ETHYLENE BIOSYNTHESIS IN PEACH SEEDS AND ITS SUPPRESSION IN-SITU

Peach seeds evolved ethylene immediately after their removal from pits . The ethylene-producing ability remained high during early seed devel opment but decreased as the seeds matured. The seed coat tissues were the major source of ethylene; endosperm and embryo produced a negligib le amount. The internal gas composition of the seeds was 2.7% O-2, 19. 5% CO2 and 77.9% N-2. Not only high CO2 but also low O-2 concentration s suppressed the increase in 1-amino cyclopropane-1-carboxylate (ACC) content of peach seeds. ACC synthase and ACC oxidase pre-exist in the seeds in situ. Under high CO2 and low O-2 concentrations, the ethylene biosynthetic pathway seemed to be temporarily blocked before and/or a t ACC synthesis. The significance of such suppression and burst of eth ylene production in peach seeds is discussed in relation to pit splitt ing and the normal growth, development and ripening of fruit.