Effects of leaf-applied potassium, gibberellin and source–sink ratio on potassium absorption and distribution in grape fruits

Rb has similar characteristics as K, and is often used as a substitute of K due to either no suitable K isotope or having almost the same absorption and distribution traits by plants for both K and Rb. Thus, both 86Rb as a substitute of K and 3-year-old grapevines (Vitis vinifera L. × V. labrusca L. cv. Jingyou) as the plant materials were used in the experiment to explore potassium (K) absorption and distribution. After 86Rb was daubed on the leaves, much of it was absorbed into fruits, while small proportions were transported into grapevines and non-daubed leaves. Based on stages of fruit development, the distribution of 86Rb in fruits of bearing grapevines varied remarkably in the order: third stage (26.86%) > first stage (15.44%) > second stage (11.40%) > veraision (9.06%). The absorption of 86Rb by fruits was also influenced by nutritional level, gibberellin (GA) application and source–sink ratio. Either 0.5 or 1% KCl significantly suppressed transportation of 86Rb from leaves to grape fruits. At full bloom, both 50 and 100 mg L−1 GA applications resulted in high 86Rb influx into fruits, but 50 mg L−1 GA had a stronger effect. More leaves resulted in less partitioning of 86Rb from treated leaves into grape fruits, while more of 86Rb from the treated leaf was translocated into fruits by reducing the total number of fruits.