[Response of Yield, CH4, and N2O Emissions from Paddy Fields to Long-term Elevated CO2 Concentrations].

Elevated atmospheric CO2 concentrations([CO2]e) are the main driving force of global climate change, which directly and indirectly affect carbon and nitrogen cycling in the paddy ecosystems. Therefore, understanding the response of rice yield and greenhouse gas emissions to long-term(more than 10 years)[CO2]e from paddy fields is of great significance for food security and future climate change assessment. In this study, strongly and weakly responsive cultivars were used as the experimental materials. Based on a free-air CO2 enrichment(FACE) platform continuously run for 14 years, two treatments of different[CO2] were set:a control(i.e., normal[CO2] and[CO2]a) and a 200 µmol·mol-1 higher than[CO2]a condition, ([CO2]e). CH4 and N2O emissions from the rice paddy fields were monitored in situ by static transparent chamber-gas chromatography, and grain yields were also obtained. The results showed that compared with the[CO2]a treatment, long-term[CO2]e increased grain yields of the strongly and weakly responsive cultivars by 29%-31%(P<0.05) and 12%-14%(P>0.05), and CH4 emissions of the strongly and weakly responsive cultivars were reduced by 21%-59% and 11%-54%, respectively. Furthermore, N2O emissions from the strongly and weakly responsive cultivars were significantly reduced by 70%(P<0.05) and 40%(P<0.05), respectively. The short- and long-term responses of grain yields and CH4 emissions from rice paddy fields to[CO2]e were significantly different. Specifically, with the increase in the duration of[CO2]e, the increases in rice yields and CH4 emissions significantly decreased, while the N2O emissions showed no significant changes. Therefore, under long-term[CO2]e conditions, the strongly responsive cultivar has a high potential to reduce greenhouse gas emission and increase grain yields.

[Effect of Elevated CO2 on N2O Emissions from Different Rice Cultivars in Rice Fields].

Using the free air CO2 enrichment (FACE) platform, an in-situ field experiment was conducted to explore the impacts of elevated CO2 mole fraction (x[CO2]) on N2O emissions from strongly and weakly responsive rice cultivars. Under elevated x[CO2], grain yield of the strongly responsive rice cultivars increased significantly, by more than 30%, whereas the weakly responsive cultivars showed a growth rate of 10%-15%. The four treatments comprised A-W (normal x[CO2]+weakly responsive cultivar), F-W (elevated x[CO2]+weakly responsive cultivar), A-S (normal x[CO2]+strongly responsive cultivar), and F-S (elevated x[CO2]+strongly responsive cultivar). Compared to the normal x[CO2] treatments (A-S and A-W), when the strongly and weakly responsive cultivars were exposed to elevated x[CO2](F-S and F-W), N2O emissions decreased by 52.54% (P<0.05) and 38.40% (P<0.05), rice yield increased by 22.96% (P<0.05) and 12.11% (P>0.05), and N2O emission intensity decreased by 61.68% (P<0.05) and 45.13% (P<0.05), respectively. Moreover, N2O emissions of all treatments were significantly positively correlated with NH4+-N content (P<0.05), whereas not correlated with NO2--N content. Soil temperature is an important factor affecting the N2O emissions of the strongly responsive cultivar in rice fields under elevated x[CO2] conditions. Through comprehensive consideration of climate conditions, in the future, priority should be given to planting the strongly responsive cultivar, ensuring high rice yield and significant reduction in N2O emissions.

Effects of Decabromodiphenyl Ether and Elevated Carbon Dioxide on Rice (Oryza sativa L.).

We assessed the effects of carbon dioxide (CO2) and decabromodiphenyl ether (BDE-209, 0, 3 and 30 mg/kg) on rice (Oryza sativa L. cv. Wuyunjing) in field free-air CO2 enrichment system. Rice at elevated (580 ppm) CO2 had increased net photosynthetic rate, intercellular CO2 concentration, shoot biomass, yield and phosphorus content in grains. However, there were no significant changes in such parameters observed on rice at elevated CO2 combined with BDE-209 (3 and 30 mg/kg). Elevated CO2 alone had no significant effects on sugar or starch content in rice grains, whereas its combination with BDE-209 (3 mg/kg) significantly decreased grain sugar and starch content. In conclusion, rice reared in soil polluted by BDE-209 under elevated CO2 modulates the effects in grain feature.

[Effects of elevated atmospheric CO2 concentration on chemical composition of rice straw]. / 大气CO2浓度升高对水稻秸秆化学组成的影响.

Rice straw is a potential material for bioenergy production. Elevated atmospheric carbon dioxide (CO2) concentration changed the quantity and quality of rice straw, thus changing its bioenergy production potential. In this experiment, we collected rice straw from China Free Air CO2 Enrichment Platform (FACE). Three rice varieties, Wuyunjing 27, Y Liangyou 900 and Nipponbare N16, were selected from the FACE platform (the CO2 concentration in the experimental group was controlled at 570 µmol ·mol-1, which was 200 µmol ·mol-1 higher than the control group), the chemical composition of which was analyzed. The results showed that elevated CO2 concentration significantly increased C content, C/N, and the content of non-structural carbohydrates in straw. Elevated CO2 concentration significantly increased total sugar release by 8.8%, 6.7% and 9.9% in Wuyunjing 27, Y liangyou 900 and N16, respectively. Elevated CO2 concentration significantly enhanced the biomass of N16 straw, but had no effect on the straw biomass of the other two rice varieties. The total sugar yield of N16 increased most significantly with elevated CO2 concentration, reaching 19.2%. Our results indicated that elevated CO2 concentration could improve the quality and quantity of rice straw, thereby increasing the utilization potential of biofuel.

