Variations in relative stomatal and biochemical limitations to photosynthesis in a young blackbutt (Eucalyptus pilularis) plantation subjected to different weed control regimes

Foliar gas exchange and carbon (delta(13)C) and oxygen (delta(18)O) isotope ratios were measured in a young blackbutt (Eucalyptus pilularis Sm.) plantation subjected to four weed control treatments defined by the width of the weed-free strip maintained for the first 12 months after planting. Treatments were: 2-m-wide weed-free strip (50% of plot area, 2.0MWC), 1.5-m-wide weed-free strip (37.5% of plot area, 1.5MWC), 1-m-wide weed-free strip (25% of plot area, 1.0MWC) and no weed control (NWC). Our objectives were to determine (1) if decreasing the width of the weed control strip (decreasing herbicide use) affected growth and leaf photosynthesis of the plantation, and (2) the effects of the weed control regimes on variations in relative stomatal and biochemical limitations to photosynthesis. Trees in the 1.0MWC treatment had lower foliar light-saturated photosynthetic rate (A(sat)) than trees in the 2.0MWC treatment. An increase in metabolic limitation was responsible for the decrease in A(sat) in the 1.0MWC trees, which was also partly confirmed by the isotopic data. Compared with trees in the 1.0MWC, 1.5MWC and 2.0MWC treatments, A(sat) of NWC trees was significantly lower, a difference that was attributable mainly to stomatal limitation and to a lesser extent to biochemical limitation. The results support the conclusion that different weed control regimes cause differences in relative stomatal and biochemical limitations to plantation photosynthesis. This report contributes to a growing body of literature on competition for soil resources between trees and weeds. Our results highlight the usefulness of the stable isotopic method in supporting analysis of the response of net photosynthesis to varying intercellular CO(2) concentration for determining the relative stomatal and non-stomatal limitations to photosynthesis under experimental conditions in the field.     

Baicalin suppresses expression of Chlamydia protease-like activity factor in Hep-2 cells infected by Chlamydia trachomatis

In this study, we tested the ability of Baicalin to block Chlamydia trachomatis infection and found that the Baicalin blocked infection of Hep-2 cells. Then, we looked into the expression of RFX5 and CPAF gene in Chlamydia-infected cells. We found that RFX5 and CPAF were up-regulated and down-regulated respectively by Baicalin. Since CPAF is responsible for degrading RFX5, we suggest that CPAF was a primary target of Baicalin and played an important role in regulating RFX5. Our findings demonstrate that Baicalin can inhibit C. trachomatis effectively and therefore, can be considered as potential agents for therapy of Chlamydia infectious diseases.     

泉州市发展城市林业的思考

从发展城市林业的意义和泉州市城市林业建设现状,分析了城市林业建设存在的主要问题,提出了泉州市发展城市林业的建议。     

广西岩溶区烟草栽培地土壤养分、微生物与病害发生的调查分析

对广西岩溶区靖西县栽培的烟草根际土壤养分、微生物数量和主要病害的发生情况进行了调查分析。结果表明：该地区土壤pH偏高,营养元素除了速效钾含量较低外,有机质、全氮、速效磷、有效锰、有效铁、有效铜、有效锌含量均为丰富,总体肥力较好,其中水田土壤的有机质、全氮含量显著高于旱田（P<0.01）。土壤中微生物总量为1.21×107~9.91×107个/g,其中细菌数量占绝对优势,放线菌次之,真菌最少,水田细菌数量显著高于旱田（P<0.05）。3种病害总体以马铃薯Y病毒病为主,发生范围最广,黒胫病次之,青枯病偶有发生。相关分析表明,土壤有机质和全氮含量对细菌数量或总量有很大的影响,土壤速效磷和pH值对植株发病率的影响较大。     

