IMPACT OF DROUGHT AND HEAT STRESS ON THE PHOTOSYNTHETIC APPARATUS OF QUERCUS PUBESCENS: A FIELD STUDY

摘要

A better understanding of the impact of hot and dry periods on plant growth and survival is in the context of global warming of growing importance, as the accelerated climatic changes will have agricultural, ecological and economical consequences. Heat and drought stress negatively affect a number of physiological processes, but inhibition of photosynthesis is considered to be of particular significance (Berry & Bjorkman 1980, Lawlor 1995). Most of our knowledge concerning the effects of drought andheat stress on the photosynthetic apparatus is based on studies that focused on crop plants and/or plants grown in a more or less controlled environment. Accordingly, little information is hitherto available concerning the situation prevailing in tree species growing in their natural environment. In this study, the response of the photosynthetic apparatus to drought and heat stress was examined in the field in the leaves of Quercus pubescens, a thermophylous oak species, which under harsh conditions develops as a shrub. Photosynthetic parameters were recorded over the course of the day during periods within which the plants experienced different stress situations.