College of LAS « Illinois

Plant Biology

Shedding Light on Insect Damage

Photo of Evan H. DeLucia

As if the sight of insects making a meal out of your garden leaves weren't distressing enough, a new photographic tool developed in LAS shows that the damage extends far beyond the insects' bite.

Photographs taken with a photosynthesis-measuring device developed by a team of LAS plant biologists, entomologists, and biochemists indicate that the damage by hungry insects isn't confined to the hole where tissue once was. In laboratory studies of wild parsnip leaves that had been munched on by hungry cabbage loopers, three to six times more of the leaf's surface was affected.

The images the researchers gathered clearly recorded blue halos, representing damage to patches of cells surrounding the insect-caused holes, and varying levels of red fluorescence, denoting precise reductions in photosynthesis activity. They also found an almost 80-fold increase in the synthesis of furanocoumarins, a defensive chemical, suggesting that a plant may purposely turn down its photosynthetic machinery to boost its defensive capacity.

"We don't know how our results will hold up in a real ecosystem, but this study does suggest that we are greatly underestimating the impact of herbivores on plants," says Evan H. DeLucia, an LAS professor of plant biology and the project's leader. In a normal year, losses in agricultural and forest systems to dining insects range from 2 percent to 24 percent. The loss in plant photosynthesis, however, could be much greater and have potential management implications if carbon dioxide levels increase as projected under global warming scenarios.

The device consists of a high-speed camera linked to specially designed parallel processing computers. A momentary flash of bright light hits a leaf's surface, and the computers instantaneously collect data, providing high-resolution images.

Photo by Bill Wiegand