Seasonal Concentrations of Non-structural Carbohydrates of Five Actinidia Species in Fruit, Leaf and Fine Root Tissue

Abstract

To characterize seasonal patterns of carbohydrate concentrations in Actinidia species from dierent natural habitats, leaf, fruit and ne root tissue samples from ve species (A. arguta, A. deliciosa, A. chinensis, A. polygama and A. eriantha) were collected over one season, and analysed for fructose, glucose, sucrose, myo-inositol and starch concentrations. Sucrose and starch peaked in leaf tissue around owering time. In fruit, hexose sugars and/or myoinositol transiently increased early in development. Starch accumulated in fruit of all species, beginning sooner after anthesis in A. arguta and A. polygama than in the other species. Sucrose accumulation coincided with onset of net starch degradation in A. arguta but was delayed in the other species. At nal fruit sampling, concentrations of glucose and fructose were greater than sucrose in all species except A. arguta. myo-Inositol concentrations constituted 410% of total sugars for most of the season in leaf and fruit tissues of all species except A. polygama. Fine roots of A. arguta and A. polygama contained signicantly more starch and sucrose for most of the year than those of the other species. Observed dierences in seasonal carbohydrate patterns may reect dierent natural habitats, with A. arguta and A. polygama growing naturally in colder climates than the other species. Transient accumulation of sugars in fruit during early stages of development has been considered to act as primary osmoticum for cell expansion. However, the presence of only low sugar concentrations in A. eriantha questions this hypothesis.