玉米苗期调亏灌溉的复水补偿效应

利用盆栽人工控水的方法,在玉米苗期造成不同强度的干旱胁迫,并在拔节期复水至充分供水和轻度胁迫,研究不同程度的水分亏缺对苗期玉米生长发育、水分利用效率和根系活力的影响以及复水后的补偿效应。结果表明,干旱胁迫对玉米苗期的植株生长、干物质累积和分配、气孔导度、光合速率、蒸腾速率以及根系活力产生了不同程度的影响;拔节期复水后,各种指标表现出不同程度的补偿生长效应。     

内陆石羊河灌区灌溉和施氮对夏玉米苗期生长及生理特性的影响

以夏玉米为材料,设4个灌水水平:337.5、6751、012.5、1 350 m3/hm2;4个施氮水平:75、150、225、300 kg N/hm2,研究限量灌溉和施氮对夏玉米苗期生长及生理指标的影响。结果表明:严重干旱会抑制玉米的生长。在玉米苗期,充分供水和高氮对玉米的生长不利,轻度亏缺与中氮组合使玉米苗期处于最佳生长状态,水氮共同作用对玉米的光合速率有促进作用;玉米苗期适度经受水分亏缺,有利于根系的生长;在同一施氮水平下,不同程度水分亏缺处理的根冠比(R/S)大于充分供水的处理。玉米苗期叶水势随灌水量的增大而增大,在灌水量相同时,叶水势随施氮量的增加而逐渐变大;干旱会使玉米光合速率下降,但适量增施氮肥可增加玉米的光合速率。     

硫营养对小麦苗期根系导水率的影响

以小偃503号小麦为试材,通过室内水培、盆栽试验,比较了干旱及硫胁迫情况下小麦苗期根系导水率的变化。其中水培以PEG6000模拟干旱胁迫,1/2强度Hoagland全营养液和1/2强度Hoagland无硫营养液控制硫素水平;盆栽采用重量法控制水分。结果表明:无论在正常供水还是干旱胁迫时,供硫处理的根系导水率始终高于无硫处理,硫营养显示出对根系导水率的调节能力。旱后复水过程中,供硫处理的导水率较无硫处理有显著的增加,供硫处理显示出较强的恢复能力。水培和盆栽试验的结果均证实了硫营养对小麦根系导水率有明显的调节作用。     

秸秆覆盖和根系互作对间作玉米生理特性及产量的影响

通过盆栽试验研究了不同秸秆覆盖水平和玉米/大豆间作系统中根系互作对玉米的影响。结果表明：秸秆覆盖 和根系互作可增加玉米成熟期单株绿叶面积和不同生育时期的叶绿素含量,且根系互作的作用随覆盖水平的提高而增强;玉米成熟期的植株含水量和根伤流显著受到覆盖的影响,而受根系互作的影响不显著(P＞0.05);覆盖和根系互作可提高玉米光合速率、气孔导度和蒸腾速率,而降低胞间CO₂浓度,其中相同隔根处理下,T1和T0间的差异显著;覆盖和根系互作可改善玉米产量各构成因素,并提高成熟期单株生物产量和经济产量。相关分析发现,玉米单株绿叶面积、叶绿素含量、根伤流速度、光合速率均与产量存在直线正相关关系。得出,覆盖和根系互作有利于改善玉米生理特性,提高产量,且根系互作的优势作用随覆盖水平的提高而增强。     

