Studies on the scavenging function of hygrohpytes to methane induced in the severely reduced conditions

在严重减少的条件下，湿地湿生植物的植被降低了土壤甲烷的浓度。土壤甲烷浓度的下降幅度从大到小依次为万金菊(E)、田葵(S)、芦苇(R)、水稻(I)、野生稻(M)。根际土壤产甲烷活性的大小顺序为I、M、R、>，无湿生植物>、E、S。无湿生植物的根际土壤甲烷氧化活性略高，不同类型湿生植物的根际土壤甲烷氧化活性差异不大。在模型实验中（气体系统甲烷浓度为70%，液体系统甲烷浓度为1%），先前在低氧浓度条件下水培的植物产生了溶解性通气，并且通过其茎部释放的甲烷量比在好氧条件下预培养的植物要多。气体系统中植物对甲烷的释放能力明显高于液体系统，根系释放大气氧的顺序为M b> R> I> S> E，过氧化物酶和过氧化氢介导的α -萘胺的氧化能力依次为E> R，S> M> I，且在根尖部分的氧化能力更高。根际Eh的提高力大小依次为E、S、R、M、I。严重还原性土壤溶液中检测到高浓度的Fe^<2+>。在体外实验中，H_2O_2与Fe^<2+>共存时，溶解甲烷显著减少。甘露醇是羟基自由基的清除剂，甘露醇的加入对甲烷浓度的降低没有影响，这也说明了Fenton反应产生的羟基自由基可以直接清除根外体中的甲烷。在添加Fe^<2+>的溶液中，湿生植物尤其是E和S显著降低了甲烷浓度。综上所述，E和S不仅可以通过其根的强氧化能力抑制根际土壤甲烷的产生活性，而且还具有直接清除外质体甲烷的功能。这些发现为培育新的植物提供了新的重要数据，即能够耐受严重减产条件的植物，以及通过植物具有高度抑制甲烷排放能力的植物。对蔬菜、水果和草类中黄酮类和酚类化合物的抗氧化作用也进行了阐述。少

Vegetation of hygrophytes in wetland decreases the concentration of soil methane produced in the severely reduced conditions. The order of the decreasing power of the concentration of soil methande was erect bur marigold (E), sesbania (S) >reed (R) >rice (I) >Manchurian wild rice (M). The order of activity of methane production in rhizosphere soil was I,M,R>without hygrophytes>E,S.The activity of methane oxidation in rhizosphere soil was a little higher in the soil without hygrophtes and was hardly different among the soils overgrown with different kind of hygrophytes. In the model experiments (methane concentration in gas system was 70%, and that in liquid system was 1%), plants cultured previously in hydroponically under the low oxygen concentration developed lysigenous aerenchyma and emitted larger amounts of methane through their shoot than those precultured in aerobic conditions. The emission ability of methane through plants was considerably higher in gas system than in liquid sy … More stem, and the order was M> I,R,E> S.The order of release of atmospheric oxygen from roots was M> R> I> S> E.The order of oxidizing power of alpha-naphthylamine mediated both by peroxidase and hydrogen peroxide was E> R,S> M> I,and this power was higher in the tip portions of roots. The order of raising power of rhizosphere Eh was E,S> R> M,I.High concentration of hydrogen peroxide was detected in the apoplast of epidermis and cortex of E and S.High concentration of Fe^<2+> was detected in the solution of the severely reduced Soil. In vitro experiments, the dissolved methane was significantly decreased in the co-existing conditions of H_2O_2 and Fe^<2+>. Negation of the decrease in methane concentration by the addition of mannitol which is known as the scavenger of hydroxyl radical also suggests the direct scavenging of methane in the apoplast of roots with hydroxyl radical which is produced by Fenton reaction. Hygrophytes especially E and S considerably decreased the methane concentration in the solution added Fe^<2+>. In conclusion, E and S not only can suppress the production activity of methane in rhizosphere soil by their strong oxidizing power of roots but also possess the function to scavenge methane directly in their apoplast. These findings offer the novel and important data for the creation of new plants i.e., plants tolerant to the severely reduced conditions, and plants having highly suppressive ability of methane emission through plants. The antioxidative function of flavonoids and phenolic compounds in vegetables, fruits, and grasses was also elucidated. Less