Effect of foliar application of GA<inf>3</inf>, kinetin, and salicylic acid on ions content, membrane permeability, and photosynthesis under salt stress of sweet sorghum [Sorghum bicolor (L.) Moench]

Abiotic stresses remain the greatest constraint to crop production worldwide. It has been predicted that more than 50% of yield reduction is the direct result of abiotic stresses. Salinity is one of the most serious environmental factors limiting crop productivity because most glycophytes are sensitive to salinity. A considerable amount of land in the world is affected by salinity which is increasing year by year. Crop stress tolerance can be improved by a number of means including selection and breeding, genetic modifications, and use of osmoprotectants and growth regulating substances. In this regard, attention has come to be focused on the use of plant growth regulators, such as gibberellic acid (GA3), kinetin, and salicylic acid which are known to regulate plant responses to adverse external environment and to control a number of stress-induced genes. A few studies have, however, demonstrated the ability of foliar treatment with plant growth regulators to overcome deleterious effects of NaCl stress. Therefore, the objectives of this study were to investigate whether the foliar spraying of GA3, kinetin, and salicylic acid could improve photosynthesis and decrease membrane permeability and ions accumulation in the leaves of sweet sorghum plants.

We found that high salinity increased Na content and membrane permeability, but decreased photosynthetic parameters and K content. Spraying sweet sorghum plants with GA3 or kinetin solutions at suitable concentrations increased photosynthetic rate, stomatal conductance, and transpiration rate. However, Na+ content and membrane permeability were decreased by these hormones under salt stress. More research is needed to investigate whether or not the mixture of these hormones could produce better effects than the application of individual hormone.