Salinity is one of the major problems facing crops worldwide. Salinity can severely affect plants in a negative manner. This study aimed to evaluate the impact of NaCl on morpho–physiological, biochemical, structural and ultrastructural properties in Solanum melongena seedlings under different NaCl concentrations. Plants treated with high concentrations of NaCl showed a nonsignificant decrease in shoot height compared to the controls. However, NaCl concentration of 50 mM and above significantly decreased leaf area, while 75 mM and above significantly reduced the photosynthetic rate (PN) and leaf total sugar content when compared with plants treated with less-concentrated NaCl and the controls. Thick root sections from plants grown in 100 and 150 mM NaCl exhibit severe deformation in the epidermal and cortical layers. Additionally, TEM micrographs of plants treated with 75, 100, and 150 mM exhibited bulgy chloroplasts with loss of integrity thylakoid membranes associated with large starch grains. The changes in plant ultrastructure observed in this study broaden our knowledge about the impact of salinity at the cellular level.

Heavy metals are characterised by a relatively high density and cause genotoxic, cytotoxic and mutagenic effects on plants, animals and humans. Lead (Pb) is one of the heavy metals that causes toxicity to plants and animals.• This experiment was conducted using a hydroponic technique to study the effects of Pb(NO 3 ) 2 on physiological, biochemical and ultrastructural characteristics in Leucaena leucocephala seedlings. Plants were grown in a growth chamber for 21 days in Hoagland's solution supplemented with 0 (control), 25, 50, 100, 300, 500 and 700 µM Pb(NO 3 ) 2 .• Shoot heights as well as root lengths decreased significantly in Pb-treated plants with 300, 500 and 700 µM. In Pb-treated plants with high Pb concentrations, photosynthesis rate (P N ), stomatal conductance (g s ) and transpiration rate (E) decreased. Total protein and carbohydrate content in Pb-treated plants with 300, 500 and 700 µM increased significantly in leaves. Moreover, in Pb-treated plants with 300, 500 and 700 µM Pb(NO 3 ) 2 , mesophyll cells had enlarged chloroplasts with disrupted thylakoid membranes associated with large starch grains. In contrast, Pb treatments with 25, 50 µM and 100 µM were not toxic to the plants. Thick sections of roots of Pb-treated plants with 300, 500 and 700 µM Pb showed distinct changes in structure of epidermal and cortical cells. Moreover, thin sections of roots of Pb-treated plants with 300, 500 and 700 µM Pb had thickened walls of xylem cells.• These results will shed more light in understanding the effects of heavy metal stress on plants.