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Effective microorganisms improve growth performance, alter nutrients acquisition and induce compatible solutes accumulation in common bean (Phaseolus vulgaris L.) plants subjected to salinity stress Abstract No information is available concerning effective microorganisms (EM) influence on the ionic and osmotic responses in plants grown in salty soils. Therefore, as a first approach, this study focuses on the contribution of EM to nutrient acquisition and compatible solutes accumulation in salt-stressed plants. It assesses some mechanisms underlying alleviation of salt toxicity by EM application, and also directs to establish a possible interrelationship between EM application as well as ionic and osmotic stresses tolerance in plants exposed to saline soils. Phaseolus vulgaris cv. Nebraska plants were grown under non-saline or saline conditions (2.5 and 5.0 dS m -1 ) with and without EM application. Salinity stress significantly decreased growth, productivity, membrane stability index, relative water content, concentrations of N, P, K ? , Fe, Zn and Cu, and the ratios of K ? /Na ? , Ca 2? /Na ? and Mg 2? / Na ? . However, EM application protected plants against the detrimental effect of salinity and significantly improved the above parameters. Concentrations of Ca ?2 , Mg ?2 , soluble sugars, free amino acids, proline and glycinebetaine were increased under saline conditions; moreover they further increased in salt-stressed plants treated with EM. Lipid peroxidation, hydrogen peroxide content, electrolyte leakage and Na ? level were increased in response to salinity and significantly decreased when stressed plants treated by EM. Reduction in Na uptake together with a concomitant increase in N, P, K, Ca, Mg, Fe, Zn and Cu absorption and a high compatible solutes accumulation may be an efficient mechanism used by EM-treated plants to gain tolerance against salinity stress.

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The efficacy of arbuscular mycorrhizae (AM) on nutrients, organic solutes, and antioxidant enzymes of wheat under salt stress was investigated and related to root colonization and plant productivity. The mycorrhizal inoculation increased N, P, K, Ca, and Mg uptake, soluble sugars, free amino acids, and proline accumulation, as well as peroxidase and catalase activities under saline conditions as compared to nonmycorrhizal plants. On the other hand, Na concentration was lower in mycorrhizal than in nonmycorrhizal plants grown under saline conditions. Arbuscular mycorrhizae protected wheat against the detrimental effects of salinity and stimulated its productivity. Hence, mycorrhizal colonization can play a vital role in the mitigation of the adverse effects of salinity by improving the wheat osmotic adjustment response, enhancing its defense system, and alleviating oxidative damage to cells. Arbuscular mycorrhizae are able to alter plant physiology in a way that empowers the plant to grow more efficiently on salt‐affected lands.

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Salicylic acid (SA) and melatonin (MT) have been shown to play important roles in plant salt tolerance. However, the underlying mechanisms of SA–MT-interaction-mediated ionic homeostasis in salt-stressed plants are unknown. As a first investigation, this study aimed to clarify how SA–MT interaction affects H+-pump activity in maintaining the desired ion homeostasis under saline conditions and its relation to ROS metabolism. Wheat (Triticum aestivum L.) plants were grown under non-saline or saline conditions and were foliar sprayed with 75 mg L−1 SA or 70 μM MT. The SA+MT combined treatment significantly increased N, P, K+, Fe, Zn, and Cu acquisition, accompanied by significantly lower Na+ accumulation in salt-stressed plants compared to non-stressed ones. Additionally, it significantly enhanced ATP content and H+-pump activity of the roots. The mitigation was also detected in the reduced superoxide radical content, electrolyte leakage, and lipoxygenase activity, as well as increased superoxide dismutase, catalase, peroxidase, and polyphenol oxidase activities; K+/Na+, Ca2+/Na+, and Mg2+/Na+ ratios; relative water content; membrane stability index; and free amino acid accumulation in treated plants. The novel evidence shows that the higher root H+-pump activity in treated plants is a tolerance mechanism that increases the salt tolerance via maintaining ionic homeostasis.

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