配施矿物质质有机肥及化肥减量对玉米水肥资源利用率的影响

采用单因素试验设计,在大田栽培条件下研究了配施矿物质有机肥及化肥减量对玉米产量构成及水、肥资源利用率的影响。结果表明,配施矿物质有机肥可以显著的提高玉米的产量、水分利用效率和氮肥、磷肥利用率。在配施矿物质有机肥的条件下,化肥施量较当地最佳施肥水平减量15%和30%时,玉米产量分别达到13948 kg/hm2 、12782 kg/hm2,水分利用效率分别达到1.74 kg/m3、1.62 kg/m3,氮肥利用率分别达到35.97%、30.04%,磷肥利用率分别达到25.93%、21.55%。其中,在当地最佳施肥水平下减量15%并配施矿物质有机肥与当地最佳施肥水平处理的玉米产量没有显著性差异。表明在合理配施矿物质有机肥的条件下,将当前的化肥施量降低15%以内在生产实践中是可行的。     

Assessment of partial resistance to powdery mildew in Chinese wheat varieties

Field trials in two cropping seasons and two locations in central China were conducted on 60 Chinese autumn‐sown wheat varieties to assess their partial resistance to powdery mildew. Mean levels of disease severity ranged from close to 0 to more than 90%. The method of inoculation and the location in which trials were conducted affected the relative performance of the varieties, but these effects were much smaller than the main effect of variety. The area under the disease progress curve was highly correlated with final disease severity, but both were poorly correlated with apparent infection rate. Disease severity was regressed against frequencies of virulence in the Blumeria graminis (syn. Erysiphe graminis) f sp. tritici populations in the trial plots. A vertical distance (D) from the mean mildew severity to the fitted line was calculated for each variety and was used to quantify partial resistance. Five of the 60 varieties, ‘Hx8541’, ‘E28547’, ‘Chuan1066’, ‘Zhe88pin6’ and ‘Lin5064’, consistently expressed relatively low levels of disease despite high frequencies of virulence in the pathogen and had consistently high D‐values. They may therefore have good levels of partial resistance.     

建立山水林田湖草一体化国家公园的机遇分析

指出了推动山水林田湖草一体化国家公园建设,对于我国生态文明建设理论与实践具有十分重要的理论和现实意义。近年来,国家公园建设取得显著成效和积极进展,但同时我国国家公园仍面临诸多问题与挑战,如环境资源保护及人地关系矛盾突出、景区划分混乱及配套设置薄弱、生态保护及自我保护意识薄弱、治理机制不严格等。特别是目前我国新型冠状病毒疫情的爆发,更是反映出我国国民对于生态保护及自我保护意识的薄弱问题。为此,提出了通过签订保护地役权、分区建设、多方合作、联合发展及完善治理体系等四大措施积极推动我国山水林田湖草一体化国家公园体制建设。     

国土空间背景下的城市绿色空间体系规划研究

国土空间规划是生态文明建设的重要内容,也是国土空间治理体系现代化的基础,探讨在国土空间背景下的绿色空间体系规划、划定严格的空间保护建设等级和严格分类管理,对于国土资源统筹保护和修复具有重要的意义。文章以北京市二道绿隔平原区为研究区域,首先提出适用于二道绿隔地区的绿色空间定义;其次从基质完形、廊道构建和斑块保护3方面构建完整的绿色空间体系;最后综合提出绿色空间体系的优化对策。     

江西省薄壳山核桃产业及苗木生产现状分析

薄壳山核桃树形挺拔、树冠优美,果仁营养丰富,木材质地优良,是一种极具市场竞争力的高效生态经济型木本油料树种;但在江西省还处于初始发展阶段,科研基础薄弱,产业发展相对滞后;本文通过分析江西薄壳山核桃产业发展与苗木生产现状及存在问题,总结提出了今后科研开展的方向及促进产业发展的对策。     

宜兴市官林污水处理厂工艺设计

介绍了宜兴市官林污水处理厂的工艺设计过程，该污水厂针对处理对象的水量和水质采用了循环式活性污泥法。