ISHS Acta Horticulturae 175: Symposium on Physiology of Productivity of Subtropical and Tropical Tree Fruits
TREE GROWTH AND PRODUCTIVITY - THE ROLE OF ROOTS |
| Author: | D. Richards |
| Abstract:
In many studies on fruit tree growth and productivity only the growth of the above-ground parts has been of concern, the role of roots often being largely ignored or overlooked. It is obvious, however, that roots and shoots interact in their growth and function. These interactions undoubtedly reflect the inter-dependence of each organ for their carbohydrate and mineral nutrient contributions and requirements. Moreover, recent developments indicate that plant hormones, particularly cytokinins and possibly gibberellins, supplied by the roots play an important role in the balance and apportionment of the plants resources. The growing root apex appears to be the site of synthesis of these hormones and thus points to the importance of root number, as well as root surface area, in adequately describing the root system. The identification and understanding of this close co-ordination between roots and shoots opens up the possibility that above-ground growth can be altered by below-ground manipulation. One novel treatment, root restriction, where the root system is confined to a small volume, appears to have merit as a means of controlling plant size. The necessity to control shoot vigour and plant size is of particular importance in the fruit crop industry especially for large-growing and low-yielding tree crops. Limiting root development can be a very effective means of reducing vegetative vigour without adversely affecting fruit production. Alteration of the reproductive and vegetative balance by root manipulation appears similar to affects produced by the use of dwarfing rootstocks. In fruiting plants the growth of fruit places an added demand on the root and shoot systems for both mineral nutrients and for photosynthates. As fruit grow this demand would be expected to become increasingly competitive with vegetative growth. Indirect evidence indicates that both root restriction and rootstocks may influence the hormonal output of the root system thereby limiting shoot vigour. In these circumstances flower and fruit development can proceed without excessive competition from growing shoots. The inclusion of the root in studies on the dynamics of shoot and fruit interactions has so far received little attention. A better understanding of the whole plant can only come from more thorough investigations of root:shoot:fruit interactions. | |
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