云南烟草丛枝症病害研究Ⅺ病原研究：类病毒问题

 感染云南烟草丛枝症病害的病苗的细胞切片中观察到类似于旁壁体的质膜体,旁壁体是类病毒侵染植物形成的特征病变结构,但多次双向电泳实验均未检测到类病毒分子,质膜体的形成可能和莫笑晗等发现的与云南烟草丛枝症病害相关的稳定RNA有密切关系,但线性开环结构和失活温度说明其不具有类病毒核酸特征。     

基于碳、氮稳定同位素技术的大亚湾紫海胆食性分析

为掌握大亚湾紫海胆(Heliocidaris crassispina)的食性特征,应用碳、氮稳定同位素技术对2015年8月所采集紫海胆样本的稳定同位素特征、营养级和食性特征进行了初步研究。结果表明,大亚湾紫海胆平均δ~(13)C值为-(13.35±1.21)‰,平均δ~(15)N值为(9.14±0.38)‰,平均营养级为2.11±0.14。不同壳径紫海胆之间的碳、氮稳定同位素比值无显著性差异(P0.05)。大亚湾海域紫海胆生活环境周围生物δ~(13)C值分布范围为-20.76‰~-9.93‰,δ~(15)N值分布范围为-0.16‰~14.99‰,营养级范围为1.34~3.77。大亚湾主要生物种类可划分为悬浮物、初级生产者和初级消费者、次级消费者、顶级消费者4个营养组群,其中紫海胆属于次级消费者。8月份调查海域珊瑚稀少,大型海藻密度低且死亡降解形成颗粒有机物(Particulate Organic Matter,POM),陆源POM随降雨大量流入大亚湾,导致紫海胆在8月份摄食偏向碎屑食物链,主要食物来源为POM,平均贡献率为67.3%;其余摄食种类为沉积物(Sediment Organic Matter,SOM)、裂叶马尾藻(Scagassum siliquastrum)、底栖硅藻、浮游动物及浮游植物,平均贡献率分别为9.7%、9.3%、6.7%、3.7%及3.3%。大亚湾紫海胆摄食种类与其栖息地底栖生物存在重叠,具有一定的食物竞争关系。研究表明,分析紫海胆食性特征对了解其所在生态系统中营养级水平具有重要意义。     

稻田生物固氮研究进展及方向

稻田淹水产生的合适pH和氧化-还原条件为固氮微生物的固氮提供了适宜环境条件,使得稻田在多年不施氮肥条件下仍能维持一定产量,而旱地产量则逐年下降。随着化学氮肥用量的增加,导致了严重的环境污染,迫切需要增加生物固氮来保证粮食生产和减少环境污染。为发挥稻田生物固氮功能,我们对稻田生物固氮的研究方法、固氮量、固氮微生物、影响因素、调控及其研究方向进行综述,以期为稻田生物固氮研究提供参考。     

国审小麦品种山农20高产稳产、广适性表现及遗传解析

山农20是山东农业大学利用常规育种与分子标记辅助选择育成的多抗、广适、高产且稳产小麦品种,先后通过国家黄淮南片、北片、新疆和甘肃审定。山农20含有长穗偃麦草和美国种质血缘,表现抗病、大穗和大粒等优异农艺性状。通过基因功能标记或与基因紧密连锁的微卫星标记的检测,分析了山农20含有的控制重要农艺性状的关键基因,得出山农20含有Pm2、Pm24和Pm30白粉病抗性基因,在田间表现出较好的白粉病抗性;含有Yr15和Yr26抗条锈基因、Lr21抗叶锈基因和Ses1抗纹枯病基因,在田间表现出较好的条锈病、叶锈病及纹枯病抗性;聚合了控制小麦产量三因素的基因位点,即粒重位点QGw6A-29和QTaGW4B.4、穗粒数位点QGns2B-2、穗长位点QS12D-3、分蘖成穗位点QMtw5D-1和QMtw6A,这与其高产、稳产和广适性是一致的。以上信息为深入认识山农20重要农艺性状分子机理提供了线索,对未来小麦遗传改良中高效利用该品种的重要基因具有实用价值。     

