ISHS Acta Horticulturae 383: Mineral Nutrition of Deciduous Fruit Plants
SOURCE-SINK RELATIONS IN FRUITS. VIII. THE EFFECT OF NITROGEN ON FRUIT/LEAF-RATIOS AND FRUIT DEVELOPMENT IN APPLE |
| Authors: | T. Toldam-Andersen, P. Hansen |
| Keywords: | Fruit development, fruit/leaf -ratio, internal competition, nitrogen, nitrogen/carbon -balances, source-sink |
| Abstract:
Apple trees growing in pots were irrigated with nutrient solutions comprising six levels of nitrogen, ranging from deficiency to a high level, as illustrated by the nitrogen concentrations in the leaves. Effects on vegetative growth were relatively small, while crop level was affected distinctly. In one experiment treatments were initiated on flowering trees of a good nitrogen status: the number of fruits per tree dropped when nitrogen levels were augmented. In another experiment treatments were applied for two years. In the second year, when flowering and fruiting were allowed to take place, fruit drop was accelerated at the lower nitrogen levels, resulting in smaller fruit/leaf-ratios. In both experiments fruits were affected according to the effects on fruit/leaf-ratios, as fruit size and concentrations of total dry matter, soluble dry matter and titratable acids were negatively related to the fruit/leaf-ratios. However, in the latter experiment, when compensating for the effects of fruit/leaf-ratios, a direct effect of nitrogen was demonstrated, rendering smaller fruits with higher concentrations of soluble dry matter and titratable acids in nitrogen-deficient trees. In both experiments, red over colour on fruits developed more intensively at the lower nitrogen levels. | |
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