Abstract
The sensitivity of cotton to salt stress depends on the genotypes and salt types. Understanding the mechanism of ion homeostasis under different salt stresses is necessary to improve cotton performance under saline conditions. A pot experiment using three salt stresses saline stress (NaCl+Na2SO4), alkaline stress (Na2CO3+NaHCO3), and saline-alkaline stress (NaCl+Na2SO4+Na2CO3+NaHCO3) and two cotton varieties (salt-tolerant variety L24 and salt-sensitive variety G1) was conducted. The growth, ion concentrations, and Na+ transport-related gene expression in the cotton varieties were determined. The inhibitory effects of saline-alkaline stress on cotton growth were greater than that of either saline stress or alkaline stress alone. The root/shoot ratio under alkaline stress was significantly lower than that under saline stress. The salt-tolerant cotton variety had lower Na and higher K concentrations in the leaves, stems and roots than the salt-sensitive variety under different salt stresses. For the salt-sensitive cotton variety, saline stress significantly inhibited the absorption of P and the transport of P, K, and Mg, while alkaline stress and saline-alkaline stress significantly inhibited the uptake and transport of P, K, Ca, Mg, and Zn. Most of the elements in the salt-tolerant variety accumulated in the leaves and stems under different salt stresses. This indicated that the salt-tolerant variety had a stronger ion transport capacity than the salt-sensitive variety under saline conditions. Under alkaline stress and salt-alkaline stress, the relative expression levels of the genes GhSOS1, GhNHX1 and GhAKT1 in the salt-tolerant variety were significantly higher than that in the salt-sensitive variety. These results suggest that this salt-tolerant variety of cotton has an internal mechanism to maintain ionic homeostasis.
Highlights
Salt stress, which decreases crop yield and restricts the use of agricultural land, is a main threat to environmental resources and human health [1, 2]
Ion homeostasis and Na+ transport-related gene expression in cotton under different salt-alkali stresses million hectares of land is saline or sodic, and between 25% and 30% of irrigated lands are salt-affected [3], which affects more than 20% of the total cultivated and 33% of irrigated agricultural lands [4]
There was no significant difference in the total biomass of L24 under low saline stress (S1) and Biomass (g plant-1) Shoot 1.87±0.06 b 1.81±0.03 b 1.50±0.04 d 2.04±0.07 a 1.75±0.09 bc 1.70±0.02 c 1.64±0.11 cd 1.57±0.03 a 1.06±0.03 c 0.94±0.02 d 1.16±0.01 b 1.04±0.01 c 0.86±0.01 e 0.60±0.03 f
Summary
Salt stress, which decreases crop yield and restricts the use of agricultural land, is a main threat to environmental resources and human health [1, 2]. Ion homeostasis and Na+ transport-related gene expression in cotton under different salt-alkali stresses million hectares of land is saline or sodic, and between 25% and 30% of irrigated lands (or about 70 million hectares) are salt-affected [3], which affects more than 20% of the total cultivated and 33% of irrigated agricultural lands [4]. Saline soils are the main salt-affected soils, amounting to 60% of the total salt-affected soils, while alkaline soils and saline-alkaline soils account for 26% and 14%, respectively [6]. Previous studies have shown that alkaline salt stress is quite different from neutral salt stress and these stresses should be called alkaline stress and saline stress, respectively [7]. Understanding the response of plants to different salt stresses is essential for improving the salt tolerance of plants
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