Alkali Stress
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2021 ◽  
Vol 12 ◽  
Qian Ma ◽  
Caoyang Wu ◽  
Shihan Liang ◽  
Yuhao Yuan ◽  
Chunjuan Liu ◽  

Broomcorn millet (BM), one of the earliest domesticated cereal crops originating in northern China, can tolerate extreme conditions, such as drought and high temperatures, which are prevalent in saline-alkali, arid, and barren landscapes. However, its adaptive mechanism to alkali stress is yet to be comprehensively understood. In this study, 80 and 40 mM standard alkali stress concentrations were used to, respectively, evaluate the alkali tolerance at the germination and seedling stages of 296 BM genotypes. Principal component analysis (PCA), Pearson's correlation analysis, and F-value comprehensive analysis were performed on the germination parameters (germination potential, germination index, germination rate, vigor index, root length/weight, sprout length/weight, and alkali damage rate). Based on their respective F-values, the BM genotypes were divided into five categories ranging from highly alkali resistant to alkali sensitive. To study the response of seedlings to alkaline stress, we investigated the phenotypic parameters (plant height, green leaf area, biomass, and root structure) of 111 genotypes from the above five categories. Combining the parameters of alkali tolerance at the germination and seedling stages, these 111 genotypes were further subdivided into three groups with different alkali tolerances. Variations in physiological responses of the different alkali-tolerant genotypes were further investigated for antioxidant enzyme activity, soluble substances, malondialdehyde (MDA) content, electrolyte leakage rate, and leaf structure. Compared with alkali-sensitive genotypes, alkali-tolerant genotypes had high antioxidant enzyme activity and soluble osmolyte content, low MDA content and electrolyte leakage rate, and a more complete stomata structure. Taken together, this study provides a comprehensive and reliable method for evaluating alkali tolerance and will contribute to the improvement and restoration of saline-alkaline soils by BM.

2021 ◽  
Vol 12 ◽  
Chunxin Li ◽  
Tingting Song ◽  
Lifeng Zhan ◽  
Chunlong Cong ◽  
Huihui Xu ◽  

Rare cold-inducible 2/plasma membrane protein 3 (RCI2/PMP3) genes are ubiquitous in plants and belong to a multigene family whose members respond to a variety of abiotic stresses by regulating ion homeostasis and stabilizing membranes, thus preventing damage. In this study, the expression of MsRCI2A, MsRCI2B, and MsRCI2C under high-salinity, alkali and ABA treatments was analyzed. The results showed that the expression of MsRCI2A, MsRCI2B, and MsRCI2C in alfalfa (Medicago sativa L.) was induced by salt, alkali and ABA treatments, but there were differences between MsRCI2 gene expression under different treatments. We investigated the functional differences in the MsRCI2A, MsRCI2B, and MsRCI2C proteins in alfalfa (Medicago sativa L.) by generating transgenic alfalfa plants that ectopically expressed these MsRCI2s under the control of the CaMV35S promoter. The MsRCI2A/B/C-overexpressing plants exhibited different degrees of improved phenotypes under high-salinity stress (200 mmol.L–1 NaCl) and weak alkali stress (100 mmol.L–1 NaHCO3, pH 8.5). Salinity stress had a more significant impact on alfalfa than alkali stress. Overexpression of MsRCI2s in alfalfa caused the same physiological response to salt stress. However, in response to alkali stress, the three proteins encoded by MsRCI2s exhibited functional differences, which were determined not only by their different expression regulation but also by the differences in their regulatory relationship with MsRCI2s or H+-ATPase.

