Growth, ionic homeostasis, and physiological responses of cotton under different salt and alkali stresses

Abstract

To better understand the mechanism of salt tolerance, we analyzed cotton growth and the ionomes in different tissues under different types of salt–alkali stress. Cotton was exposed to the soil salt and alkali stresses, NaCl, Na2SO4, and Na2CO3 + NaHCO3, in a pot study. Salt and alkali stress significantly inhibited cotton growth, significantly reduced root length, surface area, and volume, and significantly increased relative electrical conductivity (REC) and malondialdehyde (MDA) content but also significantly increased antioxidant enzyme activities, and proline (Pro) content. The REC in leaves was higher under salt stress than under alkali stress, but the effects on Pro were in the order Na2CO3 + NaHCO3 > NaCl > Na2SO4. Principal component analysis showed a significant difference in ion composition under the different types of salt–alkali stress. Under the three types of salt–alkali stress, concentrations of Na and Mo increased significantly in different organs of cotton plants. Under NaCl stress, the absorption of Ca was inhibited, the transport capacity of P, Mg, and Cu was reduced, and the ion balance was maintained by promoting the uptake and transport of Zn, Mn, Al, and Mo. Under Na2SO4 stress, the absorption of P and Ca was inhibited, the transport capacity of Mg, B, and Cu was reduced, and the ion balance was maintained by promoting the uptake and transport of S, Zn, Fe, Mo, Al, and Co. Under Na2CO3 + NaHCO3 stress, the absorption of P and S was inhibited, the transport capacity of Mg and B was reduced, but that of Al and Fe increased, and the ion balance was maintained by promoting the uptake and transport of Mn, Mo, Ni, and Co. The relative expression of GhSOS1 and GhNHX1 in leaves increased significantly under salt stress but decreased under alkali stress. These results suggest that cotton is well-adapted to salt–alkali stress via the antioxidant enzyme system, adjustment of osmotic substances, and reconstruction of ionic equilibrium; neutral salt stress primarily disrupts the ion balance, whereas alkali stress decreases the ability to regulate Na and inhibits the absorption of mineral elements, as well as disrupts the ion balance; and the changes in the expression of salt tolerance-related genes may partially explain the accumulation of Na ions in cotton under salt–alkali stress.

Ion homeostasis and Na+ transport-related gene expression in two cotton (Gossypium hirsutum L.) varieties under saline, alkaline and saline-alkaline stresses

“…Overall, the Mo concentration in the leaves, stems, and roots of the two cotton varieties increased significantly and was positively correlated with the Na concentration under different salt stresses. This is in agreement with the results of a previous study [ 40 ]. Under saline stress, ionic imbalance restricts nutrient access and transport within plants, resulting in reduced concentrations of Mg, Ca, P and N in the roots and leaves [ 27 ].…”

“…Our results showed that the Na concentration in the leaves, stems, and roots of cotton increased significantly with increasing stress level and that the increase in Na concentration was higher under saline-alkaline stress than under saline stress or alkaline stress alone. Guo et al [ 40 ] also observed that saline and alkaline stresses increased the Na concentration of cotton plants, but the increase in Na concentration was higher in the leaves, stems, and roots under alkaline stress than under saline stress. We found that the Na concentration of the salt-tolerant variety was significantly lower than that of the salt-sensitive variety under saline, alkaline, and saline-alkaline stresses.…”

“…This result indicated that the inhibition of ion absorption and transport of salt-sensitive varieties was greater under alkaline stress and saline-alkaline stress than under saline stress. Guo et al [ 40 ] also showed that the inhibition of ion absorption was greater under alkali stress than under salt stress. In addition, we found that the variation of ion concentration of the salt-tolerant variety under alkaline stress and saline-alkaline stress was similar to that under saline stress.…”

“…In contrast, the expression of GhNHX 1 in the salt-sensitive variety after A2 and SA1 treatment was the same or lower than that in the CK group. Guo et al [ 40 ] also found that saline stress significantly increased the relative expression of GhNHX 1 in the roots and leaves of cotton, but alkaline stress had no significant effect on the relative GhNHX 1 expression. In this study, GhNHX 1 expression in the salt-tolerant variety was significantly higher than that in the salt-sensitive variety under saline, alkaline and saline-alkaline stresses.…”

Physiology Response and Resistance Evaluation of Twenty Coconut Germplasm Resources under Low Temperature Stress

“…The structure and function of cell membranes produce important influences on the adaptability of crops to adversity [25]. The material exchange between plant cells and the external environment is carried out through biofilms, and the effects of various adversities and damages on plant cells also perform on biofilms first [26].…”