الفهرس 
IntroductiionOnly 14 pages are availabe for public view
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Abstract
The objective of this study was to investigate the effect of stigmasterol and/or sitosterol each with four concentrations (10-10, 10-8, 10-6 and 10-4 molar) on growth parameters, photosynthetic pigment, carbohydrate content, nitrogen fractions, antioxidant enzymes and endogenous level of phytohormones of the shoot of Sesamum indicum L. (sesame) and Zea mays L. (maize) throughout three stages of growth and development. In addition, yield attributes and chemical aspects of the yielded seeds and grains; total protein, glycerol content, oil content, antioxidant enzymes and different fatty acids were determined. Also particular interest was focused on the performance of these treatments to ameliorate the toxicity effects exerted by the foliar application of insecticide malathion. In the majority of cases and during the three stages (vegetative, flowering and fruiting) of sesame and maize growth and development, the obtained results cleared that, treatment with malathion alone decreased the determined growth parameters (shoot length, number of leaves/plant, number of nodes/plant, shoot fresh weight, shoot dry weight and leaves area/plant) and relative water content either significantly in sesame plant or non-significantly in maize plant during flowering and fruiting stages, whereas, treatments with stigmasterol and / or sitosterol either alone or in combination with malathion caused a general significant increase in all of the estimated growth parameters. Throughout the experimental stages of Sesamum indicum and Zea mays plants, the foliar application of malathion alone decreased all estimated photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophylls and carotenoids and consequently total pigments) significantly. Meanwhile, treatment with stigmasterol and/or sitosterol at different concentrations with or without malathion led to a general significant increase in all estimated photosynthetic pigments. On the other hand, chlorophyll a/ chlorophyll b ratio seemed to be non-significantly affected in both plants in response to the above mentioned treatments in relation to the control values. Application of malathion decreased all the determined carbohydrate (glucose, sucrose, total soluble sugars, polysaccharides and total carbohydrates) and nitrogen (ammonia-n, amino-n, amide-n, total soluble nitrogen, total nitrogen and protein nitrogen) fractions. Whereas, the effect of stigmasterol and/or sitosterol with or without malathion treatments led to general significant increases in carbohydrate and nitrogen fractions at the three stages of sesame and maize growth and development. During the three stages (vegetative, flowering and fruiting) of growth and development of sesame and maize plants, catalase, peroxidase and polyphenol oxidase, in general, significantly increased in the two tested plants in response to all treatments with malathion and / or different concentrations of stigmasterol and / or sitosterol in relation to control values. This response was more pronounced by presoaking of the seeds and grains in stigmasterol and/or sitosterol in addition to malathion. During flowering stage, total auxins, cytokinin and GA3 non-significantly decreased and ABA significantly increased under the effect of foliar application of sesame and maize plants with malathion. Meanwhile, the used treatments induced a progressive increase in the estimated growth promoters (auxins, cytokinin and GA3) and a non-significant decrease in ABA content in the variously treated plants. It is worthy to mention that, throughout the three stages of growth and development, the maximum promotive effect on both sesame and maize plants was recorded by stigmasterol and / or sitosterol either alone or in combination with malathion at 10-6 molar. Treatment with malathion decreased the yield attributes (crop yield, grain yield, straw yield, relative grain yield, number of capsules/plant, plant tall, plant height, ear length, number of grains/ ear and seed index) of sesame and maize plants non-significantly. Meanwhile, these yield attributes showed general significant increments by various treatments with stigmasterol and sitosterol as compared with control values. As regards the biochemical aspects of the yielded sesame seeds and maize grains, malathion led to a significant decrease in glycerol content, protein content and oil content. Meanwhile, different concentrations of stigmasterol and/or sitosterol either alone or in combination with malathion in general, significantly increased these estimated chemical compounds. At yield stage, treatment of sesame and maize plants with malathion and / or different concentrations of stigmasterol and / or sitosterol led to a general significant increase in the estimated antioxidant enzymes (catalase, peroxidase and polyphenol oxidase) in the yielded sesame seeds and maize grains compared to the untreated values. This response was more pronounced by presoaking of the seeds and grains in stigmasterol and/or sitosterol in addition to malathion especially at 10-6 molar. Treatment of sesame and maize plants with malathion and/or different concentrations of stigmasterol and/or sitosterol led to marked changes in fatty acids content in the yielded sesame seeds and maize grains, ranging from increase or decrease to slight; if any change in fatty acids content and this is dependent on the plant and the concentration used. On the other hand, the ratio of the unsaturated/ saturated fatty acids either decreased (in response to malathion treatment) or increased (in response to different concentrations of stigmasterol and/or sitosterol with or without malathion) in the yielded sesame seeds and maize grains. The present results are discussed in relation to the action of the malathion or stigmasterol and/or sitosterol and in the light of those recorded by other investigators concerned with different mechanisms of action.