Physiological responses of three contrasting plant species to groundwater level changes in an arid environment

Plants growing on both sides of the Tarim River in western China serve as a natural barrier containing the deserts and protecting the oasis, and their growth is greatly affected by water conditions in their local habitat. We studied the physiological responses of three different types plants (i.e. Populus euphratica Oliver, Tamarix ramosissima L., and Apocynum venetumas Linn) to changing groundwater levels by analyzing changes in chlorophyll, soluble sugar, proline (Pro), malondialdehyde (MDA), superoxide dismutase (SOD), peroxidase (POD), indoleacetic acid (IAA), giberellic acid, abscisic acid (ABA) and cytokinin (CK). Relationships between these physiological characteristics and groundwater levels were analyzed in order to assess the drought tolerance of the three plant species based on the values of average membership function. We found that MDA, SOD and ABA were more susceptible to changes in groundwater level, followed by POD, IAA and CK. Among the three plant species, Populus euphratica responded physiologically less to changing groundwater level than T. ramosissima and A. venetumas