聚乙二醇（PEG6000）模拟干旱胁迫抑制矮沙冬青种子的萌发     

于军  焦培培 《广西农业生物科学》2010,(2):355-360

本研究以新疆特有濒危保护植物矮沙冬青（Ammmopiptanthus nanus（M．Pop．）Chengf）的种子为材料,用不同渗透势浓度的聚乙二醇（PEG6000）模拟干旱胁迫,探讨干旱胁迫对矮沙冬青种子发芽率、平均发芽速度、胚轴和胚根长度及发芽指数、活力指数的影响。结果表明,不同浓度PEG胁迫处理均降低了种子的发芽率,延缓了矮沙冬青种了萌发进程;种子的发芽率、发芽指数和活力指数均随胁迫强度的增加呈明显下降趋势。当-1．20MPa的PEG胁迫处理的种子在试验结束时仍未能萌发,表明-1．20MPa是矮沙冬青种子萌发的临界水势。PEG模拟十旱胁迫中,当PEG处理为-0．2MPa时,虽然最终发芽率与对照一样,但其胚根、胚轴的长度都比对照短,说明矮沙冬青胚根、胚轴的生长比发芽率对干旱胁迫更敏感。干旱胁迫可能是导致矮沙冬青种群天然更新能力弱的原因之一。本研究将为矮沙冬青种质资源的保护和种群的恢复提供科学依据。  相似文献   

土壤颗粒分布体积分形维数与数量分形维数之间的关系     

李毅  李敏  Si Bingcheng  贺缠生 《农业工程学报》2012,28(23):82-91

土壤的体积颗粒分布(PSD)可用于同时确定数量分形维数(DN)和体积分形维数(DV)。以往的试验和理论研究均未直接比较DV和DN的关系。为建立DV和DN的关系并分析其参数的敏感程度,在中国各地取了12种不同质地土壤,利用激光粒度仪进行了测定。提出了含3个参数Rupper(颗粒半径的上限),Ri(第i个半径)和Rlower(半径下限)的DV-DN理论关系,该关系可说明为什么DN可能大于3。在未调整的幂定律范围内(PLR),DV的幂定律半径为38.6～85.8μm,DN的幂定律半径为53.2～358μm,估算的DV值(2.18～2.69)比DN值(2.38～3.19)小。调整后的PLR比未调整的窄。在调整的PLRs范围内,估算的DV值变化范围为2.11～2.56,而DN变化范围为2.28～3.02。调整和未调整PLRs得出的DV和DN的差异说明,Rupper,Rlower,Ri和Rlower/Rupper均可能影响DV与DN关系,有必要进行参数的敏感性分析。进行敏感性分析可基于敏感系数(C)来鉴别DV-DN关系中各参数改变所引起的DV和DN相对变化,从而找出对该关系影响最大的参数。就不同情况下计算的C值而言,Rupper是影响DN值的最重要参数,小的Rupper值可能导致估算DN的准确度降低。PLR范围越大,DN的估算越准确。根据DV估算DN的相对误差的绝对值在12%范围内,说明得出的DV-DN理论关系是正确的。  相似文献   

苦荞种子灌浆期全长cDNA文库的构建及部分表达序列标签分析     

陈鹏  贾鹏  王聪  张海纳  淡荣 《农业生物技术学报》2012,20(5):576-584

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Studies on post‐reddening changes in amino acid content leaves of hirsutum cotton and its control with chemicals     

Arvind M. Dhopte  P. Ratnakar  S.B. Lall 《Journal of plant nutrition》2013,36(5):413-422

The aspartic acid,tyrosine and serine contents of leaves were found reduced in prematurely reddened leaves of hirsutum cotton (Gossypium hirsutum) as compared to healthy green leaves. Amino acids other than those listed above were higher in the affected red leaves. Amino acids threonine and proline increased 63.7 and 2.3 fold over green leaves respectively. Chemical sprays not only maintained the levels of various amino acids at par with green leaf but tended to increase the concentration above the levels obtained in normally found green leaf. However, threonine level was dropped in treated leaves as compared to partly affected red leaf and chemical sprays significantly reduced the leaf reddening when it was sprayed before flowering. It can be suggested that the leaf reddening can possibly be arrested by monitoring threonine content in leaves of hirsutum cotton ov. L‐147.  相似文献   

