Melatonin (MT) is a crucial hormone that controls and positively regulates plant growth under abiotic stress, but the biochemical and physiological processes of the combination of melatonin seed initiation and exogenous spray treatments and their effects on maize germination and seedling salt tolerance are not well understood. Consequently, in this research, we utilized the maize cultivars Zhengdan 958 (ZD958) and Demeiya 1 (DMY1), which are extensively marketed in northeastern China’s high-latitude cold regions, to reveal the modulating effects of melatonin on maize salinity tolerance by determining the impacts of varying concentrations of melatonin on maize seedling growth characteristics, osmoregulation, antioxidant systems, and gene expression. The findings revealed that salt stress (100 mM NaCl) significantly inhibited maize seed germination and seedling development, which resulted in significant increases in the H₂O₂ and O₂⁻ content and decreases in the antioxidant enzyme activity and photosynthetic pigment content in maize seedlings. However, exogenous melatonin considerably reduced the development inhibition caused by salt stress in maize seedlings. Moreover, exogenous melatonin alleviated NaCl-induced membrane damage and oxidative stress, and reduced Na⁺ content and excessively large quantities of reactive oxygen species (ROS). In addition, exogenous melatonin increased antioxidant enzyme activity and the expression of the antioxidant enzyme genes ZmSOD4, ZmCAT2, and ZmAPX2. This study demonstrates the potential role of combined melatonin seed initiation and foliar spray treatments in mitigating the detrimental effects of salt stress on maize growth, giving a theoretical foundation to future research on the possible advantages of exogenous regulating chemicals in attaining sustainable production in salt-alkaline soils.

The present study aimed to evaluate the anaerobic co-digestion process of chicken manure and corn stover to identify the key parameters that influence methane production. Results from both batch and semi-continuous tests showed that co-digestion enhanced methane production, with an optimal chicken manure to corn stover ratio of 2:1 under experimental conditions. When this ratio was maintained, methane production increased by 36% in batch tests, resulting in a biochemical methane potential of 333 mL/g VS. In semi-continuous tests, co-digestion at a hydraulic retention time of 30 days resulted in a methane production increase of 39%, corresponding to a methane yield of 318 mL/g VS. The inclusion of chicken manure proved effective in improving buffer capacity by generating ammonium bicarbonate, which facilitated stable operation during the digestion process. The observed improvement in methane production could be ascribed to the C/N ratio and the increased biodegradability of chicken manure. These findings offer valuable insights into optimizing anaerobic co-digestion to achieve higher methane production levels.

Enterobacter species are plant growth-promoting rhizobacteria with the potential to enhance crop tolerance to abiotic stresses, but the molecular and physiological mechanisms remain incompletely understood. In this study, a salt-tolerant bacterial strain, Enterobacter asburiae LL-1, was isolated from the rhizosphere of maize grown in severely saline-alkali soil. The strain exhibited multiple plant growth-promoting traits, including phosphorus solubilization, nitrogen fixation, and indole-3-acetic acid production, and showed exceptional salt tolerance (up to 1500 mM NaCl). Pot experiments demonstrated that LL-1 inoculation significantly alleviated salt-induced growth inhibition in maize, as evidenced by increased plant height, root length, root biomass, and leaf chlorophyll content. Furthermore, LL-1 inoculation reduced Na⁺ accumulation, enhanced K⁺ uptake, improved antioxidant enzyme activities (catalase and superoxide dismutase), and elevated proline levels, thereby mitigating oxidative damage. At the molecular level, LL-1 upregulated the expression of maize antioxidant enzyme genes (ZmSOD4, ZmCAT2, ZmAPX2) and salt tolerance genes (ZmNHX1, ZmNHX2, ZmDREB2A). Genome analysis identified multiple genes potentially involved in salt tolerance (such as nhaA, nhaB, maeN) and plant growth promotion. These results indicate that E. asburiae LL-1 enhances maize salt tolerance through coordinated effects on ion homeostasis, antioxidant capacity, photosynthesis, and stress-responsive gene expression. This study provides a promising microbial resource and correlative evidence for further mechanistic research on PGPR-mediated salt tolerance in crops.