[Changes in some defensive enzyme activity induced by the piercing-sucking of brown planthopper in rice]

The effects of brown planthopper on the activities of some key enzymes involved in defense response and the H(2)O(2) content were investigated in rice. From the fact that after piercing-sucking of brown planthopper, malondialdehyde (MDA) content of rice plant was increased rapidly (Fig.3), one can conclude that it induced lipid peroxidation; lipoxygenase (LOX), hydroperoxide lyase (HPL) and phenylalanine ammonia-lyase (PAL) activities were increased significantly in plants of resistant and susceptible varieties by piercing-sucking of brown planthopper (Figs.1,2,4); whereas the catalase activity and the H(2)O(2) content were significantly different between resistant and susceptible plants by piercing-sucking of brown planthopper, the former being decreased and the latter increased in resistance plants of variety RH (Oryza sativa L. cv. Rathu Heenati), while the reverse was true in the susceptible plants of variety TN1 (Oryza sotiva L. cv. Taichung Native 1) (Figs.5,6). The effect of brown planthopper on the PAL activity and the H(2)O(2) content were systemic (Figs.4,6), but the effect on the LOX activity occurred only in stem, the organ which brown planthopper sucking (Fig.1).