The Upside Down World of Orchid Flowers

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Did you know that most orchid flowers you see are actually blooming upside down? That's right, referred to as "resupination," the lower lip of many orchid flowers is actually the top petal and, as the flower develops inside the bud, the whole structure makes a 180° rotation. How and why does this happen?

The lip of an orchid flower usually serves to attract pollinators as well as function as a landing pad for them. The flower of an orchid is an incredibly complex organ with an intriguing evolutionary history. Basically, the lip is the most derived structure on the flower and, in most cases, it is the most important structure in initiating pollination.

The non-resupinate flowers of the grass pink ( Calopogon tuberosus ) showing the lip on top.

The non-resupinate flowers of the grass pink (Calopogon tuberosus) showing the lip on top.

As an orchid flower bud develops, it begins to exhibit gravitropic tendencies, meaning it responds to the pull of gravity. By removing specific floral organs like the column and pollinia, researchers found that they produce special hormones called auxins that tell the developing bud to begin the process of resupination. The ovary starts to twist, causing the flower to stand on its head.

Not all orchids exhibit resupinate flowers. Grass pinks (Calopogon tuberosus) famously bloom with the lip pointing up as it does in the early stages of bud development. It is an interesting mechanism and serves to demonstrate the stepwise tendencies that the forces of natural selection and evolution can manifest. But why does it occur at all? What is the evolutionary advantage of resupinate flowers?

Not only are  Dracula  flowers resupinate, many species also face them towards the ground.

Not only are Dracula flowers resupinate, many species also face them towards the ground.

The most likely answer to this biological twist is that, for orchids, resupination places the lip in such a way that facilitates pollination by whatever the flowers are attracting. For many orchids, this means providing an elaborate landing strip in the form of the lip. For the grass pinks, which operate by slamming visiting bees downward onto the column to achieve pollination, placing the lip at the top makes more mechanical sense. When a bee visits the upward pointing lip thinking it will find a pollen-rich meal, the lip bend at the base like a hinge. Anything goes in evolution provided the genes are present for selection to act upon and nowhere is this fact more beautifully illustrated than in orchids.

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

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

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

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

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

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

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

Photo Credit: Suetsugu Kenji

Further Reading:

[1]

The Orchid Mantis Might Not be so Orchid After All

Here we see a juvenile orchid mantis perched atop a man-made orchid cultivar that would not be found in the wild.

Here we see a juvenile orchid mantis perched atop a man-made orchid cultivar that would not be found in the wild.

The orchid mantis is a very popular critter these days, and rightly so. Native to southeast Asia, they are beautiful examples of how intricately the forces of natural selection can operate on a genome. The reasoning behind such mimicry is pretty apparent, right? The mantis mimics an orchid flower and thus, has easy access to unsuspecting prey.

Not so fast...

Despite its popularity as an orchid mimic, there is no evidence that this species is mimicking a specific flower. Most of the pictures you see on the internet are actually showing orchid mantids sitting atop cultivated Phalaenopsis or Dendrobium orchids that simply do not occur in the wild. Observations from the field have shown that the orchid mantis is frequently found on the flowers of Straits meadowbeauty (Melastoma polyanthum). A study done in 2013 looked at whether or not the mantids disguise offers an attractive stimulus to potential prey. Indeed, there is some evidence for UV absorption as well as convincing bilateral symmetry that is very flower-like. They also exhibit the ability to change their color to some degree depending on the background.

Orchid mantis nymphs are more brightly colored than adults.

Orchid mantis nymphs are more brightly colored than adults.

Despite our predilection for finding patterns (even when there are none) it is far more likely that this species has evolved to present a "generalized flower-like stimulus." In other words, they may simply succeed in tapping into pollinators' bias towards bright, colorful objects. We see similar strategies in non-rewarding flowering plants that simply offer a large enough stimulus that pollinators can't ignore them. The use of colored mantis models has provided some support for this idea. Manipulating the overall shape and color of these models had no effect on the number of pollinators attracted to them.

The most interesting aspect of all of this is that the most convincing (and most popular) mimicking the orchid mantis displays is during the juvenile phase. Indeed, most pictures circulating around the web of these insects are those of immature mantids. The adults tend to look rather drab, with long, brownish wing covers. However, they still maintain some aspects of the juvenile traits.

