forest dominated entirely by a single species of tree. Why the sudden change? How did this monoculture develop? You, my friend, have just found yourself on the edge of a Devil's garden. 

Devil's gardens are said to be the resting place of an evil spirit known to local tribes as Chullachaki. Anyone unlucky enough to stumble into his garden is said at risk of attack or curse. In reality, these gardens have a biological origin. The real gardeners are a handful of ant species which seem to have rather specific gardening preferences. Careful inspection would reveal that the gardens largely consist of trees in one of three genera - Duroia, Tococa, or Clidemia

Tococa sp. (Melastomataceae)

Tococa sp. (Melastomataceae)

The reason that ants are so fond of these genera has to do with housing. These plant groups contain species which produce swellings along their stems and petioles known as domatia. These domatia are hollow and are the favorite nesting spots of various ant species. Ant colonies set up shop within. As anyone who has ever blundered into an ant colony can attest, ants are quite voracious at defending their home. 

By providing ant colonies with a home base, these plants have essentially hired body guards. It is a wonderful form of symbiosis in which the ants aggressively defend against anything that might want to take a bite out of their host tree. Any herbivore trying to take up residence or lay eggs within the Devil's garden is viciously attacked. In doing so, the ants are protecting their host trees at the cost of all other plants unlucky enough to germinate within the garden. Still, this anti-herbivore behavior doesn't totally explain the monoculture status these host trees achieve within the garden itself. Why are these gardens so ominously devoid of other plant species?

To answer this, one would have to watch how the ants behave as they forage. While scouting, if ants encounter a seedling of their host tree, nothing really happens. They go about their business and let the seedling grow into a future home. When they encounter a non-host tree, however, their behavior completely changes. 

Behold - A Devil's Garden

Behold - A Devil's Garden

The ants begin biting the stem of the plant, exposing its vascular tissue. As they bite, the ants also sting the foreign seedling, injecting minute amounts of formic acid into the wound. One or two ants isn't enough to bring down a seedling but one thing ants have on their side are numbers. Soon an entire platoon of ants descend upon the hapless seedling, stinging it repeatedly. In no time at all, the seedling succumbs to the formic acid injections and dies. By repeating this process any time a foreign plant is found growing within the vicinity of the garden, the resident ants ensure that only trees that will produce domatia are allowed to grow in their garden. Thus, a Devil's garden has been formed. 

Although this relationship seems incredibly beneficial for each party, it does come at some cost to the plants themselves. Certainly forming the domatia is a costly endeavor on the part of the plant, but research has also shown that growing in such high, monoculture-like densities in the jungle has its downsides. It has been found that individual host trees can actually experience more herbivore pressures when growing within a Devil's garden than if it was growing alone, elsewhere in the forest. 

Despite their aggression towards herbivores, the ants simply cannot be everywhere at once. As such, the high densities of host tree species within a Devil's garden act like a dinner bell for any insect that enjoys feeding on that particular type of plant. Essentially, the ants are concentrating a potential food source. Experts believe that this might explain why Devil's gardens never completely take over entire swaths of forest. Essentially, there are diminishing returns to living in such high densities. Still, benefits must outweigh costs if such mutualisms are to be maintained and it is quite obvious that both plant and ant benefit from this interaction to a great degree. 

Photo Credits: [1] [2] [3] [4]

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

The Elusive White Walnut

Today we go in search of the elusive white walnut (Juglans cinerea). Many of you may know it by its other common name - the butternut. Sadly, being able to find large, mature specimens of this wonderful tree is getting harder and harder. Watch and find out why...

 

Music by:
Artist: Somali Yacht Club
Track: Loom
https://somaliyachtclub.bandcamp.com/

The Early Days Of A Symbiosis?

aglao10.jpg

Despite the ubiquitous nature of symbioses across the globe, evidence of their origins is scant to say the least. Mostly we look for clues of their origin hidden within the fossil record. Excitingly, a series of fossils discovered in Scotland reveal what very well be the early days of plant-cyanobacterial interactions. Thanks to these exquisitely preserved fossils, we now have the earliest record of an association between these two groups of organisms.

