z. asrar

Salinity is one of the main stresses that have negative effectcs on seedling growth, and plant production. It inhibits growth of plants through disturbance of the balance between production of ROS and antioxidant defense mechanism which results in oxidative stress. Because, arginine is a vital regulator of physiological and developmental processes the effect of different concentrations of arginine pretreatment of the plant on alleviation of oxidative stress induced by salt 50 and 100Mm NaCl was investigated. Arginine pretreatment increased chlorophyll a, b, carotenoid and seedling growth under salinity condition. Results also showed that salt stress increased proline, protein, H2O2, soluble sugar and the activity of ascorbate peroxidase, guaiacol peroxidase and catalase. Pretreatment of plants with Arg reduced proline, soluble sugar, H2O2 and antioxidant enzymes activity content significantly. The conclusion is that in garden cress plants, pretreatment with concentration of 5 µM and 10 μM arginine may protect cress under salinity stress, probably through the contracting with ROS and or induction of anti-oxidative enzymes.

One of the methods employed to enhance plant secondary metabolite production is the use of abiotic elicitors in plants. In this research، the effect of heavy metal nickel as abiotic elicitors was studied on some physiological parameters in Hyoscyamus niger L. to investigate the use of unstressful concentration of this metal in order to increase secondary metabolite synthesis in later researches. This research was carried out in the Department of Biology of Shahid Bahonar University of Kerman in a complete randomized design with three treatments and three replicates. The seeds of Hyoscyamus germinated in germinator under gibberellin treatment and then were transfered to the pots of sand and peat. After 40 days of growth، the plants were treated with 50 and 100 µM nickel in hydroponics condition (nickel amounts were added to nutrient solution). According to the obtained results، photosynthetic pigments reduced under Ni treatment while hydrogen peroxide، lipid peroxidation and antioxidant enzymes activity increased. Investigation of Ni stress on main macromolecules such as protein، membrane lipids and chlorophyll showed that the effects of 50 and 100 µM Ni was same، while the PAL activity and polyphenols synthesis were the second responses of plants to stress obserevd in 100 µM concentrations. Therefore، it seems that the higher concentration of Ni (100 µM) was more effective for the increment of secondary metabolite in this plant.