Sepals and Petals and Lips Oh My!

All orchids have 3 sepals and 3 petals, with one petal modified to form the "lip" or labellum. The ancestral condition (the flower structure of the last shared common ancestor of all orchids) likely had 3 identical sepals, forming an outer whorl which encases the flower during bud growth, and 3 identical petals, forming an inner whorl only revealed when the sepals open or are cut away. You can see this simple structure in the iris family Iridaceae, which is a close relative of the orchid family Orchidaceae. Though irises have their own complicated elaborations, they retain the 3 identical sepals (apparently called "falls" in horticulture) and 3 identical petals (called "standards"). In what was probably a key event in evolution of orchids, one the three petals was drastically modified and became the labellum.

The special structure of the lip is nearly impossible to ignore if you look at most orchid flowers, or read even the briefest article on orchid flowers. In many orchids, the other two petals are nearly identical to each other, as are the three sepals (to each other). But some orchids have a dramatically altered one of the sepals as well. Look at the Scaphosepalum flower below and try to figure out what parts you are looking at (yeah, yeah, most people just gasp and say "beautiful!" or "weird!" or "phallic!", but c'mon lets dig beneath the skin, plumb the depths of nature, and generally get all geeky).

Even if you are familiar with a lot of orchid flowers, you will probably have trouble telling what is what, and if you guess you will probably be wrong. This is one weird flower. The first confusing thing is that it is non-resupinate (the flower is not twisted around, so its lip is at the top, not the bottom as usual). The second really confusing thing is that the "dorsal" sepal (bottom sepal in this flower) is barely even recognizable - it is the purple projection sticking out like... well ya know. I thought at first that this was the lip, but in fact the lip is tiny and buried in the middle of the flower and is barely visible here. The two other sepals end in those yellow spikes, which look to me like the glorious waxed moustache of a vain blond Victorian gentleman. They also include a fused base that is sheet-like and spotted and forms the entire back of the flower from this view. Except for being long and narrow, the two types of sepals look almost nothing alike. By the way, the understated petals are the two small tan-gold flanges near the base of the modified sepal.

This genus of orchids has TWO totally different lips (yes, that is wrong term to use) - one of the three petals and one of the three sepals. Asymmetry of this sort is quite difficult to evolve, as molecular genetic studies show - it requires additional genes whose expression breaks the usual radially symmetric pattern of flowers. 

By the way, I am not aware of any information on why Scaphosepalum flowers look like this - some of them are even more exaggerated than this one (for example Scaphosepalum gibberosum and Scaphosepalum swertiifolium). Surely not to induce Victorian ladies swoon at the glorious moustache. Scaphosepalum are reported to be pollinated by small flies of some sort but really, what about this looks like it is meant to attract flies? It doesn't look (or smell) like a fruit (fruit flies), or a fungus (fungus gnats), or dung (dung flies), or rotting meat (corpse flies). A fly that admires abstract sculptures? That must be it.

Supine, Resupine, and Reresupine

One of the many lines of evidence supporting the ancient origin of life and its evolution by modification and natural selection is the pervasiveness of workaround solutions in biology. For examples: land vertebrates breath and swallow using the same tube (the 3,000 US citizens who die each year from choking on food unanimously agree with me that this is a terrible design); the blood supply and connective tissue in the vertebrate retina is in front of the light detecting cells; wisdom teeth; the panda's thumb; and a zillion less familiar examples.

Orchids also provide examples, perhaps the best of which is the twisting of flowers during bud development to situate the lip of the flower either above or (more commonly) below the rest of the flower. The lip is a highly modified petal that ancestrally was in the dorsal position (at the "top" of the flower). A great deal of the diversity of orchid pollination depends on elaborations of the amazing lip structure, but that is another story. Some orchids position their lip at the top of the flower (e.g. Prosthechea cochleata, below), but most position their lip at the bottom of the flower to act as a gravity-assisted landing pad for their pollinators. 

