抄録
The application of ethephon (ETP), an ethylene generating chemical, to press-injured rice leaves induced PAL (EC 4.3.1.6) activity. This induction disappeared when the concentration was low. A Scatchard plot for ligand binding gave a linear relationship between the PAL reaction rate at the time for the maximum rate of induction (tm) along the sigmoidal progress and the ratio of the PAL reaction rate versus ETP in a specific range of concentration. A similar application of glutamate (Glu) induced PAL activity, and the application of 1-aminocyclopropane-l-carboxylic acid (ACC) also induced PAL activity. The induction of rice leaf PAL with Glu was inhibited in the presence of tiron (TR), a superoxide scavenger, was weakly inhibited with aminooxyacetic acid (AOA), but was not inhibited with abscisic acid (ABA). The induction with ACC was also inhibited in the presence of TR, was weakly inhibited with AOA, and further was weakly inhibited with ABA. The inoculation of blast fungus conidia or application of fungal proteoglucomannan (RIF) to press-injured rice leaves induced PAL activity. The induction proceeded along sigmoidal curve accompanying the distinct auto-inactivation phase. Each approximated tm (midpoint of an individual sigmoidal curve) was determined; tm = 2.4hr with an incompatible race, tm = 5.3 hr with a compatible race, and tm= 11.0 hr with RIF stimulation. The 3 inhibition profiles of TR, AOA and ABA upon rice leaf PAL induction either with inoculation or with stimulation were quite similar to the inhibition profiles upon PAL induction with Glu.
