Plant Salinity Stress: Many Unanswered Questions Remain

Abstract

Salinity is a major threat to modern agriculture causing inhibition and impairment of crop growth and development. Here, we not only review recent advances in salinity stress research in plants but also revisit some basic perennial questions that still remain unanswered. In this review, we analyze the physiological, biochemical, and molecular aspects of Na + and Cl − uptake, sequestration, and transport associated with salinity. We discuss the role and importance of symplastic versus apoplastic pathways for ion uptake and critically evaluate the role of different types of membrane transporters in Na + and Cl − uptake and intercellular and intracellular ion distribution. Our incomplete knowledge regarding possible mechanisms of salinity sensing by plants is evaluated. Furthermore, a critical evaluation of the mechanisms of ion toxicity leads us to believe that, in contrast to currently held ideas, toxicity only plays a minor role in the cytosol and may be more prevalent in the vacuole. Lastly, the multiple roles of K + in plant salinity stress are discussed.

OsRuvB transgene induces salt tolerance in pigeon pea

“…This in turn leads to the synthesis of reactive oxygen species and initiation of oxidative stress. Oxidative stress result in damage to cellular components, degradation of chlorophyll and peroxidation of the membrane lipids; all of which result in impaired plant metabolism and improper growth of the crop plant and thereby poor yield (Rasool et al 2013;Isayenkov and Maathuis 2019).…”

“…Higher salt concentrations impair the water-plant relations and in lieu of the disturbed osmotic potential the relative water uptake is reduced in plants. This result in drought-like symptoms and reduced stomatal conductance, so as to conserve water, in the plants (Rasool et al 2013;Isayenkov and Maathuis 2019). Relative water content is a physiological index used to study the water retention capacity and it acts as an appropriate parameter to measure water status and osmotic adjustments of plants under abiotic stresses (Ravikumar et al 2014).…”

“…ROS in turn damages cell components, degrades chlorophyll and brings about membrane lipid peroxidation. These parameters are indicative of salinity and stress (Rasool et al 2013;Isayenkov and Maathuis 2019) and thus were considered in the current study.…”

Airborne medicine: bacterial volatiles and their influence on plant health

“…Likewise, later work focusing on another Bacillus strains revealed that bacterial volatiles themselves could serve as nutrient sources, as elegantly demonstrated by plants taking up bacterial dimethyl disulphide synthetized from labelled sulphate in a split Petri dish setup (Meldau et al, 2013). Salinity stress, an everincreasing world-wide problem, is caused by both water shortage and toxic level accumulation of ions such as sodium (Na) or chloride (Isayenkov & Maathuis, 2019). Using the same Bacillus GB03 model strain, Zhang and colleagues demonstrated the salinity stress-alleviating potential of bacterial volatiles, which led to tissue-specific expression modulation of an Na exporter in A. thaliana.…”

Salinity Stress-Mediated Suppression of Expression of Salt Overly Sensitive Signaling Pathway Genes Suggests Negative Regulation by AtbZIP62 Transcription Factor in Arabidopsis thaliana

“…This abiotic stress affects the agricultural sector on a global scale. Salt stress induction leads to impaired plant growth and development (i.e., reduced rate of leaf surface expansion, cessation of expansion with the intensification of stress), crop failure, and cytotoxicity due to excessive ions, such as from sodium uptake and nutritional imbalance [5,6]. To cope with salt stress conditions, plants acquired diverse mechanisms that function to maintain a balanced reduction-oxidation state, reduced cellular hyperosmolarity, and ion disequilibrium [7].…”