Flexible flower fertility

by David Sugarman

Imagine this. You're a flower. Stuck in one spot, not able to move much, but you're able to fertilize yourself. Sounds OK — you don't have to look for a mate (and many, many organisms go through a lot just to find a partner and reproduce).

The catch is that self-fertilization can produce weaker offspring - you don't get the healthy mixing of genes that sex provides. But if you've got the right parts to self-fertilize, how do you prevent it?

Well, some members of the ginger family have a nifty strategy to ensure they don't self-fertilize. Members of the genus Alpinia manage to have the male and female flower parts available at different times of the day. Each plant produces about 10 flowers that last for only a day.

Scientists from China and the U.S. have found that in the nine rainforest species of Alpinia they investigated, the flowers prevent self-fertilization by actually moving the female part — the stigma — away from the pollen-producing anther.

Each species has two varieties of flower; in one, the stigma elongates and moves above the anther, and in the other type, the stigma moves below, and away from the anther. The timing of pollen release is perfectly coordinated to ensure that the different flower types pollinate each other. No pollen is released until after the stigmas have moved out of the way. The pollen of one flower type is released when the stigma of the other flower type is in a position to receive it.

So not only is self-pollination prevented, but so is pollination among flowers of the same type.

There's always something surprising going on in the quiet of the forest.