Tomentose

Day 108: Botanical word for the day: tomentose, i.e., a covering of fine, woolly hairs. It derives from Latin "tomentum" which, to my great amusement, means "cushion stuffing," although today's cushions are largely stuffed with polyurethane foam. What advantages would there be for a plant to have evolved tomentose foliage? Several, as it turns out, the first being that the woolly surface is more difficult for insects to navigate and thus they tend to avoid tomentose leaves. The matted hairs of the tomentum (here used in the non-cushion sense) also insulate tender surface cells from frost and wind. They also reduce the rate of transpiration and reflect harsh sunlight. Harking back to an earlier point in this discussion, an article in a recent issue of Scientific American suggests that plants which have more textured leaf surfaces are affected by fewer insect pests. Scientists monitored the difficulties beetles had in traversing leaves with various microscopic surface structures and found that they took longer to cross a given distance on a textured leaf than on a smooth-surfaced one.