Effects of Different Concentrations of Nickel (Ni) on the Vegetative and Reproductive Growth Parameters of Nigella sativa L.

The present study was based on a hypothesis that excess nickel (Ni) in the soil reduces the growth and seed yield of black cumin plants. A pot experiment was conducted to investigate the above hypothesis on the vegetative and reproductive growth parameters of black cumin. The black cumin plants were grown in pots filled with garden soil which contaminate with different dilutions of Ni viz., 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 millimoles (mM) except control. All doses of the Ni show a marked impact on the vegetative and reproductive growth parameters of black cumin in a concentration-dependent manner and all the growth parameters were reduced severely. Fruit production was also reduced significantly from the dose of 1.5 to 4.0 mM Ni solution. Both chlorophyll a and b levels in the tissues of fresh leaves decreased significantly in each Ni dose. Chlorophyll b (64%) content was more severely decreased than chlorophyll a (60%). The presence of a high concentration of Ni in the soil also decreases the seed yield of the plants. Ni accumulated in the seeds of all treated plants exceeded the permissible limits of the World Health Organization (WHO).