
Source: Oxford Scientific, Sexual Encounters of a Floral Kind
Floral Arrangements (Audio Description) (Video)
NARRATOR: In most cases, to reproduce, a plant needs to be fertilized by another plant of the same species. But, plants are literally rooted to the ground, so they must rely on other organisms or forces to spread their pollen.
Flowers help this along. Flowers are attractive not just to humans, but to other organisms. Their color, shape and scent have evolved to attract pollinating go-betweens. Although many plants rely on the wind to disperse their pollen, others rely on insects...or birds...or even mammals.
In Australia, the coral gum tree is fertilized by the acrobatic honey possum. With its agile body, the honey possum eats the tree's nectar. It uses its long snout and tongue to reach beyond the stamen, unwittingly collecting pollen on its fur and spreading it from one bloom to the next.
Not all pollination strategies benefit the go-between. Bush fires in Western Australia make way for the hammer orchid, which looks and smells very much like the female thynnid wasp. Female thynnids don't have wings. They eat beetle larvae and spend most of their lives underground. They only surface to mate, perching atop plants and releasing a pheromone to attract a mate.
But it's all in the timing. Several weeks before the female wasps emerge from underground, the hammer orchids bloom. Hammer orchids have evolved to mimic the appearance and scent of the female thynnid wasp. They rely solely on the male wasps for pollination (wasp buzzing).
It is to their advantage to bloom before the female wasps emerge, lessening the competition for male wasps. When the male attempts to carry off his mate, the hammer motion ensures that the bundles of pollen are transferred from the orchid to the wasp's back.
The next orchid he mistakes for a female wasp receives the pollen from the first. This time the hammer motion deposits the pollen onto the stigma and the second plant is fertilized.
Loading Standards
Teachers' Domain is proud to be a Pathways portal to the National Science Digital Library.