抽穗后干旱复水对双季杂交晚稻产量形成和叶片δ13C及内源激素水平的影响

为探明生育后期干旱复水对双季杂交晚稻不同产量潜力品种产量的影响及其形成的生理机制,选择超级稻品种五丰优T025和对照品种金优207,于抽穗后进行干旱8d复水处理,分析了2个品种结实和产量、干旱前后倒二叶稳定碳同位素组成(δ13C)及内源激素含量的差异性。结果表明,干旱复水处理下2个品种水稻的结实率、千粒重及单株产量较对照(保持水层)表现出不同程度下降。其中,结实率五丰优T025和金优207分别下降12.07%和7.67%,千粒重下降5.23%和9.09%,单株产量下降13.54%和27.14%,差异均达显著或极显著水平,未发现产量补偿效应。抽穗后干旱处理下倒二叶δ13C值,五丰优T025大幅上升,复水后呈现出先下降,至第6天又开始上升的特点,金优207则大幅下降,复水后呈现先上升后下降再上升的特点,五丰优T025较金优207干旱复水处理与对照之间的差距更大。总体上,对照条件下,抽穗至其后20d,随生育推进,2个品种倒二叶内源ABA和GA₃含量呈上升而IAA含量则下降趋势,ZR表现出先上升再下降特点。干旱处理下2个品种表现为ABA含量上升,复水后呈先下降后上升特点,五丰优T025较金优207处理与对照之间差距更大;干旱复水处理条件下:2个品种IAA含量均下降,五丰优T025处理与对照间的差距明显小于金优207;五丰优T025 GA₃含量表现出先上升后下降再上升,金优207表现出干旱处理结束日急剧下降至最低点,复水后缓慢上升特点;2个品种ZR含量呈现出先上升至最高值再下降特点,五丰优T025较金优207处理与对照之间差距更小。抽穗后干旱处理将启动稻株体内抗衰老机制,复水后将在一定程度一定时间内激活稻株体内生长促进因子并抑制生长抑制因子,但其效果十分有限。     

瑞氏木霉碳源阻遏相关基因Cre1的分子改造

为了提高瑞氏木霉（Trichoderma reesei）纤维素酶的活力,用类似基因改组的方法改造其碳源阻遏相关基因cre1。以瑞氏木霉基因组DNA为模板PCR扩增cre1基因,用DNaseⅠ消化cre1基因后,回收50-100 bp的DNA片段,用T4 DNA连接酶连接,以连接产物作为模板进行无引物PCR,并将PCR产物转入瑞氏木霉原生质体,通过测定滤纸酶活的方法筛选突变菌株,并在NCBI上比对分析突变菌株的cre1基因。结果表明,筛选获得1株纤维素滤纸酶活比出发菌株提高0.7倍的突变菌株cre2-3。cre2-3菌株在液体培养基中呈棉花状,而出发菌株呈小颗粒状,菌株cre2-3发酵液的颜色比出发菌株的更黄亮。推测cre1基因与瑞氏木霉菌株的生长代谢有关。     

耕作对旱区坡耕地土壤碳素转化及冬小麦产量的影响

利用长期定位试验(1999开始保护性耕作,2004年采样测定),在豫西旱区坡耕地上进行了不同耕作对土壤有机碳、微生物态碳及水分利用效率的影响研究。结果表明:深松覆盖和免耕覆盖处理的耕层有机碳增加较明显,以深松覆盖有机碳含量最高为6.79gkg-1,比传统耕作高13.82%,其次是免耕,较传统高11.58%,而少耕却较传统降低了1.38%,随着土层的加深,土壤有机碳含量降低,0～60cm有机碳平均值,深松和免耕较传统分别增加了14.08%、5.41%,少耕较传统减少1.12%。土壤微生物碳对耕作敏感,其含量免耕>深松>传统>少耕,分别为206.87mgkg-1、138.43mgkg-1、115.42mgkg-1和112.57mgkg-1,较传统增加79.3%、19.9%和-2.5%。土壤有机碳和土壤微生物态碳都有坡下富集现象。少耕、免耕、深松和传统的SMBC/SOC的值分别为1.91%、3.11%、2.04%和1.93%,免耕和深松对培肥地力、改善环境有好的应用前景;同时免耕覆盖与深松覆盖可提高产量,增产分别达10.22%与9.26%;可提高水分利用效率。     