The fossils themselves date back to the early Devonian, some 400 million years ago. They hail from a hot spring community which allowed wonderfully detailed preservation of everything down to the cellular level. Needless to say, this was a drastically different time for life on this planet. Plants were really starting to dominate the landscape. In the case of the fossil discoveries in question, one plant in particular is the star of this show. 

Meet Aglaophyton major. This odd looking plant would have been a common site in these sorts of habitats. It largely consisted of a small, leafless stem that branched as it ambled over the ground. These stems bore the stomata, which allowed gas exchange to occur. Every once in a while, a stem would throw up a reproductive structure called a sporangium, which housed the spores. At the ground level, the stems would occasionally produce root-like rhizoids that have been found in association with fossilized mycorrhizal fungi in the soil.

In total, A. major only stood about 18 cm in height. Though abundant, it was relatively small compared to some of the other vegetation coming online at this point in time. It is likely that A. major could tolerate occasional flooding. In fact, some have speculated that flooding may have been necessary for the germination of its spores. It's this periodic inundation with water that likely led to an interesting and tantalizing relationship with cyanobacteria. 

1. Transverse section through two typical axes showing the simple internal organization; slide P1828; bar = 1 mm. 2. Anatomy of the prostrate mycorrhizal axis (E = epidermis; OC = outer cortex; MAZ = mycorrhizal arbuscule-zone; IC = inner cortex; PIT = phloem-like tissue; CT = conducting tissue); slide P1612; bar = 150 μm. 3. Dense aggregate of cyanobacterial filaments in an area where the axis is injured and has exuded some type of wound secretion (opaque mass); slide P1289; bar = 100 μm. 4. Detail of Plate I, 3, showing part of the cyanobacterial aggregate; bar = 100 μm. 5. Intercellular cyanobacterial filaments near the mycorrhizal arbuscule-zone of the cortex (darker tissue in lower third of image); slide P3652; bar = 50 μm. 6. Group of filaments passing through the intercellular system of the outer cortex; slide P3652; bar = 20 μm.

1. Transverse section through two typical axes showing the simple internal organization; slide P1828; bar = 1 mm. 2. Anatomy of the prostrate mycorrhizal axis (E = epidermis; OC = outer cortex; MAZ = mycorrhizal arbuscule-zone; IC = inner cortex; PIT = phloem-like tissue; CT = conducting tissue); slide P1612; bar = 150 μm. 3. Dense aggregate of cyanobacterial filaments in an area where the axis is injured and has exuded some type of wound secretion (opaque mass); slide P1289; bar = 100 μm. 4. Detail of Plate I, 3, showing part of the cyanobacterial aggregate; bar = 100 μm. 5. Intercellular cyanobacterial filaments near the mycorrhizal arbuscule-zone of the cortex (darker tissue in lower third of image); slide P3652; bar = 50 μm. 6. Group of filaments passing through the intercellular system of the outer cortex; slide P3652; bar = 20 μm.

Cyanobacteria are probably best known for their contribution of oxygen to Earth's early atmosphere. What's more, many also fix nitrogen. That is why the fossil discovery of A. major with cyanobacteria in and around its cells is so exciting. These 400 million year old fossils provide the first evidence of a plant and cyanobacteria in an intimate association.

As mentioned above, the fossilization process was so thorough that it preserved subcellular structures. After thin sectioning some A. major stems, a team of researchers found filaments of cyanobacteria in the process of invading the plant and taking up residence. The cyanobacteria appears to be entering the plant through the stomatal openings along the stem. Once inside, the cyanobacteria show signs of colonazation of substomatal chambers as well as intercellular spaces within the plants tissues.