次降雨事件下雨养区典型小流域土壤水分运移规律

以黄土丘陵沟壑区典型小流域为研究对象,采用稳定同位素分析法,结合野外调查和室内试验,对绥德县王茂沟小流域次降雨事件后不同土地利用下包气带土壤水稳定氢同位素(δ2 H)变化规律进行剖析,为黄土丘陵沟壑区包气带土壤水分运移机理、模型参数确定以及生态保护与建设提供科学依据。结果表明:(1)草地、林地和农地土壤含水率的变化范围分别为6.74%~21.42%,6.74%~19.08%和7.86%~20.74%,土壤蓄水量的变化范围分别为265.6~384.0,275.1~368.7,289.5~334.6mm,土壤水δ2 H的变化范围分别为-113.41‰~-71.84‰,-115.10‰~-50.98‰和-112.28‰~-63.78‰。(2)草地、林地和农地土壤含水率变化趋势均存在时间节点。(3)不同土地利用下的包气带土壤水氢稳定同位素变化存在显著性差异,农地和草地较林地更有利于赋存土壤水分。(4)不同土地利用下土壤蓄水量峰值与蓄水能力呈负相关关系,峰值越大,相应的蓄水能力越低。(5)林地、草地和农地均存在优先流现象,草地和林地能显著延伸优先流发生路径,农地可能与地下水水质与补给密切相关。     

Changes in δC composition of soil carbonates driven by organic matter decomposition in a Mediterranean climate: A field incubation experiment

The current view on the relationship between the δ¹³C of pedogenic carbonates and soil organic matter is based on static studies, in which soil profiles are analysed at a given moment of their development. A dynamic approach to this question should also be possible by studying under field conditions how the δ¹³C of carbonates changes as organic matter decomposes. No such study has been undertaken owing to the slowness of the changes in the δ¹³C of carbonates, since it has been calculated that a detectable change will occur only after millenia. Nevertheless, this may not be true where soil CO₂ efflux is intense, as expected in soil zones with high microbial activity. In this paper we test the latter assumption by incubating mixtures of plant material and carbonate-rich red earth in the field at depths of 5, 20 and 40 cm. Four types of plant material were tested: Medicago sativa, Eucalyptus globulus, Quercus ilex and Pinus halepensis. Because the isotopic composition of these plant materials is known, we can determine the isotopic composition of the respired C and study how it relates to the (expected) changes in the δ¹³C. After two years of field incubation, the changes in δ¹³C of carbonates were high enough to be reliably detected and quantified, thus showing that the isotopic composition of soil carbonates can change quite rapidly in biologically active soil horizons. The observed changes are possible only if we assume that the increase in δ¹³C in the overall path respired C → pedogenic carbonate is much higher than the usually applied standard factors (about 15‰). These enrichments can be explained by assuming, as does the currently accepted paradigm, that the precipitation of new carbonates occurs in an open system in which the penetration of free-air CO₂ plays a major role. On the other hand, these enrichments can also be explained by an alternative interpretation, which assumes that the dissolution–precipitation carbonate cycles occur in systems that can be at least temporarily closed. Thus, we suggest that both possibilities (carbonate dissolution and precipitation in either an open or closed system) can coexist in a given soil, even though one or the other will dominate in any given time period.     

