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Salt stress is one of several major abiotic stresses that affect plant growth and development, and there are many evidences that silicon can ameliorate the injuries caused by high salinity. This study presents the results of an assay concerning: (1) the effect of NaCl induced salt stress in barely plant (cultivar Giza 123) and (2) the possible mitigating effect of silicon in saline conditions. In these study, different concentrations of NaCl (200 & 300 mM) used singly or in combination with silicon (0.5&1.0 mM potassium silicate). Morphological characters of shoot and roots, membrane stability index, relative water content, sodium, potassium, silica, photosynthetic pigments content and some antioxidant enzymes, as well as leaf electron microscope were evaluated. The results showed that, all parameters analyzed decreased except antioxidant enzymes and sodium content were drastically increased by increased salt levels. The supply of silicon (1mM) has successfully mitigated the effect of salinity at 300 mM NaCl. In conclusion, we affirmed that, salt stress is harmful for cape barley plants and the addition of silicon showed effective in mitigating the saline effects.

A pot experiment was conducted to study the effects of cadmium and lead on some metabolic products of flax (Linum usitatissimum Giza 5) and canola (Brassica napus Serw 4) at two growth stages; vegetative and flowering stages. The soil enriched with different levels of Cd as Cd (NO 3) 2 (25, 50, 100 and 150 mg/kg soil) and Pb as Pb (NO 3) 2 (250, 500, 1000 and 1500 mg/kg soil) in addition to control. The results showed that a significant reduction in pigment fractions while proline, total soluble sugars, thiols, lipid peroxidation, ascorbic acid and activity of catalase as well as peroxidase increased significantly in both plants with increasing concentration of Cd and Pb. The results also showed that there was an increase in pigment fractions, proline, ascorbic acid and total soluble sugar while lipid peroxidation, thiols and enzymatic activity were decreased as plants proceeded from vegetative to flowering stages.

n the present work, some of the adaptive responses against dehydrative factors were evaluated in two true xerophytic plants, for their medicinal importance; [Launaea spinosa (Forssk.) Sch. and Leptadenia pyrotechnica (Forssk.) Decne.] growing naturally (wild plants) at Wadi Hagul, Eastern Desert of Egypt during both wet and dry seasons. The results reveled that Launaea spinosa achieved the highest significant ash concentration during the dry season and this was mainly due to accumulation of Na + , K + , Cland SO 4 2-, meanwhile the opposite was found in Leptadenia pyrotechnica, which accumulated Ca 2+ , Mg 2+ and P 3+ during the wet season. The highest significant concentrations of total carbohydrates, insoluble sugars as well as phytohormones were recorded during the wet season, while organic acids, free thiols, total fibers, and soluble sugars were accumulated, in both species, during the dry season. From the results it is clear that, ethyl acetate extracts for both species possessed the highest antimicrobial activity against all tested fungal and bacterial strains. The obtained results showed that the studied species have different mechanisms to adapt and tolerate the various environmental conditions.

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The present work was designed to study ecophysiological responses of two non-succulent xerophytes, Launaea spinosa and Leptadenia pyrotechnica growing naturally in wadi Hagul, estern desert of Egypt during dry and wet seasons. The results revealed that organic constituents including, crude protein, free amino acids and nucleic acids were generally increased during wet season in the studied species. However, soluble protein, was significantly higher during dry season. Concentrations of protein amino acids, at both seasons of Launaea spinosa were greater than that of Leptadenia pyrotechnica. Electrophoretic protein fractions showed variations due to the differences in growing seasons.