ANTINUTRITIVE AND OXIDATIVE COMPONENTS AS MECHANISMS OF INDUCED RESISTANCE IN COTTON TO HELICOVERPA-ZEA

Induced resistance in cotton (Gossypium hirsutum) foliage and squares to herbivory by Helicoverpa tea (Lepidoptera: Noctuidae) is reported i n this study. Induced resistance was indicated by decreased larval gro wth when larvae fed on previously damaged foliage or squares compared to the controls. Herbivory caused a significant decline in host nutrit ional quality as shown by a reduction in protein and most amino acids in both foliage and squares. Peroxidase, ascorbate oxidase, and diamin e oxidase activities increased in both damaged foliage and squares, wh ereas levels of the nutritional antioxidant, ascorbate, were depressed after larval feeding. Larval feeding also markedly enhanced lipoxygen ase activity and lipid peroxides in square tissues. Moreover, feeding damage altered the quantitative levels of phenolic compounds in foliag e and squares. These results indicate a significant shift in the oxida tive status of cotton plants following herbivory as indicated by incre ased oxidative enzyme activity, decreased levels of the nutritional an tioxidant ascorbate, and increased levels of phenolic prooxidants (i.e ., chlorogenic acid) and lipid peroxides.