C and N natural abundance of the soil microbial biomass

Stable isotope analysis is a powerful tool in the study of soil organic matter formation. It is often observed that more decomposed soil organic matter is ¹³C, and especially ¹⁵N-enriched relative to fresh litter and recent organic matter. We investigated whether this shift in isotope composition relates to the isotope composition of the microbial biomass, an important source for soil organic matter. We developed a new approach to determine the natural abundance C and N isotope composition of the microbial biomass across a broad range of soil types, vegetation, and climates. We found consistently that the soil microbial biomass was ¹⁵N-enriched relative to the total (3.2 ‰) and extractable N pools (3.7 ‰), and ¹³C-enriched relative to the extractable C pool (2.5 ‰). The microbial biomass was also ¹³C-enriched relative to total C for soils that exhibited a C3-plant signature (1.6 ‰), but ¹³C-depleted for soils with a C4 signature (−1.1 ‰). The latter was probably associated with an increase of annual C3 forbs in C4 grasslands after an extreme drought. These findings are in agreement with the proposed contribution of microbial products to the stabilized soil organic matter and may help explain the shift in isotope composition during soil organic matter formation.     

Tillage-induced environmental conditions in soil and substrate limitation determine biogenic gas production

Tillage changes soil environmental conditions and controls the distribution of residues in the soil, both actions that affect the production and emission of soil biogenic gases (CO₂, N₂O, and CH₄). The objective of this study was to determine how tillage-induced environmental conditions and substrate quality affect the mineralization rate of easily metabolizable compounds and the subsequent production of these gases. Carbon compounds, with and without nitrogen, were applied to soil cropped to maize under tilled and no-till systems. Following substrate application in the spring and summer, biogenic gases were measured periodically at the soil surface (flux) and within the profile (concentration) at 10-, 20-, and 30-cm depths (i.e., within, at the bottom of, and below the plough layer). Strong CO₂ and N₂O responses to sucrose and glycine in both the field and the laboratory indicate that the soil was C- and N-limited. Surface fluxes of CO₂ and N₂O were greater in soils amended with glycine than with sucrose and were greater in tilled than no-till soils. Transient emission of CH₄ following the addition of glycine was observed and could be attributed to inhibition of N mineralization and nitrification processes on CH₄ oxidation. Laboratory and field measurements indicated that the larger substrate-induced CO₂ emission from the tilled soils could not be attributed to differences in the total biomass or the basal respiratory activity of the soils. Thus, there appears to be no underlying difference in the functional capacity of the microbial communities under different tillage regimes. Comparison of gas profiles indicates relative accumulation of CO₂ at depth in soils under no-till, as well as greater decline in profile CO₂ content with time in the tilled compared to the no-till soil. These results support the conclusion that greater CO₂ efflux from the tilled soils resulted from more rapid gas diffusion through the profile. Hence, the observed differences in gas fluxes between tilled and no-till soils can be attributed to differences in physical environment.     

Crop management effects on soil carbon sequestration on selected farmers’ fields in northeastern Ohio

Soil organic carbon (SOC) pool is the largest among terrestrial pools. The restoration of SOC pool in arable lands represents a potential sink for atmospheric CO₂. Restorative management of SOC includes using organic manures, adopting legume-based crop rotations, and converting plow till to a conservation till system. A field study was conducted to analyze soil properties on two farms located in Geauga and Stark Counties in northeastern Ohio, USA. Soil bulk density decreased with increase in SOC pool for a wide range of management systems. In comparison with wooded control, agricultural fields had a lower SOC pool in the 0–30 cm depth. In Geauga County, the SOC pool decreased by 34% in alfalfa (Medicago sativa L.) grown in a complex rotation with manuring and 51% in unmanured continuous corn (Zea mays L.). In Stark County, the SOC pool decreased by 32% in a field systematically amended with poultry manure and 40% in the field receiving only chemical fertilizers. In comparison with continuous corn, the rate of SOC sequestration in Geauga County was 379 kg C ha⁻¹ year⁻¹ in no-till corn (2 years) previously in hay (12 years), 760 kg C ha⁻¹ year⁻¹ in a complex crop rotation receiving manure and chemical fertilizers, and 355 kg C ha⁻¹ year⁻¹ without manuring. The rate of SOC sequestration was 392 kg C ha⁻¹ year⁻¹ on manured field in Stark County.     

