Elevated CO2 does not necessarily enhance greenhouse gas emissions from rice paddies.

Elevated atmospheric carbon dioxide (eCO2) greatly impacts greenhouse gas (GHG) emissions of CH4 and N2O from rice fields. Although eCO2 generally stimulates GHG emissions in the short term (<5 years) experiments, the responses to long-term (≥10 years) eCO2 remain poorly known. Here we show, through a series of experiments and meta-analysis, that the eCO2 does not necessarily increase CH4 and N2O emissions from rice paddies. In an experiment of free-air CO2 enrichment for 13-15 years, CH4 and N2O emissions were decreased by 11-54% and 33-54%, respectively. The decline of CH4 emissions was related to the reduction of CH4 production and enhancement of CH4 oxidation via raising soil Eh and soil-water interface [O2] under eCO2. Moreover, the eCO2 significantly decreased NH4+-N content, suggesting a reduction of soil nitrification and thereby N2O emissions. A meta-analysis showed that CH4 and N2O emissions were stimulated under short-term eCO2 while reduced under long-term eCO2. The eCO2-induced increase in yield and biomass and the ratio of mcrA genes/pmoA genes declined with eCO2 duration, indicating an eCO2-stimulation of methanogenesis lower than that of methanotrophy over time by fewer increased substrates. Upscaling the results of meta-analysis, the eCO2-induced global paddy CH4 and N2O emissions shifted from an increase (+0.17 Pg CO2-eq year-1) in the short term into a decrease (-0.11 Pg CO2-eq year-1) in the long term. Our findings suggest that the effect of eCO2 on GHG emissions changes over time, and this should be considered in future climate change research.

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.

[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.