Ethylene Biosynthesis in Peach Seeds and its Suppression in Situ

Abstract

Peach seeds evolved ethylene immediately after their removal from pits. The ethylene-producing ability remained high during early seed development but decreased as the seeds matured. The seed coat tissues were the major source of ethylene ; endosperm and embryo produced a negligible amount. The internal gas composition of the seeds was 2.7% O₂, 19.5% CO₂ and 77.9% N₂. Not only high CO₂ but also low O₂ concentrations suppressed the increase in 1-aminocyclopropane-1-carboxylate (ACC) content of peach seeds. ACC synthase and ACC oxidase pre-exist in the seeds in situ. Under high CO₂ and low O₂ concentrations, the ethylene biosynthetic pathway seemed to be temporarily blocked before and/or at ACC synthesis. The significance of such suppression and burst of ethylene production in peach seeds is discussed in relation to pit splitting and the normal growth, development and ripening of fruit.