Although the authors cannot say whether this association was mutualistic or not, it nonetheless represents a model situation detailing how such a symbiotic relationship could have evolved in the first place. Because the cyanobacteria in question here is thought to be aquatic, the only way for it to move into the plant would have been during periodic flooding events. The idea that this could be simply an infection following the death of the plant was considered. However, the non-random distribution of cyanobacteria within A. major cells suggests that this relationship was no accident.

For now, the relationship between A. major and cyanobacteria was likely an "on-again–off-again incidental association" centered around flood events. The fact that A. major was already associated with mycorrhizal fungi at this point in Earth's history certainly suggests that the genetic adaptations necessary for symbiotic relationships were already in place. Though it isn't a smoking gun, these fossils provide the earliest evidence of plants' relationship with cyanobacteria.

Photo Credits: [1]

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

A Common Plant With An Odd Pollination Mechanism

12991773875_03b66ba799_o.jpg

Pollination is not an altruistic enterprise. Each party involved is trying to maximize its gains while minimizing its losses. Needless to say, cheaters abound in natural systems. As such, plants have gone to great lengths to ensure that their reproductive investments pay off in the long run. Take, for instance, the case of the fragrant water-lily (Nymphaea odorata). 

Most of us have encountered this species at some point in our lives. Those who have often remark on the splendor of their floral displays. Certainly this is not lost on pollinators either. Coupled with their aromatic scent, these aquatic plants must surely be a boon to any insect looking for pollen and nectar. Still, the flowers of the fragrant water-lily take no chances.

Close observation will reveal an interesting pattern in the blooming cycle of this water-lily. On the first day that the flowers open, only the female portions are mature. The structure itself is bowl-like in shape. Filling this stigmatic bowl is a viscous liquid. After the first day, the flowers close for the evening and reopen to reveal that the stigma is no longer receptive and instead, the anthers have matured.

Many insects will visit these floating flowers throughout the blooming period. Everything from flies, to beetles, and various sorts of bees have been recorded. Seed set in this species is pollen limited so any insect visiting a female flower must deposit pollen if reproduction is to be achieved. This is where that bowl of sticky liquid comes into play. The liquid itself is rather unassuming until you see an insect fall in.

Due to the presence of surfactants, any insect that falls into the fluid immediately sinks to the bottom. The flowers seem primed to encourage this to happen too. The flexible inner stamens that surround the bowl bend under the weight of heavier insects, thus dumping them into the liquid below. Only by observing this process under extreme magnification does all of this make sense.

The liquid within the bowl essentially washes off any pollen that a visiting insect had stuck to its body. As the pollen falls off, it drifts down to the bottom of the bowl where it contacts the receptive stigma. Thus, cross-pollination is achieved. Most of the time, insect visitors are able to crawl out without any issue. However, the occasional insect will drown within the fluid. Alas, that is no sweat off the water-lily's back. Having dropped off the pollen it was carrying, it is of little use to that flower anymore.

Once a water-lily flower has been fertilized, its stem begins to curl up like a spring. This draws the ovaries underwater where they can develop in relative safety. It also ensures that, upon maturing, the seeds are more likely to find a suitable underwater site for germination. To think that this drama plays out time and time again unbeknownst to the casual observer is something I find endlessly fascinating about the natural world.

Photo Credit: [1] [2]

Further Reading: [1] [2]

The First Trees Ripped Themselves Apart To Grow

Pseudosporochnales_reconstruccion.jpg

A new set of fossil discoveries show that the evolutionary arms race that are forests started with plants that literally had to rip themselves apart in their battle for the canopy. The first forests on this planet arose some 385 million years ago and were unlike anything we know today. They consisted of a clade of trees known scientifically as Cladoxylopsids, which have no living representatives in these modern times. How these trees lived and grew has remained a mystery since their fossilized trunks were first discovered but a new set of fossils from China reveals that these trees were unique in more ways than one.

