[Carbon footprint of major grain crops in the middle and lower reaches of the Yangtze River during 2011-2020]. / 2011­2020年长江中下游地区主要粮食作物生产碳足迹.

The middle and lower reaches of the Yangtze River is one of main grain production areas in China, which is of great significance to food security. Understanding the carbon footprint of major grain crop production is helpful to develop high-yield and low-carbon agriculture. Based on the data of yield, sown area and farmland production input of main grain crops (rice, wheat and maize) in six provinces (Jiangsu, Anhui, Jiangxi, Hubei, Hunan, and Zhejiang) in the middle and lower reaches of the Yangtze River from 2011 to 2020, we estimated carbon footprint in the production of the three grain crops. The results showed that from 2011 to 2020, yield per unit area, planting area, and total yield of rice, wheat and maize were the highest in Jiangsu Province. In terms of area-scaled carbon footprint, rice in the middle and lower reaches of the Yangtze River had the highest area-scaled carbon footprint, with an average of 2.0 t CE·hm-2, followed by wheat and maize. The area-scaled carbon footprint of the three staple crops was increasing. In terms of yield-scaled carbon footprint, rice was the highest, with an average of 0.8 kg CE·kg-1, followed by wheat and maize. In terms of carbon input structure, irrigation electricity, chemical fertilizers and pesticides accounted for a relatively high proportion. Irrigation electricity accounted for 35.0%, 36.3%, and 33.2% of the total carbon input of rice, wheat and maize, respectively. Chemical fertilizers accounted for 28.8%, 32.5%, and 32.5%, respectively, while pesticides accounted for 24.2%, 13.3% and 11.5%, respectively. In terms of carbon efficiency, maize had the highest (3.9 kg·kg-1 CE), followed by rice and wheat. With the green development of agriculture, carbon emission in the production of major grain crops in the middle and lower reaches of the Yangtze River could be reduced by improving irrigation efficiency, fertilizer utilization efficiency, pesticide utilization efficiency and mechanized operation efficiency, as well as diversification of straw returning, cultivation of new varieties and policy leverage.

Regulation of Gene Expression in the Remobilization of Carbon Reserves in Rice Stems During Grain Filling.

Carbon reserves in rice straw (stem and sheath) before flowering contribute to a significant portion of grain filling. However, the molecular mechanism of carbon reserve remobilization from straw to grains remains unclear. In this study, super rice LYP9 and conventional rice 9311 showed different carbon reserve remobilization behaviors. The transcriptomic profiles of straws of LYP9 and 9311 were analyzed at three stages of grain filling. Among the differentially expressed genes (DGs), 5,733 genes were uniquely up- or down-regulated at 30 days after anthesis (DAA) between LYP9 and 9311 in comparison with 681 at 10 DAA and 495 at 20 DAA, suggesting that the gene expression profile of LYP9 was very different from that of 9311 at the late stage of grain filling. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and Gene Ontology (GO) classification of DGs both showed that the carbohydrate catabolic pathway, plant hormone signal transduction and photosynthesis pathway were enriched in DGs, suggesting their roles in carbon reserve remobilization, which explains to a certain extent the difference in non-structural carbohydrate content, photosynthesis and ABA content between the two cultivars during grain filling. Further comparative analysis and confirmation by quantitative real-time PCR and enzyme assays suggest that genes involved in trehalose synthesis (trehalose-phosphate phosphatase and trehalose 6-phosphate synthase/phosphatase), starch degradation (ß-amylase) and sucrose synthesis (sucrose-phosphate synthase and sucrose synthase) were important for carbon reserve remobilization, whereas ABA content was determined by the counteraction of NCED1 and ABA8ox1 genes. The higher expression level of all these genes and ABA content in 9311 resulted in better efficiency of carbon reserve remobilization in 9311 than in LYP9.

The role of different glutamate receptors in the mediation of glutamate-evoked excitation of red nucleus neurons after simulated microgravity in rat.

The present study investigates changes in red nucleus (RN) neuronal activity and the role of glutamate receptors (GluRs) after simulated microgravity (tail-suspension) in the rat using single-unit recording and microinjection. The results showed that tail-suspension for 3, 7, and 14 days could induce a significant decrease in spontaneous firing rate of RN neurons in a time-dependent manner. Unilateral microinjection of glutamate into the RN significantly increased the firing rate of RN neurons, but the increased firing rate was significantly reduced following tail-suspension time. Microinjection of the NMDA receptor antagonist MK-801 or the non-NMDA receptor antagonist DNQX into the RN blocked this excitatory effect induced by glutamate. However, microinjection of the metabotropic glutamate receptor (mGluR) antagonist (+/-)-MCPG into the RN had no effect. These results suggest that simulated microgravity can reduce excitability of RN neurons following a functional impairment of glutamate receptors. NMDA and non-NMDA receptors, but not mGluRs, are involved in the mediation of glutamate-evoked excitation of RN neurons. The decrease in excitability of RN neurons may be involved in simulated microgravity-induced muscle atrophy.