a sticky end

Some flowers will go to extreme lengths to become pollinated, says MARTYN ROBINSON

Summer is the season to see waterlilies and lotuses. They’re gorgeous plants but they do employ some rather underhanded tricks to get themselves pollinated. On a waterlily’s first day of flowering, the receptive female stigmas in the centre are surrounded by a ‘fence’ of as-yet-immature male anthers on the end of stalks called stamens. The pollinating insect finds this centre hard to escape as the stamens bend inward, making the insect fall back in. The centre is full of a clear liquid with properties a bit like detergent so the insect sinks to the bottom and any pollen on it does as well, pollinating the flower.

While some insects manage to climb out, many of them drown. At the end of the day, the flower closes on the drowned or trapped pollinators, and when it opens the next day its pollen is ready for insects to carry to other flowers. By now, the anthers have folded over the lethal centre parts so it is safe for insects to visit and then fly off to pollinate another flower where, sadly, they might meet a less-than-pretty death.

Lotuses also imprison some of their pollinators. On the first day, the blooms partially open and scent is released. The stigmas are sticky and ready to receive pollen but the anthers are as yet inactive. Insects, especially flower-feeding beetles, climb into the flowers to feed but can’t easily get out.

When night falls, the flower closes and traps them inside. It then raises its temperature so the insects continue to climb all over the inside of the flower – if their body temperature drops too low they will just sleep. Meanwhile, any pollen from other lotuses they’ve visited sticks to the stigmas. The next day, the flower produces pollen and opens completely so the insects can feed and fly off, hopefully to get trapped in another newly opened lotus.