Partitioning of Carbohydrates in Annual and Perennial Cotton (Gossypium hirsutumL.)

An analysis of the partitioning of carbohydrates in annual and perennial cotton was made to ascertain the distribution of assimilates and constitution of reserves. Root/shoot dry matter ratio is high in perennial cotton and this plant shows a preferential accumulation of dry matter in roots corresponding to its adaptation to drought. Starch content is also higher in perennial cotton roots than in annual. It can be said that the earlier maturing the cultivar, the lower the root/shoot ratio and the lower the starch content. Nevertheless, at the whole plant level in annual cotton the starch content is highest in leaves where it is accumulated before migration, and stem wood, and lowest in root and bark. While starch content in roots of annuals declines after 3 months, it is still increasing in perennials. Accumulation of carbohydrates as reserve material can be modified by selection and such selection is accompanied by an increase in the activities of β-amylase in exporting organs: leaves, woody tissue of the stem, and bark but not in roots. Invertase activities were highest in leaves but did not respond to selection. Non-irrigated cotton had a higher activity of β-amylase in leaves and stem wood corresponding to the mobilization of reserve assimilates. Smaller increases were observed in the activity of invertase. High yielding annual cottons show a higher activity of β-amylase and invertase in leaves corresponding to a higher capacity of assimilate transfer. Also a comparison was made from emergence to 4 months of the partitioning of carbohydrates between leaf, stem and roots in annual and perennial cotton. In conclusion perennial cotton apparently owes its drought resistance to a partitioning of assimilates that favours the growth of the root system and the accumulation of starch reserves in roots.