Laying eyes on a full grown Cladoxylopsid would be a strange experience to say the least. Their oddly swollen base would gradually taper up a trunk that stretched some 10 to 12 meters (~30 - 40 feet) into a canopy of its relatives. They had no leaves either. Instead, their photosynthetic organs consisted of branch-like growths that were covered in twig-like projections. Whereas most fossils revealed great detail about their outward appearance, we have largely been in the dark on what their internal anatomy was like. Excitingly, a set of exquisitely preserved fossils from Xinjiang, China has changed that. What they reveal about these early trees is quite remarkable.

As it turns out, the trunks of these early trees were hollow. Unlike the trees we know today, whose xylem expands in concentric rings and forms a solid trunk, the trunk of Cladoxylopsid was made up of strands of xylem connected by a network of softer tissues. Each of these strands was like a mini tree in and of itself. Each strand formed its own concentric rings that gradually increased the size of the trunk. However, this gradual expansion did not appear to be a gentle process.

As these strands increased in size, the trunk would grow larger and larger. In doing so, the tissues connecting the strands were pulled tighter and tighter. Eventually they would tear under the strain. They would gradually repair themselves over time but the effect on the trunk was quite remarkable. In effect, the base of the tree would literally collapse in on itself in a controlled manner. You could say that older Cladoxylopsids developed a bit of a muffin top at their base. 

A cross section of a Cladoxylopsid trunk showing the hollow center, individual xylem strands, and the network of connective tissues.

A cross section of a Cladoxylopsid trunk showing the hollow center, individual xylem strands, and the network of connective tissues.

Although this seems quite detrimental, the overall structure of the tree would have been quite sturdy. The authors liken this to the design of the Eiffel tower. Indeed, a hollow cylinder is actually stronger than a solid one of the same dimensions. When looked at in the context of all other trees, this form of growth is pretty unique. No other trees are constructed in such a manner.

The authors speculate that this form of growth may be why these trees eventually went extinct. It would have taken a lot of energy to grow in that manner. It is possible that, as more efficient forms of growth were evolving, the Cladoxylopsids may not have been able to compete. It is anyone's guess at this point but this certainly offers a window back into the early days of tree growth. It also shows that there has always been more than one way to grow a tree.

Photo Credits: [1] [2]

Further Reading: [1]

Bird Pollination Of The Bird Of Paradise

Strelitzia_reginae_1.jpg

Who hasn't stared in wonderment at the inflorescence of a bird of paradise? One doesn't need too much of an imagination to understand how these plants got this common name. Flowers, however, did not evolve in response to our aesthetic tastes. They are solely for sex and in the case of bird of paradise, Strelitzia reginae, pollination involves birds.

In its native range in South Africa, S. reginae is pollinated by sunbirds, primarily the Cape weaver (Ploceus capensis). That alluring floral morphology is wonderfully adapted to maximize the chances of successful cross-pollination by their avian visitors. Cape weavers are looking for a sip of energy rich nectar. To get at said nectar, the birds must perch on the inflorescence. Not any position will do either.

Starr_061224-2882_Strelitzia_reginae.jpg

To get their reward, the birds must perch so that their beaks are at just the right angle to reach down into the floral tubes. The plant ensures this by providing a convenient perch. Those fused blue petals are structurally reinforced and actually serve as a convenient perch! Upon alighting on the perch, the hidden anthers are thrust outward from their resting chamber, brushing up against the bird's feet in the process. The Cape weaver doesn't move around much once on the flower so self pollination is minimized.

When the bird visits another plant, the process is repeated and pollination is achieved. Seed set is severely pollen limited. This is a good thing considering how popular they are in cultivation. Plants growing outside of South Africa rarely set seed without a helping hand. However, here in North America, some birds seemed to have figured out how to get at bird of paradise nectar.

1-s2.0-S0254629910002462-gr1.jpg

Observations made in southern California found that at least one species of warbler, the common yellowthroat (Geothlypis trichas), not only made regular visits to a stand of S. reginae, it also seemed to figure out the proper way to do so. Individuals were seen perching on the floral perch and drinking the nectar. They were pretty effective visitors at that. Of the 14,400 inflorescence found within the study area, 88% of them produced viable seed! It seems that far from its native range, S. reginae has a friend in at least one New World warbler. Armed with this knowledge, land owners should be vigilant to ensure this plant doesn't become a problem in climates suitable for its growth.

