Alleviating effects of humic acid on germination and vegetative growth of canola under salinity stress

Salinity is an effective abiotic stress on plants production that the application of suitable organic materials reduces its consequences. Thus, in this experiment, the mitigating effects of humic acid (0, 500 and 1000 mg.l-l) on salinity (EC; 0, 4, 8 and 12 dS.m-1) was evaluated at germination and vegetative stages of canola. According to the results, inhibitory effects of salinity on seed germination, germination rate, radicle and shoot length, and dry weights of radicle and shoot were significant. Also, salinity decreased the leaves chlorophylls contents and their membrane stabilities. Humic acid treatment increased chlorophyll (chl) a, total chl and carotenoid contents at 1000 mg l-1 concentration. Regarding to significant interaction effects of humic acid and salinity on membrane stability, seed gemination, germination rate and radicle length traits, results represent a mitigating effect of humic acid on mentioned traits under salinity condition. The humic acid at 1000 mg.l-1 level alleviates seed germination percentage at EC 4 dS.m-1, as well as improved germination rate under EC 8 dS m-1. Likewise, mitigating effect of humic acid on membrane stability at EC 8 and 12 dS.m-1 was noticeable. It was concluded that, under moderate levels of salinity, application of humic acid as seed treatments is recommended to alleviate the stress effects.