牧食损害对伊乐藻(Elodea nuttallii)生长的影响

在室外实验条件下,研究了模拟牧食损害（动物牧食所造成的损害）对伊乐藻植株生长的影响。结果表明：3种人工损害方式（去除植株50%叶片,去除植株顶端,以及同时去除植物顶端与50%叶片）对伊乐藻的生长率、主枝与分枝长度的增长、植物的干物质、氮、磷含量等均有不同程度的影响。其中,去叶与去顶去叶损害显著抑制了伊乐藻的生长,相对生长率分别占未受损植株的62.8%与74.4%;去顶与去顶去叶损害使伊乐藻主枝生长几乎停止,却显著促进了植物分枝的生长;去叶损害对植株的生长率、主枝与分枝长度的生长无明显抑制并却显著地降低了分枝的重量。对受损伊乐藻生长的机理进行了分析,探讨了东太湖伊乐藻现存量近年来迅速增加的原因并认为植物残体是伊乐藻种群扩张的重要因素之一。     

解集GCM输出模拟黄土塬区土壤水分平衡的潜在变化

土壤水分平衡对气候变化存在着响应,在全球变化的大背景下,研究土壤水分的可能变化是气候变化影响评估中非常重要的一项内容。目标是利用经验统计方法解集GCM网格逐月的降水和温度数据,并使用建立的气候变化情景作为WEPP的输入文件评估黄土高原王东沟流域2010～2039年土壤水分平衡(土壤水分、蒸发、渗漏和蒸腾)的可能变化。结果表明,3种情景预测2010～2039年王东沟流域年均降水可能增长1.8%～17.5%,年最高温度和最低温度分别可能增长0.5～0.9℃和2.0～2.3℃。作物蒸腾变化主要在4～6月份,土壤蒸发变化主要发生在7～9月份;作物蒸腾年均变化-5%～19%,土壤水分年均变化-4%～4%,土壤蒸发年均变化-7%～7%,均为A2a减少,B2a和GGal增大;A2a的土壤水分渗漏增长最大,GGal次之,B2a基本不变。这些结果表明气候变化及其导致的作物生长变化对土壤水分平衡存在重要的影响。     

古尔班通古特沙漠生物结皮固氮活性

利用乙炔还原法对新疆古尔班通古特沙漠不同类型的生物结皮(藻结皮、地衣结皮、苔藓结皮)的固氮活性(nmolC2H4m-2h-1)进行了定量研究。结果表明,不仅采样时段和结皮类型对生物结皮的固氮活性具有显著的影响(p<0.05),二者的交互效应同样对生物结皮的固氮活性具有极显著的影响(p<0.01)。各类型生物结皮固氮活性变化趋势表现为:3～5月间,藻结皮(2.26×103)>地衣结皮(6.54×102)>苔藓结皮(6.38×102)。6～10月份,各类型生物结皮的固氮能力显著提高(p<0.05),藻结皮的固氮活性最高(9.81×103),依次为地衣结皮9.06×103、苔藓结皮2.03×103。11月～翌年2月间,月均温都低于0℃,抑制了生物结皮的固氮活性,藻结皮、苔藓结皮的固氮活性降幅极显著(p<0.01),分别低达4.18×102、5.43×102,地衣结皮降低至2.78×103。生物结皮成为古尔班通古特沙漠除豆科植物外重要的氮源,为该沙漠1年生浅根系草本植物的种子萌发与植物体的生长提供丰富的有机质源,从而有利于这些植物种群的繁衍与更新,并与之共同促进对沙面的固定。     

太湖马来眼子菜(Potamogeton malaianus)生物量变化及影响因素

2006年5月和10月在太湖马来眼子菜分布区进行了定点采样,分析了马来眼子菜的生物量在不同水域变化特征及影响其生物量主要因素。结果表明：不同水环境中,马来眼子菜的生物量变化较大,介于526~4843 g/m²,个体植株生物量依次为叶>根>茎,其中叶的生物量占总生物量的55%~80%。水深增加能促进植株高度和生物量的增加,但单位面积生物量变化不明显。群落的自疏效应使马来眼子菜生物量与资源供应维持在一个动态平衡的水平上。马来眼子菜的生物量与水体中TN呈显著正相关,P是影响其生物量变化的间接限制因子,根、茎、叶的N/P介于16.92~59.88之间,叶片的N/P达到42.33。马来眼子菜对水环境的形态可塑性响应是其在水环境长期变化中逐步成为幸存者和优势种的重要原因之一。底泥的深度和营养含量对其分布和生物量具有显著影响。围网捕捞、养殖以及航运的发展是造成局部地区马来眼子菜生物量急剧下降的主要人为因素。不同水域的生物量的差异是水深、水体营养盐、底质特征、水体透明度、人类活动等因素综合作用的结果。同时,对水环境变化在形态上较强的可塑性响应,也是马来眼子菜生物量变化的重要原因之一。     

外源氮对沼泽湿地CH4和N2O通量的影响

三江平原沼泽湿地受到大气沉降、地表径流、农业排水等外源氮素的输入,对湿地生态系统CH4和N2O通量有重要影响。采用野外原位施肥试验模拟外源氮输入,设0,60,120,240kgN·hm^-24种试验处理,探讨外源氮对沼泽湿地CH4和N2O通量的影响。结果表明,外源氮促进了CH4和N2O排放。与对照处理比较,各施氮水平CH4平均排放通量分别增加了181％,254％和155％,N2O排放通量分别增加了21％,100％和533％。外源氮输入对CH4排放的季节变化形式影响不大,而N2O的季节变化形式随着氮输入表现出波动变化的趋势。不同施氮水平对CH4排放的促进作用与植物生长阶段和产CH4的微生物过程密切相关,N2O排放通量随氮输入量呈指数增加（R^2=0．97,P〈0．01）。外源氮通过影响湿地微生物过程来进一步影响CH4和N2O的排放。     