不同基因型玉米自交系苗期根系抗旱性向水性及解剖结构研究

试验旨在研究旱胁迫下不同基因型玉米自交系苗期根系形态、生理生化、解剖结构的差异变化,为玉米自交系抗旱种质的筛选提供可借鉴的指标、方法,为玉米自交系苗期根系抗旱遗传机理研究提供依据。试验选用了14份玉米自交系,采用PEG-6000胁迫处理,测定玉米自交系苗期13个与抗旱紧密相关的根系形态与生理生化指标,并通过方差分析、关联分析及聚类分析,对各自交系的抗旱性进行综合评价,并对其中两个抗旱性差异明显的自交系,通过石蜡切片-显微镜观察根系横切面结构的差异。结果表明:干旱胁迫下,不同玉米自交系苗期的单株根干质量、单株地上部干质量、根系长度、根直径、根伸长速率、根失水率、根系还原力均呈不同程度的下降趋势,根系可溶性糖、脯氨酸均呈不同程度的上升趋势,且不同自交系的变化幅度差异较大。随着诱导物倾斜角的增大,不同自交系根系的向水性弯曲增强,不同自交系间的差异较大,高湿度梯度条件下,自交系Mo17向水性弯曲较对照增加134%,增加幅度最大,WN897向水性弯曲增加20%,增加幅度较小。利用不同抗旱指标的加权抗旱指数,综合评价不同基因型玉米自交系的抗旱性,并将14个玉米自交系种质聚类划分为强抗旱型、中抗旱型和旱敏感型、高旱敏感型4个抗旱级别。石蜡切片结果显示,抗旱性差异明显的自交系根系解剖结构差异较大,抗旱性自交系昌7-2皮层占根系直径比例较低,不抗旱自交系WN897皮层占根系直径比例大于昌7-2,且WN897的导管直径较大。结论:采用方差分析、关联分析及聚类分析等相结合的方法对不同玉米自交系苗期抗旱性进行评估,可以较好地揭示根系性状与抗旱性的关系。根系还原力、根系可溶性糖、根系长度、根向水性对干旱胁迫的反应较其他指标敏感,可作为玉米苗期的抗旱能力和抗旱自交系选育时优先考虑的鉴定指标。旱胁迫下,抗旱性差异明显的玉米自交系根系解剖特征差异显著,强抗旱型自交系苗期根系皮层厚度较小,皮层占根系直径比例较低,根系导管直径也较高旱敏感型自交系小。     

灌水方式对轻度盐化土壤玉米生长及土壤水分的影响

以盆栽玉米为研究对象研究了直接浇灌、滴灌、微润灌等3种灌水方式下玉米的生长、叶绿素含量和光合速率、蒸腾速率等生理生态指标及土壤水分垂直分布的特征,结果表明:灌水方式对玉米生理生态指标有较大影响,苗期滴灌玉米生长较快,拔节前期,微润灌条件下玉米生长最为迅速,滴灌次之,直接浇灌生长最慢;滴灌条件下叶绿素含量最高,拔节期需水旺季时微润灌叶绿素含量最低.三种灌水方式对玉米光合速率的影响为:微润灌＜滴灌＜直接浇灌.土壤水分特征表明:微润灌稳定后土壤水分主要分布在10～ 30 cm土层,滴灌主要分布在10～ 40 cm土层;苗期、拔节期灌水后取样测定的土壤含水率表明,作物根系层内微润灌与滴灌均大于直接浇灌时的土壤含水率.     

干热河谷紫色土区不同复合肥施肥量对玉米苗期光响应特性的影响

采用3种模型在不同复合施肥量下对玉米苗期光响应特性的影响进行模拟,比较不同拟合模型的优劣,旨在筛选出不同复合施肥量下最优的光合作用光响应模型,并采用最优的光合作用光响应模型模拟玉米苗期的光合参数,为研究紫色土区玉米种植的氮磷钾营养生理和科学施肥提供科学依据。以长城799玉米为研究材料,在模拟小区定位施肥的基础上,采用LI-6400型便携式光合测定仪测定苗期叶片在不同光强下的光合速率,研究不同施肥量下玉米苗期叶片的光合作用响应特征,采用直角双曲线、非直角双曲线和直角双曲线修正3种不同模型对光响应曲线进行拟合,对比决定系数(R_2)、表观量子效率(α)、最大净光合速率(Pn_(max))、光饱和点(LSP)、光补偿点(I_c)和暗呼吸速率(R_d)6个参数,比较3种模型的差异。结果显示:(1)3种模型均能较好地拟合玉米苗期叶片光响应曲线。从决定系数来看,光合参数拟合值与实测值相关度较高(R~20.98),拟合效果优劣排序为直角双曲线修正模型非直角双曲线模型直角双曲线模型。(2)直角双曲线修正模型对不同复合肥施肥量下玉米叶片的光响应的Pnmax、LSP、Ic和Rd4个光合参数的估计更准确。(3)玉米苗期叶片的净光合速率、胞间CO_2浓度、气孔导度和蒸腾速率都随施肥量增加而升高,用量过高时则下降。合理地提高施肥量能够提高玉米苗期叶片的叶绿素含量,延长较高的光合持续期。因此,直角双曲线修正模型可以直接得出饱和光强和最大净光合速率,能够较好地拟合不同复合施肥量下玉米苗期叶片的光响应过程及其特征参数,拟合值较符合植物实际的生理情况,更接近实测值,且确定的适宜施肥量为1.12 t·hm~(-2)(N-P2O5-K2O=0.190-0.190-0.190 t·hm~(-2))和1.49 t·hm~(-2)(N-P2O5-K2O=0.253-0.253-0.253 t·hm~(-2))。     

