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Accueil du site → Doctorat → Royaume-Uni → 1985 → The leaf energy balance of a desert plant Citrullus colocynthis (L.) Schrad. with special reference to water economy

University of Edinburgh (1985)

The leaf energy balance of a desert plant Citrullus colocynthis (L.) Schrad. with special reference to water economy

Althawadi, A.M. 

Titre : The leaf energy balance of a desert plant Citrullus colocynthis (L.) Schrad. with special reference to water economy

Auteur : Althawadi, A.M. 

Université de soutenance : University of Edinburgh

Grade : Doctor of Philosophy (Ph.D.) :1985

Résumé
It was the aim of this study to investigate the water relations of a desert cucurbit Citrullus colocynthis. This species uses much water in transpirational cooling even though water in the desert is in short supply. Energy balance theory was used in conjunction with the measurement of the leaf temperature and other climatological parameters, to estimate the transpiration rates and the leaf surface conductances. C. colocynthis leaves did indeed display high transpiration rates and frequently had temperatures cooler than the ambient air. In comparison with desert plants, Citrullus has relatively high stomatal conductance and a low boundary layer conductance in ordinary conditions. The lethal temperature of the plant is rather low in relation to other desert plants, being around 50 OC though some kind of damage does occur at even lower temperatures. By its high transpiration rate, the plant avoids lethal temperatures. The transpirational cooling is not always displayed. It seems probable that this response is only displayed in the hottest part of the year. The plant has the ability to grow tap roots which penetrate deep into the water table to sustain the rate of transpiration. The transpiration rate and leaf cooling is sensitive to radiation interception which to some extent is under control through stomatal response and aerodynamic changes. Preliminary calculations suggest that vegetation containing Citrullus and similar species may consume significant quantities of water which otherwise could be available to field crops.

Mots Clés : Desert plant transpiration Human anatomy Human anatomy

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