ISHS Acta Horticulturae 487: VI International Symposium on Processing Tomato & Workshop on Irrigation & Fertigation of Processing Tomato
THE PHYSIOLOGICAL BASIS FOR IMPROVING TOMATO FRUIT QUALITY |
| Author: | L.C. Ho |
| Keywords: | tomato, Lycopersicon esculentum, sugar, calcium, blossom-end rot |
| Abstract:
Both the sugar and acid concentrations of the ripe fruit determine the soluble solids and pH of the product. The sugar concentration is determined independently by the transport of photoassimilate into individual fruit, and by the water relations of the plant, for a given water status, the sugar concentration and composition of the fruit will be determined by the transport of sucrose into the storage cells, by the cleavage of sucrose into hexose and the storage of sugars in the vacuole. For a given cultivar, the sugar concentration can be readily manipulated by altering the water relations of the plant through irrigation. Therefore, the dry matter of the fruit tissue or the soluble solids in the fruit juice can be manipulated by light, temperature and water supply during cultivation. Among the defects, blossom-end rot (BER) can cause serious loss of marketable yield. BER is a physiological disorder caused by Ca deficiency in the distal fruit tissue. The induction of BER occurs in the distal pulp tissue, if Ca levels there are low, when the fruit is expanding rapidly. Although there is a wide range of susceptibility to BER among cultivars, BER can be induced by low Ca status in the plant (due to water stress or osmotic stress), or by low Ca status in the fruit (due to high canopy transpiration or high resistance in xylem transport inside the fruit), or by extra demand of Ca to maintain the cell membrane permeability (due to accelerated cell enlargement). By controlling the growing conditions to regulate the uptake and transport of Ca. and to regulate the fruit expansion rate, the incidence of BER can be substantially reduced. Sprays of Ca to fruit at critical stage of fruit development has been found to be effective in BER prevention. | |
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