PP333对花生生长和叶片结构的影响

以不同浓度的氯乙唑（Paclobutrazol.PP333)溶液施用于5叶期的花生幼苗,施方法分为喷施和土施。地上部施用部位又分为涂叶和涂茎,40天后测量植株生长,蒸腾速率和气孔阻力,观察叶片结构,结果表明：1．PP333抑制花生主茎的生长,减少地上部分干重,对根部干重无影响甚至略增,根茎比增大,气孔阻力大,蒸腾速率下降,贮水细胞体积增大,这些解剖和生物特征,有利于抵抗水分胁迫,2．PP3333可使叶片表皮细胞变小,叶绿体的基粒片层数目少,基质片层也稀疏,抑制叶绿体发育。3．土施PP333对花生生长抑制效应比喷施显著得多,根部吸收的抑制效果最大,茎部居中,叶片最不明显。     

干旱对浑善达克沙地榆叶片解剖结构的影响

采用石蜡切片法对浑善达克沙地流动沙丘顶部、丘间草地处的浑善达克沙地榆及呼和浩特市白榆叶的解剖结构进行了对比观察和分析,以期探讨浑善达克沙地榆在解剖学方面适应干旱的机理。结果表明,虽然属同种植物,但由于环境条件的不同,叶片的解剖结构表现出明显的差异。生境条件最差的流动沙丘顶部的浑善达克沙地榆的抗旱性最强,具体表现为:叶片厚,表皮细胞大,具有较厚的表皮细胞外壁与角质层;栅栏组织发达,细胞缩小,排列紧密。     

硅对生姜叶片水、二氧化碳交换特性的影响

为探讨硅对生姜植株的生理效应,以莱芜大姜为试材,研究了水培营养液中不同硅素水平对生姜植株生长、硅含量及叶片光合作用和蒸腾作用的影响.结果表明：植株各器官硅含量及生物量均随营养液硅素水平的升高而显著增加,1.0 (T₁)、1.5 (T₂)、2.0 (T₃) mmol·L^-1硅(Si)处理植株叶片硅 (SiO₂) 含量分别比CK增加604.4%、834.8%和1130.4%,单株生物量分别比CK增加9.4%、19.4%和22.8%.随着硅素水平的升高,叶片Mg²⁺ TPase、Ca²⁺ ATPase活性及光合速率(P_n)和水分利用效率(WUE)提高,蒸腾速率(T_r)降低.一天中在11:00时,T₁、T₂、T₃处理的生姜叶片P_n和WUE分别比CK提高11.2%、21.8%、28.2%和23.1%、55.9%、54.8%,T_r分别比CK降低6.3%、17.1%和19.2%.此外,硅素还显著提高了生姜叶片光合作用饱和光强、CO2羧化效率及类胡萝卜素含量,但对叶绿素含量无显著影响.本试验条件下,以15～20 mmol·L-1硅素(Si)处理效果最好.     

外源硅对盐胁迫下黄瓜幼苗叶绿体活性氧清除系统的影响

以黄瓜为材料,研究了外源硅（K2SiO3 1．0mmol／L）对NaCl（50mmol/L）胁迫下黄瓜幼苗叶绿体中Na^＋、K^＋向叶绿体分配及活性氧清除系统的影响。结果表明：盐胁迫下硅处理使叶绿体在K^＋与Na^＋之间选择性吸收K^＋,从而降低了叶绿体内Na^＋的含量;同时Si处理可以显著降低盐胁迫下叶绿体中过氧化氢（H2O2）和丙二醛（MDA）含量,提高超氧化物歧化酶（SOD）、抗坏血酸过氧化物酶（APX）、谷胱甘肽还原酶（GR）和脱氢抗坏血酸还原酶（DHAR）的活性及抗坏血酸（ASA）、还原型谷胱甘肽（GSH）含量。说明Si不仅能降低叶绿体对Na^＋的选择吸收,还能增强叶绿体活性氧清除系统清除活性氧的能力,缓解盐胁迫对叶绿体膜的伤害。     

