South African Avocado Growers ’ Association Yearbook 1997. 20:63-67 What do Carbohydrate Reserves Tell us about Avocado Orchard Management?

Carbohydrate reserves (stored mainly as starch) in tree crops represent the currently unutilized and stored component, mainly in the trunk, branches and leaves of avocado trees. They are the difference between manufacture (in photosynthesis) and utilization (growth and respiration).They follow a seasonal pattern, peaking just before flowering, declining rapidly during flowering and fruit set, remaining low until mid-summer, and rising through autumn and winter. It has been suggested that the levels of starch reserves at critical periods can be used in orchard management decisions. Data are presented, mainly from delayed harvest trials in KwaZulu-Natal and Queensland, to indicate that there is a broad relationship between starch concentration and key aspects of tree performance, e.g. yield and root growth. However, carbohydrate reserves are but one of many factors, potentially limiting, which affect yield, and by themselves provide only some useful information. A far more meaningful guide to tree performance, and an aid to management, is the pheno-physiological model of Whiley (1994), of which the starch reserves are but one component. Avocado trees appear to accumulate high levels of carbohydrate reserves as an adaptation to water stress and drought