Exogenous glucose irrigation alleviates cold stress by regulating soluble sugars, ABA and photosynthesis in melon seedlings

Effects of Biochar on the Yield of Melon and the Diversity of Rhizosphere Soil Microbial Communities Under Saline-Alkali Stress

In this study, the melon variety 'Da Shetou' was used as the test material, and pot cultivation was employed with soil collected from Da'an City to investigate the effects of biochar addition on melon yield and quality, rhizosphere soil physicochemical properties, and soil microbial community. The experiment was set up with five treatments: saline-alkali soil (B0), 1% biochar and 99% saline-alkali soil (B1), 3% biochar and 97% saline-alkali soil (B3), 5% biochar and 95% saline-alkali soil (B5), and 7% biochar and 93% saline-alkali soil (B7). This study found that the addition of 3% biochar increased the fruit yield of melons. Compared to the control, the soil bulk density was reduced by 4.99%, 8.66%, 1.77%, and 7.71% under the 1%, 3%, 5%, and 7% biochar treatments, respectively. Biochar addition increased organic matter, alkaline-hydrolyzable nitrogen, available phosphorus, and available potassium concentrations in the rhizosphere soil. Additionally, the total nitrogen, salt concentration, and exchangeable sodium percentage were also reduced. Compared to the B0 treatment, the concentrations of K+, Ca2+, and Mg2+ increased to varying degrees across different treatments, while the concentrations of Na+ and Cl- decreased. The relative abundance of dominant bacterial phyla in the soil varied across different treatments. The dominant bacterial phyla included Proteobacteria, Actinobacteriota, Acidobacteriota, and a total of 10 others. The dominant fungal phyla included Ascomycota, Basidiomycota, Mortierellomycota, and a total of seven others. Redundancy analysis (RDA) identified key drivers. Available potassium in the rhizosphere soil of melons was the dominant factor influencing bacterial community composition at the phylum level. Soil bulk density, exchangeable sodium percentage, and total nitrogen were identified as the dominant factors influencing fungal community composition at the phylum level. This study confirmed that 3% biochar application synergistically regulated nutrient cycling and microbial functional groups, thereby enhancing yield of thin-skinned melons (yield increase: 45.22%).

Molecular and Physiological Responses of Plants that Enhance Cold Tolerance

Low-temperature stress, including chilling and freezing injuries, significantly impacts plant growth in tropical and temperate regions. Plants respond to cold stress by activating mechanisms that enhance freezing tolerance, such as regulating photosynthesis, metabolism, and protein pathways and producing osmotic regulators and antioxidants. Membrane stability is crucial, with cold-resistant plants exhibiting higher lipid unsaturation to maintain fluidity and normal metabolism. Low temperatures disrupt reactive oxygen species (ROS) metabolism, leading to oxidative damage, which is mitigated by antioxidant defenses. Hormonal regulation, involving ABA, auxin, gibberellins, and others, further supports cold adaptation. Plants also manage osmotic balance by accumulating osmotic regulators like proline and sugars. Through complex regulatory pathways, including the ICE1-CBF-COR cascade, plants optimize gene expression to survive cold stress, ensuring adaptability to freezing conditions. This study reviews the recent advancements in genetic engineering technologies aimed at enhancing the cold resistance of agricultural crops. The goal is to provide insights for further improving plant cold tolerance and developing new cold-tolerant varieties.

Study of the mechanism by which Bacillus subtilis improves the soil bacterial community environment in severely saline-alkali cotton fields

Soil salinization severely damages the soil bacterial community environment. Bacillus subtilis can improve bacterial communities and enhance crop nutrient absorption. However, the mechanism by which B. subtilis improves the bacterial community environment in heavily saline-alkali-treated cotton fields is currently unclear. Therefore, this study adopted a field plot experiment and established four bacterial treatments (0, 9, 12, and 15 kg·ha-1) to investigate the environmental improvement mechanism of B. subtilis on soil bacterial communities in severely saline alkali cotton fields was studied. Compared with the CK treatment, the application of B. subtilis significantly increased the available nitrogen (25.34 %), available phosphorus (50.894 %), available potassium (86.87 %), and urease (112.961 %) contents but significantly reduced the soil pH (1.07 %) and salt content (39.73 %) and significantly increased the proline (245.116 %) and superoxide dismutase (237.46 %) contents in the leaves and significantly reduced the malondialdehyde content (47.30 %). This is mainly because B. subtilis enhances the diversity of bacterial communities and affects catalase, urease, phosphatase, and protease activities, thereby promoting nutrient release in the soil and improving soil fertility; specifically, B. subtilis promotes the secretion of oxalic acid, formic acid, malic acid, and soluble total sugars in cotton roots. The organic acids in root exudates lower the soil pH and chelate with salt ions in the soil, reducing the concentration of soluble salts and providing a suitable environment for B. subtilis. Soluble total sugars can provide energy and carbon sources for bacteria, maintaining the health and diversity of rhizosphere bacterial communities. The results of the principal component analysis revealed that the application rate of B. subtilis was 12 kg·ha-1, which had the greatest effect on improving the soil bacterial community in severely saline-alkali cotton fields. The research results provide a theoretical basis and practical reference for microbial improvement in severely saline-alkali land in arid areas.