Seasonal changes in tissue elasticity in chaparral shrubs

Abstract

An important physiological feature of chaparral shrubs is the development of low water potentials during periods of drought characteristic of southern Californian summers. Changes in tissue elasticity may be an important characteristic allowing these low water potentials to be reached and maintained without the development of detrimental water deficits. To examine this possibility, seasonal changes in tissue elasticity were measured in 3 species of chaparral shrubs, Arctostaphylos glandulosa Eastw., Quercus dumosa Nutt. and Ceanothus greggii Gray., by the pressure‐volume method. Tissue elasticity was characterized using graphs of the modulus of elasticity plotted as a function of turgor pressure, and maximum values of the elastic modulus. The moduli of elasticity of the shrubs increased following leaf emergence in the spring, were highest during periods of low soil water potential, and tended to decrease following the summer‐fall drought period. Increases in tissue elasticity facilitate water uptake from drying soils, but result in greater turgor loss during tissue dehydration.