July 15, 2009

Sex found involved in plant defense

U.S. biologists say they've determined some sexually produced plants better withstand insect attacks than do asexually produced plants.

North Carolina State University and Duke University researchers said the finding is an important step toward learning more about how plants have evolved defenses against insect herbivores.

In the study, the researchers performed laboratory and field experiments on evening primrose (Onagraceae), a plant family that has 259 different species -- 85 percent of which reproduce sexually with the remainder reproducing asexually -- to gauge the effects of plant sex on defense mechanisms.

The researchers found so-called generalist herbivores -- those that eat a variety of plants -- preferred to feed on the asexual species and lived longer while doing so.

However, the scientists found so-called specialist plant eaters that prefer just one kind of food were more apt to eat sexually reproduced species of plant.

North Carolina Assistant Professor Marc Johnson, the study's lead author, said that most likely occurs because specialized plant-eaters evolve alongside their hosts and have found ways to co-opt plant defenses. Instead of being deterred by certain chemical compounds produced as defenses by the plant, the specialized plant-eaters are attracted to them.

The study is detailed in the Proceedings of the National Academy of Sciences.