Prosthechea cochleata, from Wikimedia Commons

This "lip at the bottom" form is called resupinate (meaning literally: again brought to lie on the back with face up). If you look closely at the stem holding your favorite orchid flower you may be able to make out how this happens: the lip starts out dorsally (when the bud has just begun to form) and the flower stem twists around 180° before opening. Many orchid flower stems have ridges that make this apparent in the mature flower, obvious in the flower facing left in the photo below. The twist is usually most obvious near the base of the stem so you may have trim away the bract covering the stem base to see the twist. (Unfortunately the common Phalaenopsis that I have inspected have nearly perfectly cylindrical flower stems so the twist is very hard to see.) This is The Exorcist head-twisting approach to lip positioning.

Anacamptis picta var. alba from wildnaturespain.blogspot

Okay, so far this is fairly strange - the lip forms on the top of the flower and then the flower twists around to get the lip on the bottom where it has to be to facilitate pollination. But here is the kicker: some orchid flowers (e.g. Angraecum superbum, also called A. eburneum) that are non-resupinate (lip at the top) start with the lip at the top, then twist it around 360° as the flower grows! Let me restate this bizarre fact: the lip starts where it should be, then twists around to where it shouldn't be, then keeps right on twisting around until it is back exactly where it started. How did this happen? Nobody is sure, but most likely these species have ancestors that are resupinate (lip at the bottom) but something changed that made it advantageous for the lip to be at the top. There are two ways to adapt to this change: eliminate the twist altogether, or continue the twist for twice as far. Apparently the second possibility is what actually happened, at least in some cases - what Steven Jay Gould called contingency or historical contingency. Charles Darwin noted the 360° twist in Angraecum superbum and used it as an argument for evolution (not natural selection necessarily, but an historical process evident in current life).

It would be interesting to find a study of what fraction of non-resupinate flowers have no twist vs. the double twist. Anybody known of cases? I have not heard of a flower that is resupinate with a 1.5 twist (540°) - it would presumably have evolved from an ancestor that had 1 twist, which had an ancestor with 0.5 twists, which had an ancestor with no twists. Vizzini of The Princess Bride would have loved that one if he had survived the poison duel.

Orchids from Seed and Symbiotic Fungi

Orchid seeds are tiny and have no stockpiled nutrients to help them start growing. This condition is probably an adaptation to allow production of huge numbers of seeds at low cost, and for allowing them be spread easily by wind. (In case you never noticed, avocados go to the other extreme, much to the consternation of epicures.) The vast majority of seeds end up in an inhospitable place and never germinate - this is true for many plants but it is probably more extreme for orchids. Even when an orchid seed lands in a prime spot, for example lodged in a crevice in damp bark with the right sun exposure and at the right altitude, its trials are not over. There the seed needs to encounter a symbiotic fungus that will provide sugar to get growth started (later the orchid will reciprocate but as far as I have read this street starts off one-way). The seeds need various other nutrients just like all plants, but it is mostly sugar that is provided by the fungus (or other small organic molecules in some cases) - sufficient minerals leach into the rainwater after it falls. The seeds do not carry the fungus with them - perhaps the fungi are widespread enough to make it unnecessary or perhaps it is hard to evolve a fungus-carrying seed. Once the tiny orchid plant starts photosynthesis it can fix carbon from the air, but it can't get to that point on its own.

In the early days of orchid horticulture, before all this was known, attempts to grow orchid seeds were miserable failures. The seeds just sat there or grew mold, quietly mocking the botanists and Victorian millionaires. For a few orchids, it was noticed that seed would sprout if it was just next to the parent plant, which provided an early tip that something else was necessary - something associated with the parent plant. In 1909, Bernard discovered that germinating orchid seeds depend on a mycorhizal fungus (more abundant near the parent plant), but this discovery did little to improve the practical problem for horticulturists. Finally, in 1922 Knudson showed that many orchid seeds would germinate on a defined medium containing nothing but a few salts and sugar. The orchids don't need the fungus - they only need the sugar the fungus provides! This was the breakthrough for humans trying to raise orchids from seed, though precise definition of the optimal salts and organic compounds for different types of orchids is still being worked out.

Since Knudson, orchid seed is grown aseptically with only appropriate salts and sugars (and light and air) provided, typically with agar to provide a gel base. The method is common enough that you can find many how-to guides for the process and you can even buy prepared commercial agar medium to get started. The process is still a bit involved because bacteria and (bad) fungi also love this medium and will kill the slow-growing orchid embryo, so you have get rid of the bad guys. With care though, apparently you can do this in your kitchen with only a pressure cooker for sterilizing media and minimal laboratory equipment such as glass flasks.

