Morphological Structure and Water Balance of Four Chilean Shrub Species

Abstract

The morphological structure and water balance of two evergreens, Kageneckia oblonga and Lithraea caustica, and two deciduous shrubs, Trevoa trinervis and Satureja gilliesii, from the Chilean matorral, were studied. Deciduous species evade the drought by completely reducing their leafy evaporative surface. The maximum water stress was observed at fall and the plants showed a significant recovery after the first rains when vegetative growth started. T. trinervis is synchronic with the rains in initiating its vegetative growth. Transpiration loss is high in the deciduous shrubs throughout the vegetative period, owing to the lack of stomatal closure and to their mesomorphic foliar structure. Water loss was somewhat restricted in S. gilliesii thanks to the presence of trichomes and to the thickness of their cuticle. The leaves of both deciduous plants last only for one year. The evergreens tolerate fairly well the unfavourable period: K. oblonga - subjected to increasing water stress - recovers after the rains. When water is available transpiration loss is high in K. oblonga but is counteracted by its stomatal closure. L. caustica, whose water strfss is not too severe, controls water loss the year round. Both evergreens possess xeromorphic leaves. Major growth occurs in these plants during spring and summer.