Relationship Between Ion Accumulation and Plant Biomass of Alfalfa Under Salt Stress

Abstract Salinity is one of the major abiotic challenges influencing plant productivity worldwide. To examine the response of two alfalfa cultivars (Bami and Hamedani) to six levels of water salinity (۰, ۲۵, ۵۰, ۷۵, ۱۰۰, ۱۲۵ mM L-۱ NaCl), a glasshouse experiment was conducted at the College of Agriculture, Shiraz University, Shiraz, Iran in ۲۰۰۸. The results showed that in Bami (which appeared to be more tolerant to salinity), with increasing salt stress from ۷۵ to ۱۲۵ mM L-۱, dry weight per pot was significantly decreased from ۱۵.۱ to ۱۰.۳ g, while in Hamedani decrease in dry weight was started from ۵۰ mM L-۱ salinity level. In both Bami and Hamedani cultivars leaf area per pot was significantly decreased when salt stress was higher than ۷۵ mM   L-۱. There was a significant difference in leaf relative water content (RWC) between the two alfalfa cultivars in ۷۵, ۱۰۰ and ۱۲۵ mM L-۱ NaCl salinity levels. With increase in salinity level, the Na+ concentration was increased from ۲۲۰ to ۵۶۵ mmol kg-۱ dry weight in Bami, and from ۲۳۸ to ۶۴۳ mmol kg-۱ dry weight in Hamedani. The Cl- concentration in Hamedani (۶۲۲ mmol kg-۱ dry weight in ۱۲۵ mM L-۱ NaCl) was higher than that in Bami (۵۰۳ mmol kg-۱ dry weight in ۱۲۵ mM L-۱ NaCl). The K+ concentration was increased from ۲۰۳ to ۶۰۴ mmol kg-۱ dry weight in Bami, and from ۱۳۵ to ۵۷۱ mmol kg-۱ dry weight in Hamedani. Furthermore, phytomass production in Bami was significantly correlated with K+ (r=۰.۹۷), and Ca۲+ (r=۰.۹۶) concentrations, as well as with leaf area (r=۰.۵۰) and plant height (r=۰.۸۷). Path analysis showed that there were significant direct effects of leaf area (p=۰.۷۳), Ca۲+ (p=۱.۰۲) and K+ (p=۰.۵۹) on dry weight in Bami. In Hamedani, there were significant direct effects of K+ (p=۰.۶۱) and Ca۲+ (p=۱.۰۷ on dry weight. Overall, based on both correlation and path analyses, it was concluded that measurements of K+ and Ca۲+ concentrations may be appropriate criteria for evaluating susceptibility of cultivars to salt stress. These results may also be used for screening the salt resistant cultivars of alfalfa.

Keywords:

Alfalfa , Correlation , Ion concentration , Path analysis , Salt stress