Adult orchid mantids take on a relatively drab appearance compared to their juvenile form.

Adult orchid mantids take on a relatively drab appearance compared to their juvenile form.


The fact of the matter is, we still don't know very much about this species. It is speculated that the mimicry is both for protection and for hunting. As O'Hanlon (2016) put it, "The orchid mantis' predatory strategy can be interpreted as a form of 'generalized food deception' rather than 'floral mimicry'." It just goes to show you how easily popular misconceptions can spread. Until more studies are performed, the orchid mantis will continue to remain a beautiful mystery.

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

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

The Cranefly Orchid (Tipularia discolor)

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Look closely or you might miss it. Heck, even with close inspection you still run the risk of overlooking it. At this time of year, finding a cranefly orchid (Tipularia discolor) can present a bit of a challenge. At other times of the year the task is a bit easier. If you can find one in bloom, however, you are rewarded with, in my opinion, one of the most unique terrestrial orchids in temperate North America.

For most of the year, the cranefly orchid exists as a single leaf, which is produced in the fall and lasts until spring. It is thought that this orchid takes advantage of the dormancy of its neighbors by sucking up the light the canopy otherwise intercepts during the growing season. Any of you curious enough to look will have noticed that the underside of this leaf is deep purple in color. This very well may be an adaptation to take full advantage of light when it is available. There is some evidence that such coloration may help reflect light back up into the leaf, thus getting more out of what makes it to the forest floor. Evidence for this, however, is limited. It is far more likely that the purple coloration are pigments produced by the leaves that act as a sort of sun screen, shielding the sensitive photosynthetic machinery within from an overdose of sun.

By the end of spring, the single leaf has senesced. If energy stores were ample that year the plant will then flower. A lanky brown spike erupts from the ground. Its purple-green color is subtle yet beautiful. The flowers themselves are a bit odd, even by orchid standards. Whereas most orchid flowers exhibit satisfying bilateral symmetry, the flowers of the cranefly orchid are distinctly asymmetrical. The dorsal sepal, along with the lateral petals, are scrunched up on either side of the column. This has everything to do with its pollinators.

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The cranefly orchid has coopted nocturnal moths in the family Noctuidae for pollination. These moths find the flowers soon after they open and stick around only as long as there is nectar still present in the long nectar spurs. The asymmetry of the bloom causes the pollinia to attach to one of the moth's eyes. In this way the orchid is able to ensure that its pollen is not wasted on the blooms of other species.

As in all plants, the production of flowers is a costly business. Sexual reproduction is all about tradeoffs. It has been found that cranefly orchids that flowered and successfully produced fruit in one year were much less likely to do so in the next. What's more, the overall size of the plant (leaves and corms) were greatly reduced. Its hard to eek out an existence on the forest floor.

What I find most interesting about this species is where it tends to grow. Any old patch of ground simply won't do. Research indicates that the cranefly orchid requires rotting wood as a substrate. It's not so much the wood they require but rather the organisms that are decomposing it. Like all orchids, the cranefly cannot germinate and grow without mycorrhizal associations. They just happen to partner with fungi that also decompose wood. Such a relationship underscores the importance of decaying wood to forest health.

Further Reading:
http://bit.ly/29RSylm

http://bit.ly/29MAEz7

http://bit.ly/29K3UdZ

http://bit.ly/29WAycl

http://bit.ly/2a6fO19

The Ghosts of Florida

 

There are ghosts haunting the Florida Everglades. I'm not talking about the metaphysical kind either. The ghosts I am talking about come in the form of a plant. A strange, mystical, and beautiful plant at that. Growing amongst things like panthers, snakes, palms, ferns, and more mosquitoes than I care to imagine are these rare and endangered plants which have been made famous by court cases, books, and even a Hollywood movie.

If you haven't guessed it by now, I am talking about the ghost orchid (Dendrophylax lindenii). In what is one of Nicolas Cage's best onscreen roles (a close second to Raising Arizona), these orchids were made famous the world over. Based on the book "The Orchid Thief" by Susan Orlean, the movie takes a lot of creative licenses with the story of these orchids.

