Short-term effects of combined freeze–thaw and saline–alkali stresses on the physiological response in highland barley (

Abstract

Highland barley (Hordeum vulgare L.), as the dominant crop on the Qinghai-Tibetan Plateau, is a typical representative of plants adapted to extreme environmental conditions. However, the harsh environment, severe salinisation and frequent freezing and thawing in the Qinghai-Tibetan Plateau are main limiting factor for crop growth in this region. The physiological response of highland barley to salinisation and freeze–thaw stresses was studied in this paper. Under the combined stresses of 60 mmol/L NaCl·60 mmol/L NaHCO3 and freeze–thaw cycles (10, −5, and 10°C), the changes in the relative moisture content, relative electrical conductivity, soluble protein, malondialdehyde (MDA) and photosynthetic indices Pn and E in seedling leaves of eight groups of treatments (CK, S, A, S-A, CK (FT), S (FT), A (FT), and S-A (FT)) were analysed. Results showed that a single stress did not cause a change in the MDA content. All of the combined stresses in S-A, CK (FT), S (FT), A (FT), and S-A (FT) treatments increased the MDA content of barley seedlings, and the MDA content of S-A (FT) reached 28.438 at T2 (−5°C) μmol/g. During the freeze–thaw cycle, the cell membrane of seedlings was damaged more seriously by alkali stress, which showed a significant increase in relative conductivity. The relative moisture content value of seedlings was more than 100% because the seedlings could absorb more moisture due to mechanical injury. The protein content of osmoregulatory substances in highland barley seedlings increased with increasing stress, indicating resistance to stress. Moreover, the effect of freeze–thaw stress on photosynthesis was more significant. The changes in indices proved that an appropriate amount of salt stress could improve the resistance of the plant cell membrane. Alkali stress had a significant effect on the growth of highland barley seedlings. Freezing and thawing can aggravate the damage of saline–alkali stress to highland barley seedlings, resulting in changes in the biological membrane permeability and photosynthesis of seedlings. The fluctuation of osmoregulation substance content confirmed that highland barley seedlings had a certain degree of stress resistance. Freeze–thaw cycles will aggravate the damage of land salinisation to highland barley seedlings. To better reduce the impact and loss of land salinisation and freeze–thaw disasters on agriculture in the Qinghai-Tibetan Plateau, priority should be given to solving freeze–thaw stress in the process of grain production.

Response of salt stress resistance in highland barley (Hordeum vulgare L. var. nudum) through phenylpropane metabolic pathway

“…Therefore, in recent years, more and more researchers have begun to study the stress resistance mechanism of highland barley, which not only helps to cultivate highland barley crops suitable for different adverse environments, but also provides a reference for the improvement of stress resistance of other crops. However, the current research on stress resistance in highland barley has mainly focused on the content analysis of metabolites [31][32][33], and gene mining and verification through omic, the work for the identification of metabolic…”

“…Therefore, in recent years, more and more researchers have begun to study the stress resistance mechanism of highland barley, which not only helps to cultivate highland barley crops suitable for different adverse environments, but also provides a reference for the improvement of stress resistance of other crops. However, the current research on stress resistance in highland barley has mainly focused on the content analysis of metabolites [ 31 – 33 ], and gene mining and verification through omic, the work for the identification of metabolic pathways related to stress resistance is unsatisfactory. This study used the germination of highland barley seeds under salt stress to simulate the unfavorable environment of highland barley crops, and the effective improvement of related genes in the phenylpropane metabolic pathway was located through the transcriptional level of highland barley seeds during different stages under salt stress.…”