Partial drying of tomato root-zone: physiological effects and implications for solute transport mechanisms

Abstract

An examination was made of the effect of partial root zone drying (PRD) treatment on fruit growth of tomato plants, photosynthesis, transpiration, water potential, activity of cell wall peroxidase, fruit yield, sugars, lycopene minerals and dry weight. Pedicel vasculature area and ion accumulation measurements were performed to determine hydraulic implications for solute transport to fruit. Plants were grown in compost with the root system equally divided between two plastic pots. During the experimental period, half of the root system of PRD plants was exposed to drought, while the remainder was irrigated. After about 10 days, treatment was reversed. Control plants received the same amount of water on both sides of the root system. PRD treatment reduced the plant's height, number of leaves and ¯ower trusses, but not fruit growth, photosynthesis, ion content and pedicel vasculature. The effect on stomata depended on the stage of plant development. PRD caused a signi®cant increase in peroxidase activity and sugar content in mature fruits and crop water-use ef®ciency. The effect of PRD treatment on tomato fruit growth and biochemistry appeared not to be mediated through greater hydraulic isolation of PRD fruits from the vegetative parts of plants. Another physiological mechanism must be considered for full understanding of the PRD effect.