Changes in metabolomics and tissue architectural alterations jointly ameliorate salt mediated injuries in Nigella sativa L.

This study evaluated plant resistance to salinity across varying salt concentrations: 0, 50, 100, 150, and 200 mM NaCl. Thestudy revealed how these salt levels affected the morphological, physiological, biochemical, and developmental characteristics of theplants. At the 50 mM NaCl treatment level, plant height dropped by 8% in comparison to the control. The shoot fresh and dry weightsof every plant subjected to different levels of salt stress decreased noticeably. At 200 mM NaCl, the plants fresh weight of root decreasedby the greatest percentage (42.8%). The total number of chlorophyll a and chlorophyll b in Nigella sativa L. was significantly lower at 200mM salinity by 88% and 78.5%, respectively than in the control. Furthermore, in comparison to the control, exposure to 200 mM NaClraised the levels of proline, catalase activity, malondialdehyde, total free amino acids, and H2O2 by 38%, 27.6%, 28%, 186%, and 165%,respectively. The stem and root anatomy of Nigella sativa L. showed significant variation reflecting differential adaptation to salinity.Notably, at 200 mM NaCl, there was 73.33% and 69.23% reduction in stem and root epidermal thickness respectively. Similarly, markedreduction in epidermal cell area of stem and root (84.52%, 78.8%), cortical cell area (66.66% and 55.17% in the stem and root), vascularbundle cell area of stem and root (69.23% and 61.80%), and metaxylem cell area (66.66% and 60.26% in the stem and root) was recordedas compared to control plants. Overall, the variations in antioxidant levels, osmoprotectants, and photosynthetic pigments, along withchanges in root and stem structure, played a crucial role in salinity tolerance of the plants.