Science: Plant v. Plant

Most plants are sociable and snuggle up close to plants of other species. But the brittlebush (Encelia farinosa) of California and Arizona deserts is a killer that tolerates no neighbors: it always grows alone in a patch of ground bare of potential competitors. Dr. James Frederick Bonner of Caltech has now found out how the brittlebush keeps itself exclusive.

About a year ago, Dr. Bonner and his assistant gathered fallen leaves from under a brittlebush, spread them around the stems of potted tomato plants, and sprinkled them with water. In three or four days, the tomato plants were dead.

Next, Dr. Bonner made a brew of brittlebush leaves and extracted from it a chemical called 3-acetyl-6-methoxybenzaldehyde (AMB for short), which kills several plants, including corn and peppers, but is harmless to the brittlebush and its close relatives. AMB seems to prevent the roots from absorbing water—a very effective way of cutting competition in a water-starved desert.

If AMB can be synthesized cheaply, Dr. Bonner thinks that it may prove a useful “selective weed killer.” But he is chiefly interested in it as a proof that peaceful-appearing plants can carry on a vicious chemical warfare.