Salinity and its tolerance strategies in plants

Abstract Soil salinity is a worldwide problem deteriorating around 950 million hectares (mha) hectare of land with salts including about 250 mha irrigated lands causing about $27.3 billion per annum loss in world revenue. Soil degradation due to salinization must be addressed to ensure the food quality and food security for world. Salinity in irrigated lands is to be taken as genuine issue as it implies stress to growing plants causing their growth retardation, hormonal imbalance, and oxidative stress initiation. Plant tends to counter these stresses by adopting different mitigating strategies involving solute accumulation in roots to reduce root internal water potential, modifying proline metabolism by modifying hormonal signaling, innating Na efflux by cellular signaling or by operating high-affinity potassium transporters (HKTs) to mitigate Na toxicity and initiating and stimulating different genes to insure ion homeostasis. Besides endogenous mitigating strategies, some exogenous inputs also have significant role in managing saline agriculture. Increasing indigenous plant growth-promoting rhizobacteria or arbuscular mycorrhizae count in rhizosphere helps plant in withstanding severe salinity by producing growth-promoting hormones and absorbing more nutrients. Organic and inorganic amendments are helpful in mitigating soil salinity by improving soil physicochemical properties and nutrient supplement. Similarly, exogenous plant hormones and different soil conditioners improve plant growth, reproductive development modification, phyto-morphogenesis, and defense against salt stresses. Recently, genetic engineering is being focused on screening and introducing halotolerant varieties to provide economic and more effective strategy to tolerate against salinity without or low input of exogenous amendments. This technology is becoming more popular than conventional breeding as it involves the transfer of concerned gene, combating with the osmo deregulations, to high-yielding strains to get engineered plants. These genetically modified plants have better ionic homeostasis and tolerance against salinity, ensuring high-yield potentials under stressed environment. This chapter summarizes all possible strategies and mechanisms involving tolerance and mitigation of salinity, which will help in finding means for food security for the world.