Growth-promoting bacteria and natural regulators mitigate salt toxicity and improve rapeseed plant performance

Salinity is a major environmental stress that limits plant production and portraits a critical challenge to food security in the world. In this research, the impacts of plant growth–promoting bacteria (Pseudomonas RS-198 and Azospirillum brasilense RS-SP7) and foliar application of plant hormones (salicylic acid 1 mM and jasmonic acid 0.5 mM) on alleviating the harmful effects of salt stress in rapeseed plants (Brassica napus cv. okapi) were examined under greenhouse condition. Salt stress diminished rapeseed biomass, leaf area, water content, nitrogen, phosphorus, potassium, calcium, magnesium, and chlorophyll content, while it increased sodium content, endogenous salicylic and jasmonic acids, osmolyte production, H₂O₂ and O₂^•− generations, TBARS content, and antioxidant enzyme activities. Plant growth, nutrient content, leaf expansion, osmolyte production, and antioxidant enzyme activities were increased, but oxidative and osmotic stress indicators were decreased by bacteria inoculation + salicylic acid under salt stress. Antioxidant enzyme activities were amplified by jasmonic acid treatments under salt stress, although rapeseed growth was not generally affected by jasmonic acid. Bacterial + hormonal treatments were superior to individual treatments in reducing detrimental effects of salt stress. The best treatment in rectifying rapeseed growth under salt stress was combination of Pseudomonas and salicylic acid. This combination attenuated destructive salinity properties and subsequently amended rapeseed growth via enhancing endogenous salicylic acid content and some essential nutrients such as potassium, phosphorus, and magnesium.

     

Biochar Increased Plant Growth-Promoting Hormones and Helped to Alleviates Salt Stress in Common Bean Seedlings

Journal of Plant Growth Regulation - Salinity seriously disrupts the growth and physiology of plants, whereas phytohormones play an important role in regulating plant responses to salinity stress....     

Changes in Oil Accumulation and Fatty Acid Composition of Soybean Seeds under Salt Stress in Response to Salicylic Acid and Jasmonic Acid

greenhouse experiment with factorial arrangement based on randomized complete block design with four replications was conducted in 2015 to evaluate the effects of salicylic acid (SA) (1 mM) and jasmonic acid (JA) (0.5 mM) on oil accumulation and fatty acid composition of soybean oil (Glycine max L.) under salt stress (Non-saline, 4, 7, and 10 dS/m NaCl). Oil percentage of soybean seeds declined, while oil content per seed enhanced with increasing seed filling duration. Foliar application of SA improved oil content per soybean seed at different stages of development under all salinity levels. Although JA treatment enhanced seed oil percentage, oil yield of these plants decreased as a result of reduction in seed yield per plant. In contrast, the highest oil yield was recorded for SA treated plants, due to higher seed yield. Salinity had no significant effects on percentage of palmitic acid and stearic acid, but treatment with JA significantly reduced stearic acid percentage. Oleic acid content of seeds increased, but percentages of linoleic acid, linolenic acid and unsaturation index (UI) of soybean oil decreased with increasing salinity. Foliar application of SA and JA improved oil quality of soybean seeds by reducing oleic acid and enhancing linoleic acid, linolenic acid contents and UI. Exogenous application of SA had the most beneficial effects on soybean seeds due to enhancing oil yield and quality under saline and non-saline conditions.     

Biochar improved nodulation and nitrogen metabolism of soybean under salt stress

To investigate salt stress and biochar application effects on nodulation and nitrogen metabolism of soybeans (Glycine max cv. M7), an experiment was conducted under the control condition. The treatments comprised three biochar rates (non, 50 and 100 g kg^?1 soil) and three salinities (0, 5 and 10 dS m^?1 NaCl), with four replications of treatments. Salt stress diminished the number of nodules and their weights in the soybean roots. Nitrogen content and metabolism decreased in nodules, roots and shoots, while reducing the activity of glutamate dehydrogenase (GDH), glutamine synthetase (GS), glutamine oxoglutarate aminotransferase (GOGAT) and nitrate reductase (NR). Also, salinity brought down root and shoot weight, total plant biomass, chlorophyll content, leaf area (LA) and rubisco activity in the soybean. On the other hand, application of biochar improved nodulation, nitrogen content, rubisco activity, GDH, GS, GOGAT and NR activities in different parts of the soybean and nodules under salt stress, and consequently improved chlorophyll content, LA, root and shoot weight. Both the 50 and 100 g kg^?1 biochar rates showed similar effects in improving nitrogen metabolism and plant performance under salt stress. Generally, biochar increased nodulation and nitrogen metabolism of the soybean under saline conditions.