Soil freeze-thaw cycle experiments: Trends, methodological weaknesses and suggested improvements

Although freeze-thaw cycles can alter soil physical properties and microbial activity, their overall impact on soil functioning remains unclear. This review addresses the effects of freeze-thaw cycles on soil physical properties, microorganisms, carbon and nutrient dynamics, trace gas losses and higher organisms associated with soil. I discuss how the controlled manipulation of freeze-thaw cycles has varied widely among studies and propose that, despite their value in demonstrating the mechanisms of freeze-thaw action in soils, many studies of soil freeze-thaw cycles have used cycle amplitudes, freezing rates and minimum temperatures that are not relevant to temperature changes across much of the soil profile in situ. The lack of coordination between the timing of soil collection and the season for which freeze-thaw cycles are being simulated is also discussed. Suggested improvements to future studies of soil freeze-thaw cycles include the maintenance of realistic temperature fluctuations across the soil profile, soil collection in the appropriate season and the inclusion of relevant surface factors such as plant litter in the fall or excess water in the spring. The implications of climate change for soil freeze-thaw cycles are addressed, along with the need to directly assess how changes in soil freeze-thaw cycle dynamics alter primary production.     

减少蔬菜碳足迹的主要肥料合理用量分析——以浏阳蔬菜生产合作社为例

肥料是影响作物产量和农业碳排放的主要因子之一。研究基于减少单位产量碳足迹,探讨主要肥料的合理用量。对浏阳4个合作社中黄瓜、苦瓜、豆角、莴笋、苋菜、茄子等8种蔬菜生产进行3年定点调查,并对相关数据进行统计分析。结果表明:每季蔬菜生产氮肥、磷肥、钾肥、厩肥施用量依次为:0、327.2、0、48936 kg/hm2,可使单位产量碳足迹减少85.85%,产量提高24.11%。因此,浏阳发展高效低碳蔬菜种植产业关键施肥技术在于减少氮肥与钾肥的使用,控制磷肥的用量,增施厩肥。     

不同基因型抗虫棉的光合生产与叶源特征

以33B为对照,对早发型常规Bt棉鲁棉研17、鲁棉研21,晚发型Bt棉鲁棉研22,杂交Bt棉鲁棉研15、鲁棉研20进行了2年的种植和比较。早发型品种中前期干物质积累和叶面积增长快,但后期干物质积累慢、叶面积下降快,表现出明显的早发早熟和干旱年份易早衰的特点;晚发型品种前期干物质积累和叶面积增长慢,但后期增长快,表现出明显的晚发甚至贪青晚熟的特点。两个杂交棉品种表现出与早发型品种基本相同的生育规律,但中前期叶面积系数和干物质积累量显著高于其它供试品种。盛铃期以前,未见品种间功能叶光合速率的显著差异,但在干旱年份,早发型品种在始絮期功能叶的光合速率显著低于晚发型品种。早发型品种中后期的根冠比和功能叶含K量显著低于晚发型品种,而叶面积载荷量却显著高于晚发型品种。不同品种干物质产量和熟相的差异可能分别与叶面积系数大小和库源比例不同有关。     

不同施肥条件对鱼腥草碳氮代谢生理指标的影响

【研究目的】结合前期对产量、品质的研究，探讨不同施肥条件下鱼腥草叶片主要碳氮代谢指标的变化及其与产量形成的关系。【方法】采用单因子随机区组设计进行施肥实验，测定鱼腥草叶片光合速率、硝酸还原酶活性、叶绿素和粗蛋白的含量。【结果】各施肥处理中以较低施肥水平人粪尿处理的鱼腥草叶片含叶绿素总量最高，达2.552 mg/gFW，以中等施肥水平鸭粪的净光合速率最高，为8.306μmol/(m2·s)。施用不同肥料的鱼腥草叶片硝酸还原酶活性大小为：鸭粪>猪粪>常规施肥>化肥>人粪尿，各处理以中等施肥水平的猪粪处理的硝酸还原酶最高，达46.2μg NO2-/(h·g)FW；粗蛋白以施用较高水平化肥的最高（13.31%）。【结论】施用有机肥能显著提高鱼腥草叶片的碳代谢，这有利于其产量的形成；但施用人粪尿不利于提高鱼腥草叶片硝酸还原酶活性和蛋白质的形成与积累。