黄瓜叶片对草酸铁的还原作用

铁还原作用在植物叶片对铁素吸收及利用过程中起关键作用。本研究表明：相对于其它几种常用的铁螯合物如二乙基四乙酸铁（Fe^ⅢEDTA）或柠酸铁,草酸铁更有利于黄瓜活体叶片及铁还原酶的作用,即表现出更高的铁还原活力。缺铁降低了黄瓜叶片中的铁还原活性。缺铁时叶片中的草酸含量不受影响,而富含在石灰性缺铁土壤中的碳酸氢根离子能使叶片中草酸含量显著提高。     

黄瓜叶片对草酸铁的还原作用

铁还原作用在植物叶片对铁素吸收及利用过程中起关键作用.本研究表明相对于其它几种常用的铁螯合物如二乙基四乙酸铁(FeⅢEDTA)或柠檬酸铁,草酸铁更有利于黄瓜活体叶片及铁还原酶的作用,即表现出更高的铁还原活力.缺铁降低了黄瓜叶片中的铁还原活性.缺铁时叶片中的草酸含量不受影响,而富含在石灰性缺铁土壤中的碳酸氢根离子能使叶片中草酸含量显著提高.     

马蔺叶片解剖结构特征与其抗旱性关系研究

通过温室模拟干旱胁迫试验,从中国北方不同生境生长的15份野生马蔺种质材料鉴定出3个不同抗旱性群体(强抗旱、中度抗旱和弱抗旱),从中选择具代表性的不同抗旱级别的4份马蔺种质,进行其叶片组织解剖结构特征的观察和比较,以进一步证实马蔺叶片解剖结构特征及其与抗旱性的关系。结果表明,各种质材料间叶片厚度、上下表皮细胞厚度、角质层厚度、气孔密度、栅栏组织厚度、海绵组织厚度、栅栏组织/海绵组织厚度、CTR值和SR值等结构参数指标均与马蔺种质材料抗旱性存在密切的关系。其中,强抗旱种质材料的叶片厚度、上下表皮细胞厚度和角质层厚度大,气孔密度大,栅栏组织和海绵组织较发达,叶片组织紧密度大、疏松度小,栅栏组织/海绵组织厚度比较高;弱抗旱种质材料的叶片厚度、上下表皮细胞厚度和角质层厚度小,气孔密度小,栅栏组织和海绵组织较薄,叶片组织紧密度小、疏松度大,栅栏组织/海绵组织厚度比较低。     

PP333对花生生长和叶片结构的影响

以不同浓度的氯乙唑（Paclobutrazol.PP333)溶液施用于5叶期的花生幼苗,施方法分为喷施和土施。地上部施用部位又分为涂叶和涂茎,40天后测量植株生长,蒸腾速率和气孔阻力,观察叶片结构,结果表明：1．PP333抑制花生主茎的生长,减少地上部分干重,对根部干重无影响甚至略增,根茎比增大,气孔阻力大,蒸腾速率下降,贮水细胞体积增大,这些解剖和生物特征,有利于抵抗水分胁迫,2．PP3333可使叶片表皮细胞变小,叶绿体的基粒片层数目少,基质片层也稀疏,抑制叶绿体发育。3．土施PP333对花生生长抑制效应比喷施显著得多,根部吸收的抑制效果最大,茎部居中,叶片最不明显。     

硅对连作黄瓜幼苗光合特性和抗氧化酶活性的影响

以‘津研四号’黄瓜品种为试材,研究了叶面喷施不同浓度硅(Si)(0、1、2、3、4、5mmol·L-1)对连作黄瓜幼苗生长、光合特性和抗氧化酶活性的影响.结果表明:在一定浓度(1~3 mmol·L-1Si)范围内,施Si可降低幼苗叶片电解质渗漏率(EL)和丙二醛(MDA)含量;提高叶绿素a(Chl a)、叶绿素b(Chl b)、类胡萝卜素(Car)和总叶绿素含量,叶片净光合速率(Pn)升高;超氧化物歧化酶(SOD)、过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)和过氧化氢酶(CAT)活性均有所提高;黄瓜幼苗株高、茎粗、叶面积及干物质积累量增加.随施Si浓度的进一步增加(4~5 mmol·L-1),叶片中EL和MDA含量升高,但仍低于对照;抗氧化酶活性和光合作用下降,幼苗生长受到显著抑制.说明外源Si可通过提高黄瓜幼苗叶片抗氧化酶活性来降低膜脂过氧化,通过增加光合作用来提高黄瓜幼苗长势,进而增强对连作障碍的抗性.以2 mmol·L-1Si处理效果最好.     

