VARIATIONS OF GLUCOSE, GLUCOSE-6-PHOSPHATE AND ATP IN ARUM SP. DURING DIFFERENT PHENOLOGICAL STAGES.

The linkage between energy metabolism in hypogeous storage organs and phenology is a topic not yet fully elucidated. In this work, the variations of some energetic parameters were examined in Arum italicum and A. maculatum, tubers. These organs were monthly collected and analyzed for glucose, glucose-6-P and ATP. Proximal and distal portions of tuber, with respect to the shoot, were used. In both species the level of metabolites was strictly linked to the phenological stage of the plant. Glucose was low at the shoot emission and then increased till the fruit maturation, being always higher in the distal zone. The level of glucose-6-P showed high amounts in the proximal part of the tuber during the vegetative stages, followed by a slight decrease during anthesys and plant senescence. ATP level increased in the proximal side during leaf development; it was maximal in all the tuber during flowering while decreasing in senescence. These results indicate that the removal and accumulation of storage starch is mainly localized in the peripheral parts of the tuber. Then, it is maintained high during the plant grown and flowering, falling down only at the beginning of the fruit ripening.