CHANGES IN ACTIVITY OF ENZYMES INVOLVED IN CARBOHYDRATE-METABOLISM DURING DEDIFFERENTIATION OF MATURE CELLS OF RIELLA-HELICOPHYLLA (BORY ET MONT) MONT

When cellular correlations between mature cells and meristematic cells of Riella helicophylla are interrupted by isolation of tissue fragments of mature cells, the cells of the adaxial fragment zone reactivate nucleic acid synthesis and divisional functions. Additionally, in these cells starch is accumulated in high amounts. ADPGlc-pyrophosphorylase activity per cell remained unchanged 48 h after isolation. Invertase activity was increased in the adaxial and in the peripheral zone. Sucrose synthase activity as well as sucrose-phosphate synthase activity increased in the adaxial zone and decreased in the peripheral zone. Also at the end of the dark period, the adaxial zone showed high starch accumulation and phosphorylase activity increased drasticly. UDPGlc produced by sucrose synthase could possibly serve as a precursor for starch synthesis by phosphorylase. During this process as well as during sucrose synthesis by sucrose-phosphate synthase, Pi is liberated and available for RNA synthesis. In the peripheral zone starch is completely decomposed during darkness. However, phosphorylase remains active in these cells. Therefore, it is assumed that phosphorylase is involved in starch degradation in the peripheral zone. There is no indication of sucrose transport from the peripheral zone to the adaxial zone, but hexose phosphate or triose phosphate could possibly be carriers for Pi from the peripheral zone to the adaxial zone. © 1990, Gustav Fischer Verlag, Stuttgart. All rights reserved.