Physiological studies on the effect of uniconazole and selenium on growth, certain metabolic activities and productivity of canola plants grown under salinity stress

Abstract

Salt stress causes deleterious physiological changes which restrict canola growth and yield. The objective of this work was to study the effects of foliar applications of different concentrations of the growth retarding chemical uniconazole and selenium on canola plants (Brassica napusL.) grown under salts stress conditions by investigating plant growth, yield and changes in phytohormones, photosynthetic pigments, carbohydrates, proline, nitrogenous constituent, certain mineral ions content, activities of some antioxidant enzymes of canola plants and fatty acid composition of the yielded seeds. For this purpose canola plants were irrigated with different levels of saline solution (0, 2000, 4000 and 6000 mg L-1, prepared according to Stroganov equation), then the effect of different dosage of uniconazole (10, 20 and 40 mg L-1) or Se (2.5, 5 or 10 mg L-1 selenium as sodium selenate) were examined as foliar spray on 60 and 75 –days old plants (in case of uniconazole treatment) and 50 and 65 – days old plants (in case of selenium treatment). Then samples were collected for analysis from82– days old plants treated with uniconazole and 72 – days old plants treated with selenium. Salinity led to significant inhibition in plant growth, yield components, photosynthetic pigment contents, quantity and quality of seed oil. The detected inhibition was directly related to the applied concentrations of salt. Uniconazole or selenium applied alone or in combination with salt treatment significantly increased plant growth, yield, photosynthetic pigment content and improved the quality of canola oil comparing with the corresponding control plants. The most effective concentration of uniconazole was 20 mg L-1 and for Se was 5 mg L-1. In addition, plants treated with Se or uniconazole exhibited various defense mechanisms to cope with salt stress including increased endogenous proline content, phytohormones content (particularly cytokinins and abscisic acid), enhanced catalase activity and increased magnesium and phosphorus ion contents. Moreover, the current study revealed changes in the protein profile of canola leaves; some proteins were disappeared and synthesis of a new set of protein was induced, some of these responses were observed in response to selenium treatment alone or in combination with salt stress whereas some other changes in protein profile were detected in untreated plants subjected to salt stress.