Ghosts orchids are epiphytes. In Flordia, upwards of 80% of them can be found growing on the bark of pop ash trees (Fraxinus caroliniana). Finding them can be tricky unless you know what to look for. Ghost orchids belong to a group of orchids that have forgone leaf production. No, they are not parasites like Corallorhiza. Instead, they photosynthesize through their long, ambling roots. Pores along their length allow for gas exchange. For most of the year all you will ever see of a ghost is a tangle of roots growing among the moss and lichen on the bark of a tree. 

When a ghost decides to flower, it is easy to see where all the hype comes from. Large white flowers shoot out from the center of the roots, each one with its own twisted pair of tendrils on the lip, which are said to resemble the ghostly outline of a frog jumping through the air. Each flower is also equipped with a long nectar spur. This along with the white coloration and the fact that each flower is most fragrant at night points to the identity of the ghost orchids sole pollinator, the giant sphinx moth. It has a long proboscis that is exactly the length of that nectar spur. No other organism has what it takes to pollinate a ghost. 

The presence of the ghost orchid in southern Florida has everything to do with water. Predominantly a species of the Caribbean, ghost orchids cannot handle frost. In the Everglades, ghosts grow in and around topographical features known as sloughs. Sloughs are ditches that are filled with water for most of the year. Because water has a high specific heat, the sloughs keep the surrounding area cool in the summer and warm in the winter. When Florida experiences hard frosts, these sloughs never get below freezing. This means that these regions are essentially tropical. All these factors combine to make southern Florida the most northerly spot you will ever see a ghost (and many other plant species) growing in the continental United States. 

Sadly, ghost orchids are not doing so hot in the wild. The habitat they rely upon is disappearing at an alarming rate. If you have been to Florida in the last 100 years you can certainly understand. Over half of the Everglades have been drained and developed since 1900 with plenty more of it degraded beyond any hope of repair. Invasive species run amok for the same reasons that the native plants do so well, crowding out some of Florida's most unique flora and fauna. 

To add insult to injury, poaching of ghost orchids is serious business. Despite its difficulty in cultivation and the fact that most wild ghosts quickly die in captivity, there are those out there that will still pay insane prices to have a ghost in their collection. Nursery produced specimens are becoming more common, so with time this should alleviate some of that pressure. Still, there is no end to the senseless greed of some orchid fanatics. 

There is hope on the horizon. Researchers are starting to unlock some of the secret to ghost orchid reproduction. Plants are now being grown from seed in specialized labs. In time, this new generation of ghost orchids will be planted back into southern Florida in hopes of increasing population sizes. 

Photo Credits: Big Cypress National Preserve

Further Reading:
http://bit.ly/24NiqT9

http://bit.ly/1XTqh38

http://bit.ly/21jegSg

http://bit.ly/1PZlKJu

One Orchid Two Colors

Bumblebees are no dummies. Far from being mindless drones whose sole purpose it to benefit the colony, these industrious insects are quite capable of learning and memory. They are constantly evaluating their foraging strategies and are quick to abandon a food source that doesn't deliver. For plants that rely on bumblebees, this presents a particular challenge. 

Of course, plants want to maximize their reproductive effort while at the same time minimizing their energy investments. For this reason, some plant species have foregone any sort of reward. Nectar is costly to produce after all. This non-rewarding strategy is particularly widespread among the orchids. Take for instance the case of the elder-flowered orchid (Dactylorhiza sambucina) of Europe. A species of meadows and alpine grasslands, it prefers calcarious conditions. What is most stunning about this species are its floral displays. 

Its inflorescence is made up of a dense cluster of flowers. Unlike what we are used to with most flowering plants, the flowers of the elder-flowered orchid come in two distinct color morphs - purple and yellow. They are so drastically different that one could be excused for thinking they were two different species. What's more, the different color morphs cooccur throughout the species' range. What could be causing this dimorphism? The answer lies in the flowers themselves. 

The edler-flowered orchid is one of those non-rewarding species. It has no nectar and its pollen is bunched up in sacs called pollinia that bees can't really harvest. The main pollinators of this species are bumblebees. As I have hinted, bumblebees are all about optimizing their foraging efforts. They quickly learn which plants are worth visiting and which plants are not. They do this via a highly tuned search image. Any plant that doesn't give them what they want will soon be shunned. 

