The Effect of Water Stress on Photosynthesis, Respiration and Relative Chlorophyll Index of the Desert Plant Calotropis Procera

Abdellah Akhkha

Department of Biology, Taibah University, Al-Madinah Al-Munawwarah Kingdom of Saudi Arabia.

Corresponding Author E-mail: abdellah99@gmail.com

ABSTRACT: The objective of these experiments was to examine how water deficit stress affects the physiological processes in a desert plant species Calotropis procera. Photosynthesis, respiration and chlorophyll index were examined in order to determine how much changes in these processes could be involved in the reductions of dry matter production observed in our laboratory. It was found that water deficit did not affect the rate of photosynthesis at low water regimes (30%) compared to the 80% water regime. In contrast, moderate water regime (50%) increased the level of photosynthetic rate as a compensatory mechanism. Dark respiration was increased by the 30% water regimes and dramatically lowered by the 50% water regime. Chlorophyll content measured as chlorophyll index was increased in both low and moderate water regimes, explaining why the photosynthesis rate was not affected and suggesting that water deficit stress does not affect the photosynthetic machinery. Mechanisms involved in protecting the photosynthetic machinery and its efficiency from water deficit stress are discussed.

KEYWORDS: Water stress; photosynthesis; Chlorophyll index; Calotropis procera

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