Comparative study of cadmium nitrate and lead nitrate [Cd(NO 3 ) 2 and Pb(NO 3 ) 2 ] stress in cyto-physiological parameters of Capsicum annuum L.

This study was conducted to understand the toxic effects of cadmium nitrate and lead nitrate [Cd(NO 3 ) 2 and Pb(NO 3 ) 2 ] and their mitigating role on the Capsicum annuum L. cultivar. The biological effects of Cd and Pb were investigated using stress response indicators such as stomata, gas exchange parameters, proline, and defensive enzyme systems. Fresh seeds were treated with different concentrations (100, 200, 300, 400, and 500 ppm) of both Cd and Pb for 6 h. Cytological effects were observed under a microscope by crushing acetocarmine-stained anthers on glass slides. Stomata size was determined with a scanning electron microscope. Photosynthetic and transpiration rates were measured using an infrared gas analyzer. Chlorophyll and carotenoid pigments were determined analytically with a spectrophotometer. An expected decrease in chlorophyll and carotenoid content was observed with increasing concentrations. Cytotoxic effects of Cd and Pb resulted in various changes in chromosomes including laggard, stickiness, multi-nucleate, and disturbed polarity. The size of stomata decreased at higher concentration and measured to 2.20and 4.6 μM with low stomata conductance at 500 ppm of Cd and Pb. Photosynthetic and transpiration rates showed a moderate trend with increasing concentrations, where high photosynthetic and transpiration rates were measured to 20.20 and 23.40 m −2 s −1 at 200 ppm concentration. Maximum SOD and CAT activity was 2.82 and 6.34 unit mg −1 at 300 ppm of Cd. These results are valuable for understanding how crop plants respond to heavy metals, especially when using them as inducing agents during cyto-physiological experiments.