Assessment of Root Growth and Physiological Responses of Four Bread Wheat (Triticum aestivum L.) Cultivars to Salinity Stress

Enlarged root systems that extend into the salt affected soil improve water and nutrient capture by plants and can increase plant productivity. In order to examine root system characteristics of four bread wheat cultivars contrasting in salt tolerance (Arg, Ofoq, Tajan and Morvarid) a greenhouse experiment was conducted with applying two salinity levels (0 and 150 mM NaCl) on plants grown in PVC tubes. Salinity led to decreases in total root length, seminal root length, shoot dry weight, root dry weight, shoot K+ and shoot K+/Na+ ratio and increases in shoot Na+, leaf temperature and chlorophyll content compared to control. Seminal root length was greater in salt tolerant cultivars (Arg and Ofoq) than salt sensitive ones, under saline conditions. Ofoq maintained a greater total root length and Arg indicated a greater reduction (64%) in root length, but total root length was not significantly different among all cultivars under salinity stress. Adverse effects of salinity on shoot dry weight was not notably different in salt tolerant (16%) and salt sensitive (18%) cultivars. There were no significant differences in leaf temperature and chlorophyll content between cultivars. Our results illustrate that initial roots growth reduction is mainly due to the osmotic effects of the salt in roots environment and the extent of salt-induced decreases were similar in salt sensitive and salt tolerant cultivars. Given the effects of salt stress on root system characteristics and root growth response to salinity, it seems that rooting attributes can be used as valuable indices for screening salinity tolerance. The comparison of roots and shoots response to salinity showed that regulation of rooting and nutrient uptake under salt stress conditions is more crucial to salt tolerance than regulation of stomatal conductance.