不同水氮磷钾耦合条件下玉米干物质与养分累积动态变化

采用盆栽正交设计方案,研究不同水、氮、磷、钾耦合处理玉米干物质、养分N、P、K吸收累积的动态变化。结果表明,不同水、氮、磷、钾耦合条件下,玉米干物质、养分累积量随玉米生育期的延长而增加,累积趋势都呈"S"型曲线,可用指数方程y=aexp(-b/t)拟合。玉米干物质累积速率和养分累积速率用y=aexp(-b/t)求导可得,最大累积速率出现的时间可对指数方程y=aexp(-b/t)求二阶导数得出。不同处理玉米干物质累积最大速率出现时间为玉米出苗后33.56~68.06 d,N累积最大速率出现时间为出苗后14.73~64.19 d,P累积最大速率出现时间为出苗后45.23~80.64 d,K累积最大速率出现时间为出苗后18.80~53.91 d。     

磷对大麦根系导水率的调节作用研究

在控制土壤磷素供应水平及控制灌水量的盆栽试验中,采用静态压力室法测定了三叶期大麦根系导水率(Lpr)的变化。结果表明:无磷处理植株的导水率(Lpr)远远低于有磷植株,即使在正常供水条件下,仅为有磷处理植株的近19%,表明磷营养可以调节大麦幼苗细胞到细胞途径水通道蛋白(AQP)的表达量。无磷处理随干旱程度加重,其导水率下降较有磷处理更为剧烈,旱后复水过程中,导水率恢复能力也显著低于有磷处理,表明磷营养对增强大麦对干旱胁迫的适应性及提高恢复能力具有非常重要的作用。     

文丘里施肥器喉部负压的影响因素分析

为了了解文丘里施肥器的工况特性,通过理论分析与试验测定,研究了进、出口压力,喉部水流流速和局部水头损失系数对喉部负压的影响及变化规律。喉部负压的变化随进口压力的增大呈负相关线性函数递减,当喉部负压降到最低值-0.09 MPa后,进口压力的增大将不再影响喉部负压变化;出口压力对水流通过喉部有阻滞作用,从而影响喉部负压的产生。出口压力越大,喉部负压的产生以及达到最小负压所需的进口压力越大;喉部水流流速对喉部负压的产生及变化与进口压力对其影响相似;对于不同的局部水头损失系数ξ₁和ξ₂,ξ值越大,喉部负压随进口压力的增大而降低的速度越缓慢,达到最小值-0.09 MPa时所需的进口压力越高。     

Propagule pressure cannot always overcome biotic resistance: the role of density‐dependent establishment in four invasive species

Successful invasions result from species functional traits interacting with the receiving community. Some have proposed that propagule pressure, or the size and number of introductions, can overcome high invasion resistance. However, few studies empirically investigate the relationship among functional traits, community composition, and propagule pressure. Here, we empirically examined how propagule pressure influenced the invasive success of four species in four resident communities (bare ground, grass‐only, forb‐only, and full resident community). The four species represented both small‐ and large‐seeded grasses and forbs, and propagule sizes (the number of individuals in an introduction event) ranged from 16 to 160 000 seeds m^?2. Invasion probability varied among species and communities and was strongly influenced by the propagule size. The large‐seeded species had the highest invasion success in all communities, while the grasses did as well or better, respectively, in the grass‐only and bare ground communities. However, contrary to existing assumptions, we found that the establishment probability of individual seeds decreased exponentially with increasing propagule size. Therefore, increased propagule pressure was subjected to severely diminishing returns on invasiveness. Thus, while propagule pressure played a role in determining invasion success, it was not always able to overcome communities with high invasion resistance, particularly for species that experienced strong density‐dependent inhibition. The role of propagule pressure in invasion is more complex than previously thought and may present important trade‐offs for bet‐hedging colonisation strategies.     