Microbial immobilization of ammonium and nitrate in relation to ammonification and nitrification rates in organic and conventional cropping systems

Agricultural systems that receive high or low organic matter (OM) inputs would be expected to differ in soil nitrogen (N) transformation rates and fates of ammonium (NH₄⁺) and nitrate (NO₃⁻). To compare NH₄⁺ availability, competition between nitrifiers and heterotrophic microorganisms for NH₄⁺, and microbial NO₃⁻ assimilation in an organic vs. a conventional irrigated cropping system in the California Central Valley, chemical and biological soil assays, ¹⁵N isotope pool dilution and ¹⁵N tracer techniques were used. Potentially mineralizable N (PMN) and hot minus cold KCl-extracted NH₄⁺ as indicators of soil N supplying capacity were measured five times during the tomato growing season. At mid-season, rates of gross ammonification and gross nitrification after rewetting dry soil were measured in microcosms. Microbial immobilization of NO₃⁻ and NH₄⁺ was estimated based on the uptake of ¹⁵N and gross consumption rates. Gross ammonification, PMN, and hot minus cold KCl-extracted NH₄⁺ were approximately twice as high in the organically than the conventionally managed soil. Net estimated microbial NO₃⁻ assimilation rates were between 32 and 35% of gross nitrification rates in the conventional and between 37 and 46% in the organic system. In both soils, microbes assimilated more NO₃⁻ than NH₄⁺. Heterotrophic microbes assimilated less NH₄⁺ than NO₃⁻ probably because NH₄⁺ concentrations were low and competition by nitrifiers was apparently strong. The high OM input organic system released NH₄⁺ in a gradual manner and, compared to the low OM input conventional system, supported a more active microbial biomass with greater N demand that was met mainly by NO₃⁻ immobilization.     

一次注射法适宜采血时间的确定

给绝食、强饲无氮日粮 (NFD)、分别以豆粕或棉粕为唯一氮源的CP2 0 %半合成饲粮的蛋青鸡 ,静脉一次注射 3 0 μCi3H Leu/kgBW ,于注射后 5、3 0min、4、2 4、3 6、48h翅静脉采血 ,测定各时间点的去蛋白血浆比放射性强度及 48h内排泄物的比放射性强度。通过定积分分析 ,一次静脉注射法检测内源氨基酸损失量的适宜采血时间为注射3H Leu后 2 0～2 4h。     

氧化铁对土粒强胶结作用的矿物学证据

DCB脱铁处理高铁土壤前后用NaOH -超声波分散的四个粒级 (<2 μm、2～ 2 0 μm、2 0～ 2 5 0 μm和 2 5 0～2 0 0 0 μm)的矿物组成变化研究表明 :氧化铁对土壤颗粒有很强的胶结能力 ,它可与高岭石、蒙脱石等粘粒矿物胶结形成非常稳定的大颗粒团聚体 ,这些团聚体即使用NaOH -超声波也很难分散     

Relationships Between Carbon Isotope Discrimination and Yield of Spring Wheat Under Different Water and Nitrogen Levels

ABSTRACT

A greenhouse experiment was conducted to investigate the relationships between foliar carbon isotope discrimination (Δ) and above ground dry matter (ADM) at different stages during a plant's life cycle, and grain carbon isotope discrimination and grain yield (GY) at maturity of spring wheat (Triticum aestivum L.) under different nitrogen (N) and water levels. Results showed that ADM and GY both increased significantly with decreasing water stress, while the effects of nitrogen on ADM and GY varied with the water conditions. Foliar and grain carbon isotope discrimination decreased with increasing water stress and increasing nitrogen levels. For all water conditions, relationships between carbon isotope discrimination (foliar and grain) and yields (ADM and GY) were significantly positive (P < 0.001) at various growth stages. However, at the same water level, the correlations were complex, and under well-watered conditions, ADM and GY were strongly and negatively correlated with foliar and grain carbon isotope discrimination at all growth stages (P < 0.001). The correlations were inconsistent and not significant at moderate water level, but were positive under drought. Our results showed that water and nitrogen both significantly affected the relationships between yield and carbon isotope discrimination of spring wheat, that there are interactions between these two parameters, and that environmental conditions such as water and fertilizer must thus be considered in future research on the relationship between yield and carbon isotope discrimination of spring wheat.