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11963
Lijuan Yang ◽  
Yufeng Wang ◽  
Kejun Yang

Background Saline-alkali soil is mainly distributed in the northern and coastal areas of China. The Songnen Plain, located in the northeast of China, is a region with a relatively high concentration of saline-alkali soil and is also one of the more at-risk areas in the country. Every year, the increasing spread of saline-alkali soil areas has a serious impact on the growth of agricultural crops. The maize crop is sensitive to saline-alkali stress, which seriously affects its growth and development. Our previous study determined that Klebsiella variicola performs a variety of biological functions, as well as improves the rhizosphere microenvironment and promotes the growth and development of maize seedlings in saline-alkali soil environments. The present study further analyzed the mechanism that enables K. variicola to alleviate saline-alkali stress at the level of the antioxidant system. Methods The accumulation of O2− was observed directly via histochemical staining. The activities of several antioxidant enzymes were determined using the nitro blue tetrazolium and the guaiacol methods. The contents of non-enzymatic antioxidants were determined using the dithionitrobenzoic acid method. Results The contents of the superoxide anion and hydrogen peroxide in leaves and roots of maize seedlings increased under saline-alkali stress conditions. The higher level of reactive oxygen species increased the degree of membrane lipid peroxidation. There were differences in the degree of oxidative damage and performance of the antioxidant defence system in maize seedlings under saline-alkali stress. Following the application of increasing concentrations of K. variicola, the activity of antioxidant enzymes increased by 21.22%–215.46%, and the content of non-enzymatic antioxidants increased as well, the ratios of ASA/DHA and GSH/GSSG in leaves increased by 4.97% and 1.87 times, respectively, and those in roots increased by 3.24% and 1.60 times, respectively. The accumulation of reactive oxygen species was reduced, and the content of H2O2 decreased by 26.07%–46.97%. The content of O2− decreased by 20.18%–37.01%, which alleviated the oxidative damage to maize seedlings caused by saline-alkali stress. Conclusion K. variicola reduced ROS-induced peroxidation to membrane lipids and effectively alleviated the damage caused by saline-alkali stress by increasing the activities of antioxidant enzymes in maize seedlings, thus enhancing their saline-alkali tolerance. A bacterial concentration of 1×108 cfu/mL was optimal in each set of experiments.

2021 ◽  
Yunke Qu ◽  
Jie Tang ◽  
Ben Liu ◽  
Hang Lyu ◽  
Yucong Duan ◽  

Abstract Soil inorganic carbon (SIC) is the main existing form of soil carbon pool in arid saline-alkali land, and its quantity distribution affects the pattern of soil carbon accumulation and storage. Previous studies on soil carbon mostly focus on organic carbon (SOC), and pay little attention to SIC. The purpose of this study was to investigate the effect of microorganisms and soil enzymes on the transformation of SOC and SIC in the rhizosphere soil of three maize fields (M1, M2 and M3) and three paddy fields (R1, R2 and R3) under saline-alkali stress, which is a new research topic of soil carbon cycle in saline-alkali soil region. The results showed that the root - soil - microorganism interaction was changed by saline-alkali stress. The results of RDA analysis showed that Proteobacteria, Gemmatimonadetes, Planctomycetes, Nitrospirae, catalase, invertase, amylase and β-glucosidase had significant effects on the transformation of SOC and SIC (P<0.05). SOC and SIC in maize and rice rhizosphere soil were mainly driven by soil enzymes and microorganisms under saline-alkali stress, exchangeable sodium percentage (ESP) and pH were the main factors affecting the conversion process of SOC and SIC.

2021 ◽  
Vol 12 ◽  
Shumei Fang ◽  
Xue Hou ◽  
Xilong Liang

As two coexisting abiotic stresses, salt stress and alkali stress have severely restricted the development of global agriculture. Clarifying the plant resistance mechanism and determining how to improve plant tolerance to salt stress and alkali stress have been popular research topics. At present, most related studies have focused mainly on salt stress, and salt-alkali mixed stress studies are relatively scarce. However, in nature, high concentrations of salt and high pH often occur simultaneously, and their synergistic effects can be more harmful to plant growth and development than the effects of either stress alone. Therefore, it is of great practical importance for the sustainable development of agriculture to study plant resistance mechanisms under saline-alkali mixed stress, screen new saline-alkali stress tolerance genes, and explore new plant salt-alkali tolerance strategies. Herein, we summarized how plants actively respond to saline-alkali stress through morphological adaptation, physiological adaptation and molecular regulation.

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