不同载畜率对荒漠草原三种土壤酶活性的影响

以内蒙古短花针茅荒漠草原为对象,对不同载畜率下(轻度放牧、中度放牧、重度放牧)三种土壤酶(脱氢酶、脲酶、碱性磷酸酶)活性进行分析,并探讨植物群落生物量以及土壤pH值、有机质、全氮、全磷含量等环境因子与土壤酶的相互作用。结果表明,三种土壤酶活性随载畜率增加呈降低趋势,脱氢酶活性在禁牧区(197.51μgTPF/g·h)最高,脲酶活性在轻度放牧区(40.64mgNH+4-N/g·h)和重度放牧区(40.78mgNH+4-N/g·h)最高,磷酸酶活性在轻度放牧区(53.93μgphenol/g·h)最高;脱氢酶和脲酶活性在中度和重度放牧区不同土层内有显著差异(P<0.05),0~10cm土层酶活性高于10~20cm土层;不同载畜率下磷酸酶活性0~10cm土层高于10~20cm;三种酶之间相关性较低,但三种酶皆与环境因子有着密切联系。     

火炬松木质素合成中CAD基因单核苷酸多态性检测

该研究以美国南部重要的造纸工业用材树种火炬松为材料 ,利用Transgenomic公司最近推出的Wave DNA片段分析系统 ,快速检测肉桂醇脱氢酶 (CAD)基因在个体间的单核苷酸多态性 ,获得了令人满意的结果 .首先利用Oligo5 .1软件对火炬松CAD基因全序列分区域进行引物设计 ,当设定每一区域能扩增出 10 0～ 2 0 0bp产物时 ,共在 8个碱基区域 (S1～S8)分别设计出了最佳正向引物和反向引物 ;以来自火炬松 12株优树自由授粉种子的胚乳中提取的DNA为材料 ,对CAD基因 8个碱基区域分别进行PCR扩增 ,有 5个碱基区域 (S3 ,S5 ,S6 ,S7,S8)得到了唯一的并且与预期碱基长度基本一致的PCR扩增产物 ,对其余 3个碱基区域进一步进行FailSafeTM PCR扩增 ,它们均在某些PCR缓冲液中得到了唯一的扩增产物 ;利用Wave DNA片段分析系统 ,对 6个碱基区域 (S2 ,S3,S5 ,S6 ,S7,S8)进行单核苷酸多态性检测 ,结果表明来自优树 2 2的种子与其它 11株优树的种子之间存在碱基序列变异 ,其中在S5 ,S6区域检测到了较大的单核苷酸多态性 ,这两个区域分别位于CAD基因的第 2和第 3内含子 (Intron2 ,Intron3) .     

冬小麦生育期间根系脱氢酶活性的初步研究

用红四氮唑法（ＴＴＣ法）对冬小麦根系脱氢酶活性进行了系统测定．结果表明：冬小麦的根系脱氢酶活性随生育进程而逐渐降低,可能与新根的比例下降和老根的比例提高有关;施氮较多的处理,各生育时期的根系脱氢酶活性均较高;播期较晚的处理,在返青期前根系脱氢酶活性高于早播处理;不同品种之间的根系脱氢酶活性也存在差异;根系脱氢酶活性与叶片的叶绿素含量呈正相关关系,与籽粒产量也呈正相关关系。文中还对脱氢酶活性作为根系活力指标的可能性及通过栽培措施调控根系和地上部协调发展的重要性进行了讨论。     

长期培肥黑土脱氢酶活性动态变化及其影响因素

对东北典型黑土区长期不同培肥黑土脱氢酶活性在作物生长季的动态变化进行研究。结果表明,施用有机肥,生长季黑土总体脱氢酶活性显著高于施用化肥和不施肥,其生长季脱氢酶活性保护容量在5.5 mg TPF/kg土.h以上,黑土总体脱氢酶活性施用高量有机肥>低量有机肥>不施肥>化肥,季节性变化波动性大。长期施用高量有机肥脱氢酶活性最大峰值出现在拔节期,施用低量有机肥、化肥和不施肥最大峰值出现在完熟期;长期施用不同数量和种类肥料所引起的黑土总体脱氢酶活性差异并未因玉米生长影响而改变,说明长期施用高量有机肥黑土微生物氧化活性能力增强,土壤自身调解和维持肥力能力增强。黑土脱氢酶活性的动态变化与绝大多数土壤生物、理化特性指标的动态变化没有显著的相关性;总体脱氢酶活性与多数土壤生物、理化特性因子、植物全磷、钾含量有极显著和显著正相关关系。     

