Flower stamens that strike insects maximize pollination

Newswise — For centuries, scientists have observed that when a visiting insect’s tongue touches the nectar-producing parts of certain flowers, the pollen-containing stamen straightens. The new study proves that this action helps increase the reproductive success of the flower while reducing the costs of insects that linger too long and feed on the flower’s nectar, such as in a restaurant, where table turnover is crucial. to maximize profits.

“We tested three scenarios,” says lead author Deng-Fei Li, a doctoral student at the Institute of Evolution and Ecology, School of Life Sciences, Central China Normal University, Wuhan. , in China. “These included whether brittle stamens help flowers by controlling how much pollen each insect takes up, filtering out less competent pollinators, or reducing the amount of nectar taken by each visitor.”

Li and his colleagues immobilized the stamen of barberry flowers by soaking the floral pedicel in an alcohol bath for 35 to 45 minutes. They confirmed that alcohol treatment, or the lingering smell of alcohol, did not deter pollinators. They then compared insect behavior and pollination success of flowers with mobile or immobilized stamens under glass containers in the laboratory and directly outdoors. They also stained flower pollen to track how efficiently the insects carried it to other nearby flowers.

Their work showed that insects visiting flowers with immobilized stamens stayed 3.6 times longer and took more nectar than those visiting flowers with mobile stamens. However, insects deposit half as many pollen grains per floral visit as insects visiting flowers with mobile stamens. Additionally, the team found that insect visitors deposited motile flower pollen on about 3 times as many flowers and on flowers farther apart, increasing the plant’s likelihood of reproductive success.

The team found no evidence that the snapping stamens helped exclude less helpful pollinators. The five species of bees and flies that were tested visiting flowers stayed about four times longer on flowers with immobile stamens.

“Our study helps solve the mystery of the purpose of insect-triggered movement of flower parts that has puzzled botanists since Linnaeus first observed movable stamens in 1755,” says lead author Shuang-Quan Huang. , professor at the Institute of Evolution and Ecology of School of Life Sciences, Central China Normal University. “We have shown that plants use fast-moving stamens to enhance the turnover of bees and flies on their flowers, thereby reducing their nectar costs per pollen grain successfully transported.”

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