Comparison of some physiological root traits of bread and durum wheat cultivars under salt conditions

Faster and more extensive root growth is important for good plant growth and such a root system is expected to extract more available soil water in salt conditions. In order to examine root system and some physiological characteristics of four bread wheat contrasting in salt tolerance (Arg, Ofoq, Tajan and Morvarid) and two durum wheat cultivars (Behrang and Shabrang), a greenhouse experiment was conducted with two salinity levels (0 and 13.5 dS/m NaCl) growing in PVC tube. Salt stress decreased root dry weight, shoot dry weight, seminal root length, total root length, root and shoot K+, shoot K+/Na+, root K+/Na+ and tillers and increased root Na+,shoot K+ leaf temperature and chlorophyll content compared to control. Seminal root growth did not affect by salinity stress in Arg andno significant differences was observed between Arg and Shabrang in this aspect. Although, reduction in seminal root length was less in Arg (5%) and Shabrang (32%), but these cultivars had more reduction in total root length by 64% and 68% respectively under saline conditions. Root growth reduction in cultivars was due to osmotic stress of salt solution out of the roots and the values for total root length in bread wheat cultivars was more under salt stress. Finding of this study on root lentgh identify it as one of the valuable index for improved adaptation to osmotic stress in wheat.

In order to examine root system and some physiological characteristics of four bread wheat contrasting in salt tolerance (Arg, Ofoq, Tajan and Morvarid) and two durum wheat cultivars (Behrang and Shabrang), a greenhouse experiment was conducted with two salinity levels (0 and 150mM NaCl) growing in PVC tube. Treatments were imposed when the leaf 2 was fully expanded. Leaf temperature of plants was acquired in the greenhouse 5 days after imposing the salt treatments. At 21 days after salt treatment plants were harvested and traits were measured. Seminal root length, total root length, Chlorophyll content, K+ and Na+ root, root and shoot dry weight in all cultivars were investigated.

Salt stress decreased root dry weight, shoot dry weight, seminal root length, total root length and increased root Na+, leaf temperature and chlorophyll content compared to control. Seminal root growth did not affect by salinity stress in Arg and no significant differences was observed between Arg and Shabrang in this aspect. Although, reduction in seminal root length was less in Arg (5%) and Shabrang (32%), but these cultivars had more reduction in total root length by 64% and 68% respectively under saline conditions. Differences in root Na+ concentration between some wheat cultivars were less obvious in 21 days after salt treatments and it seems the roots exposed to salinity were reduced in growth mainly because of the osmotic effect of the salt, rather than a salt-specific or toxic effect. Seminal root length reduction in cultivars was due to osmotic stress of salt solution out of the roots and the values for total root length in bread wheat cultivars was more under salt stress. Shabrang showed the highest and significant increase in leaf temperature among cultivars and the most reduction in shoot dry weigh was observed in this cultivar under salt conditions. In more extended studies, shoot growth was more inhibited than root growth in saline and dry soils, however, in this study, there was little effect on shoot growth. Thus, assimilate supply was not limiting root growth.

The ability of wheat to retain seminal and total root length improved osmotic tolerance and extending root system in salt tolerant cultivars would allow water acquisition from deeper in the soil profile, thus helping to overcome osmotic stress. Results showed that osmotic tolerance may be in bread wheat to the same extent as in durum wheat cultivars and the finding of this study on root traits identify it as one of the valuable index for improved adaptation to osmotic stress in wheat. Under salt conditions or in some wheat cultivars, modification of root water uptake capacity plays a more important role compared with stomatal closure in avoiding stress-induced growth reduction.