长期施肥条件下潮土不同组分有机质的动态研究

采用相对密度分组法对潮土有机质进行分组分析,研究长期施肥条件下不同施肥处理的土壤有机质、轻组有机质和重组有机质的动态变化.结果表明,在现有的施肥条件下,不施肥处理的土壤有机质、轻组有机质和重组有机质含量基本保持不变,而NPK(化肥)和有机肥处理的土壤有机质、轻组有机质和重组有机质含量均随施肥年限呈增加趋势,但前者年际间波动较大,增加幅度也远不如后者.回归分析发现,NPK处理的土壤有机质、轻组有机质和重组有机质均与施肥年限呈线性相关,而有机肥处理的土壤有机质、轻组有机质和重组有机质则随施肥年限呈对数函数变化规律.     

长期施肥对土壤微生物的影响及其在养分调控中的作用

为揭示长期施肥条件下土壤微生物类群及其与土壤养分的关系,对北京褐潮土定位试验田第12年的土壤微生物以及土壤养分因子进行了测定和分析．结果表明,NPK与有机肥长期配合施用能明显提高土壤各养分含量,增加土壤微生物的数量．猪粪比玉米秸秆能更好地培肥地力,创造有利于土壤微生物生长繁育的土壤生态化学环境．土壤微生物与土壤养分之间具有很好的相关性．其中,细菌、固氮菌数量与有机质、全氮、碱解氮、全磷、速效磷含量呈显著正相关;本研究未观察到真菌、放线菌数量与土壤养分因子之间有明显的相关性．     

外源水溶性有机物及温度对红壤铜形态的影响

利用模拟培养试验研究了外源水溶性有机物（DOM）添加量和培养温度对红壤中Cu形态的影响. 结果表明: 与不添加DOM比较, 添加不同量的DOM均可提高土壤中交换态Cu的含量、降低铁锰结合态Cu含量; 随着培养时间的延长,不同DOM添加量下土壤交换态Cu含量呈逐渐下降趋势;至试验结束时,DOM添加量为250 mg·L^-1时土壤交换态和碳酸盐结合态Cu含量最高, 添加量为500 mg·L^-1时铁锰结合态Cu含量最高;不同DOM添加量下, 土壤中有机结合态Cu含量较CK增加10.67%～23.66%. 在25 ℃和45 ℃温度条件下, 添加DOM后土壤交换态和铁锰结合态Cu含量均随培养时间的延长呈下降趋势, 但在5 ℃下变化趋势相反; 3种温度下添加DOM后土壤碳酸盐结合态Cu含量有随培养时间延长而增加的趋势. 随着培养温度的升高,土壤有机结合态Cu含量增加, 但在温度较低(5 ℃)时土壤残渣态Cu含量下降.     

Some effects of plant ash on the chemical properties of soils and aqueous suspensions

Summary Laboratory studies indicate that percolation of water through accretions of plant ash will markedly increase the pH of solutions entering the underlying soil. Ash derived from graminaceous straws raised the pH of an aqueous suspension (1 g ash: 500 ml H₂O) to 10.6, compared to 9.3 for a saturated solution of CaCO₃. However, on a weight basis these ashes possess only approximately 5–15% of the alkalising power of CaCO₃ in terms of their ability to neutralise acid or elevate soil pH. The effect of ash on soil pH, and pH dependent soil properties, is determined by the amount and composition of the ash deposited and on the buffering capacity of the soil.High field rates (2480–6750 kg ha^–1) of ash added to a podzolic soil increased the pH of the soil solution by up to 3 units. A pH rise of 1 unit is sufficient to increase the solubility of native soil organic carbon (O.C.) in water (i.e. mobilize readily metabolizable microbial substrate) and stimulate respiration rate.In more strongly buffered krasnozem soil, maximum rise in pH of the soil solution did not exceed 0.7 unit. However, even such small pH shifts significantly reduced the solubility of soil O.C. in water; probably by changing the character (and hence solubility) of organo-mineral chelation complexes. High rates of ash application also slightly decreased respiration rate in this soil type.The application of neutralized ash, which added metal ions to the soil solution, had a similar but smaller effect to unneutralized ash on the solubility of soil O.C. in podzolic soil, but little effect in krasnozem soil.     

