Effects of salinity on growth, ion content, and osmotic relations in Halopyrum mucronatum (L.) Stapf.

Halopyrum mucronatum (L.) Stapf, is a perennial grass found on the coastal dunes of Karachi, Pakistan. Halopyrum mucronatum plants were grown in 0, 90, 180, and 360 mol m(-3) NaCl in a sand culture using a sub-irrigation method. Fresh and dry weight of roots and shoots peaked at 90 mol m(-3) NaCl. A further increase in salinity inhibited plant growth, ultimately resulting in plant death at 360 mol m(-3) NaCl. The relative growth rate of plants was highest between 60 and 90 days after final salinity concentrations were reached. Maximum succulence was noted in 90 mol m(-3) NaCl. Water potential and osmotic potential of plants became more negative with an increase in salinity, while plants lost turgor with increasing salinity. Time of harvest did not have any significant effect on the water relations of plants. Sodium (Na) and chloride (Cl) content of plants increased with an increase in salinity, while calcium (Ca), magnesium (Mg), and potassium (K) content decreased. Glycinebetaine content of shoots increased significantly only at the highest salinity (360 mol m(-3) NaCl).