Grafting, seed soaking/priming, soil amendment, and foliar application as tools to increase abiotic stress tolerance of crops

Abstract

Climatic changes had negative impact on crop productivity and this effect was obviously detected by elevating abiotic stresses, including water scarcity [drought stress], salinization [salt stress] and raising temperature [heat stress]. In last decade, several tremendous attempts were made to increase plant tolerance to abiotic stress/es. Focusing on different application methods, grafting technique were used to solve soil salinity by grafted salt-sensitive plant onto salt tolerant rootstock. It could be able to substitute root system of salt-sensitive plant with root system of salt tolerant one. Grafting could be considered as indirect methods to enhance salt tolerance of several crops. Transplanting takes also into account. Seed soaking and priming in different chemical or bio-regulators offer another alternative application to increase abiotic stress tolerance. Soil amendment by the addition humic acid, compost, biochar, and seaweed extract alleviates salinity and drought or heavy metal stresses. Foliar application of different bio regulators, growth regulators, osmolytes, and nutrient element enhance crop tolerance to abiotic stresses. Salicylic acid, ascorbic acid, brassinosteroid, polyamines, glycine betaine, kinetin, thidiazuron, boron, CaCl<inf>2</inf>, KCl, and silicate were usually used in this concern. Physiological mechanisms of abiotic stress tolerant crops were investigated in view of water status (water potential, water use efficiency, relative water content, stomatal conductance/resistance, and transpiration rate), plant pigments, osmolytes (proline, amino acid and sugars), lipid peroxidation and antioxidant enzymes.