集约和粗放经营下毛竹林土壤活性有机碳的变化

以集约和粗放经营的毛竹(Phyllostachys heterocycla ‘Pubescens’)林为研究对象, 探讨了春季毛竹林集约经营后土壤有机碳的变化。结果表明: (1)集约经营后毛竹林0-10和10-20 cm土层土壤总有机碳含量分别下降了7.01%和18.90%, 易氧化碳含量分别下降了31.22%和46.03%, 0-20 cm土层轻组有机质含量下降了19.87%。(2)两种毛竹林的土壤有机碳含量在剖面上整体上均随土层深度的增加而呈下降趋势, 但下降幅度不同。粗放经营的毛竹林土壤易氧化碳的剖面特征与总有机碳相似, 而集约经营的毛竹林存在明显差异。轻组有机质具有表聚性, 主要分布在土壤表层(0-20 cm)。(3)土壤总有机碳、易氧化碳、轻组有机质与土壤养分之间的相关性均达到极显著水平(p < 0.01), 总有机碳与速效磷显著相关(p < 0.05)。(4)集约经营后, 毛竹林0-10 cm土层土壤易氧化碳的碳素有效率和土壤碳库活度分别下降了26.01%和50.52%, 差异显著(p < 0.05); 10-20 cm土层分别下降了35.51%和54.41%。因此, 施加适当配比的有机肥和无机肥, 有利于土壤中各种有机碳的积累, 也可改善土壤的生物化学活性。     

六种泥炭藓形态结构特征对其持水能力的影响

本研究选取贵州都匀市毛尖镇螺蛳壳风景区沼泽湿地的6种泥炭藓属(Sphagnum)植物,分别测量其主茎粗、株高,计数侧枝数和分枝数,并计算其饱和吸水率、外吸水率、内吸水率、透明细胞面积占比、侧枝密度等指标.结果显示:(1)6种泥炭藓饱和吸水率大小依次为狭叶泥炭藓(S.cuspidatum Ehrh)(2518.99％)>...     

不同施肥管理措施对农田土壤中植物和微生物残留组分的影响

在农田生态系统中,施肥是维持和提高土壤有机碳(SOC)水平的重要管理措施。微生物代谢和植物组分存留共同控制着有机碳的截获过程。本研究利用肥料与肥力长期(30年)定位试验,以氨基糖和木质素分别作为微生物和植物残留组分标识物,探讨长期不同施肥处理对黑土农田中微生物和植物残体组分积累及有机碳库的影响。结果表明: 与未施肥处理相比,施用无机肥(单施氮肥或有机无机肥配施)可增加作物生物量和土壤氨基糖的积累,但对木质素和SOC含量无显著影响,说明无机肥施入刺激了微生物底物同化,加速了有机碳和木质素在耕层的周转。与无机肥相比,长期施用有机肥促进了SOC的累积(增幅38.3%),但是氨基糖在土壤有机碳中所占的比例并未发生显著变化,说明微生物残留物对SOC积累的贡献具有饱和性;而有机肥施入增加了木质素在SOC中的比例,即增加了植物残体对SOC长期积累的贡献。与单施有机肥相比,有机无机肥配施增加了微生物残留物对SOC的积累。因此,长期施肥可以调节微生物残留物和植物残留组分的不同积累过程,从而影响SOC的积累和稳定机制。     

Effects of exogenous abscisic acid on leaf carbohydrate metabolism during cucumber seedling dehydration

