Effect of growth regulators on growth, yield and ions accumulation of rice (Oryza sativa L.) under salt stress

A pot experiment was conducted in glass-house to assess the role of Abscisic acid (ABA), Benzyleadenine (BA) and Cycocel (CCC) on growth, yield, ion accumulation and proline production in three rice cultivars viz, Super Basmati, Shaheen Basmati (fine cultivar) and IR-6 (coarse cultivar) differing in yield. Seeds of each cultivar were soaked prior to sowing with ABA and BA each at 10-5 M and CCC 10-6 M for 24h. Salinity of 5dS/m was developed by adding NaCl salt in five equal splits daily to fifteen days old plants of all the cultivars. Plants were harvested two weeks after salt treatment. Shoot and root dry weight decreased at salinity stress as compared to control, however ABA, BA and CCC treatment caused a substantial increase in shoots and root dry weight over that of salt alone. Salt treatment increased the level of Na+ and CI- but decreased K+ content in flag leaves as well as in roots of three rice cultivars. ABA and CCC treated plants s howed significant decrease in Na+ content but increased K+ content in flag leaves of all the cultivars at salt stress. ABA was more effective to increase Ca2+ content in flag leaf as well as in roots of all the cultivars as compared with BA and CCC. The levels of ions (Na+, K+, Ca2+ and Cl-) were relatively higher in roots than in flag leaves, however higher accumulation of K+ and Ca2+ content with lower accumulation of Na+ and CI- in IR-6. The ranking of growth regulators for their effects on grain yield and 1000-grain weights were ABA greater than BA greater than CCC. Higher grain yield and 1000-grain weight was recorded by IR-6. ABA and CCC treatment further augmented the stimulatory effect of salts on proline accumulation. Higher proline accumulation was observed in IR-6 as compared to Shaheen Basmati and Super Basmati. Rice cv. IR-6 performed better. The relatively low accumulation of Na+ and CI- and less translocation to flag leaf of IR-6 concomitant with high K+ accum u lation, better proline content and greater leaf area under salt stress make this variety salt tolerant. These traits are augments by ABA more effectively than BA.