Adaptive behaviour of roots under salt stress correlates with morpho- physiological changes and salinity tolerance in rice

Salinity screening of five commercially available rice (Oryza sativa L.) genotypes i.e., KS-282, Super Basmati, KSK-133, Shaheen Basmati and DilRosh was performed at 100 mM sodium chloride (NaCl) concentration to investigate the effect of salt stress on root architecture and to understand the role of roots in salinity adaptation. Morpho-physiological attributes and water conservation level were monitored in all genotypes under control and stress conditions. Among the tested genotypes, KS-282 was found to be fairly tolerant while Super Basmati was found to be highly sensitive. Changes in the root architectural dynamics were analyzed using WinRhizo pro software program. Na + and K + content in the roots and shoots were correlated with morpho physiological growth parameters and variations in root geometry. A significant decrease in the root length, lateral root density combined with reduced surface area was evident in the tolerant genotype within the first three days of salt treatment. Growth was sustained gradually after this initial delay while no such response was recorded in the sensitive genotype. Similarly, Na + content was found to be significantly lower in the roots and shoots of the tolerant genotype as compared to the sensitive plants. Our data highlights a primal reduction in the total root length and surface area as a major component in tolerance against Na + accumulation and salinity induced damage. Our data can be used to understand root growth and adaptation in other rice species as well as many other forage grass and cereal species under salt stress.