Developmental acquisition of salt tolerance in the halophyte Atriplex halimus L. is related to differential regulation of salt inducible genes

The present study investigated the developmental tolerance of Atriplex halimus to osmotic and/or ionic stress. A. halimus was exposed to NaCl (0, 100, 250 and 400 mM), KCl (0, 100, 250 and 400 mM) and sorbitol (0, 200, 500 and 800 mM) at the level of germination, seedling emergence and vegetative stages. The response of A. halimus to different salts was stage dependent especially to NaCl that had a remarkable effect on A. halimus growth at each stage. At the germination stage, the growth reduction could be attributed to osmotic effect and HRD may have a role in that osmotic sensitivity. At this stage, the accumulation of Na⁺ into vacuole could be a strategy for alleviating the osmotic effect. At the seedling emergence stage, the inhibition of growth could be mainly attributed to the ionic effect that may have resulted from excessive accumulation of Na⁺ along with inconsistent regulations of Na⁺ manipulating genes. A. halimus at the vegetative stage was an obligate halophyte with regulated mechanisms of tolerance to both ionic and osmotic components of salt stress. A. halimus exhibits glycophytic features at the early growth stages but it is an obligate halophyte at the vegetative stage.