Starch Level in the Trunk as a Measure of Compatibility Between Stock and Scion in Citrus

Abstract

SummaryStudies were carried out on the assumption that incompatibility and dwarfness of budded citrus trees result from impaired carbohydrate movement through the bud union. During autumn and winter, carbohydrates move from the tree tops to the roots and accumulate there as starch. The starch level can therefore serve as a measure of this movement.This study included seven rootstock varieties all budded with Shamouti orange scion. Unbudded rootstocks were included for purposes of comparison.The starch level was determined in the winter at three locations along the trunk, below and above the bud union.No clear indication was found of impaired carbohydrate movement through the bud union of stock-scion combinations showing very low growth vigour.The starch level in bark and wood in the rootstock portion of trunks of budded trees was found to be negatively correlated with tree size. This indicates that the level of starch in the trunk results from the growth vigour of the tree and is not a factor which affect...