甘蓝型油菜G3PDH和PK基因对氮肥的响应

氮肥作为植物生长最重要营养元素,其施用量的多少也是至关重要的。为了研究氮肥施用量对油菜含油量以及相关基因表达水平的影响,本研究以甘蓝型油菜宁油22作为材料,在0 kg/hm2、320 kg/hm2和640 kg/hm2三个不同氮肥水平下分别测定宁油22种子和角果皮的含油量,同时检测G3PDH和PK基因在不同氮肥水平下以及不同组织中的表达含量。结果发现,随着施氮量的增加,宁油22含油量下降,在0 kg/hm2和320 kg/hm2水平下下降不明显,在640 kg/hm2水平下明显下降,并且G3PDH和PK基因随着施氮量的增加,两个基因表达量均增强。本研究还分别分析了G3PDH和PK基因在种子跟角果皮中的比值以及开花30天后跟开花15天后的表达比,结果表明G3PDH基因在种子与角果皮的比值跟开花30天后跟15天后的表达比,均在640 kg/hm2水平下达到最高;PK基因在种子与角果皮中的比值在640 kg/hm2水平下达到最高,在开花30天后跟15天后的表达比在0kg/hm2水平下达到最大。     

城市不同利用区域绿地土壤酶活性特征--以上海市为例

选择上海市钢铁厂、造船厂、试剂厂、交通区和居民区5种城市绿地,分析了过氧化氢酶、碱性磷酸酶、脲酶和脱氢酶4种土壤酶活性并讨论了土壤理化性质和重金属含量对其活性的影响。结果表明:土壤酶活性受土壤理化性质和重金属含量影响;其中过氧化氢酶活性受土壤体积质量、pH、CEC和Cr的影响最大;碱性磷酸酶受有机质、水解性氮、Pb和Zn的影响最大;脱氢酶受CEC、pH、体积质量和水解性氮的影响较大;脲酶受水解性氮、CEC、pH和体积质量影响最大。土地利用方式不同土壤酶活性也不同:调查区域土壤中过氧化氢酶活性均较高,土壤碱性磷酸酶活性普遍较低,试剂厂和交通区土壤脲酶活性较高,交通区和试剂厂土壤脱氢酶活性最高。     

Soil enzymatic response to addition of municipal solid-waste compost

Modifications of soil microbiological activity by the addition of municipal solid-waste compost were studied in laboratory incubations. Three composts were compared, one lumbricompost and two classical composts with different maturation times. Organic C mineralization and nine enzyme activities (dehydrogenase, peroxidase, cellulase, -glucosidase, -galactosidase, N-acetyl--glucosaminidase, protease, amidase, and urease) were determined in the composts and the amended soil. Initial enzyme activities varied in the soil according to the sampling date (winter or summer) and were greater in the composts than in the soil, except for urease. Generally, the youngest compost exhibited greater activity than the oldest one. In the amended soil, the composts did not increase enzyme activity in an additive way. Dehydrogenase, the only strictly endocellular enzyme, was the only one for which the activity in the amended soil increased significantly in proportion to the addition of compost. During the incubations, C mineralization and dehydrogenase activity were significantly correlated, indicating that dehydrogenase was a reliable indicator of global microbial activity. Peroxidase activity in the soil remained constant, but increased in the composts and amended soil. Addition of the oldest compost had no effect on the activity of the C cycle enzymes, but the youngest compost increased creased soil activity at the higher application rate. Enzymes of the N cycle were stimulated by all compost amendments, but the increase was only transient for amidase and urease. Lumbricomposting had no marked effect on compost enzyme activity, either before or during the incubation.     

Interactions between the arbuscular mycorrhizal fungus Glomus intraradices and the plant growth promoting rhizobacteria Paenibacillus polymyxa and P. macerans in the mycorrhizosphere of Cucumis sativus

Interactions between the arbuscular mycorrhizal (AM) fungus Glomus intraradices and bacteria from the genus Paenibacillus (P. macerans and P. polymyxa) were examined in a greenhouse pot experiment with Cucumis sativus with and without organic matter amendment (wheat bran). P. polymyxa markedly suppressed AM fungus root colonization irrespective of wheat bran amendment, whereas P. macerans only suppressed AM fungus root colonization in combination with wheat bran amendment. Dual inoculation with P. macerans and G. intraradices in combination with wheat bran amendment also caused severe plant growth suppression. Inoculation with G. intraradices was associated with increased levels of dehydrogenase activity and available P in the growth substrate suggesting that mycorrhiza formation accelerated the decomposition of organic matter resulting in mobilization of phosphorus. Inoculation with both Paenibacillus species increased all measured microbial fatty acid biomarkers in the cucumber rhizosphere, except for the AM fungus biomarker 16:1ω5, which was reduced, though not significantly. Similarly, inoculation with G. intraradices increased all measured microbial fatty acid biomarkers in the cucumber rhizosphere, except for the Gram-positive bacteria biomarker 15:0 anteiso, which was overall decreased by G. intraradices inoculation. In combination with wheat bran amendment G. intraradices inoculation caused a 39% reduction in the amount of 15:0 anteiso in the treatment with P. polymyxa, suggesting that G. intraradices suppressed P. polymyxa in this treatment. In conclusion, plant growth promoting species of Paenibacillus may have suppressive effects of AM fungi and plant growth, especially in combination with organic matter amendment. The use of an inert plant growth media in the present study allowed us to study rhizosphere microbial interactions in a relative simple substrate with limited interference from other soil biota. However, the results obtained in the present work mainly show potential interactions and should not be directly extrapolated to a soil situation.