GROWTH-INDUCED WATER POTENTIAL IN LEAVES AND STEMS OF TOMATO PLANTS AND CITRUS TREES GROWN IN HYDROPONIC CULTURE

摘要

The hydroponic culture system is one of the most conventionally used systems to cultivate horticultural crops in greenhouses. In the present study, a plant physiology concept of cell elongation is applied to investigate the growth of tomato plants (Lycopersicon esculentum Mill.) and citrus trees (Citrus unshiu Marc.) cultivated in hydroponic culture under greenhouse conditions. When cell elongation occurs, water needs to be absorbed by elongating cells, and thus, a water potential gradient inevitablyexists between the elongating cell and its surroundings. Such a water potential gradient is called the growth-induced water potential (Nonami and Boyer, 1993). Tomato plants and citrus trees are used to demonstrate that growth rates in leaves and stemsof both plants are controlled by the size of the growth-induced water potential. Because tomato plants arc herbaceous plants and citrus trees are woody plants, these two species can be considered to be representing wide ranges of horticultural crops, andthus, it is most probable that the concept of growth-induced water potential can be applicable to any crops used for horticultural purposes.