Sulfur storage changed by exotic Spartina alterniflora in coastal saltmarshes of China

For the purpose of ecological engineering, Spartina alterniflora was introduced to China in 1979 and now covers about 112,000 ha of China's coastal lands. It was hypothesized that S. alterniflora could actively change the habitat environment, thus facilitating its competition over native species. In Yancheng Nature Reserve, sulfur storage of sediments and plant tissues was compared among marshes dominated by the exotic S. alterniflora and adjacent native Suaeda salsa and Phragmites australis and bare mudflat. Results showed that the S. alterniflora marsh contained the highest content of water-soluble, adsorbed, carbonate-occluded and total sulfur in the sediment. The sulfur levels were higher in the center than at the edges of the S. alterniflora marsh. Native marshes showed no significant difference in sediment sulfur levels. With greater biomass and higher tissue sulfur concentrations, plant sulfur storage of S. alterniflora vegetation was also larger than those of the native vegetations. Because higher concentrations of sulfur increase the competitive advantage of S. alterniflora over native halophytes, the results of the research showing that S. alterniflora increased marsh sulfur storage may shed light on the mechanism of expansion of monospecific vegetation in coastal China.     

念珠菌—上皮细胞互作研究进展

念珠菌作为共生菌定植于机体黏膜表面,一般情况下并不引起感染,但当机体出现免疫力下降或微生态失衡等状况时,可引发口咽念珠菌病、外阴阴道念珠菌病等黏膜感染。对于念珠菌黏膜感染的治疗,虽然抗菌药物是不可或缺的因素,但宿主自身的免疫力,尤其是黏膜上皮细胞作为抵御念珠菌感染的第一道防线,发挥着重要作用。本文将念珠菌—上皮细胞相互作用研究进展作一综述。     

低pH、铝和钙离子对菌根菌赭丝膜伞的毒性和超氧化物歧化酶的影响

应用急性毒性生物测试方法,研究了低pH和铝离子对菌根菌赭丝膜伞(Cortinariusrussus)的毒性效应.试验表明,在pH为6.8、5.5和4.3,铝离子在低pH(4.3)时对菌根菌毒性最强,96h EC₅₀为5.05mg·L^-1,菌根生长受到明显的抑制;低pH和铝离子能诱导菌根菌体内SOD,与对照组相比,菌根菌体内SOD活性明显升高;加入钙离子后,SOD活性下降,并随Ca的投加浓度增加,SOD活性逐渐降低,表明在低pH条件下,钙离子和铝离子对菌根的影响具有拮抗作用.     

淡水水生植物化感作用研究进展

水生植物的化感作用对淡水生态系统中水草的可持续管理和湖泊富营养化的生态控制具有非常重要的意义。本文综述了淡水水生植物化感作用的发展历史和研究现状,讨论了水生植物化感作用研究过程中所涉及的实验方法、生物测试方法、化感物质分离方法以及影响水生植物化感研究的环境因素。抑藻圈试验、藻类生长试验和浮萍生长试验是常用的生物测试方法;采用共生培养或单独培养的方法,从种植水中分离、鉴定化感物质,对证实复杂水环境中水生植物化感作用的存在,研究它们化感物质的释放途径和作用机理都具有十分重要的作用。     

几种湿地植物净化生活污水COD、总氮效果比较

以无植被、基质为河砂的潜流型人工湿地为对照,研究了石菖蒲、灯心草和蝴蝶花3种类型植被、基质均为河砂的潜流型人工湿地净化生活污水COD、总氮的效果．结果表明,在污水COD浓度小于200mg·L^-1、总氮浓度小于30mg·L^-1的低浓度范围里,无植被的人工湿地和有植被的人工湿地对污水中COD、总氮均有很好的去除效果,两者差异不大,其COD去除率均达90％以上,总氮的去除率达80％以上．随着污水中COD和总氮浓度的增加,无植被人工湿地和有植被人工湿地去除COD和总氮的效果均有不同程度下降,两者差异明显,有植被的人工湿地能维持较高的COD、总氮的去除效果,无植被的人工湿地COD和总氮去除效果下降很快,植被在人工湿地系统去除污水COD和总氮过程中起着重要的作用．在整个试验阶段,石菖蒲植被人工湿地COD和总氮平均净化效率分别为80．46％和77．77％、灯心草人工湿地分别为75．53％和71．17％、蝴蝶花人工湿地分别为70．50％和66．38％,无植被人工湿地分别为61．39％和55．81％．同无植被人工湿地COD和总氮净化效果相比,石菖蒲植被人工湿地净化效果最好;其次为灯心草植被人工湿地,再次为蝴蝶花植被人工湿地．不同类型植被的人工湿地净化污水中COD和总氮的效果与其生物量关系密切,这与植被系统吸收同化有机物质和总氮数量、根际微生物分解有机物质和硝化-反硝化作用有关。     

Callus induction,plant regeneration,and long-term maintenance of embryogenic cultures in <Emphasis Type="Italic">Zoysia matrella</Emphasis> [L.] Merr

An efficient protocol of callus induction, plant regeneration and long-term maintenance of embryogenic cultures for manilagrass was developed. Callus induction and embryogenic callus formation were influenced by cytokinins and nodal positions. Murashige and Skoog (MS) medium with 2 mg l⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D), 0.02 mg l⁻¹ kinetin (KT) or 6-benzyladenine (BA) gave the highest frequency for both callus induction and embryogenic callus formation compared with 0.02 mg l⁻¹ thidiazuron (TDZ) or N⁶-(2-isopenteny) adenine (2iP). The frequency of callus induction of different nodes (from the first to the sixth node) varied from 22.5 to 92.1%, and the embryogenic callus formation frequencies ranged from 13.3 to 25.7%. The highest frequencies of callus induction and embryogenic callus formation (92.1 and 25.7%, respectively) were observed in the fourth node group. During subculture on callus induction and maintenance medium, somatic embryos formed on the surface of the embryogenic callus. On regeneration medium, the regeneration rates of embryogenic callus varied from 96.8 to 100% during the 4-year period of subculture. The results also indicate that preservation of manilagrass callus is stable at low-temperature (4°C) over a period of 11 months. No significant differences were found in the activities of superoxide dismutase (SOD), peroxidase (POD) and proline content of the plants regenerated from the 4-year subcultured callus on different regeneration media.