Plants That Pretend to Be Sick

The similarity of the variegation patterns with the criss-cross munching traces of moth larvae, led to the idea that maybe the plants may deter the mining moth from laying its eggs. To test the idea, the researchers used white correction fluid to mimic the appearance of variegation on hundreds of healthy leaves. (a) Plain green leaf. (b) Mining moth damage. (c) Variegated leaf. (d) Leaf painted with correction fluid.

The plant feigns sickness to stop it being attacked by insect pests known as mining moths (these are a group, rather than a type of moth), which would otherwise eat its healthy leaves.

It is the first known example of a plant that mimics being ill, but could also explain a common pattern seen on plant leaves known as variegation.

The discovery is published in the journal Evolutionary Ecology.

Variegation is familiar to gardeners and affects many species of plant. Variegated plants have different colored patterns on the leaf surface, produced by a variety of causes. One of the most common is when cells in the leaf lose chlorophyll and their ability to photosynthesize, appearing white.

In theory, plants with variegated leaves should be at a disadvantage, because of this restricted ability to photosynthesize. But, a chance discovery by a team of botanists suggests this may not be true after all. Instead, some variegated plants may be mimicking illness to avoid being eaten, putting themselves at an advantage. The similarity of the variegation patterns with the criss-cross munching traces of the larvae, led to the idea that maybe the plants may deter the mining moth from laying its eggs, said the researchers. To test the idea, the researchers used white correction fluid to mimic the appearance of variegation on hundreds of healthy leaves.

After three months, they then counted the number of leaves affected by the mining moth caterpillars, comparing green leaves, variegated leaves and those painted white to appear variegated.

The results were the same, say the researchers. Visibly variegated leaves were significantly less damaged. They believe that the plant essentially fakes being ill, producing variegated leaves that mimic those that have already been damaged by mining moth larvae. That deters the moths from laying any further larvae on the leaves, as the insects assume the previous caterpillars have already eaten most of the leaves?EUR??,,????'?????<