Activities of Some Enzymes as Physiological Tests for Screening Resistance to Water Stress in Five Xerophytes

Yu. MARKOVSKA1 and D. DIMITROV2

1 University of Sofia, Department of Plant Physiology, Faculty of Biology, BG-1421 Sofia, Bulgaria
2 University of Sofia, Department of Botany, Faculty of Biology, 8, D. Tsankov Blvd., BG-1421 Sofia, Bulgaria

Abstract

MARKOVSKA, Yu. and D. DIMITROV, 1999. Activities of some enzymes as physiological tests for screening resistance to water stress in five xerophytes. Bulg. J. Agric. Sci., 5: 849-857

With the aim of selecting physiological tests for the screening of drought tolerant species, we have studied the behaviour of xerophyte leaf discs treated with PEG 600 (-1.13 MPa) for 4 h. The kinetics of electrolyte and Pi leakages, carbohydrate content and activities of carboxylating and decarboxylating enzymes were investigated during 24 h rehydratation of the leaf discs.These tests were related, respectively to cell and chloroplast membrane integrity and to photosynthetic restoration possibilities. The results obtained showed that stress caused by PEG induced an increase in the electrolyte and Pi leakages, and a decrease in carbohydrate content and activities of investigated enzymes. The tests used are indicators of cell and membrane integrity and they allowed us to screen other species and cultivars for drought tolerance.

Key words: osmotic stress, membrane resistance, xerophytes
Abbreviations: RuBPC-ribulose-1,5-bisphosphate carboxylase/oxygenase, PEPC-phosphoenolpyruvate carboxylase, NADP-ME NADP- malic enzyme, NAD-ME NAD malic enzyme, PEPCK phosphoenolpyruvate carboxykinase