海南省粗叶木属新记录植物五种

报道发现于海南省鹦哥岭的粗叶木属(Lasianthus Jack)海南省新记录种5种,并描述了它们的主要辨认特征。其中4种(华南粗叶木Lasianthus austrosinensis H.S.Lo、长梗粗叶木L.filipes Chun ex H.S.Lo、西南粗叶木L.henryi Hutch.、台湾粗叶木L.formosensis Matsum.)在与海南邻近的广东省与广西壮族自治区均有记录,而大叶粗叶木L.rigidus Miq.则在热带亚洲具有明显的间断性分布。     

Molecular characteristics and expression analysis of calreticulin in Chinese shrimp Fenneropenaeus chinensis

Calreticulin (CRT), as an endoplasmic reticulum luminal resident protein, plays important roles in Ca(2+) homeostasis and molecular chaperoning. CRT on the surface of the cell can modulate cell adhesion, phagocytosis and integrin-dependent Ca(2+) signaling. The full length cDNA of calreticulin (FcCRT) was cloned from Chinese shrimp Fenneropenaeus chinensis. It consists of 1672 bp with an open reading frame of 1221 bp, encoding 406 amino acids. This is the first reported cDNA sequence of calreticulin in Crustacea. The deduced amino acid sequence of FcCRT showed high identity with those of Bombyx mori (88%), Drosophila melanogaster (83%), Mus musculus (82%) and Homo sapiens (82%). Highest expression of FcCRT was detected in ovary by Northern blot and in situ hybridization. Different mRNA levels of FcCRT were detected at various molting stages. Expression of FcCRT was induced significantly after 3 h of heat shock treatment, reached the maximum at 4 h and dropped after that. Differential expression profiles of FcCRT were observed in hepatopancreas and haemocytes when shrimp were challenged by white spot syndrome virus (WSSV). From the above results, we inferred that FcCRT might play important roles in Ca(2+) homeostasis, chaperoning and immune function in shrimp.     

cDNA cloning and mRNA expression of heat shock protein 90 gene in the haemocytes of Zhikong scallop Chlamys farreri

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone contributing to the folding, maintenance of structural integrity and proper regulation of a subset of cytosolic proteins. The full-length cDNA of Zhikong scallop Chlamys farreri HSP90 (designated CfHSP90) was cloned by EST and rapid RACE techniques. It was of 2710 bp, including an open reading frame (ORF) of 2181 bp encoding a polypeptide of 726 amino acids with all the five HSP90 family signatures. BLAST analysis revealed that the CfHSP90 gene shared high similarity with other known HSP90 genes. Fluorescent real-time quantitative RT-PCR was used to examine the expression pattern of CfHSP90 mRNA in haemocytes of scallops exposed to Cd²⁺, Pb²⁺ and Cu²⁺ for 10 and 20 days, respectively. All the three heavy metals could induce CfHSP90 expression. There was a clear dose-dependent expression pattern of CfHSP90 after heavy metals exposure for 10 days or 20 days. Different concentrations of the same metal resulted in different effects on CfHSP90 expression. The results indicated that CfHSP90 responded to various heavy metal stresses with a dose-dependent expression pattern as well as exposure time effect, and could be used as a molecular biomarker in a heavy metal polluted environment.     

Cloning,characterization, and transformation of the phosphoethanolamine <Emphasis Type="Italic">N</Emphasis>-methyltransferase gene (<Emphasis Type="Italic">ZmPEAMT1</Emphasis>) in maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.)

N-methylation of phosphoethanolamine, the committing step in choline (Cho) biosynthesis in plants, is catalyzed by S-adenosyl-l-methionine: phosphoethanolamine N-methyltransferase (PEAMT, EC 2.1.1.103). Herein we report the cloning and characterization of the novel maize phosphoethanolamine N-methyltransferase gene (ZmPEAMT1) using a combination of bioinformatics and a PCR-based allele mining strategy. The cDNA sequence of ZmPEAMT1 gene is 1,806 bp in length and translates a 495 amino acids peptide. The upstream promoter sequence of ZmPEAMT1 were obtained by TAIL-PCR, and contained four kinds of putative cis-acting regulatory elements, including stress-responsive elements, phytohormone-responsive elements, pollen developmental special activation elements, and light-induced signal transduction elements, as well as several other structural features in common with the promoter of rice and Arabidopsis homologies. RT-PCR analysis showed that expression of ZmPEAMT1 was induced by salt stress and suppressed by high temperature. Over-expression of ZmPEAMT1 enhanced the salt tolerance, root length, and silique number in transgenic Arabidopsis. These data indicated that ZmPEAMT1 maybe involved in maize root development and stress resistance, and maybe having a potential application in maize genetic engineering. Note: Nucleotide sequence data are available in GenBank under the following accession numbers: maize (Zea mays, ZmPEAMT1, AY626156; ZmPEAMT2, AY103779); rice (Oryza sativa, OsPEAMT1/Os01g50030, NM_192178; OsPEAMT2/Os05g47540, XM_475841); wheat (Triticum aestivum, TaPEAMT, AY065971); Arabidopsis (Arabidopsis thaliana, AtNMT1/At3g18000, AY091683; AtNMT2/At1g48600, NM_202264; AtNMT3/At1g73600, NM_106018); oilseed rape (Brassica napus, BnPEAMT, AY319479), tomato (Lycopersicon esculentum, AF328858), spinach (Spinacia oleracea, AF237633).