Effects of varying soil moisture on water potential and water loss in the ericoid shrub Philippia evansii

Abstract

Xylem water potential and water loss were measured in the ericoid shrub Philippia evansii N.E. Br. under varying conditions of soil moisture and atmospheric evaporative demand (AED). Minimum water potential stabilizes at ca. -1 500 kPa and increasing soil water by irrigation, at a time when AED was high, did not significantly affect minimum water potential or water loss. It is concluded that P. evansii controls water loss by stomatal closure at high water potentials. The implications of strict control of water loss are discussed in the context of habitats colonized and geographical distribution of the species. S. Afr. J. Bot. 1985, 51: 460–464 Xileem-waterpotensiaal en waterverlies vir die erikoiede struik Philippia evansii N.E. Br. is onder wisselende toestande van grondvog en atmosferiese verdampings-aanvraag (AVA) gemeet. Minimum waterpotensiaal stabiliseer by ca. - 1 500 kPa en verlaging van grondwater deur besproeiing toe die AVA hoog was, het nie ‘n beduidende invloed op die minimum waterpotensiaal of waterverlies gehad nie. Die gevolgtrekking is dat P. evansii waterverlies deur huidmondjiesluiting by hoe waterpotensiale beheer. Die implikasies van streng beheer van waterverlies word bespreek teen die agtergrond van habitatte wat gekoloniseer word en die geografiese verspreiding van die spesie. S.-Afr. Tydskr. Plantk. 1985, 51: 460–464