Changes in the activities of oxidative enzymes (indole acetic acid oxidase, peroxidase and catalase), endogenous hormones (gibberellic acid (GA3), indole acetic acid (IAA), abscisic acid (ABA) and cytokinins (AsZeatin), photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids), total carbohydrates, total soluble sugars, amino acid proline and vegetative growth parameters were used as indicators to explain the physiological role of the growth retardant prohexadione-calcium on Vicia faba seedlings 40 days after sowing under salinity stress for 30 days. The obtained results show that soaking faba bean seeds prior to sowing at different concentrations of prohexadione-calcium (0, 10, 20 and 30 ppm) significantly increased the activities of indole acetic acid oxidase (IAA-oxidase) and peroxidase enzymes, but decreased the catalase enzyme activity as compared with their respective control. Application of prohexadione-Ca caused markedly decreases in the endogenous contents of gibberellins and indole acetic acid (IAA) but increased the levels of natural growth inhibitor abscisic acid (ABA) and cytokinins in the shoots of faba bean seedlings. All the prohexadione-Ca concentrations increased the contents of amino acid proline, photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids), total carbohydrates and total soluble sugars in faba bean seedlings grown under salt stress. Application of prohexadione-Ca decreased significantly seedling height and shoot fresh weight but significantly increased shoot dry weight.
endogenous hormones; faba bean; growth retardant; oxidative enzymes; salinity
