CROP LOAD AND NUTRIENT TRANSLOCATION

Understanding of the specific role of the fruit in the translocation and distribution of mineral elements within fruit trees is an important part of the general understanding of translocation and related processes.
It is also of major significance for the nutritional requirement of the tree as a whole because fruit mineral content largely determines storage quality.

Heavily cropping and non-cropping trees are two extremes of variation of crop loads, and hence can be used to study the potential influence of fruiting.
In this paper several experiments where fruiting and non-fruiting trees were compared are discussed with one experiment in which different crop levels were also compared.
Translocation of mineral elements to the fruits is discussed in relation to parallel effects on nutrient uptake, growth of vegetative parts, and performance of leaves.

Long-distance transport of mineral elements may take place in the xylem and in the phloem as discussed earlier in this book by Wiersum, Bowling and Ferguson (Chapters 15, 18, 21) and also by Lüttge (1973).

Fruits are supplied through the phloem with most of their organic compounds (carbon and nitrogen) and part of their water (Pate, 1976). In apples the major part of their potassium (which is present in large amounts), and also their phosphorus, nitrogen, and magnesium, is translocated into the fruits nearly linearly with dry matter (Tromp, 1975), indicating phloem transport of these compounds.
In contrast calcium is transported into the fruits in only small quantities, mainly following the water distribution via the xylem (Wiersum, 1966) during the early stages of fruit development, as a shift from xylem into phloem transport may occur at a fruit size of about 30 g (Redmond, 1975).

Symposium on Mineral Nutrition and Fruit Quality of Temperate Zone Fruit Trees

P. HANSEN

https://doi.org/10.17660/ActaHortic.1980.92.23