Sodium selenite seed priming improves seed germination, seedling growth and rhizosphere microbial community structure of Sugar Beet (Beta vulgaris L.) under salt stress

Description

This study deeply explored the multiple impacts of sodium selenite priming on the germination, growth, physiology, and rhizosphere microbial community of sugar beet seeds under salt stress. The results showed that salt stress had a significant inhibitory effect on the germination and growth of sugar beet seeds and seedlings. Using sodium selenite as a seed priming agent to soak sugar beet seeds, the experiment found that low-concentration sodium selenite soaking could significantly improve the germination and growth of sugar beet seeds and seedlings under salt stress, but when the sodium selenite concentration was too high (such as 40 μM), it had an inhibitory effect on the germination and growth of sugar beet seeds and seedlings. In addition, sodium selenite seed soaking could increase the contents of chlorophyll and carotenoids, maintain ion balance, increase the content of soluble sugar and soluble protein, maintain cell elasticity and cell membrane stability, and improve the plant's resistance to salt stress. Salt stress led to a significant increase in the content of malondialdehyde (MDA) in sugar beet seedling leaves, and after sodium selenite soaking, the MDA content could be significantly reduced, reducing the accumulation of reactive oxygen species (ROS) and lipid peroxidation of cell membranes. At the same time, it could increase the activities of antioxidant enzymes (SOD, POD, CAT, and APX), promote the clearance of intracellular ROS, and protect plants from oxidative damage. Low-concentration sodium selenite soaking could increase the richness and diversity of the rhizosphere bacterial community of sugar beets under salt stress. Different concentrations of sodium selenite soaking would lead to different enriched bacteria in the microbial community. Microorganisms might interact with plants, participate in plant growth and development, maintain species diversity and community structure stability, and thus improve the salt tolerance of sugar beets. Sodium selenite soaking made the differential species in each group different, and they might be important species for maintaining the health of saline-alkali soil, but their specific functions still needed further research. As a priming agent, sodium selenite still needed further in-depth research on the specific molecular mechanism of improving plant salt tolerance. In the future, multi-year field trials could be carried out to verify its effect in actual production, and the use concentration of sodium selenite could be further optimized to better play its role in improving the salt tolerance and yield of sugar beets, providing new ideas and methods for improving the cultivation and production of sugar beets.

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I. Experimental Locations and Setup The experiments were conducted at the Beet Quality Supervision, Inspection and Testing Center of the School of Modern Agriculture and Ecological Environment, Heilongjiang University. II. Solution Preparation and Experimental Conditions Seed Germination Solutions Prepare a salt solution with a concentration of 100 mmol/L using NaCl and distilled water. Prepare seed soaking solutions with concentrations of 10, 20, 30, and 40 μmol/L using sodium selenite and distilled water. Conduct the seed germination experiment in an artificial climate chamber. Soil for Seedling Growth The soil was collected from the Hulan campus of Heilongjiang University. Take 700 g of soil and put it into a pot for sowing. III. Measurement and Analysis Methods Seed Germination Measurements Record the number of germinated seeds daily during the seed germination test. Measure the germination potential and germination rate of beets on the 5th and 7th days respectively. Seedling Growth Index Measurements Measure plant height by extending a rope from the base of the seedling stem to the top growth point and measure root length with a meter ruler. Use an area scanner to measure the leaf area and root area of a single plant. Weigh the fresh weight of the plant with an electronic balance, then put the sample in the oven at 105°C for 30 min and dry it at 75°C to a constant weight. Physiological and Biochemical Indicator Measurements Chlorophyll content: determined by the ethanol - acetone extraction method. Ion content (Na and K): measured using a flame photometer. Soluble protein content: determined by the Coomassie brilliant blue method. Soluble sugar content: determined by the anthrone colorimetry method. MDA content: determined by the thiobarbituric acid method. Antioxidant enzyme activities: SOD activity: determined by inhibiting the photochemical reduction of nitroblue tetrazolium (NBT). CAT activity: determined according to Aebi's method. APX activity: determined according to Nakano's method. Rhizosphere Microbial Community Analysis Use the root shaking method to collect the rhizosphere soil of beets under different treatments. Send the beet rhizosphere soil samples to Lianchuan Biotechnology Company for 16S rDNA high-throughput sequencing to study the composition of the microbial community in the environmental samples and interpret the diversity, richness, and community structure of the microbial community. IV. Data Analysis Perform one-way analysis of variance using SPSS 23.0 software. When p < 0.05, the results are considered significant. Conduct data analysis and plotting of rhizosphere soil microorganisms on the cloud platform of Lianchuan Biotechnology Company.

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