Seasonal variations in plant water status of four desert halophytes from semi-arid region of Karachi

Halophytes in arid and semi arid zones of the world are often subjected to extremely variable drought,salinity and temperature. these fluctuations may bring about changes in their osmoregulation and gas exchange responses besides other physiological and biochemical processes. the purpose of this study was to detect temporal changes in plant water status and osmotic adjustment in four desert halophytes viz.,suaeda fruticosa,heliotropium curassavicum,haloxylon stocksii and atriplex stocksii from an inland community at karachi university campus. during the dry period (november to january) water and osmotic potentials of all test species increased with higher values in a. stocksii (salt secretor) than those of s. fruticosa and h. stocksii (salt includer) and h. curassavicum (salt excluder). proline increased substantially and was highest in h. curassavicum followed by a. stocksii in comparison to the two salt includers. the lowering of osmotic potential corresponded to an increase in na and cl,lower stomatal conductance and chlorophyll content indicating reduced gas exchange during the dry period. the increase in proline may have little role in osmoreglation but could contribute in scavenging reactive oxygen species.