Do flowering plants have sexes?

Most flowering plants have what are known as “perfect flowers” – each flower contains both male and female parts.

That means a pollinator – an insect, bird, or moth – can easily pick up and deposit pollen in the same visit.

Meanwhile, some plants don’t rely on animal pollinators. Many desert plants use the wind instead. They often have separate male and female flowers, which means they may end up pollinating themselves – and not getting the genetic benefits of mating with other plants.

But there’s a desert shrub that’s solved this problem in a remarkable way. Within a population of the shrub, known as Zuckia brandegei, half the plants open with male flowers first, and half open with female flowers first. Then a few weeks later, they switch. Male and female flowers shrivel up, and a new flower of the opposite sex emerges.

Because of this unusual adaptation, these wind-pollinated shrubs are able to reliably “outcross,” or mate with other flowers. But these aren’t the only plants that produce male and female flowers at separate times. People have been speculating as to why plants might do that have since Charles Darwin. Among other plants, some maples, walnuts, and filberts have similar sexual adaptations.

May 1, 2008

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