الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
This investigation includes a series of experiments carried out in order to estimate the appropriate optimum concentrations of the used adaptive compounds and compare the attempted growth, metabolic, biochemical and molecular changes, maintained in the broad bean (Giza 3) seedlings, in response to chilling conditions used either alone or in combination with the determined optimum concentration of each of the adaptive compounds. The purpose of this detailed investigation was to maintain a basis for expected mechanisms involved in this type of stress as well as to check up ways of partial or complete recovery from the induced stress. Exposure of broad bean seedlings to chilling stress induced pronounced significant changes in growth parameters, the total amount and in the relative composition of pigment fraction contents. Furthermore, significant variable decreases in PS II activity. Also there are significant variable changes in the total amount and in the relative composition of the carbohydrate pool. There are significant variable increases in total phenolic compounds as well as in anthocyanin contents, high accumulation of both glycine and proline amino acids. Changes in protein banding patterns were apparent. There are significant decreases in antioxidant (enzymic and non-enzymic) system. Chloroplasts and mitochondria were deformed. There are significant increases in H2O2 content, lipid peroxidation and electrolyte leakage. All these harmful effects were nullified when seeds were primed in salicylic acid or ascorbic acid before being exposed to chilling stress. Molecular approaches through application of DDRT-PCR to investigate the effects of chilling stress on the expression of ABR17 gene in Vicia faba seedlings revealed that the mRNA level was induced in all treated broad bean seedlings. In control (untreated) samples the ABR17 expression was not detected although another band with higher molecular weight was detected. The mRNA expression using RT-PCR was also confirmed by SDS-PAGE where commassie-stained bands were detected in the treated samples (SA+Ch, AsA and ASA+Ch). Estimation of the molecular mass of the unique band using molecular marker indicate that this corresponds to the ABR17 molecular mass. This could further illustrate the tolerance to chilling stress of both SA+Ch- and AsA+Ch- treated broad beans.