'Love' enables plants to defend themselves better

Why do some plants defend themselves from insect attacks better than others? New evidence suggests that the difference might be because they're - or are not - getting any plant love.

North Carolina State University (NCSU) and Duke University scientists discovered that sexually produced evening primrose plants withstand attacks from caterpillars better than plant kin that reproduce by themselves.

The findings are important steps to learning more about how plants have evolved defences against insect herbivores, said Marc Johnson lead study co-author.

"The variation in sexual reproduction has a large impact on the ability of plants to evolve defences against herbivores," Johnson said.

Researchers performed both lab and field experiments on evening primrose, a plant family with 259 different species, 85 percent of which reproduce sexually while the rest reproduce asexually, to gauge the effects of plant sex on defence mechanisms.

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

The results were a bit different for so-called "specialist" plant-eaters, however. Those insects that prefer just one kind of food were more apt to munch on sexually reproduced species of plant.

This most likely occurs, Johnson said, because specialised plant-eaters evolve alongside their hosts and have found ways to co-opt plant defences.

Instead of being deterred by certain chemical compounds produced as defences by the plant, the specialized plant-eaters are attracted to them. Johnson said the nuanced results make sense, said an NCSU release.

"Sex shuffles up genes and allows individual plants to get rid of bad genes and keep good ones," he said. "That helps them evolve defences against generalist herbivores. "In the end, asexual reproduction appears to be an evolutionary dead-end."

These findings were published in Proceedings of the National Academy of Sciences,

Last updated on Jul 14^th, 2009 at 15:49 pm IST--IANS