Cucumber (Cucumis sativus L.) seeds were pretreated with exogenous abscisic acid (ABA) prior to germination. After germination, seedlings with three leaves were exposed to gradual dehydration. The effects of ABA on photosynthetic rate (Pn), daily water loss (WL) and water utilization efficiency (WUE) during dehydration were investigated, in addition to the variation of carbohydrates in leaves. ABA improved the Pn, WL and WUE of cucumber seedlings during dehydration. After rehydration, the seedlings pretreated with ABA showed a higher recovery in Pn, WL and WUE, as compared to those without an ABA pretreatment. Subsequent to dehydration, concentration of stachyose, raffinose, sucrose, glucose, and fructose increased in seedlings pretreated with ABA. Dehydration altered the proportions of the sugars in the total carbohydrates, and accelerated the accumulation of stachyose, raffinose and sucrose. After rehydration, carbohydrate concentrations of seedlings pretreated with ABA recovered to levels observed prior to dehydration. These results demonstrated that pretreatment of seeds with exogenous ABA enhanced carbohydrate tolerance to dehydration of cucumber seedlings.     

Density fractionation of forest soils: methodological questions and interpretation of incubation results and turnover time in an ecosystem context

Soil organic matter (SOM) is often separated by physical means to simplify a complex matrix into discrete fractions. A frequent approach to isolating two or more fractions is based on differing particle densities and uses a high density liquid such as sodium polytungstate (SPT). Soil density fractions are often interpreted as organic matter pools with different carbon (C) turnover times, ranging from years to decades or centuries, and with different functional roles for C and nutrient dynamics. In this paper, we discuss the development and mechanistic basis of common density-based methods for dividing soil into distinct organic matter fractions. Further, we directly address the potential effects of dispersing soil in a high density salt solution on the recovered fractions and implications for data interpretation. Soil collected from forested sites at H. J. Andrews Experimental Forest, Oregon and Bousson Experimental Forest, Pennsylvania was separated into light and heavy fractions by floatation in a 1.6 g cm⁻³ solution of SPT. Mass balance calculations revealed that between 17% and 26% of the original bulk soil C and N content was mobilized and subsequently discarded during density fractionation for both soils. In some cases, the light isotope was preferentially mobilized during density fractionation. During a year-long incubation, mathematically recombined density fractions respired ∼40% less than the bulk soil at both sites and light fraction (LF) did not always decompose more than the heavy fraction (HF). Residual amounts of tungsten (W) present even in well-rinsed fractions were enough to reduce microbial respiration by 27% compared to the control in a 90-day incubation of O_a material. However, residual W was nearly eliminated by repeated leaching over the year-long incubation, and is not likely the primary cause of the difference in respiration between summed fractions and bulk soil. Light fraction at Bousson, a deciduous site developed on Alfisols, had a radiocarbon-based mean residence time (MRT) of 2.7 or 89 years, depending on the interpretation of the radiocarbon model, while HF was 317 years. In contrast, both density fractions from H. J. Andrews, a coniferous site developed on andic soils, had approximately the same MRT (117 years and 93 years for LF and HF). At H. J. Andrews the organic matter lost during density separation had a short MRT (19 years) and can account for the difference in respired CO₂ between the summed fractions and the bulk soil. Recognition and consideration of the effects of the density separation procedure on the recovered fractions will help prevent misinterpretation and deepen our understanding of the specific role of the recovered organic matter fractions in the ecological context of the soil studied.     

Effects of plant functional group removal on structure and function of soil communities across contrasting ecosystems

Loss of plant diversity has an impact on ecosystems worldwide, but we lack a mechanistic understanding of how this loss may influence below‐ground biota and ecosystem functions across contrasting ecosystems in the long term. We used the longest running biodiversity manipulation experiment across contrasting ecosystems in existence to explore the below‐ground consequences of 19 years of plant functional group removals for each of 30 contrasting forested lake islands in northern Sweden. We found that, against expectations, the effects of plant removals on the communities of key groups of soil organisms (bacteria, fungi and nematodes), and organic matter quality and soil ecosystem functioning (decomposition and microbial activity) were relatively similar among islands that varied greatly in productivity and soil fertility. This highlights that, in contrast to what has been shown for plant productivity, plant biodiversity loss effects on below‐ground functions can be relatively insensitive to environmental context or variation among widely contrasting ecosystems.