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Publication Type J
Authors Pyankov, V. I., A. A. Vasilev, A. N. Kuzmin, E. D. Demidov and A. I. Maslov
Title Daily Dynamics of Physiological Processes in Succulent Halophilic Plants with the C-3 and C-4 Types of Photosynthesis from the Arid Zone of Central Asia
Source Soviet Plant Physiology
Author Keywords 2312_92 2 lateral roots of 2 desert succulents, hydraulic conductivity, crassulacean acid metabolism, drying soil, stem water storage, c-4 plants crassulacean acid metabolism, pathway halophytes, metabolism, organic acids, cam
Abstract We studied the daily dynamics of photosynthesis, pH value, and titratable acidity of the cell sap in the succulent halophytes Suaeda paradoxa, Halostachys caspica, and Lycium rutencium (C3 species); and Climacoptera transoxana, S. arcuata, and S. microphylla (C4 species) during the summer in Southern Tadzhikistan. All of the species exhibited a similar dependency of the daily course of photosynthesis: assimilation of CO2 was high throughout the entire light period with a maximum at 10:00-12:00 h and decline of CO2 fixation at midday. The rate of nighttime CO2 fixation did not exceed 1.3-3.6% (C4 species) or 1.7-2.9% (C3 species) of daylight photosynthesis. The level of dark fixation depended on neither the potential activity of PEP carboxylase (C3 and C4 plants) nor its activity in water-bearing tissue (C4 species). The range of daily oscillations of acidity (DELTApH) was insignificantly higher in the group of C4 plants (0.5-0.8) than in C3 species (0.3-0.7). Regardless of the type of photosynthesis, maximal acidification was recorded during the period of transition from light to darkness (20:00-23:00 h), acidification being registered during the period of active photosynthesis before noon in C4 Species. The investigated species do not possess CAM photosynthesis, but elevated heterotrophic CO2 fixation and extensive pools of organic acids possibly enable them to maintain high osmotic pressure and synthesize protective substances, which is of great significance for life under conditions of solonchaks.
Year Published 1992
Volume 39
Issue 5 Part 1
Beginning Page 599-605
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