The response of the photosynthesis and antioxidant enzyme activities in Phragmites australis to S2- and Na+ stress

The soil sulfur content and Na+ are very high in the tidal wetland. The physiological ecological response of P. australis to S2–stress and S2– & Na+ joint stress is unclear. Using P. australis from the high tidal marsh in the Yellow River Delta as experimental materials, two comparison experiments were conducted(The same S2– concentration: 50 mmol·L–1 Na2 S VS. K2 S; The same Na+ concentration: 40 mmol·L–1 Na2 S VS. 80 mmol·L–1 NaCl). The effects of S2-, Na+ and their joint stress on photosynthesis and antioxidant enzyme activities were compared. The results showed that: Na)2 S inhibited the photosynthetic rate more strongly than the K2 S and NaCl, and thus the joint effect of S2– and Na+ stress was more serious than their single effect. Furthermore, for the antioxidant enzyme activities, under 50 mmol·L–1 Na2 S stress, the activities of H2 O2, POD and SOD were higher than the control treatment, thus POD and SOD played an important role in resisting Na2 S stress. Overall, the coexistence of S2– and Na+ depressed the P. australis more severely, and POD and SOD played an important role in resisting S2- and Na+ stress

Effects of environmental and biotic factors on soil respiration in a coastal wetland in the Yellow Ｒiver Delta，China

采用Li-8150多通道土壤呼吸自动测量系统对黄河三角洲滨海湿地土壤呼吸进行全年连续测定,同步测量了温度、土壤含水量、地上生物量以及叶面积指数等环境因子和生物因子.结果表明:土壤呼吸日动态在全年尺度上多呈单峰型,但在受到土壤封冻和地表积水干扰时,土壤呼吸日动态呈多峰型.土壤呼吸具有明显的季节动态特征,总体呈单峰型,年平均土壤呼吸速率为0.85&mu;mol CO_2&middot;m~(-2)&middot;s~(-1),生长季平均土壤呼吸速率为1.22&mu;mol CO_2&middot;m~(-2)&middot;s~(-1).在全年尺度上,土壤温度是滨海湿地土壤呼吸的主要控制因子,可解释全年土壤呼吸87.5%的变化.在生长季尺度上,土壤含水量和叶面积指...</p

Physiological and ecological responses of hetan and chaotan Phragmites australis to salt stress

Characterizing the different physiological and ecological responses of Phragmites australis from two habitats in the Yellow River delta to salt stress can provide important theoretical support for the selection of P. australis types for the ecological restoration of degraded coastal wetlands. The Na+ content, photosynthetic parameters, H2O2 content, antioxidant enzyme activity, malondialdehyde content, and proline content of leaves from hetan（low-salt habitat, riverside） and chaotan（high-salt habitat, high marsh） P. australis grown under salt stress conditions（300 mmol/L NaCl） were compared, along with the Na+ flux of the root growth area. Salt stress significantly increased the Na+ content in the hetan leaves but had no significant effect on that of the chaotan leaves. Furthermore, non-invasive micro-test technology（NMT） revealed greater Na+ efflux in the chaotan plants(（1982.05±122.74） pmol cm-2 s-1 vs.（87.93±12.94） pmol cm-2 s-1, P<0.01)than in the hetan plants(（1574.16±458.90） pmol cm-2 s-1 vs.（-126.88±23.01） pmol cm-2 s-1, P<0.01), which could be attributed to the need for chaotan P. australis to effectively regulate intracellular ion balance. In addition, the photosynthetic rate of the chaotan plants(（16.36±1.09） μmol m-2 s-1 vs.（22.79±0.67） μmol m-2 s-1, P<0.01) was significantly greater than that of the hetan plants(（12.71±0.97） μmol m-2 s-1 vs.（23.81±0.55） μmol m-2 s-1, P<0.01)after 7 d of salt treatment. Salt stress induced significant increases in the H2O2, malondialdehyde, and proline contents of leaves from both P. australis types, as well as in the activity of antioxidant enzymes. Moreover, the activity of glutathione reductase（GR）in chaotan P. australis was increased significantly（（6.90±1.73） U/mgprot vs.（3.54±0.54） U/mgprot, P<0.05）. These results indicate that chaotan P. australis is more adaptable to salt stress than hetan P. australis, as indicated by the greater Na+ efflux of its roots, greater proline content, and greater antioxidant enzyme activity, which promote salt-stress tolerance. Therefore, in the ecological restoration of degraded coastal wetlands in the Yellow River delta, P. australis from the high marsh should be selected as the material for vegetation restoration