Development from seed to adult flowering plant is still agonizingly slow, but at least it is routine. As you know if you grow orchids yourself, pretty much everything about orchids happens in slow motion. Some orchids take 10 years to go from seed to flowering plant, about the same as small trees. Some grow one new leaf per year. No bean or basil or avocado seedlings in the orchid world! Nearly all orchids are highly adapted to very low nutrient conditions, so only slow growth works. Even most terrestrial orchids occur in low nutrient environments and follow the same rule. Some types of orchids make impressively rapid growth at the start of their wet season (e.g. Catasetum and relatives), but this is deceptive - they are converting nutrients from their fat pseudobulbs from the previous year, painstakingly acquired over the growing season. Their averaged growth rate is much less impressive. I suspect this slow growth is part of the magic of orchids - how can a plant that hardly seems to do anything at all from week to week produce these amazing flowers!? That will be another post - there is an answer.

As ye sow, so shall ye reap. But be sure to add sugar.

Dendrophylax lindenii - Orchid of the Month, May 2017

Dendrophylax lindenii by Mick Fournier,
Pompano Beach, Florida

Here is an orchid that has it all - strangeness, rarity, fragrance, and a drop-dead gorgeous flower. Dendrophylax lindenii, the Ghost Orchid, is a leafless orchid that grows epiphytically on the trunks of trees in swampy lowland forests in south Florida and some Caribbean islands. The entire genus Dendrophylax is leafless and they perform photosynthesis with their roots, as do a number of related genera from Africa and Madagascar. The roots are flattened and grow uncovered and plastered against tree bark; in their natural condition they look a lot like a Phalaenopsis with most of the stem and all the leaves torn off (in fact, some Phalaenopsis species are nearly leafless). The loss of leaves in these orchids is probably an adaptation to a seasonally dry climate.

Many Dendrophylax species have lovely flowers, but those of D. lindenii are especially large, graceful, and unusual in form. They have a long curved flower spur and are said to be pollinated by the long-proboscised (long-tongued? long-proboscis owning? well-proboscis-endowed?) sphinx moth Cocytius antaeus, which is seeking the nectar hidden away at the end of the spur [note - I have not yet been able to track this claim to a primary source]. This coadaptation is reminiscent of Angraecum sesquipedale from Madagascar, which was famously predicted by Charles Darwin to be pollinated by a moth with a very long proboscis, because its flower is white, nocturnally fragrant, and has a very long nectar-bearing spur. Unlike D. lindenii though, A. sesquipedale is endowed with abundant dark green leaves.

A few commonly cultivated orchids appear to be leafless when in flower because they are deciduous and flower in their leafless phase (some Lycaste, Mormodes, Clowesia, and Dendrobium species). These plants are remarkable looking when in bloom - a few half-dead looking pseudobulbs mysteriously shooting out a plethora of flowers.

Mormodes paraensis, photo by QT Luong

Dendrophylax lindenii is endangered and should never be collected from the wild. They are also notoriously difficult to grow in culture and you should not acquire one unless you are well informed and committed to its care and you know the plant was raised from seed in captivity. If you want to grow a leafless orchid, choose one that is more easily grown, such as a Chiloschista species.

Unlike most orchid species, there is a good Wikipedia article on Dendrophylax lindenii, which provides some additional technical information but lacks the wit, grace, and brilliant insight (meandering hodgepodgieness) of my blog posts.

Orchidarium 3

The new intermediate orchidarium continues to come together slowly. Below is a photo of the current state. The grapewood burls have been fastened together and put in their permanent location and a few additional plants added. Gradually I will be mounting plants directly on the grapewood and hanging others from it, with pots sitting on the tray at the bottom. The purpose is to have something that looks reasonably natural but with some of the plants easily removable for display and photography. I plan to be cautious mounting directly on the grapewood because it will be harder to reverse and I want to be sure they have the right light exposure. Grapewood is reputed to be very rot resistant, but of course eventually the whole thing will have to be replaced, which will be a big pain in the neck.

