Seasonal variation in water relations of. desert shrubs from Karachi, Pakistan

摘要

Seasonal variation in water potential, stomatal conductance, chlorophyll a and b, and proline content were measured in both young and old leaves of three. desert species viz., Calotropis procera, Senna holosericea and Aerva javanica. Water status of young and old leaves showed similar pattern of seasonal fluctuation in all species studied. With an increase in water stress, water potential and xylem pressure potential became more negative. Stomatal conductance was highest in July when humidity was the highest. Overall chlorophyll b concentration of was higher in comparison to chlorophyll a. Proline concentration showed a peak during August and September. Lack of rainfall caused reduction of water potential and water evaporation with a corresponding decrease in proline content.