T HIS STUDY investigate the efficacy of β-sitosterol (10-3, 10-5 and 10-7 molar) or gibberellic acid (100ppm) on alleviating harmful effects of temperature stress (10 o C and 45 o C) on three cultivars of Lycopersicum esculentum Mill., mainly Fayrouz, Aziza and N23-48 to the purpose the activities of some antioxidant enzymes, protein patterns and DNA finger print in order to focus on the role of β-sitosterol or gibberellic acid for enhancing plant tolerance against temperature stress. It was found that, temperature stress (10 o C and 45 o C) decreased the activities of catalase and peroxidase, while β-sitosterol (10-3 , 10-5 and 10-7 molar) or gibberellic acid (100ppm) enhanced these enzymes activity. The electrophoresis studies showed that some new protein bands and DNA finger print were observed probably to increase plant tolerance against temperature stress. These results give a positive indication of the use of β-sitosterol specially 10-5 molar or gibberellic acid in field application to ameliorate the toxic effects of temperature on tomato plants.

In recent studies, sodium alginate (SA) has mainly been a plant growth promoter for many plants and crops as a novel bio stimulating materials for increasing plant growth under various conditions. Pot testing was done to examine the impacts of various levels of SA (25, 50 and 100 ppm) on the growth and physiological activities of Corchorus olitorius (molokhya), Vicia faba (faba bean) and Zea mays (corn) plants in two vegetative stages after 10 and 40 days from sowing. Treatment with different SA concentrations improved significantly the physiological characters of the used plants. The data indicated that the used SA concentrations increased photosynthetic pigments, carbohydrate contents, nitrogen contents, antioxidant enzymes and overall protein significantly as compared to control values.

The objective of this study was to investigate the effects of different nitrogen fertilizers (potassium nitrate and / or urea) on root growth, leaf area ratio, pigments content and carbohydrate content of leguminous plant Vigna sinensis and non-leguminous plant Helianthus annuus, throughout two vegetative stages. Root criteria,in general non-significantly affected by the used source of nitrogen during the two vegetative stages of cowpea and sunflower plans growth. Concerning the leaf area ratio, except for the observed non-significant increase in response to treatment with 100% potassium nitrate + 100% urea at second stage, the other treatments was non-significantly decreased this ratio during the two vegetative stages of the two plants. Total chlorophyll and total pigments were increased by the used treatments at first stage of cowpea growth while these parameters were decreased during the second stage and vice versa in case of sunflower plant. Sucrose content of the two plants, was significantly increased by all used treatments at first vegetative stage. On the other hand, the different treatments led to a general increase in the determined carbohydrates (total soluble sugars-sucrose-polysaccharides-total carbohydrates) as compared to control values during second stage of the two plants. The result of this investigation demonstrated that, nitrogen fertilizers has an overall positive influence on growth, photosynthetic pigments and sugars especially in case of using (50% potassium nitrate + 50% urea) and the magnitude of response was more pronounced in case of cowpea plant.

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