Pheromonal Communication between Plants

Abstract

It has become generally accepted that plant secondary metabolites constitute an important defense of plants against attack by herbivores and other consumers.^1–3 It is also becoming clear that plants are far from static resources to herbivores, as had been widely assumed in the past. Plant nutritional quality to herbivores can vary with the degree of both physical and biotic stress experienced by plants. Physical stresses such as drought, waterlogging, depletion of soil nutrients, frost damage, and pollution often increase susceptibility of plants to herbivores.^4–6 In physically stressed plants, this increased susceptibility appears to be due to a combination of increased content of amino acids and other nutrients,^7,9 and lowered commitment to defense.^5,6 Reports of decreased nutritional quality to herbivores, as measured in bioassays or increased content of defensive compounds, in plants previously attacked by herbivores or experiencing current attack, are becoming increasingly common.^6,10,11,17 Defensive responses of plants to attack by herbivores have been reported in as many as 29 species in 13 families including herbs, grasses, a sedge, a vine and trees, so these responses may be universal.