Love life can get pretty rough for many animal species. From fierce female phalaropes and jacanas fighting over the most reliable males to raise their chicks, to male snakes and spiders jealously blocking their mates’ reproductive tracts with viscous substances or even their own mutilated penises, to greedy dragonflies and cuttlefish who wipe away any rival’s sperm previously stored by females during sex: the battle to leave offspring seems quite pervasive in the animal kingdom. But zoology is not exactly the main concern of this blog, so what about plants?
A plant’s sex life is very different to ours. First and foremost, the majority of plants are perpetually attached to the ground and incapable of engaging in vigorous fights for a mating partner. Indeed, they usually depend on mobile neighbours—whether wind, water, or any of a diverse array of animal pollinators—to carry their male reproductive cells around, so they can reach an egg cell, fuse with it into an embryo, and eventually give birth to a brand-new plant. But relying on a third-party visitor for reproduction brings along some uncertainties. For instance, pollinators might visit lots of flowers from many different plants in a short time and thus end up carrying some messy pollen mixes in their bodies. How could a plant make sure that its own pollen will be the one to get to the female parts of other flowers to become a father?
One could think that plants must settle for rather passive strategies to increase their chances of parenting, like producing more pollen or more flowers, or making them more attractive to pollinators—all of which demand quite a lot of energy. But far from it, a team of researchers from Brazil and South Africa recently documented an exciting mechanism of competitive pollen replacement for the first time among flowering plants, similar to sperm removal in animals.
Their study species was Hypenia macrantha, a South American distant cousin of mint, lavender and basil. When it is time to reproduce, this herb flaunts its beautiful tubular red flowers around the Brazilian Cerrado, luring several hummingbird species to aid in their pollination. But this plant’s intimate relations go far beyond the typical bird-pollination story. The elegant design of its apparently delicate flowers holds a secret to ensuring paternity: their anthers, the male pollen-carrying structures, are tightly packed inside a specialized petal lobe that gets triggered like a catapult upon the visit of a hummingbird, blasting the pollen with force onto the bird’s bill.
