A Common Plant With An Odd Pollination Mechanism

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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 Smallest and Rarest Water Lily

Nymphaea thermarum is both the smallest and the rarest water lily in the world. It is so rare that it no longer exists in the wild. Back in 1987 it was discovered growing in the mud of a hot spring located in Rwanda, Africa. The botanist who discovered it, Eberhard Fischer, realized that it was quite rare and collected a few specimens to bring back to Germany. Indeed it has never been found growing anywhere else. This was a wise decision on his part because after decades of habitat degradation, the hot spring was destroyed by locals in order to divert water for laundry. 

For years, the original specimens were not doing so hot in captivity. It was looking like this species was going to be lost forever. That was until a handful of seedlings ended up in the hands of plant germination specialist Carlos Magdalena of the Royal Botanical Gardens at Kew. Carlos saw a challenge in this species and realized that his efforts could possibly be the last chance this species had at survival. 

Carlos tried many avenues of approach to growing this species and none seemed to be working. He messed with water chemistry, nutrients, and water depth, all the while the plants seemed to languish, never reaching maturity. In a final attempt to make things work, Carlos returned to the original literature. Here he found something interesting. Apparently, N. thermarum was not growing in water at all. Instead, it seemed to only grow in the wet mud surrounding the hot spring. 

This was the key that unlocked the door to propagating this species. Instead of growing this water lily submerged like every other water lily species, Carlos decided to grow the plants as they once grew in the wild, in mud. This was it! Carlos successfully grew 8 new plants to maturity. This may seem like a small amount but for the last remaining members of a species, every little bit counts. Recently in 2009, the first of Carlos's plants flowered. This marked a milestone for this species. While it has been wiped out in the wild, this species can still persist in cultivation until experts can decide on what the best course of action is for its future. 

Further Reading:
http://www.kew.org/science-conservation/plants-fungi/nymphaea-thermarum