Effect of the conversion of grassland to spring wheat field on the CO2 emission characteristics in Inner Mongolia, China

Chinese grasslands have undergone great changes in land use in recent decades. Approximately 18.2% of the present arable land in China originated from the cultivation of grassland, but its impact on the carbon cycle has not been fully understood. This study was conducted in situ for 3 years to assess the comprehensive effects of cultivation of temperate steppe on soil organic carbon (SOC) and soil respiration rates as well as ecosystem respiration. As compared with those in the Stipa baicalensis steppe, the SOC concentrations at depths of 0–10 and 10–20 cm in the spring wheat field were found to have decreased by 38.3 and 17.4% respectively from 29.5 and 21.9 g kg⁻¹ to 18.2 and 18.1 g kg⁻¹ after a cultivation period of 30 years. Accordingly, the total amounts of soil respiration through the growing season (from April to September) in 2002, 2003 and 2004 were 265.2, 282.2 and 237.4 g C m⁻² respectively in the spring wheat field, which were slightly lower than the values of 342.2, 412.0 and 312.1 g C m⁻² in the S. baicalensis steppe, while ecosystem respiration of 690.9, 991.2 and 569.6 g C m⁻² respectively in the spring wheat field were markedly higher than those of 447.0, 470.9 and 429.7 g C m⁻² in the steppe plot. Similar seasonal variations of ecosystem respiration and soil respiration existed in both sample sites. Respiration rates were higher and greater differences existed in both ecosystem respiration and soil respiration during the exuberant growth stage of plants (from mid-June to mid-August). However, in the slower-growth period of the growing season (before late May and after late August), the CO₂ effluxes of the two sample sites were similar and remained at a relatively low level. The results also showed that ecosystem respiration and soil respiration were under similar environmental controls in both sample sites. Soil water content at a depth of 0–10 cm and soil temperatures at 5 and 10 cm were the main factors affecting the variations in ecosystem respiration and soil respiration rates in droughty years of 2002 and 2004 and in the rainy 2003, respectively. This study suggests that the conversion of the grassland to the spring wheat field has increased the carbon loss of the whole ecosystem due to the change of vegetation cover type and significantly reduced the carbon storage of surface soil. In addition, the tillage of grassland had different effects on ecosystem respiration and soil respiration. The effects were also dissimilar in different growth stages, which should be fully considered when assessing and predicting the effects of cultivation on the net CO₂ balance of grassland ecosystems.     

茶树己糖激酶基因CsHXK2的启动子克隆及表达特性分析

植物己糖激酶是双功能蛋白,具有磷酸化己糖和介导糖信号的关键性作用。前期研究中,我们从茶树中克隆获得4个己糖激酶基因,其中CsHXK2基因编码492个氨基酸残基,与拟南芥AtHXK3、番茄LeHXK4归为Type A类HXKs。利用RT-PCR技术,克隆获得长度为2029bp的CsHXK2基因启动子。CsHXK2基因可能受到光照、低温、病原菌、糖和多种激素等信号的调控,且可能特异性表达于叶、花、种子、根系、腋芽等组织。CsHXK2蛋白定位于叶绿体内。酵母突变体功能互补试验表明,去除叶绿体转运信号肽的CsHXK2成熟蛋白具有葡萄糖和果糖磷酸化活性。茶树组织特异性表达分析显示,CsHXK2基因在根和茎中表达量最高,而在老叶中表达量最低。CsHXK2基因的表达受低温胁迫而显著下调,经炭疽菌侵染的茶树叶片内CsHXK2基因的表达也受到显著抑制,而外源赤霉素(GA₃)处理的茶树叶片内CsHXK2基因表达显著上调。本研究结果表明,CsHXK2基因在茶树的生长发育过程和逆境胁迫响应中发挥重要的调控作用。     

可变电荷与恒电荷稻田土壤硝态氮和铵态氮淋失规律

A variable-charge (VC) and a permanent-charge paddy soil (PC) were selected to study nitrate (NO3--N) and ammonium (NH4+-N) leaching with N isotopes for one consecutive year. An irrigation and intermittent drainage pattern was adopted to mimic natural occurrence of rainfall during the upland crop season and drainage management during the flooded rice season. Treatments to each soil type were no-N controls (CK), 15N-labeled (NH4)2SO4 (NS) and milk vetch (NV) applied at a rate equivalent to 238 kg N ha–1 to unplanted lysimeters, totaling six treatments replicated in triplicates. Results indicated that the soil type dominated N leaching characteristics. In the case of PC, NO3--N accounted for 78% of the total leached inorganic N; NS was prone to leach three times more than the NV, being 8.2% and 2.4% of added 15N respectively; and > 85% of leached NO3--N came from native N in the soil. In the case of VC, NH4+-N made up to 92% of the total inorganic N in leachate. Moreover, NH4+-N leaching was detected throughout the whole incubation, and was particularly high during the flooded season. NO3--N leaching in VC occurred later at a lower rate compared to that in PC. The findings of this study indicate that NO3--N leaching during the drained season in permanent-charge paddy soils and NH4+-N leaching in variable-charge soils deserve more attention for regional environmental control.     

