Interconversions of14C-labelled Sugars in Apple Tree Tissues12

Tissue pieces excised from orchard-grown apple trees during a growing season exhibited different and changing capabilities of transferring 14C-label from sucrose, fructose and sorbitol to other soluble carbohydrates. All tissues incorporated fructose 14C into sucrose but only leaves incorporated significant amounts of label from sucrose into sorbitol. As seeds developed and matured, their ability to incorporate 14C from sorbitol and from fructose into sucrose increased. Sorbitol and sucrose are the major translocated photosynthetic products of apple leaves but whereas sorbitol appears to be an end-product of synthesis, sucrose may be considered as a substrate involved more directly in carbohydrate utilization.