In plants dehydration imposed by salinity can invoke physical changes at the interface of the plasma membrane and cell wall. Changes in hydrostatic pressure activate ion channels and cause depolarization of the plasma membrane due to disturbance in ion transport. During the initial phases of salinity stress, the relatively high osmotic potential of the rhizosphere enforces the plant to use a diverse spectrum of strategies to optimize water and nutrient uptake. Signals of salt stress are recognized by specific root receptors that activate an osmosensing network. Plant response to hyperosmotic tension is closely linked to the calcium (Ca²⁺) channels and interacting proteins such as calmodulin. A rapid rise in cytosolic Ca²⁺ levels occurs within seconds of exposure to salt stress. Plants employ multiple sensors and signaling components to sense and respond to salinity stress, of which most are closely related to Ca²⁺ sensing and signaling. Several tolerance strategies such as osmoprotectant accumulation, antioxidant boosting, polyaminses and nitric oxide (NO) machineries are also coordinated by Ca²⁺ signaling. Substantial research has been done to discover the salt stress pathway and tolerance mechanism in plants, resulting in new insights into the perception of salt stress and the downstream signaling that happens in response. Nevertheless, the role of multifunctional components such as Ca²⁺ has not been sufficiently addressed in the context of salt stress. In this review, we elaborate that the salt tolerance signaling pathway converges with Ca²⁺ signaling in diverse pathways. We summarize knowledge related to different dimensions of salt stress signaling pathways in the cell by emphasizing the administrative role of Ca²⁺ signaling on salt perception, signaling, gene expression, ion homeostasis and adaptive responses.

Given the widespread recognition of the health risks and environmental damages caused by synthetic herbicides and fertilizers, it is more than ever necessary to unravel the mechanisms underlying plant responses to naturally derived bioactive substances. Phenolic acids constitute a group of aromatic compounds that, by showing both growth-promoting and allelopathic effects, have gained momentum over the past years. We aimed to investigate the effects of some common benzoic acid derivatives, namely vanillic acid (VA), p-hydroxybenzoic acid (pHBA), gallic acid (GA), and salicylic acid (SA), and the alleviative effects of nitric oxide (NO) on phenolic acid-induced inhibition in growth parameters in spearmint (Mentha spicata L.) shoot and underlying mechanisms. pHBA and VA at 0.5 mM were the most influential phenolic acids in the inhibition of growth and increasing the contents of malondialdehyde (by 119% and 83% respectively) and H₂O₂ (by 83% and 108% respectively) and decreasing chlorophyll content despite accelerating the activities of catalase and superoxide dismutase. In contrast, 0.5 mM SA and 0.05 mM GA significantly increased shoot fresh weight (by 85.1% and 48.1% respectively) and the accumulation of total phenolics (by 302% and 31% respectively) and anthocyanins (by 79% and 49% respectively) and stimulated phenylalanine ammonia lyase (PAL) activity (by 140.4% and 107.7% respectively). NO at 100 µM was highly effective in the alleviation of pHBA and VA-induced growth reduction and lipid peroxidation. In conclusion, NO improved the negative effects of pHBA and VA by increasing PAL activity and enhancing the contents of antioxidative secondary metabolites.