Understanding the mechanisms of sodium (Na⁺) influx, effective compartmentalization, and efflux in higher plants is crucial to manipulate Na⁺ accumulation and assure the maintenance of low Na⁺ concentration in the cytosol and, hence, plant tolerance to salt stress. Na⁺ influx across the plasma membrane in the roots occur mainly via nonselective cation channels (NSCCs). Na⁺ is compartmentalized into vacuoles by Na⁺/H⁺ exchangers (NHXs). Na⁺ efflux from the plant roots is mediated by the activity of Na⁺/H⁺ antiporters catalyzed by the salt overly sensitive 1 (SOS1) protein. In animals, ouabain (OU)-sensitive Na⁺, K⁺-ATPase (a P-type ATPase) mediates sodium efflux. The evolution of P-type ATPases in higher plants does not exclude the possibility of sodium efflux mechanisms similar to the Na⁺, K⁺-ATPase-dependent mechanisms characteristic of animal cells. Using novel fluorescence imaging and spectrofluorometric methodologies, an OU-sensitive sodium efflux system has recently been reported to be physiologically active in roots. This review summarizes and analyzes the current knowledge on Na⁺ influx, compartmentalization, and efflux in higher plants in response to salt stress.

Not much information is available to substantiate the possible role of γ -aminobutyric acid (GABA) signaling in mitigating water-deficit stress in snap bean (Phaseolus vulgaris L.) plants under semiarid conditions. Present work aims to investigate the role of exogenous GABA (foliar application; 0.5, 1 and 2 mM) in amelioration of drought stress and improvement of field performance on snap bean plants raised under two drip irrigation regimes (100% and 70% of water requirements). Water stress led to significant reduction in plant growth, leaf relative water content (RWC), cell membrane stability index (CMSI), nutrient uptake (N, P, K, Ca, Fe and Zn), pod yield and its content from protein and total soluble solids (TSS). Meanwhile, lipid peroxidation (malondialdehyde content- MDA), osmolyte content (free amino acids- FAA, proline, soluble sugars) antioxidative defense (activity of superoxide dismutase- SOD, catalase- CAT, peroxidase- POX and ascorbate peroxidase- APX) and the pod fiber content exhibited significantly increase due to water stress. Exogenous GABA application (especially at 2 mM) revealed partial normalization of the effects of drought stress in snap bean plants. GABA-induced mitigation of drought stress was manifested by improvement in growth, water status, membrane integrity, osmotic adjustment, antioxidant defense and nutrient acquisition. Furthermore, GABA application during water stress in snap bean plants resulted in improvement of field performance being manifested by increased pod yield and its quality attributes. To sum up, exogenous GABA appears to function as an effective priming molecule to alleviate drought stress in snap bean plants under semiarid conditions.

Melatonin, a tryptophan-derived molecule, is endogenously generated in animal, plant, fungal and prokaryotic cells. Given its antioxidant properties, is involved in a myriad of signalling functions associated with various aspects of plant growth and development. In higher plants, melatonin interacts with plant regulators such as phytohormones, as well as reactive oxygen and nitrogen species (ROS/RNS) including hydrogen peroxide (H₂O₂), nitric oxide (NO) and hydrogen sulfide (H₂S). It shows great potential as a biotechnological tool to alleviate biotic and abiotic stress, to delay senescence and to conserve the sensory and nutritional quality of postharvest horticultural products which are of considerable economic importance worldwide. This review provides a comprehensive overview of the biochemistry of melatonin, whose endogenous induction and exogenous application can play an important biotechnological role in enhancing the marketability and hence earnings from postharvest horticultural crops.

Hydrogen peroxide (H₂O₂) is a reactive oxygen species (ROS) and a key modulator of the development and architecture of the root system under physiological and adverse environmental conditions. Nitric oxide (NO) and hydrogen sulphide (H₂S) also exert myriad functions on plant development and signalling. Accumulating pieces of evidence show that depending upon the dose and mode of applications, NO and H₂S can have synergistic or antagonistic actions in mediating H₂O₂signalling during root development. Thus, H₂O₂‐NO‐H₂S crosstalk might essentially impart tolerance to elude oxidative stress in roots. Growth and proliferation of root apex involve crucial orchestration of NO and H₂S‐mediated ROS signalling which also comprise other components including mitogen‐activated protein kinase, cyclins, cyclin‐dependent kinases, respiratory burst oxidase homolog (RBOH), and Ca²⁺flux. This assessment provides a comprehensive update on the cooperative roles of NO and H₂S in modulating H₂O₂homoeostasis during root development, abiotic stress tolerance, and root‐microbe interaction. Furthermore, it also analyses the scopes of some fascinating future investigations associated with strigolactone and karrikins concerning H₂O₂‐NO‐H₂S crosstalk in plant roots.