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 different natural habitats, leaf, fruit and fine root tissue samples from five 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 flowering time. In fruit, hexose sugars and/or myo -inositol 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 final fruit sampling, concentrations of glucose and fructose were greater than sucrose in all species exceptA. arguta . myo -Inositol concentrations constituted >10% 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 significantly more starch and sucrose for most of the year than those of the other species. Observed differences in seasonal carbohydrate patterns may reflect different 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.