[Effects of Organic Fertilization on Bacterial Community and Maize Productivity in Dryland Red Soil].

Since 2002, a long-term field experiment has been conducted to determine the effects of different organic fertilization treatments on the bacterial community characteristics and maize productivity in dryland red soil using high-throughput sequencing technology. The experiment consisted of four treatments:no manure, M0; low manure, M1; high manure, M2; and high manure with lime addition, M3. Our results showed that the different organic fertilization treatments(M1, M2, and M3) significantly promoted maize productivity with the highest values of pH, soil organic matter(SOM), total nitrogen(TN), and total phosphorus(TP) compared to that under the M0 treatment, and the high manure with lime addition(M3) treatment had the highest level of maize production. The different organic fertilization treatments significantly increased the Shannon index, Evenness index, Chao1 index, and ACE index and significantly shaped the composition of the bacterial community. TP and pH were the main variables determining soil bacterial diversity index based on random forest modeling analysis, whereas pH, SOM, TP, and TN were the main variables determining the structure of the soil bacterial community. Correlation analysis and structural equation modeling determined that TP and SOM indirectly affected maize productivity by varying the bacterial diversity and community structure. The results of this study provide the scientific basis for ensuring food security and sustainable agricultural development by improving the fertility and bacterial diversity in dryland red soil.

Cadmium tolerance in Elodea canadensis Michx: Subcellular distribution and metabolomic analysis.

The aquatic plant Elodea canadensis is considered a good candidate for ecotoxicological investigations. Cadmium (Cd) is a widespread contaminant in aquatic systems. In this study, to better elucidate the underlying tolerance mechanism and molecular impact of environmentally relevant Cd concentration in aquatic plants, subcellular distribution, chemical forms, and gas chromatography-mass spectrometry-based non-targeted metabolomics profiles were comprehensively analyzed in E. canadensis subjected to 0 and 10 µM Cd treatment for 5 d. Subcellular fractionation analysis of Cd-containing leaves showed that 67% of Cd was compartmentalized in cell wall followed by the soluble fraction (24 %) and organelles (9 %). The majority of Cd (90 %) was found in the extraction using 1 M NaCl. Metabolomic analysis using unsupervised principal component analyses and a supervised partial least squares discriminant analysis revealed clear differences in metabolic profiles between the two groups, demonstrating the metabolic effects of Cd. The 155 identified compounds altered by Cd were mainly from primary metabolism, including sugars, amino acids, organic acids, and their derivatives. Secondary metabolites such as polyphenols and phenolamides were also detected. The massive up-regulation of metabolites, including trehalose, proline, sarcosine, nicotianamine, putrescine, α-ketoglutaric acid, citric acid, and phytol might represent a detoxification mechanism. These findings highlighted the mechanistic strategies that E. canadensis employs to defend against Cd toxicity.