ISHS Acta Horticulturae 175: Symposium on Physiology of Productivity of Subtropical and Tropical Tree Fruits
IMPACT OF PHYSIOLOGICAL RESEARCH ON THE PRODUCTIVITY OF TROPICAL AND SUBTROPICAL FRUIT TREES |
| Author: | J.V. Possingham |
| Abstract:
Less information is available about the physiology of subtropical and tropical fruit trees than about deciduous species such as apple, pear, peach, etc. which have been extensively researched in both Europe and the U.S.A. Tropical fruit trees are virtually all evergreens with leaves that remain functional for long periods. They have no physiological dormant period and leaf fall occurs throughout the year. Many have a flushing habit of growth. Most originated in tropical rainforests, are large in size and have many of the characteristics of shade plants. A number of them have restricted centres of origin and have a degree of genetic uniformity. Many form apomictic seeds which form a convenient method of clonal propagation. Generally, subtropical and tropical trees flower profusely, set relatively low numbers of fruits and are biennial or irregular producers. Many have complex self incompatibility systems while others have developed simple outcrossing mechanisms involving temporal differences between pollen shed and stigma receptivity. Flower initiation in these trees occurs under conditions of variable and often low light intensity and of limited variation in day length and temperature. In some cases, water stress or conversely the alleviation of stress is thought to provide the trigger to flowering. There is an urgent need for more information on the physiology of the floral process covering aspects of flower initiation, pollination, fruit set and development. It is difficult to assess the impact of physiological research on the productivity of tropical and subtropical fruiting trees. They have been cultivated for many thousands of years and a considerable amount of traditional knowledge has been assembled about how to manage and manipulate them. Research on the physiology of crop plants commonly commences from a desire to document the basic features of the particular crop and to relate these features to the available physiological knowledge about plants in general. It is assumed that knowledge of the physiology of the crop will provide the basic information for a rational management system. It is also assumed that this knowledge will provide explanations for traditional and empirically derived management techniques on the assumption that once they are better understood it might be possible to further improve them. Current and future physiological research that will influence the productivity of tropical tree crops includes, studies of their reproductive biology, covering a knowledge of cultivar combinations and the nature of the pollinating insects required to achieve fertilisation. This work is of direct value and is also an essential prerequisite for breeding. Studies of the photosynthetic characteristics of tropical trees is another research area that should enable us to optimise overall growth and to develop appropriate orchard management systems. While studies on the partitioning of photosynthetic products may lead to ways to overcome problems such as the competition that occurs between developing fruits and flushing leaves. A knowledge of the endogenous hormones of tropical trees and fruits and of their responses to exogenously supplied hormones is an area of physiological | |
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