To explore the response of nitrogen metabolism in Masson pine (Pinus massoniana) to high CO2 concentrations, needles from one-year-old seedlings were used as materials to detect key enzyme activities, gene expression and different forms of nitrogen metabolites after CO2 stress for different durations (0 h, 6 h, 12 h, 24 h). The results show that elevated CO2 affected the efficiency of nitrogen metabolism in Masson pine needles, inhibiting the expression of key genes involved in nitrogen metabolism, including glutamate synthase (GOGAT), nitrite reductase (NiR), glutamine synthase (GS), nitrate reductase (NR) and glutamate dehydrogenase (GDH), and decreasing the activities of GOGAT, NiR, and GS. The decrease in enzyme activities and gene expression caused a decrease in different forms of nitrogen metabolites, including total nitrogen, ammonium, nitrite and specific amino acids. With prolonged stress, the nitrate content increased first and then decreased. In this study, the response pattern of nitrogen metabolism to CO2 stress in Masson pine needles was described, which may aid future research on nitrogen utilization in Masson pine.
To compare the rhizosphere communities under Masson pine trees with different carbon sequestration abilities, we sampled three families of Masson pine that showed significant differences in their carbon sequestration ability and conducted high-throughput sequencing of the 16S rRNA and ITS in the corresponding soil samples. The diversity of rhizosphere soil microorganisms, the patterns of differences in relative abundance among the different samples and the responses of microorganisms to environmental factors were analyzed. There was no significant difference in the diversity of soil bacteria or fungi among the different samples from Masson pine families with different carbon sequestration abilities, but with the increase in carbon sequestration, the dominant phyla of bacteria and fungi changed. The dominant phylum of soil bacteria changed from Proteobacteria to Acidobacteria, and that of fungi changed from Ascomycota to Basidiomycota. In addition, we investigated the core microbial communities at the genus level among the different samples, and a significant portion of the core genera were involved in carbon metabolism. The microbial communities were greatly influenced by environmental factors such as soil carbon content, soil moisture and altitude. Soil fungi were more sensitive than soil fungi to the rhizosphere activity of Masson pine.
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