Currently in the case are:

Amesiella monticola
Bulbophyllum pecten-veneris var. tingabarinum
Dendrobium laevifolium
Dracula lotax
Haraella retrocalla
Macodes petola 
Masdevalia rolfeana
Masdevalia sernae
Mediocalcar decoratum 
Restrepia brachypus
Restrepia elegans
Scaphosepalum brevi
Specklinia grobyi
Specklinia picta (possibly misidentified)
plus three species of minute epiphytic ferns

Plants I plan to add include:
Diodonopsis erinacea 
Lepanthes calodictyon 
Masdevallia hirtzii (a showy one!)
Stelis pilosa
Tristella hojieri 

[It won't surprise me if some of the plants were misidentified by the retailers as this seems to be a common problem, but the foliage for all but one of them looks right and the three that have bloomed so far appear correct. The Specklinia picta is confusing - the flower looks exactly right but the leaves are narrowly linear, which I can't find reported anywhere.]

All have been chosen to be small to very small, and tolerant of intermediate temperatures and modest light exposure. I have also avoided anything reputed to be really hard to grow, or at least I think I have. Most are not particularly "showy" because for this Wardian case I am more focused on diversity and peculiarity than beauty (by most human standards). I have lots of other orchids on windowsills that have big bright flowers, so I get my fill of showy stuff. Despite my mediocre photo postings thus far, I have good camera equipment and reasonable skills and I will post macro shots of plants and flowers as things come along. In the meantime get your fill of gorgeous photos of gorgeous flowers at the blogs "Orchids in Bloom" and "OrchidKarma".

Orchidarium 6/3/2017

Throwing Spears and Snapping Lips

Plants wave in the breeze, bend toward light, and gradually furl and unfurl their parts, though Usain Bolt doesn't spend his time worrying about competition from plants. But at least two groups of orchids have evolved fairly speedy movements, at least by plant standards (admittedly not that high). Both occur in flowers and both involve manipulating pollinators.

Male Catasetum genus flowers fire their sticky pollinia when a trigger hair is disturbed. The motion is so fast it is hard to see in real time (move over Usain!). Under natural conditions the flower hopes they stick to the male euglossine bee that was investigating the flower, and that the bee will later visit a female flower and complete their rather tenuous copulation. If you use a well-positioned toothpick to activate the trigger, the pollinia will shoot halfway across the room. Catasetum, by the way, is one of the few orchid groups that have separate male and female flowers, usually found on separate plants. Most orchids are bisexual (also called perfect), with both pollen and ovary carried on the same flower, though they usually don't self-fertilize. Like birds of paradise, it is the male flowers that are showy - the female flowers are typically smaller and green and look a bit like a Little Green Riding Hood. 

Porroglossum genus flowers are slower, but their plan is similar - attach sticky pollinia to a pollinating fly. The entire lip of a Porroglossum flower is hinged and when sufficiently disturbed it snaps up against the column, trapping the fly in place for pollen transfer either onto or off of the fly. Okay, "snaps" is a bit strong - we are not talking great white shark or chameleon tongue here. How about "closes up against the column". It typically takes several seconds, but apparently it is enough to trap a fly (move over Mr. Miyagi!). I am speculating now, but maybe if it moved faster it would scare the fly into flight. In any case, the lip opens again after several minutes, releasing the insect. The hapless fly presumably suffers briefly with post-traumatic stress syndrome, but eventually recovers enough to deliver its precious pay load to another snapping flower. And right back into psychotherapy for our doubly duped Dipteran.

You can find videos of both of these actions if you poke around on the web. I have a Porroglossum plant and will make a video when it flowers and post it on this blog!

Water Culture for Phalaenopsis

[ In case you don't read the whole post - I ended this experiment after 5 weeks when all the roots on one of the plants rotted. And I mean ALL, see photo at the end. The other two plants weren't quite as bad, but they appeared to be heading the same way, so I stopped the experiment with all of them. As several others have found with their experiments (which I knew about and ignored), do NOT USE water culture, or use at your own risk! Despite my elaborate rationale, which I have left intact below, clearly this is not a good plan, or at least not the way I did it. Yes, Phalaenopsis are not aquatic. I should add that this experiment does not rule out the possibility that new roots would be better adapted for growth in water, but I elected to save my plants. ]

Photo from http://www.phals.net/honghenensis/honghenensis-in-situ 

I have had three Phalaenopsis hybrids for many years, and they have done fine in the usual mixed bark planting medium, but I recently decided to try them in water culture. I will report on how the plants do over time. I don't know how generally pure water culture will work for orchids - probably not well for most. Growing in inert media such as sponge rock, expanded clay, or charcoal seems to work fine for a wide range of epiphytic orchids, but the water/air/root dynamic under those conditions is much more like traditional media.