水稻苗期耐低磷基因型差异研究

采用难溶性磷酸盐Ca3 (PO4) 2 液相控释方法试验研究不同水稻品种 (系 )苗期耐低P基因型差异结果表明 ,各水稻基因型耐低P胁迫能力存在极显著差异 ,其中“汕优 6 3”、“IR74”、“汕优 16 1”、“IR70 6 17 4B B19 2”、“IR6 4”5个品种 (组合 )耐低P能力最强 ;“IR70 6 5 1 3B 3 2 2 2”、“IR71331 2B 2 1”、“南川”、“IR71379 2B 10 2 3 1”和“IR72 4 13 3R 2 6 2”5个品种 (系 )对低P胁迫较敏感 ;而“IR73384 11 7 8 3 2 3 3 3”、“IR73382 111 9 19 19 2 3 1 2”、“IR72 4 17 3R 6 2”、“IR36”、“IR72 4 17 3R 8 3”和“IR72 4 12 3R 11 3”6个品种 (系 )P效率则属中间型。     

籼型三系杂交水稻单茎茎鞘干物质重的发育遗传研究

采用数量性状的加性-显性发育遗传模型分析了按NCⅡ交配设计的两套籼型三系杂交水稻单茎茎鞘干物质重的发育遗传规律. 结果表明, 在不同的发育阶段, 单茎茎鞘干物质重在前期以显性效应为主, 中期以加性效应为主, 后期加性和显性效应并重. 控制单茎茎鞘干物质重的加性和显性效应基因的表达不同, 前者趋于活跃状态, 后者则趋于     

水稻品种“佳辐占”应答细菌性条斑病病原菌侵染的蛋白质组学分析

运用双向电泳分析高抗水稻品种“佳辐占”受强毒力细菌性条斑病病原菌侵染2 d后的叶片蛋白质组变化,共发现38个蛋白质发生差异表达,其中32个上调,5个下调,1个新增。用MALDI-TOF-MS分析和数据库检索鉴定出其中的33个差异表达蛋白质,并将它们分为4个功能类群,即信号转导相关蛋白、防卫相关蛋白、代谢相关蛋白和蛋白质稳定相关蛋白。这些蛋白分别参与了信号识别、信号传递、抗氧化、糖代谢、细胞壁加固、植保素合成等抗病生理反应。研究表明,水稻对细菌性条斑病病原菌的侵染存在着一个复杂的抗病信号应答和代谢调控网络,其作用机理可以通过差异表达的蛋白质（酶）反映出来,其中差异表达的8个R蛋白和3个PR蛋白可能与水稻对细菌性条斑病的抗病性密切相关。本研究为进一步揭示水稻对细菌性条斑病的抗性机理及相关抗病基因的功能克隆提供了依据。     

茶树β-淀粉酶基因CsBAM3的克隆及其响应低温的表达模式

β-淀粉酶(BAM)是植物中参与淀粉水解的关键酶类,在应对非生物胁迫中发挥重要作用。从前期茶树冷驯化转录组分析中分离到1个参与淀粉代谢的差异表达基因,cDNA全长克隆及序列分析鉴定该基因为拟南芥BAM3同源基因,命名为CsBAM3。该基因编码548个氨基酸残基,与拟南芥的BAM1和BAM3一起归为第Ⅱ亚家族,推测为叶绿体定位、具有淀粉水解活性的β-淀粉酶编码基因。启动子克隆及序列分析显示该基因可能受生理节律、光、低温及多种激素等信号共同调控。CsBAM3在叶片中表达量最高,茎和花中表达量较低,根中基本不表达。CsBAM3在冷驯化初期被显著上调且一直保持相对较高的水平。成熟叶片及嫩芽(一芽二叶)中的CsBAM3均可以被4℃及0℃低温显著上调,且嫩芽中基因的表达量上调幅度明显高于成熟叶。模拟倒春寒低温条件下,检测不同萌发阶段新梢中CsBAM3的表达情况表明,CsBAM3在鲜叶初展的嫩芽中即可快速受低温诱导。以上结果表明,CsBAM3是茶树中调控淀粉水解的一个重要β淀粉酶编码基因,在茶树成熟叶和嫩芽受到不同低温胁迫时其表达可被快速诱导。     

松嫩平原盐碱化羊草群落中AM真菌物种资源及侵染率研究

本研究在松嫩平原西部12个地区15个重度盐碱化草地中,调查了羊草群落天然斑块中AM真菌的种类和分布、AM真菌羊草根系的侵染能力及土壤pH值的影响。共分离出AM真菌4属11种,其中球囊霉属(Glomus)占总物种数的72.42%,在各调查样点中出现频度最高,其中摩西球囊霉(G. mossea)出现频度达100.0%。土壤pH强烈抑制盐碱化草地中羊草天然群落斑块中AM真菌的物种丰富度,但对孢子密度的影响未达到显著水平。AM真菌对羊草根系的侵染频率和侵染强度显著正相关。AM真菌对羊草根系的侵染频率和侵染强度随着AM物种数量的增加而增强,随着土壤pH的增加而下降。在盐碱化羊草地中存在较丰富的侵染羊草根系的AM真菌资源,研究结果为筛选和利用耐盐碱AM真菌菌株以恢复和重建松嫩盐碱化羊草草地生态系统提供了理论依据。