The possible role of the oxidative pentose phosphate pathway in seed dormancy in winter wheat cultivars

Abstract

Seed dormancy is an important characteristic in small grain cultivars, because of its potential to prevent preharvest sprouting and the subsequent loss of quality. In this study the oxidative pentose pathway (OPP) activity in seeds of a preharvest sprouting susceptible winter wheat cultivar, Tugela-DN and that of a preharvest sprouting resistant cultivar, Betta-DN, were compared. Carbon flux through the OPP pathway was determined both indirectly (total in vitro activity of the first regulatory enzyme, Glucose-6-phosphate dehydrogenase (G6PDH) and directly (14CO2 evolution from metabolized D-[1-14C]- and D-[6-14C]-glucose, including C6/C1 ratios). G6PDH activity increased twofold in both the harvest ripe (HR) and after ripened (AR) seeds of the susceptible cultivar during the germination phase (first 24 h of incubation) and threefold during the post germinative phase up to 72 h of incubation. The latter coincided with a high germination percentage. However, the G6PDH activity remained constant in both the HR and AR seeds of the resistant cultivar during the first 24 h of incubation and increased only slightly in the HR seeds over the remaining incubation time. Moreover, a C6/C1 ratio of below unity in seeds of Tugela-DN during the germination phase, confirmed that the OPP pathway was far more active in this preharvest sprouting susceptible cultivar than in the resistant cultivar, Betta-DN, where the C6/C1 ratio remained above unity during the germination phase.