This is where having different colored flowers comes in handy. Researchers have discovered that the color ratios of any given orchid population are under what is referred to as "negative frequency-dependent selection." Here's how it works: naive bumblebees that visit a non-rewarding flower of one color (purple in this example) are then much more likely to visit a flower of a different color (yellow). It just so happens that the plant with a different flower color (yellow) often turns out to be the same species of orchid. 

The result of this behavior is that in any given population, the plants with the rarer flower color (yellow) get visited more often. Because flower color is under genetic control, that particular morph (yellow) will gradually rise in frequency. Once it becomes the dominant flower color, the reverse happens and the first color (purple) is then visited more often. 

Over time this causes back and forth shifts in flower color that eventually settles on some sort of stable ratio of purple to yellow flowers. Thus anyone botanizing a high-elevation meadow in Europe can find purple and yellow flowered orchids in the same population. By tapping into the bees' natural foraging tendencies, this non-rewarding orchid species is able to maintain its presence in the landscape without having to invest valuable energy into floral rewards. 

Photo Credit: Emilio (http://bit.ly/22CHigV)

Further Reading:
http://www.pnas.org/content/98/11/6253.full.pdf

An Underground Orchid

Are you ready to have your mind blown away? What you are looking at here is not some strange kind of mushroom, though fungus is involved. What you are seeing is actually the inflorescence of a parasitic orchid from Australia that lives and blooms underground!

Meet Rhizanthella gardneri. This strange little orchid is endemic to Western Australia and it lives, blooms, and sets seed entirely underground. It is extremely rare, with only 6 known populations. Fewer than 50 mature plants are known to exist. This is another one of those tricky orchids that does not photosynthesize but, instead, parasitizes a fungus that is mycorrhizal with the broom honey myrtle (Melaleuca uncinata). To date, the orchid has only been found under that specific species of shrub. Because of its incredibly unique requirements, its limited range, and habitat destruction, R. gardneri is critically endangered.

The flowers open up a few centimeters under the soil. They are quite fragrant and it is believed that ants, termites, and beetles are the main pollinators. The resulting seeds take up to 6 months to mature and are quite fleshy. It is hypothesized that some sort of small marsupial eats them and consequently distributes them in its droppings. Either way, the chances of successful sexual reproduction for this species are quite low. Because of this, R. gardneri also reproduces asexually by budding off daughter plants.

Despite not photosynthesizing, this orchid is quite unique in that it still retains chloroplasts in its cells. They are a very stripped down form of chloroplast though, containing about half of the genes a normal chloroplast would. It is the smallest known chloroplast genome on the planet. This offers researchers a unique opportunity to look deeper into how these intracellular relationships function. The remaining chloroplast genes code for 4 essential plant proteins, meaning chloroplasts offer functions beyond just photosynthesis.

I am so amazed by this species. I'm having a hard time keeping my jaw off the ground. What an amazing world we live in. If you would like to see more pictures of R. gardneri, please make sure to check out the following website:
http://www.arkive.org/underground-orchid/rhizanthella-gardneri/

Photo Credit: Jean and Fred Hort

Further Reading:
http://www.sciencedaily.com/releases/2011/02/110208101337.htm

http://www.eurekalert.org/pub_releases/2011-02/uowa-wai020711.php

http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=20109

A Litter Trapping Orchid From Borneo

Epiphytes live a unique lifestyle that can be quite challenging. Sure, they have a relatively sturdy place on a limb or a trunk, however, blistering sun, intense heat, and plenty of wind can create hostile conditions for life. One of the hardest things to come by in the canopy is a steady source of nutrients. Whereas plants growing in the ground have soil, epiphytes must make do with whatever falls their way. Some plants have evolve a morphology that traps falling litter. There are seemingly endless litter trapping plants out there but today I want to highlight one in particular.

Meet Bulbophyllum beccarii. This beautiful orchid is endemic to lowland areas of Sarawak, Borneo. What is most interesting about this species is how it grows. Instead of forming a clump of pseudobulbs on a branch or trunk, this orchid grows upwards, wrapping around the trunk like a leafy green snake. At regular intervals it produces tiny egg-shapes pseudobulbs which give rise to rather large, cup-shaped leaves. These leaves are the secret to this orchids success.

