Inhibition of Ethylene Biosynthesis and the Endogenous Ethylene and Chlorophyll Content of Poa pratensis Leaves Infected by Bipolaris sorokiniana

Abstract

Summary The ethylene-biosynthesis-inhibiting substances CAN, AOA, AIB, CCCP, COCL, and PG were applied to roots of intact Poa pratensis to determine their ability to decrease endogenous ethylene production and subsequent chlorophyll (Chl) loss from leaves inoculated with Bipolaris sorokiniana. Endogenous ethylene of leaf blades was measured 24, 48, 72, and 96 h after inoculation, as pathogenesis progressed, and Chl content was determined at 96 h. Endogenous ethylene was significantly decreased at each 24-h sampling period by CAN, AOA, CCCP, and PG. Loss of Chl during pathogenesis was substantially decreased by CAN and AOA, but Chlloss in response to CCCP and PG did not differ from that of the untreated, inoculated control (43% of control). The differential response of Chlloss to the ethylene inhibitors suggests that substances blocking the conversion of AdoMet to ACC are more effective at decreasing the endogenous ethylene surge and preventing Chl loss during pathogenesis than are substances that block the conversion of ACC to ethylene. The ethylene and Chl responses are discussed relative to physiological manipulation of symptom expression.