Comparative Effects of CaCl2 and NaCl Salinity on Growth and Ion Partitioning of Atriplex halimus L

Atriplex halimus L. is a native persistent perennial shrub that is used for revegetation of degraded rangeland because of its ability to cope with environmental stresses. Seedlings of Atriplex halimus L. were grown in sand culture for four weeks and then treated with half strength Hoagland solution containing 0, 50, 100 and 300 mM of NaCl and CaCl2 salts for twelve weeks. Results indicated that NaCl and CaCl2 salinity caused a significantreduction in both leaf water content and relative water content by values of 72.5% and 63.7% of that in control. Reductions in photosynthetic pigments were also observed ranging from 23 to 58% for chlorophyll a and b and45% for carotenoids at 300mM salinity. Effect of NaCl was higher than that of CaCl2 on both water content andphotosynthetic pigments. Leaves, stems, and roots dry weight and total biomass of atriplex was reduced byvalues ranging from 35 to 49% when treated with 300mM CaCl2 and from 55 to 69% when treated with 300 mMNaCl. Ion partitioning between various plant parts was also affected by average salinity. Leaves accumulatedhigher levels of Ca, Na, Cl, and K than stems and roots. Calcium content was increased by four folds in leavesand stems and two folds in roots when treated with 300mM CaCl2. Similarly, Na and Cl were also accumulatedin leaves and stems but not in roots. Results indicated that Atriplex halimus L. tolerates moderate salinity up to100mM without any significant impact on plant growth. Increased salinities greater than 300 mM starts to reduceplant growth. Presence of calcium in solution could ameliorate the problems caused by high salinity.