The cup-like appearance of the leaves is indeed functional. Each one acts like, well, a cup. As leaves and other debris fall from the canopy above, the orchid is able to capture them. Over time, a community of fungi and microbes decompose the debris, turning it into a nutrient-rich humus. Instead of having to compete for soil nutrients like terrestrial species, this orchid makes its own soil buffet!

If that wasn't strange enough, the flowers of this species are another story entirely. Every so often when conditions are just right, the plant produces an inflorescence packed full of hundreds of tiny flowers. The flowers dangle down below the leaves and emit an odor that has been compared to that of rotting fish. Though certainly disdainful to our sensibilities, it is not us this plant is trying to attract. Carrion flies are the main pollinators of this orchid and the scent coupled with their carrion-like crimson color attracts them in swarms.

The flies are looking for food and a place to lay their eggs. This is all a ruse, of course. Instead, they end up visiting a flower with no rewards whatsoever. Regardless, some of these flies will end up picking up and dropping off pollinia, thus helping this orchid achieve pollination.

Epiphyte diversity is incredible and makes up a sizable chunk of overall biodiversity in tropical forests. The myriad ways that epiphytic plants have adapted to life in the canopy is staggering. Bulbophyllum beccarii is but one player in this fascinating niche.

Photo Credits:
Ch'ien C. Lee - http://www.wildborneo.com.my/

and

Peter AJ Chong - bit.ly/1XLgFE6

Further Reading:
http://www.orchidspecies.com/bulbbeccarrii.htm

Fall Leaves of the Putty-Root Orchid

Whereas most plants here in the Northern Hemisphere have largely geared down for the long winter, there is one species that has only recently begun a new stage of growth. Though it may seem damaging to produce leaves when a hard frost is just around the corner, that is exactly what this plant is doing. What's even more bizarre is that the plant in question is an orchid.

The putty-rood orchid (Aplectrum hyemale) may seem strange to most. Though it flowers during the same time as most of our terrestrial orchids (May through June), its display can be hard to track down. In fact, lacking any knowledge of a specific location, it is more likely that you will stumble across one before you pick it out of the hustle and bustle on the forest floor.

Flowering occurs at a different time than leaf out. The solitary flower stalk gives way to a single leaf starting in late summer or early fall. Why the heck would this plant start its photosynthetic lifecycle when everything else is about ready to go dormant? The answer is competition. Summer is not a bright season for those growing on the forest floor. This is especially true for a plant that only produces a single leaf.

What the putty-root is doing with its oddly timed leaf production is taking advantage of a dormant canopy. With trees and herbaceous leaves out of the way, the putty-root is able to soak up as much sun as it can get. This is a similar strategy adopted by spring ephemerals around the globe. But what does the plant have to gain from having leaves in the fall? Why not wait until spring to leaf out?

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As it turns out, it simply doesn't have to. The photosynthetic machinery within the leaves of the putty-root perform exceptionally well at low temperatures. Whereas most plants simply can't photosynthesize when it starts getting too cold, the putty-root is able to photosynthesize at temperatures as low as 2° C (35.6° F)! Not only does this enable the plant to get a jump start come spring, its also able to make food throughout most of fall and even early winter.

There does seem to be a limit to this. Once temperatures drop below 2° C, the machinery can't keep up and photosynthesis grinds to a halt. This is further complicated by the fact that the leaves are often buried under snow for months at a time. Certainly its mycorrhizal associations help feed the plant, even when it isn’t actively photosynthesizing. Regardless, this strategy is a great way of getting an extra kick while everything else is slowing down. Stories such as this bring to mind the story of the tortoise and the hare. Sometimes slow and steady really does win the race!

Photo Credit: Lance Merry (www.lancemerry.com)

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

Time

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There is something very special about old plants. They offer us a way of appreciating a timescale that we can never fully understand. I am especially fond of finding people who have had house plants in their family for generations. I grew up with a few that had already been around for decades before I was born. Here is a wonderful example of what I am talking about. This Acronia titan orchid has been blooming for years and has acquired a wonderful little moss patch in the crux of its leaf. Out of that moss grows a fern.

This photo comes to us courtesy of Kevin Holcomb. You can find him on instagram via @orchid_beard