[Effects of elevated atmospheric CO2 concentration on the stability of soil organic carbon in different layers of a paddy soil.] / 大气CO2浓度升高对不同层次水稻土有机碳稳定性的影响.

It is vital to study the effects of elevated atmospheric CO2 concentration on the soil orga-nic carbon (SOC) stability in different soil layers for better understanding the mechanism of SOC transformation under the elevated atmospheric CO2 concentration. The paddy soil in a long-term FACE (Free Air Carbon-dioxide Enrichment) experiment was selected as the research object. Through the SOC physical fractionation and soil mineralization incubation, the effects of elevated atmospheric CO2 concentration on the soil organic carbon (SOC) content, particle organic matter (POM) content, SOC mineralization intensity, and enzyme activities were measured. Then, the effects of elevated atmospheric CO2 concentration on the SOC stability in different layers were exa-mined. The results showed that the elevated atmospheric CO2 concentration had no significant effect on SOC content, but significantly increased the POM-C content by 93.7% and the invertase and polyphenol oxidase activities by 61.1% and 83.7% in the topsoil layer, respectively. These results indicated that SOC stability of topsoil was reduced under the elevated atmospheric CO2 concentration. However, the elevated atmospheric CO2 concentration had no significant effect on the SOC stability of deep soil layer. Our results would help assess the capacity of soil sequestrated and accumulated organic carbon and provide basis for scientific management of farmland under greenhouse effect in the future.

[Effect of schisantherin A inhibit liver sinusoid endothelial cell function and action against liver fibrosis relating to angiogenesis].

To investigate the effect of schisantherin A on liver sinusoid endothelial cell function and angiogenesis. Different dosages (0-40 µmol•L⁻¹) of schisantherin A were incubated 24 h with SK-HEP-1 cells, and the toxicity of SK-HEP-1 cells was assayed by MTT method. The proliferation of SK-HEP-1 cells were induced by the vascular endothelial growth factor (VEGF), with receptor tyrosine kinase inhibitor sorafenib as the control, at the same time, set up the control group, 2, 20 µmol•L⁻¹ schisantherin A were incubated with SK-HEP-1 cells, cell proliferation was analyzed by EdU DNA cell proliferation kit. Fluorescence probe method was used to assay the intracellular NO levels and NOS activity. Tube formation was observed using cell migration and a matrigel tube formation assay. Rat aortic ring assay was performed to observe the sprouting vessels from aortic ring. The fluorescence vessels, the number of functional blood vessels, and intersegmental vessel changes of transgenic zebrafish were also observed. Compared with control group, the proliferation of SK-HEP-1 cells induced by VEGF increased and and the level of NO and NOS activity induced; compared with model group, 2, 20 µmol•L⁻¹ schisantherin A and sorafenib inhibited the proliferation of SK-Hep-1 cells induced by VEGF, and reduced the level of NO and NOS activity. At the dosage of 20 µmol•L⁻¹, schisantherin A attenuated the migration and tube formation of SK-HEP-1 cells induced by VEGF, and also inhibition the formation of rat aortic rings and intersegmental vessel changes of transgenic zebrafish, and significantly reduce the number of vessels in zebrafish. Schisantherin A has potential effects on function of endothelial cell proliferation and angiogenesis.

[Effects of O3-FACE(ozone-free air control enrichment) on gas exchange and chlorophyll fluorescence of rice leaf].

O3-FACE (Ozone-free air control enrichment) platform has been established for observing the effect of elevated tropospheric ozone concentration on the gas exchange and chlorophyll fluorescence of two rice varieties (Wuyunjing 21 and Liangyoupeijiu). The results showed that high ozone concentration decreased the net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr) of rice leaves. After 76d fumigation the decline in them for Wuyunjing 21 was as follows: 21.7%, 26.64% and 24.74% respectively, and that for Liangyoupeijiu was as follows: 25.53%, 30.31% and 25.48% respectively; however, no significant impact on leaf intercellular CO2 concentration was observed. Chlorophyll fluorescence kinetics parameters changed as can be seen by the decrease in F0 (initial fluorescence in the dark), ETR (The apparent electron transfer rate) and psiPSII (actual photochemical efficiency of PS II in the light), and the increase in NPQ (non-photochemical quenching). After 76 days of O3 treatment, the NPQ of Wuyunjing 21 and Liangyoupeijiu was enhanced by 16.37% and 11.77%, respectively. The impact of ozone on rice was a cumulative effect, and the extent of variation in the above parameters and the differences between the two varieties were enlarged as the O3 treatment time increased; At the same time because the rice leaf intercellular CO2 concentration did not significantly reduce, the inferred decrease in net photosynthetic rate was restricted by non-stomatal factors. The results of this experiment indicated that Liangyoupeijiu was more susceptible to ozone than Wuyunjing 21.