Effects of change in precipitation amount on soil respiration and photosynthetic characteristics of Phragmites australis in a coastal wetland in the Yellow River Delta,China

滨海湿地地下水位浅,淡咸水垂直交互作用明显,全球气候变化背景下降水变异改变其土壤表层水盐状况,从而影响植物光合作用与土壤呼吸.为探究降雨量变化对黄河三角洲滨海湿地土壤呼吸和光合特性的影响,采用固定式遮雨顶棚和雨水输送管道相结合的方法设置增减雨处理小区,于2015年生长季测定土壤呼吸和光合作用光响应曲线,同时连续测定土壤温度、土壤含水量、土壤含盐量等土壤环境因子.结果表明:根据土壤含水量波动情况可将生长季分为3个阶段:干旱期、湿润期、淹水期.不同土壤水分阶段,土壤呼吸和芦苇光合特性对降雨量增减的响应不同.在干旱期,增雨处理下土壤呼吸速率显著提高了31.8%,同时芦苇叶片气孔导度和光合能力显著增强;减雨处理下土壤呼吸速率降低41.1%,芦苇叶片气孔阻塞,光合能力降低.在湿润期,增雨和减雨处理使土壤呼吸速率及其温度敏感性指数(Q10)均出现下降,但二者未对芦苇各光合参数和净光合速率产生显著影响.在淹水期,增减雨处理未对土壤呼吸产生显著影响,但芦苇对淹水胁迫较为敏感,增减雨分别加重和降低了淹水对芦苇植株的伤害,光合速率由高到低为减雨>对照>增雨

近1200 a来黄河下游梁山泊沉积记录的环境变迁

利用梁山泊670 cm柱状岩芯沉积物,基于精确的AMS-14C年代测定,通过高分辨率的粒度、磁化率、总有机碳、 C/N比值等环境代用指标的综合分析,并结合历史文献记载,初步揭示了1200 a来黄河下游地区平原湖泊沉积特征及环境演化历史.结果表明,梁山泊环境演化大致分为5个阶段: 790 940 AD期间,为低湖面的沼泽沉积环境,气候冷干; 940 1215 AD期间,屡次受到黄河决溢洪水影响,湖盆扩张,湖泊水位上升,为梁山泊极盛期,气候暖湿; 1215 1310 AD期间,黄河夺淮入黄海,湖区淤积严重,湖泊萎缩减小; 1310 1470 AD期间,再次受到黄河决溢洪水影响,水位上升,面积扩张,但逊于极盛期; 1470 AD至现代,黄河河道进一步南移,远离梁山泊,湖盆淤积抬高,梁山泊最终消失,直到1855 AD,黄河第6次大改道北移,湖泊再次受到黄河洪水影响,由于前期受到泥沙淤积抬高,该地区仅作为黄河泥沙承载区.在气候变化大背景下,黄河改道决溢是梁山泊演化的主因.</p

氧离子与氖原子碰撞转移电离过程研究

采用位置灵敏探测和散射离子 反冲离子飞行时间测量技术,测量了氧离子与氖原子碰撞过程中转移电离截面与单电子俘获截面之比。通过比较,发现测量结果与文献结果的趋势一致,并对测量结果进行了解释

氧离子与氦、氖原子碰撞中转移电离过程的研究

采用位置灵敏探测和散射离子 反冲离子飞行时间测量技术,测量了氧离子与氖和氦原子碰撞过程中转移电离截面与单电子俘获截面之比。通过比较发现测量结果与文献结果的趋势一致,并对测量结果进行了讨论