Effect of Waterlogged Soil Conditions on the Production of Ethylene and on Water Relationships in Tomato Plants

Abstract

The roots of tomato plants (Lycopersicon esculentum Mill., cv. Moneymaker) were exposed to low concentrations of oxygen by waterlogging the soil or by growing the plants in nutrient solution flushed with nitrogen gas. After 24 h, the rate of ethylene production by the petioles, main stem, and shoot apex was increased by 4–6-fold and the petioles developed epinastic curvatures. Removing the roots did not reproduce these responses. The amounts of ethylene produced by shoot tissues in response to physical wounding was greatly increased by waterlogging the soil. The production of ethylene by roots was suppressed by the absence of oxygen. When the roots were transferred back to an aerobic environment ethylene production quickly exceeded that observed in roots maintained continuously in aerobic conditions. The enhanced rate of ethylene production in the shoots occurred in the absence of increased water stress as measured with a leaf pressure chamber; leaf water potentials were increased rather than decreased by waterlogging for 30 h or more. This was associated with stomatal closure and reduced transpiration. Resistance to water flow through the plant increased as transpiration decreased in response to waterlogging. However, at similar rates of transpiration, resistance was normally lower in waterlogged plants than in controls.