By Athayde Tonhasca
In ancient Greece, nymphs were deities portrayed as gorgeous maidens who would hang around ponds, rivers and other outdoor spots. But their beauty was hazardous: just like those wicked mermaids, nymphs could lure a virtuous man who happened to be passing by, leading him to madness or perdition.
Nymphs may have been the product of overstimulated male fancy, but they also inspired the name of the water lily plant family, Nymphaeaceae. And just like the Greek nymphs, some water lilies do engage in devious charming, sometimes with fatal outcomes.
The white water lily or fragrant water lily (Nymphaea odorata) is an aquatic plant from shallow lakes, ponds, and slow moving waters throughout the Americas. It’s a popular nursery choice for ornamental ponds and water gardens around the world, but its floating leaves can form thick mats of vegetation, sometimes preventing light penetration and retarding water flow. So this plant is considered invasive in some places.
When a white water lily flower opens, its female parts are shaped like a bowl with the stigma (the part that’s receptive to pollen) at the bottom. This bowl is surrounded by a wall of stamens and filled with a viscous liquid full of sugars and detergent-like substances (surfactants). If this rigging has the look of a trap, that’s because it is one.
The fragrant flower – hence the epithet odorata – is irresistible to bees, flies and beetles. When a visitor lands, it falls into the bowl. It tries to pull itself out, but the palisade of flexible stamens hinders escape. As the insect struggles, pollen attached to its body is washed off by the liquid. The pollen drifts to the bottom of the bowl where it comes into contact with the receptive stigma, pollinating the flower. The insect may eventually crawl out, or it may drown: it makes no difference to the white water lily. It has got its pollen.
At the end of first day of blooming, the flower closes. When it opens again the next day, it spreads out more widely, no fluid is produced and the stigma is no longer receptive. The stamens release their pollen on the second or third day, and this asynchrony with the female parts prevents self-fertilization. Visiting insects are safe now, so they may fly away covered with pollen – perhaps to meet a watery end on another flower with a receptive stigma. On the fourth day, the flower is pulled underwater, where the seeds mature.
In South America, giant water lilies (Victoria spp.) take unlawful detention to another level. Their flowers attract and trap beetles until the following day, when they are allowed to leave loaded with pollen. Watch a time-lapse video of a giant water lily flower opening and closing over the course of two days. The flower opens during the receptive stigma phase, closes to entrap beetles, turns pink (pollen release phase), opens again to free its pollinators, then closes before sinking in the water.
By detaining insects for a while, plants increase the probability of fertilization. This type of relationship is known as entrapment pollination, and molecular studies suggest this is one of the oldest pollination systems. Nymphaeales (the order consisting of water lilies and other plants) and beetles have been playing this game for approximately 90 million years. It has worked nicely for both gaolers and gaoled.
Scottish pollinators 