Notes on the role of water potential in the pathogenesis of fire blight,caused by Erwinia amylovora

The rate of multiplication of fire blight causing bacteriumErwinia amylovora (Burrill) Winslow et al. depends on the availability of water. Water availability can be quantified by means of the parameter water potential. The relationship between water potential and relative multiplication rate ofE. amylovora was derived from experiments of L. Shaw (1935). This relationship appears to be applicable toE. amylovora in plant tissues and in nectar of flowers.Multiplication and expansion ofE. amylovora in a restricted space, e.g. an intercellular hole, creates a pressure, which may cause schizogenic cavities in soft tissue. Strong tissue, however, may be able to resist this multiplication pressure of the bacteria, so that symptom progression can be prevented. A hypothesis is formulated on how the multiplication pressure may be quantified by means of the parameter water potential. Expansion of bacterial ooze may alo be due to absorbtion of water without increase of dry weight (e.g. a daily cycle of shrinkage and expansion). This expansion may give rise to a swelling pressure, which again may be quantified by means of the parameter water potential.Samenvatting De vermenigvuldigingssnelheid van de bacterie die bacterievuur veroorzaakt (Erwinia amylovora (Burrill) Winslow et al.,), hangt af van de beschikbaarheid van water. De beschikbaarheid van water kan worden gekwantificeerd met de parameter waterpotentiaal. De relatie tussen waterpotentiaal en relatieve vermenigvuldigingssnelheid vanE. amylovora werd afgeleid uit experimenten van L. Shaw (1935, Cornell University Agricultural Experiment Station, Ithaca. Memoir 181). Deze relatie kan zowel worden toegepast op de pathogenese in planteweefsel als op de epifytische ontwikkeling in nektar.Vermenigvuldiging vanE. amylovora in een beperkte ruimte, bijvoorbeeld in een intercellulaire holte, creëert een druk, die tot scheuren van zacht weefsel kan leiden. Sterk weefsel kan de vermenigvuldigingsdruk van de bacteriën vermoedelijk wel weerstaan, zodat uitbreiding wordt verhinderd. In een hypothese wordt beschreven hoe de vermenigvuldigingsdruk zou kunnen worden gekwantificeerd met behulp van de parameter waterpotentiaal. Wateropname door bacterieslijm zonder toename van het drooggewicht (bijvoorbeeld een dagelijkse gang van krimpen en zwellen) kan ook leiden tot een druk. Deze druk kan eveneens worden berekend met de parameter waterpotentiaal.     

山地管道恒压喷雾中喷雾压力和孔径对雾滴粒径的影响

为提高农药利用率,研究山地果园管道恒压喷雾系统中喷雾压力和孔径对雾滴粒径参数的影响,利用激光粒度仪,测量3种孔径空心圆锥雾喷头在8种压力下的6种雾滴粒径参数数据,分析各粒径级雾滴的分布情况,给出雾滴粒径大小及其随压力和孔径的变化趋势,进行了雾滴参数的多元线性回归,建立基于压力的雾滴参数模型。结果表明:粒径大于100μm的雾滴(小于0.3%)和粒径为0~20μm的雾滴(小于0.5%)可忽略不计,雾滴粒径主要分布于20~40μm(79.5%~92.8%);雾滴均较细小,全部为气溶胶;孔径越小,压力越大,雾滴越细小;6种雾滴粒径参数与孔径和压力均有良好的二元线性关系(R2分别为0.928、0.956、0.949、0.949、0.889和0.815);6种雾滴粒径参数均随压力呈二次多项式变化规律,决定系数R2均达到了0.894以上。研究结果对山地果园管道恒压喷雾中喷头的选型、喷雾压力的调整及喷雾效果的优化有重要参考意义。     

压力探针技术原理及其在植物水分关系研究中的应用

现代压力探针主要分为高等植物细胞压力探针、根压力探针、木质部压力探针和取样压力探针4个变种,并形成了相关的理论体系,广泛应用于植物生理学及其相关领域的研究中。现代压力探针技术不仅可用于高等植物细胞和组织水平水分关系、水和溶质的相互作用关系的研究,还可进行根木质部负压的测定及高等植物活体单细胞内含物的取样研究等。未来更可借助取样压力探针与微量分析技术的结合,将高等植物单细胞内的水分关系和代谢过程定量联系起来;或可试图拓宽木质部压力探针测定的压力范围,进一步研究和验证内聚力-张力学说的理论和机制。     

Spatial regression approach to estimate synthetic unit hydrograph by geomorphic characteristics of watersheds in arid regions

