上海乡土水生植物资源及其在水生态恢复与水景观建设中的应用潜力

水生植物作为水生生态系统的主体, 对发挥水生生态系统的自维持、自循环功能有重要作用。研究通过相关资料的查阅, 建立上海地区乡土水生植物名录, 并对其科属组成、区系特征、生活型、生长型等进行统计分析。结果表明上海地区乡土水生植物共计35 科83 属160 种(含变种), 单属科、单种属的比例较高, 均达65%以上; 植物区系组成丰富、成分复杂, 以热带成分占优势, 达64.6%; 生活型以挺水植物为主, 沉水植物次之, 浮水植物最少; 生长型类型丰富, 以草本型、禾草型居多, 20 种生长型可进一步归为表征相似生态学特征和功能地位的6 个生长型组。在水生态恢复与水景观建设中, 仅有68.8%的景观水体有水生植物应用,且应用种类在2 种以下的占79.2%。乡土水生植物应用不足, 一半以上为观赏性强的外来物种, 应用频率较高的为挺水植物, 对具有良好净化效果的沉水植物重视不够。因此, 在水生态恢复与水景观建设中, 建议加强乡土水生植物资源的繁育栽培, 在充分利用乡土水生植物资源配置群落的基础上, 根据水质的富营养及基底状况, 通过不同生长型组水生植物的应用, 构建沉水-浮水-挺水植物群落复合体, 并通过近自然型护岸的营造, 形成水生-湿生复合生态系统。运用植被工程学的原理和方法, 采用生态浮岛、生态沉岛等技术营造水生植被, 将强人工化的水景观建成具生命的水生生态系统。       

栲树不同生长发育阶段的枝系特征分析

对浙江天童国家森林公园内常绿阔叶优势树种栲树(Castanopsis fargesii)不同发育阶段植冠内的分枝式样特征进行了统计分析。结果表明：栲树在不同发育阶段的总体分枝率和逐步分枝率有显著变化,幼苗和幼树阶段的分枝率较低,而成株阶段的分枝率较高;幼树阶段的枝条长度、枝倾角和叶倾角明显大于幼苗和成株阶段,表现为明显的高生长对策;叶片配置在不同枝系上有较大差异,叶片主要集中于植冠内一级枝和二级枝上;叶片的大小从幼苗、幼树到成株阶段逐渐增大。研究结果表明栲树在生活史的不同生长发育阶段,分枝式样表现出一定的可塑性,反映了不同的适应对策。     

绥宁河生态修复对粒径分级叶绿素a的影响

通过对上海市的苏州河支流绥宁河治理段与非治理段水体叶绿素a分粒级分析,探讨了生态修复对水体粒径分级叶绿素a的影响．结果表明,非治理和对照以及治理采样点微型和微微型浮游植物叶绿素a占总叶绿素a的百分比均值分别为85．232、92．402和95．205％,其中微型浮游植物叶绿素a占总叶绿素a的百分比均值分别为78．460、87．943和87．211％,对全河叶绿素a的贡献平均为84．538％,是该水体叶绿素a生物量的最大贡献者;网采浮游植物对全河叶绿素a的贡献仅为9．054％．生态修复工程试验使网采浮游植物相对生物量减少,微型浮游植物相对生物量保持稳定,而微微型浮游植物相对生物量增多,对超微型浮游植物的影响不大,微型和微微型浮游植物对工程试验的反应最敏感．     

HAL1 mediate salt adaptation in Arabidopsis thaliana

INTRODUCTIONSalinity is a major environmental stress that isa substantial constraint to crop production both fordry land and irrigated agriculture. The detrimental impact of this stress is perpetuated and exacerbated by management practices used to facilitatehigh-output crop production. To overcome theselimitations and improve production efficiency in theface of a burgeoning world population, more salt tolerant crops must be developed. In contrast with traditional breeding, the direct ill…     

Regeneration of plants from callus tissues of hairy roots induced by Agrobacterium rhizogenes on Alhagi pseudoalhagi

INTRoDUCTIONThe hairy root disease is a patholOgical syndromeof dicotyledonous plants fOllowing wounding and in-fection with Agrobacterum rhjZOgenesI1]. The rhi-zogenicity is conferred to p1ant cel1s by a fragmentof DNA (Ri T-DNA), which is transferred from thelarge root--inducting (Ri) plasmid, haJrboured by thebacterium, to the genome, where it is stably inte-grated and expressed. Illtegration of a DNA segment(T-DNA) of pRi into the host genome 1eads to ac-tive proliferation of…     

Horizontal transmission, vertical inactivation, and stochastic loss of mariner-like transposable elements