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

Further Reading: [1]

 

Appalachia

Welcome to Appalachia. I have fallen in love with this corner of the world in large part because of its wonderfully rich and unique flora. Join In Defense of Plants as we take a sneak peak at a mere fraction of the botanical riches these mountains hold.

Further Readings On Appalachian Flora:

http://www.indefenseofplants.com/blog...

http://www.indefenseofplants.com/blog...

http://www.indefenseofplants.com/blog...

http://www.indefenseofplants.com/blog...

Producer, Writer, Creator, Host: Matt Candeias

Producer, Editor, Camera: Grant Czadzeck (http://www.grantczadzeck.com)

Twitter: @indfnsofplnts https://twitter.com/indfnsofplnts

Facebook: http://www.facebook.com/indefenseofpl...

Patreon: http://www.patreon.com/indefenseofplants

Tumblr: http://www.tumblr.com/indefenseofplants

Of Acorns and Squirrels

I find it fun to watch squirrels frantically scurrying about during the fall. Their usually playful demeanor seems to have been replaced with more serious and directed undertones. If you watch squirrels close enough you may quickly realize that, when it comes to oaks, squirrels seem to have a knack for taxonomy. They quickly bury red oak acorns while immediately set to work on eating white oak acorns. Why is this?

Music by:
Artist: Botanist
Track: Stargazer
https://verdant-realm-botanist.bandcamp.com/

A Bat-Pollinated Passion Flower From Ecuador

batpass1.JPG

Say "hello" to one of Passiflora's most recent additions, the bat-pollinated Passiflora unipetala. The first specimens of this vine were discovered back in 2009 by Nathan Muchhala while studying flower visiting bats in northern Ecuador. It is a peculiar member of the genus to say the least. 

One of the most remarkable features of this plant are its flowers. Unlike its multi-petaled cousins, this species stands out in producing a single large petal, which is unique for not only the genus, but the whole family as well. The petal is quite large and resembles a bright yellow roof covering the anthers and stigma. At the base of the flower sits the nectar chamber. The body of the plant consists of a vine that has been observed to grow upwards of 6 meters up into the canopy.

Flowering in this species occurs at night. Their large size, irregular funnel shape, and bright yellow coloring all point to a pollination syndrome with bats. Indeed, pollen of this species has been found on the fur of at least three different bat species. Multiple observations (pictured here) of bats visiting the flowers helped to confirm. Oddly enough for a bat-pollinated plant, the flowers produce no detectable odor whatsoever. However, another aspect of its unique floral morphology is worth noting. 

The surface of the flower has an undulating appearance. Also, the sepals themselves have lots of folds and indentations, including lots of dish-shaped pockets. It is thought that these might help the flower support the weight of visiting bats. They may also have special acoustic properties that help the bats locate the flowers via echolocation. Though this must be tested before we can say for sure, other plants have converged on a similar strategy (read here and here).

As it stands currently, Passiflora unipetala is endemic to only a couple high elevation cloud forests in northern Ecuador. It has only ever been found at two locations and sadly a landslide wiped out the type specimen from which the species description was made. As such, its introduction to the world came complete with a spot on the IUCN Redlist as critically endangered. Luckily, the two localities in which this species has been found are located on privately protected properties. Let's just hope more populations are discovered in the not-too-distant future.

Photo Credits: [1] 

Further Reading: [1]

Ants As Pollinators?

33136419732_ac876bfcae_o.jpg

Ants interact with plants in a variety of beneficial ways. They offer protection, they provide nutrients, they even disperse seeds! When it comes to pollination, however, plants have largely gone elsewhere. That's not to say ants don't get directly involved in the sex lives of plants. At least one plant species native to Spain has been found to be pollinated by ants. Certainly there are probably more examples of ant pollination throughout the plant kingdom, we simply have to look. For example, one possible ant-pollinated plant can be found growing on the west coast of North America.