Rainfall-runoff relationship in arid regions is unique and challenging to study. Studies for bridging the hydro-meteorological knowledge gap for planning, designing and managing water resources is therefore vitally important. The objective of this study is to develop a method for estimating unit hydrograph at reasonably finer time resolutions (10-min and 1-h) which can be easily adaptable by practitioners at sub-catchment levels, especially when the focus area is ungauged. Observed wadi-flow at 5-min interval and tipping bucket rainfall measurements at 1-min interval were obtained to cover 10 major watersheds in Oman. The deconvolution method was applied to derive the unit hydrographs (UHs) from wadi-flow and excess rainfall. Key catchment characteristics such as the watershed area, length of the main wadi and the length to the centroid of the catchment area were derived from digital elevation model (DEM) data. The whole study area was then divided into 515 sub-catchments with various shapes and sizes. A strong relationship was found between the wadi length and the length to the centroid of the catchment area (R²>0.89). This relationship was then adopted to simplify the classical Snyder method to determine UHs. Moreover, several parameters of the Snyder method were calibrated to the arid environment by matching the peak-flow, lag-time and three time-widths (75%, 50% and 30% of the peak-flow) of 10-min and 1-h UHs with physical characteristics of the watersheds. All developed relationships were validated with independent rainfall and wadi-flow events. Results indicate that the calibrated parameters in these arid watersheds are quite distinct from those suggested for other regions of the world. A marked difference was found between the 10-min UHs estimated by the S-hydrograph method and the deconvolution method. Therefore, it is concluded that a method depends on natural hydro-meteorological conditions would be more practical in arid region. The proposed methodology can be used for water resources management in arid regions having similar climate and geographical settings.     

Detection of beet yellows virus in sugarbeet plants by enzyme-linked immunosorbent assay (ELISA)

Beet yellows virus can be detected in leaf extracts of infected sugarbeet plants by ELISA. The use of discs was studied and proved to be a valuable and qualitatively reliable method. Leaf material could be stored at 4^o or 22°C for at least six days without affecting the detection of this virus by ELISA. A dramatic decrease in ELISA values was found when leaf extracts were frozen.In an analysis of the distribution of virus over the plant it was found that young leaves present at the moment of infection and those which had still to develop after infection will contain virus. Symptoms produced by systemic virus invasion occur on the oldest leaves containing virus.Samenvatting Het bietevergelingsvirus kan op betrouwbare wijze met de ELISA methode in geïnfecteerde bieteplanten worden aangetoond. Een aanzienlijke vereenvoudiging van de procedure kan worden bereikt met de zogenaamde disc-method, waarbij intacte ponsstukjes in de putjes van de ELISA-plaat worden geïncubeerd. Hierbij komt voldoende virus uit de ponsstukjes voor ELISA vrij. Bladmateriaal kon op verschillende wijzen bewaard worden zonder dat de mogelijkheid om het virus aan te tonen achteruitging. Met bladextracten die ingevroren waren, werden echter slechte resultaten verkregen.In een analyse naar de verdeling van het virus over het loof bleek het virus voor te komen in de geïnoculeerde bladeren, in die bladeren die op het tijdstip van inoculatie minder dan de helft van hun uiteindelijke lengte bereikt hadden en in de bladeren die nog moesten verschijnen. De symptomen ontwikkelden zich op de oudste systemisch geïnfecteerde bladeren.     

农田鼠类数量统计方法的研究

目前统计大仓鼠Cricetulus triton、黑线仓鼠C.barabensis和黑线姬鼠Apodemus agrarius等地面活动的农田鼠类广泛采用夹捕法和查洞法,夹捕法又要求连续布夹三夜。本文对用一夜、连续二夜和三夜夹捕的统计结果作了对比研究,结果表明,三种夹捕方法的统计结果一致,呈极显著正相关。作者认为只用一夜捕鼠减少了工作量和样方去除效应,可在农田鼠情常规测报中代替连续三夜捕鼠法。查洞法的统计结果不能反映农田鼠类数量的季节变化,不宜在鼠情测报中使用。     

浅淡单点校正法和标准曲线法及其在农药分析中的应用

本文从单点校正法和标准曲线法的适用前提条件出发，运用数学方法，探讨了单点校正法代替标准曲线法的条件，并为在农药分析中选择单点校正法和标准曲线法提供依据，从而简化正常农药分析步骤，避免一些分析误差。