Abstract
Salinity stress is a limiting factor for the growth and yield quality of rapeseed. The potentiality of melatonin (MT; 0, 25, 50, and 100 µM) application as a seed priming agent in mediating K+/Na+ homeostasis and preventing the salinity stress mediated oxidative damage and photosynthetic inhibition was studied in two rapeseed cultivars. We found that 50 µM MT treatment imparted a very prominent impact on growth, metabolism of antioxidants, photosynthesis, osmolytes, secondary metabolites, yield, and fatty acids composition. Days required for appearance of first flower and 50% flowering were decreased by MT application. Exogenous MT treatment effectively decreased the oxidative damage by significantly declining the generation of superoxide and hydrogen peroxide under saline and non-saline conditions, as reflected in lowered lipid peroxidation, heightened membrane stability, and up-regulation of antioxidant enzymes (catalase, superoxide dismutase, and ascorbate peroxidase). Furthermore, MT application enhanced the chlorophyll content, photosynthetic rate, relative water content, K+/Na+ homeostasis, soluble sugars, and proline content. Moreover, MT application obviously improved the oil quality of rapeseed cultivars by reducing glucosinolates, saturated fatty acids (palmitic and arachidic acids), and enhancing unsaturated fatty acids (linolenic and oleic acids except erucic acid were reduced). Yield related-traits such as silique traits, seed yield per plant, 1000 seeds weight, seed oil content, and yield biomass traits were enhanced by MT application. The anatomical analysis of leaf and stem showed that stomatal and xylem vessels traits are associated with sodium chloride tolerance, yield, and seed fatty acid composition. These results suggest the supportive role of MT on the quality and quantity of rapeseed oil yield.
Highlights
Salinity is known as one of the environmental stresses, and limits agricultural production and threatens land productivity, affecting food sustainability in many parts of the world.Globally, around 20% and 33% of cultivated and irrigated soil, respectively, is salt-influenced and degraded [1,2]
The mentioned growth traits were decreased under NaCl stress in Yangyoushuang2 by 5%, (LN), total leaves area (TLA), root dry weight (RDW), stem dry weight (SDW), and leaves dry weights
The results showed an increase in green silique traits of B. napus cultivars with MT treatments under NaCl and non-NaCl stress compared with the non-pretreated control
Summary
Salinity is known as one of the environmental stresses, and limits agricultural production and threatens land productivity, affecting food sustainability in many parts of the world.Globally, around 20% and 33% of cultivated and irrigated soil, respectively, is salt-influenced and degraded [1,2]. Salinity is an injurious stress for crop plants and reduces yield and quality. Salinity stress induces oxidative stress, which has adverse effects on photosynthesis and chlorophyll fluorescence of plants [2,3]. Salinity inhibitory effects on plant growth and development are attributed to Na+ and Cl− ions phytotoxicity, low external osmotic potential, and nutrients deficiencies [2,4,5]. Ion phytotoxicity is caused by the substitution of K+ by Na+ in biochemical reactions and the loss of function of proteins, as Na+ and Cl− ions penetrate the hydration shells and interfere with the non-covalent interaction among the amino acids [6,7,8]. Salt-stressed plants often face disruptions in water relations and ion homeostasis owing to toxic ion accumulations
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