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

Salt stress is one of the most chalanging abiotic stresses affecting natural productivity and causing significant croplosses worldwide. A greenhouse experiment was conducted to evaluate the response of two alfalfa cultivars (Bamiand 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 salinitylevels. However, Bami as compared to Hamedani, with the lowest Na+ sequestration, produced the greater dry matterweight. Leaf area per pot was significantly affected by salt stress with Bami cultivar showing a higher leaf area thanHamedani. 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 thiscultivar. Although Cl- accumulation increased with increasing salinity level in either one of the cultivars, Claccumulationwas higher in Hamedani than in the other cultivar. Similar to K+/Na+ ratio, Ca2+/Na+ ratio alsodecreased by an increase in salt stress levels and there were highly significant differences observed between 25 and125 mM of NaCl in either one of the cultivars. There was a strong positive relationship observed between plant drymatter weight and leaf relative water content for both Bami (R2=0.94) and Hamedani (R2=0.96) cultivars under saltstress conditions. All in all, it appears that less adverse effect of salinity on Bami cultivar has made it suitable forgrowth in saline soils as compared to Hamedani in saline areas prevailent in south Iran.