Effects of salt stress on germination, growth and ion contents of Cumin (Nigella sativa L.)

The general responses of black cumin (Nigella sativa) in germination and growth stages to salt stress have been investigated in two-separated experiment. Laboratory experiment was conducted in Random Completely Design (RCD) with four replications. Laboratory experiment was investigated response of black cumin to different salinity levels during germination. Germinating seeds treated with aqueous solutions of 4, 8, 12 and 16 ds.m^-1 NaCl with distilled water as control. In greenhouse experiment, treatments completely randomized in factorial experiments with three replications. The treatments were two kinds of salinity stress supply (water base and soil base salinity) and five levels of salinity including 4, 8, 12 and 16 ds.m^-1 NaCl with distilled water as control. Results show that germination percentage, germination rate, root and shoot length, root and shoot weight, total dry weight, chlorophyll content and K⁺ and Na⁺ concentration were significantly affected by salinity stress. Except K⁺ and Na⁺ concentration in germination experiment, all of mentioned traits were significantly decreased with increasing salinity. The highest salt concentrations caused a decrease in all traits compared with control except Na⁺ concentration in all treatment. The rate of germination was decreased with increasing salt concentration and all treatments of NaCl were inhibitory to root and shoot elongation of seedlings in compare to the distilled water controls. In greenhouse experiment, salinity by water was more destroyer than soil salinity. It seems that black cumin can be tolerated salinity up to 12 ds.m^-1, probably because of K⁺ accumulation in shoot at germination stage, while in growth stage cannot tolerate salinity over four ds.m^-1. It seems that black cumin is relatively more tolerant in germination stage to salinity compared to growth stage. It is therefore important to consider salinity response of black cumin at different stages of its growth when selecting for crop tolerance.