ISHS Acta Horticulturae 636: XXVI International Horticultural Congress: Key Processes in the Growth and Cropping of Deciduous Fruit and Nut Trees
CARBOHYDRATE ALLOCATION IN APPLE STEMS CAN BE ALTERED BY FRUIT LOAD |
| Authors: | J.C. McQueen, P.E.H. Minchin, W.B. Silvester, T.G.A. Green |
| Keywords: | Malus domestica, starch, storage, reserves, girdling, one-year-old limbs |
| Abstract:
Carbohydrate allocation is a key process in deciduous fruit trees. In this study, our aim was to determine whether reserve accumulation in one-year-old apple stems is controlled by carbohydrate availability. We altered the carbohydrate balance of one-year-old stems during fruit development by altering the fruit load on girdled branches. One-year-old branches of ‘Braeburn’ with fruit were girdled early in the season and the fruit load adjusted to high (6 fruit), low (2 fruit) and zero (no fruit). This fruit load was subsequently reduced at different times throughout the season. Starch concentrations in one-year-old wood were found to be inversely correlated to fruit load; limbs with zero fruit load had the highest concentrations of starch. By winter, however, all girdled branches had the same concentrations of starch, regardless of fruit loads throughout the season. This implies that there is a maximum capacity for starch storage in stems and that all branches can reach this maximum, regardless of their carbohydrate status earlier in the season. Reducing fruit loads throughout the season caused starch concentrations in one-year-old wood to increase rapidly. The results show that starch can be forced into storage out of season, implying that its accumulation is dependent on carbohydrate availability. Storage is a low priority sink, and starch is only stored when other higher priority sinks are removed or become saturated. | |
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