The dwarf owl's-clover (Triphysaria pusilla) is a small annual member of the broomrape family. It really is a dwarf species, rarely exceeding a few inches in height. What it lacks in size, it makes up for in abundance. Large colonies of these species can be found growing among other low statured herbs in wetter areas like spring-fed grasslands. Their tendency to produce lots of anthocyanin pigments in their tissues means that these maroon colonies really stand out. Like other members of the family, it is a facultative hemiparasite, tapping into the roots of surrounding vegetation with its roots, stealing nutrients and water as the situation demands.

372945290_b2491b4b9a_o.jpg

Flowering in the dwarf owl's-clover is rather inconspicuous. The dense flowering spikes produce minute, tubular, maroon-yellow flowers. It has been observed that, at any given point during the flowering season, only three flowers will have matured on any given plant. Two of these flowers mature their anthers first whereas the remaining flower matures its stigma. This is likely an adaptation for increasing the chances of cross pollination. 

33675797300_ddd511b2bf_o.jpg

Because these flowers hardly qualify as an attractive display for more commonly encountered insect pollinators, it has been hypothesized that ants are the preferred pollinator of this species. Early work even suggested that the dense leaf arrangement facilitates ant movement to and from flowers in any given colony. Although no one has yet quantified the efficacy of ants as pollinators of this species, numerous observations of ants visiting flowers and picking up pollen have been made. Famously, such a scene was filmed for the 1981 documentary "Sexual Encounters of the Floral Kind."

Whether these visits constitute effective pollination remains to be seen. It could be that the ants are nothing more than nectar and pollen thieves. What's more, many ants produce substances from specialized glands that, among other things, destroy pollen. Until someone takes the time to study this interaction, we simply do not know. Sounds like a fun research project to me! 

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

Further Reading: [1]

The Nitrogen-Fixing Abilities of Cycads

Encephalartos_turneri_-_Koko_Crater_Botanical_Garden_-_IMG_2328.JPG

Long before the first legumes came onto the scene, the early ancestors of Cycads were hard at work fixing atmospheric nitrogen. However, they don't do this on their own. Despite being plentiful in Earth's atmosphere, gaseous nitrogen is not readily available to most forms of life. Only a special subset of organisms are capable of turning gaseous nitrogen into forms usable for life. Some of the first organisms to do this were the cyanobacteria, which has led them down the path towards symbioses with various plants on many occasions. 

Cycads are but one branch of the gymnosperm tree. Their lineage arose at some point between the Carboniferous and Permian eras. Throughout their history it would seem that Cycads have done quite well in poor soils. They owe this success to a partnership they struck up with cyanobacteria. Although it is impossible to say when exactly this happened, all extant cycads we know of today maintain this symbiotic relationship with these tiny prokaryotic organisms. 

Cross section of a coralloid cycad root showing the green cyanobacteria inside.

Cross section of a coralloid cycad root showing the green cyanobacteria inside.

The relationship takes place in Cycad roots. Cycads don't germinate with cyanobacteria in tow. They must acquire them from their immediate environment. To do so, they begin forming specialized structures called precoralloid roots. Unlike other roots that generally grow downwards, these roots grow upwards. They must situate themselves in the upper layer of soil where enough light penetrates for cyanobacteria to photosynthesize.

The cyanobacteria enter into the precoralloid roots through tiny cracks and take up residence. This causes a change in root development. The Cycad then initiates their development into true coralloid roots, which will house the cyanobacteria from that point on. Cycads appear to be in full control of the relationship, dolling out carbohydrates in return for nitrogen depending on the demands of their environment. Coralloid roots can shed and reform throughout the lifetime of the plant. It is quite remarkable to think about how nitrogen-fixing symbiotic relationships between plants and microbes have evolved independently throughout the history of life on this planet.

Photo Credits: [1] [2]

Further Reading: [1] [2]