Activity of sucrose synthase and soluble acid invertase following germination of pinyon (Pinus edulis) seeds

The developmental pattern and relative activities of sucrose synthase (EC 2.4.1.13) and soluble acid invertase (EC 3.2.1.26), and the associated contents of sucrose and hexoses, were analyzed in the cotyledons, hypocotyl, and radicle of pinyon (Pinus edulis Engelm.) seedlings following radicle emergence. Sucrose synthase activity did not appear to be correlated with organ growth, but showed a close association with sucrose content. Conversely, there was a high degree of correlation between soluble acid invertase activity and growth of the various organs. Hexose content also was correlated with the level of invertase activity. Thus, soluble acid invertase appeared to be directly involved in providing respiratory and biosynthetic substrates in growing organs, while the role of sucrose synthase was less clear, being more active in tissues that are involved in sucrose import and transport and possibly sucrose to starch conversion.