Horizontal transmission has been well documented as a major mechanism for the dissemination of mariner-like elements (MLEs) among species. Less well understood are mechanisms that limit vertical transmission of MLEs resulting in the "spotty" or discontinuous distribution observed in closely related species. In this article we present evidence that the genome of the common ancestor of the melanogaster species subgroup of Drosophila contained an MLE related to the mellifera (honey bee) subfamily. Horizontal transmission, approximately 3-10 MYA, is strongly suggested by the observation that the sequence of the MLE in Drosophila erecta is 97% identical in nucleotide sequence with that of an MLE in the cat flea, Ctenocephalides felis. The D. erecta MLE has a spotty distribution among species in the melanogaster subgroup. The element has a high copy number in D. erecta and D. orena, a moderate copy number in D. teissieri and D. yakuba, and was apparently lost ("stochastic loss") in the lineage leading to D. melanogaster, D. simulans, D. mauritiana, and D. sechellia. In D. erecta, most copies are concentrated in the heterochromatin. Two copies from D. erecta, denoted De12 and De19, were cloned and sequenced, and they appear to be nonfunctional ("vertical inactivation"). It therefore appears that the predominant mode of MLE evolution is vertical inactivation and stochastic loss balanced against occasional reinvasion of lineages by horizontal transmission.      

A phylogenetic approach to the identification of phosphoglucomutase genes

The expanding molecular database provides unparalleled opportunities for characterizing genes and for studying groups of related genes. We use sequences drawn from the database to construct an evolutionary framework for examining the important glycolytic enzyme phosphoglucomutase (PGM). Phosphoglucomutase plays a pivotal role in the synthesis and utilization of glycogen and is present in all organisms. In humans, there are three well-described isozymes, PGMI, PGM2, and PGM3. PGM1 was cloned 5 years ago; however, repeated attempts using both immunological approaches and molecular probes designed from PGM1 have failed to isolate either PGM2 or PGM3. Using a phylogenetic strategy, we first identified 47 highly divergent prokaryotic and eukaryotic PGM-like sequences from the database. Although overall amino acid identity often fell below 20%, the relative order, position, and sequence of three structural motifs, the active site and the magnesium-- and sugar-binding sites, were conserved in all 47 sequences. The phylogenetic history of these sequences was complex and marked by duplications and translocations; two instances of transkingdom horizontal gene transfer were identified. Nonetheless, the sequences fell within six well-defined evolutionary lineages, three of which contained only prokaryotes. Of the two prokaryotic/eukaryotic lineages, one contained bacterial, yeast, slimemold, invertebrate, and vertebrate homologs to human PGM1 and the second contained likely homologs to human PGM2. Indeed, an amino acid sequence, derived from a partial human cDNA, that fell within the second cross-kingdom lineage bears several characteristics expected for PGM2. A third lineage may contain homologs to human PGM3. On a general level, our phylogenetic-based approach shows promise for the further utilization of the extensive molecular database.      

Short chain oligogalacturonides induce ethylene production and expression of the gene encoding aminocyclopropane 1-carboxylic acid oxidase in tomato plants

Oligogalacturonic acids (OGAs), derived from plant cell wall pectin, have been implicated in a number of signal transduction pathways involved in growth, development and defense responses of higher plants. This study investigates the size range of OGAs capable of inducing ethylene synthesis in tomato plants, and demonstrates that in contrast with many other effects, only short chain OGAs are active. Oligomers across a range of DP from 2-15 were separated and purified to homogeneity by QAE-Sephadex anion exchange chromatography using a novel elution system. The OGAs were applied to tomato plants and assayed for their ability to induce ethylene gas release and changes in steady state levels of mRNA encoding the ethylene forming enzyme aminocyclopropane-1-carboxylic acid oxidase (ACO). The study demonstrated that only OGAs in the size range of DP4-6 were active both in eliciting ACO expression and in the production of ethylene.      

Release of Membrane-Bound Trails by Trypanosoma cruzi Amastigotes onto Modified Surfaces and Mammalian Cells

ABSTRACT. Upon incubation at 37° C onto glass coverslips coated with Concanavalin A, poly-L-lysine, or a monoclonal antibody (1D9) directed to the parasite major surface glycoprotein Ssp-4, extracellular Trypanosoma cruzi amastigotes release trails of material barely visible by light microscopy. This release is not associated with parasite movements. Immunolabeling studies confirmed that the material is derived from the parasite's membrane since thin section through samples labeled with 1D9 revealed that the trails are membrane-bound structures. Scanning electron microscopy showed that the ∼0.1-μm thick trails of material emerging from the amastigotes can be uniform or beaded, indicating a tendency to vesiculation. The trails are preferentially released from the flagellar pocket region and/or at the opposite posterior end of the parasite body, and seem to be devoid of microtubules. The release is time and temperature-dependent and fixed parasites do not form trails. All attempts to inhibit trail release using drugs (antimycin A, sodium azide, cytochalasin D, nocodazole, genistein, staurosporine, EGTA) failed. The observation of trails associated with intracellular parasites and amastigotes invading Vero cells suggests that this is probably a physiological process.