Effects of Salt Stress on Vegetative Growth and Ion Accumulation of Two alfalfa (Medicago sativa L.)

Salt stress is one of the most chalanging abiotic stresses affecting natural productivity and causing significant crop losses worldwide. A greenhouse experiment was conducted to evaluate the response of two alfalfa cultivars (Bami and Hamedani) to 6 levels of salinity (0 as control, 25, 50, 75, 100, 125 mM NaCl) at the College of Agriculture, Shiraz University, Shiraz, Iran in 2008. Plant dry weight per pot in both cultivars decreased with increasing salinity levels. However, Bami as compared to Hamedani, with the lowest Na sequestration, produced the greater dry matter weight. Leaf area per pot was significantly affected by salt stress with Bami cultivar showing a higher leaf area than Hamedani. Na accumulation also increased by increase in the salinity level in either one of the cultivars; however, Na sequestration of Bami as compared to Hamedani, was lower due to Na exclusion mechanisms occurring in this cultivar. Although Cl- accumulation increased with increasing salinity level in either one of the cultivars, Cl- accumulation was higher in Hamedani than in the other cultivar. Similar to Kﳖ ratio, Ca2ﳖ ratio also decreased by an increase in salt stress levels and there were highly significant differences observed between 25 and 125 mM of NaCl in either one of the cultivars. There was a strong positive relationship observed between plant dry matter weight and leaf relative water content for both Bami (R2=0.94) and Hamedani (R2=0.96) cultivars under salt stress conditions. All in all, it appears that less adverse effect of salinity on Bami cultivar has made it suitable for growth in saline soils as compared to Hamedani in saline areas prevailent in south Iran.