S EEDS of Lupinus termis (cv. Gemmeza R 2) were primed by presoaking for six hr in 100% aqueous extract of carrot roots or 10mM CaCl 2 solution, sown and left to grow for 30 days on clay-sandy soil (2:1 w/w). Seven-day-old seedlings grown from primed and unprimed seeds were exposed to salinity stress at 150mM NaCl. Salinity stress caused decreases in lengths, fresh and dry weights of roots and shoots, leaf water content and photosynthetic pigments. Total soluble sugars, proteins, alkaloids, malondialdehyde (MDA), catalase and peroxidase activities and ascorbate content were elevated by salinity stress. Priming of lupine seeds with CaCl 2 or carrot root extract reversed all of the previous mentioned decreases and increases. Transmission electron microscope results revealed that salinity caused detachment of the plasma membrane from cell walls, degeneration of chloroplast membranes, disorganization of grana, disappearance of some nucleoli and the appearance of some abnormal nuclei. Seed priming preserved the intact cell wall structure, integrity of chloroplast membranes, normal grana organization and nuclear structure with well-defined nucleoli, comparable to those of the control seedlings.

T HE MAJOR aim was to assess the effects of lead stress on Triticum aestivum (cv. Gemmeza R2) and to evaluate the role of seed priming in the aqueous extract of Halimeda opuntia or Codium fragile in the alleviation of these harmful effects. Seven days old T. aestivum seedlings growing from primed seeds were subjected to the sub-lethal concentration (400ppm) of lead nitrate (Pb (NO 3) 2), then left to grow for 14 days. Results revealed that the lead nitrate significantly decreased root length, shoot height and fresh and dry masses of root and shoot, the content of N, PO 4 , K, Mg, Ca and Cu, photosynthetic pigments (Chl a, Chl b), total chlorophyll and photosynthetic activity of 21-days-old plants. On the other hand, carotenoid contents, total soluble sugars, Na and Fe content, the activities of catalase and peroxidase, ascorbic acid and malondialdehyde increased in leaves. The bioactive components in H. opuntia and C. fragile extracts such as minerals and phytohormones (auxins, cytokinins and gibberellins) could potentially participate in the alleviation of lead stress. Therefore, priming of T. aestivum seeds with the aqueous extracts of H. opuntia or C. fragile could mitigate all of the recorded harmful effects under lead stress.

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T HE EXPERIMENT was conducted to investigate the effects of application of rice straw waste-derived biochar on the growth and some metabolic activities of salt-stressed cowpea (Vigna unguiculata L.). Moreover, biochar as a soil amendment was evaluated with the additional rate of chemical fertilizers (NPK) under salinity stress in agro-ecosystem. The results indicate that salinity (200mM NaCl) caused a significant reduction in all measured growth parameters of cowpea seedlings compared with control. Salinity stress caused reduction in germination percentage by 54% and 14% and 17% in the lengths of shoot and root, respectively as well as leaf area (22% reduction), compared with the control. Furthermore, the activities of antioxidant enzymes (peroxidase, catalase and superoxide dismutase), malondialdehyde (MDA), ascorbic acid content and osmolytes (total soluble proteins, carbohydrates and amino acids) were increased under salinity stress. The results showed that application of rice straw-derived biochar increased the germination percentage and all the studied growth criteria under salinity stress. In addition, rice straw-derived biochar increased the photosynthetic activity and photosynthetic pigments (Chl. a, Chl. b and carotenoids) and decreased the biosynthesis of MDA and ascorbic acid. The results demonstrate that the highest values of the measured growth parameters and physiological processes of cowpea seedlings were recorded at 75% NPK combined with biochar treatment. In conclusion, application of rice straw-derived biochar reduced the additional rate of chemical fertilizer by 25%.