Root Absorption of Water and Physiological Responses to Water Deficits by Festuca arundinacea Schreb. And Trifolium repens L

Abstract

A study of water uptake by white clover (Trifoliurn repens) and tall fescue (Festuca arundinacea cv. Demeter) examined their comparative physiological responses to water deficits and the pattern of water absorptioil by their root systems. Fescue had more deep roots than clover and extracted more water from deep soil layers, finally resulting in a drier soil profile. Poor control of leaf transpiration in clover resulted in low leaf water potentials and increased leaf senescence; in fescue, better stomatal control and higher leaf water potentials prolonged its period of active growth. The relationships between soil water content, transpiration rate and pattern of water absorption by both root systems were compared using an existing theory of water uptake. Two parameters for integrating soil water potential and soil conductance down the soil profile gave more consistent relationships with the transpiration rates of fescue than with those of clover. These two parameters may be less able to account for the pattern of soil water absorption by a clover root system and a possible explanation for this effect is discussed. Relative canopy conductance ratios gave similar relationships with the relative transpiration ratios for fescue and clover. Therefore, leaf senescence in clover was apparently important for balancing its rates of transpiration and water uptake. In contrast, fescue was able to rely upon its more extensive root system, effective stomatal control and ability to roll leaves to regulate its water balance.