I got started with the idea of water culture due to one Phalaenopsis hybrid in my work office, where humidity is very low. I was growing it cased in a sealed pot sitting in a shallow bowl of water, hoping to keep local humidity up a bit, and as it grew aerial roots I started tucking their ends into the water hoping to keep it happy. The roots clearly loved being in the water - they grew fast and they looked fat and sassy and they were bright green. The plant thrived. Yes, it is a grocery store hybrid Phalaenopsis (i.e. only my friend Theresa is capable of killing it) and most of the plant is still in bark medium in a pot, but the idea germinated of tossing the pot and growing in a bowl of water.
Look at the roots in the in situ photo, photographed in situ in mountains in Burma growing low on the trunk of a tree (the roots are the silvery green ribbons plastered all over the bark). This species of Phalaenopsis has very few leaves and apparently does much of its photosynthesis with its roots. Most Phalaenopsis species have more leaves but they all have light-exposed greenish roots, and a few species are leafless or seasonally leafless. Their roots provide most or all of the photosynthesis. Growing Phalaenopsis mounted directly on tree bark is most natural, but it isn't convenient unless you happen to live in the right place or have a greenhouse and are willing to wet them every day.


Back at home with my test plants: the containers I am using for my full water culture trial are glass bowls that are approximately spherical with a slice off the top of the sphere. This sort of vase is relatively easy to find on-line - a search at [a certain large retailer named for a South American river] for "glass bowl vase" finds them readily. The idea is that the narrow mouth will support the plant and keep the humidity inside the container high and the clear sides will allow the roots to green up and become photosynthetic, which is the natural condition of Phalaenopsis plants in the wild. The broad leaves of the plant rest on top of the vase and the entire plant body and most of the roots are not immersed. The roots would never naturally grow under water, but keeping the water very shallow will hopefully keep them well aerated. The base of the plant stem is at least 5 cm from the water and it is dry. The root core presumably transports water up the leaves but the root velamen is dry to the touch above the water line. I will be surprised if I have a problem with stem rot as others have reported for their tests. The setup I am using would be harder to arrange for plants with different shapes, but for Phalaenopsis in the right sized bowl they just sit that way naturally.

Phalaenopsis unknown hybrid day 1 (5/11/2017)

I am using a rather small amount of deionized water in the bowl (about 2 cm deep) with a bit of complete fertilizer added (the kind designed for pure water - it has calcium and magnesium and all the trace elements in addition to all the usual stuff. Don't you just love that plants require molybdenum? What!?). Tap water is probably fine too as long as it doesn't have a lot of dissolved minerals. I dump the water out for a day or two once a week, as various sources on the web suggest - the idea is to inhibit too much bacterial and fungal growth and to mimic occasional dryness in nature.

The photo above is one of my plants, for which I am keeping a photographic record. This plant just came out of bark medium and you can see that most of the roots are bone white, with only a few green bits - the parts that were aerial when potted. Two weeks later, as I write this post, the roots are already getting a pale green blush - I will update or make a new post when the difference is more obvious. So far no roots have died.

As a side note, it is interesting that the natural plant (above) is growing "sideways" - from pictures and comments I have found on the web, this is usual for Phalaenopsis, and quite often they grow slanting downward or even completely upside down (how the seeds stick and germinate on the bottom of a branch I don't know). This explains why culture guides warn that you risk rot if you wet the growing crown of Phalaenopsis, yet natural rain doesn't present a problem. They don't grow right side up! Um well, we don't grow them right side up.

And ... experiment over because here are the roots after 5 weeks (I cut them off as they rotted one by one, but I stuck with it to the bitter end). You can't see the plant leaves above, but this is the same plant - I just moved it temporarily to rescue spaghnum moss and my experience is that it will recover without much trouble because it is a Phalaenopsis hybrid and they are tanks. If you look closely you can see one new root tip, which started while still in water culture.

Same plant on 6/17/2017