Sensitivity of Seed Germination to Salt Stress in Black Cumin (Nigella sativa L.)

Black cumin is an annual oilseed crop, native to the Mediterranean region and widely used for nutritional and medicinal purposes. Reduced seed germination and early seedling growth under saline conditions are considered as major factors limiting the establishment of crops. The objective of this study was to investigate the effect of salinity due to NaCl on germination of black cumin seeds. A set of experiments was conducted under completely randomized design with four replications of 200 seeds at two different suboptimal germination temperatures (15 and 20 degrees C) in the dark for 16 days. In order to create salt stress conditions during the germination process, five solutions were used (0 as control, 80, 160, 240 and 320 mM NaCl). The germination performance was evaluated by final germination percentage and mean germination time. The effect of salinity on seed germination percentage and mean germination time was significant at p<0.01. Germination of the controls was 96% and 95% at 15 degrees C and 20 degrees C, respectively. The presence of NaCl, regardless of temperature, reduced germination. This reduction was more severe at 15 degrees C (15%, and 19% germination in cases of 80 and 160 mM concentration respectively) than at 20 degrees C (65% at 80 mM salinity level) and no germination was observed from 240 mM onwards. The mean germination time increased with increased NaCl levels, especially at the lower temperature of 15 degrees C. The overall results of this experiment showed the inhibitory effects of salt stress on seed germination parameters of black cumin.