淮南矿区煤矸石风化物特性及有机碳分布特征   总被引：2，自引：1，他引：2  

郑永红  张治国  胡友彪  姚多喜  陈孝杨 《水土保持通报》2014,(5):18-24

以淮南矿区潘一矿煤矸石山为研究对象,通过对煤矸石风化物的理化特性、电镜扫描(SEM)、能谱(EDS)和总有机碳(TOC)含量分析,初步研究了煤矸石风化物有机碳分布和释放规律,以及煤矸石山堆积淋溶作用对周边土壤溶解性有机碳(DOC)含量的影响。结果表明,从山顶、山腰到山脚煤矸石风化物中的总有机碳(TOC)含量依次减小,随着采样深度的增加总有机碳(TOC)含量逐渐变大。煤矸石风化物中总有机碳含量与煤矸石风化物粒径大小呈正相关,与煤矸石风化物的风化程度成负相关。不同粒径煤矸石风化物淋滤液中溶解性有机碳(DOC)的含量随着淋溶时间增大而减小,在96h淋滤液中溶解性有机碳含量趋于稳定,且值较为接近。距离山脚2~100m内,随着采样距离的增加土壤中溶解性有机碳含量(DOC)呈减少趋势。在距离煤矸石山80~100m处土壤溶解性有机碳含量接近正常农田土壤含量。  相似文献   

延安地区降雨引发黄土泥流的试验研究     

陈海霞  王家鼎 《水土保持通报》2013,33(2):39-42

在野外模拟降雨条件下,研究了黄土粒度分布和微结构在降雨前后的变化及其对泥流启动的影响.结果表明,采自径流沉积物的降雨后土样中的细黏粒、粗黏粒体积含量分别相对增加了22％和18％,而粗粉粒、微砂体积含量分别相对减少了7.6％和3.3％.坡面残余土的粒度“粗化”,降雨后土骨架连接松散,这些由降雨引起的黄土的粒度和微结构变化说明降雨后黄土的抗剪强度和抗压能力将降低,导致泥流启动的可能性增加.随着降雨入渗,当沿坡面的黄土重力分力与抗剪强度间的平衡被打破,黄土开始滑移并发展成泥流.有效防止坡面土粒度“粗化”是遏制水土流失的关键.  相似文献   

Surface-active properties of particle size fractions in two humic acids     

Masayuki Kawahigashi  Nobuhide Fujitake 《Soil Science and Plant Nutrition》2013,59(4):497-505

The relationships between surface active properties and humic acid (HA) particle sizes were investigated. Two HAs from an Ando soil and a Brown forest soil were separated into 6 particle size fractions by gel permeation chromatography. Surface-active properties characterized by surface excess value (\gT mol cm^-2), cross-sectional surface area per molecule (A nm²), critical micelle concentration (CMC g L^-1), efficiency and effectiveness of water surface tension reduction were obtained by the measurement of the surface tension of HA solutions from different particle size fractions. For the HA from the Ando soil, except for the smallest particle size fraction, increasing particle size enhanced the efficiency of reduction of the water surface tension and decreased the CMC, while the effectiveness of reduction of the water surface tension was about the same. The surface activity of the HA from the Ando soil increased with increasing particle size. This phenomenon was similar to the surface activity of a homologous series of surfactants, which increased with increasing alkyl chain length. For the HA from the Brown forest soil, the smallest particle size fraction and three large fractions showed a high efficiency, namely a high surface activity. The smallest fraction from the Brown forest soil showed the highest efficiency and the lowest CMC value. In both HAs, the smallest particle size fraction showed exceptional surface-active properties compared with the other fractions and three fractions with large particle size showed a higher surface activity than other smaller fractions.  相似文献   

Drop size dependence of soil-water contact angle in relation to the droplet geometry and line tension     

Dewpura A. L. Leelamanie  Jutaro Karube 《Soil Science and Plant Nutrition》2013,59(6):675-683

The soil-water contact angle is used as a measure of the surface hydrophobicity of soils. The contact angle for particular solid–liquid combination is considered to vary with the drop size. In this paper, we focused on examining the drop size dependence of contact angle on soil surfaces compared with homogeneous solid surfaces, and determining its relation to the droplet geometry and line tension. The contact angle estimated using geometric parameters of the droplets (θ _G) showed decreasing trend with increasing drop size from 5 to 50?µL irrespective of the deformations in the droplet shape in larger drops. This was considered to be a result of the corresponding deviations of the geometric parameters of the droplets. The directly measured contact angle (θ _A) first decreased and then increased with increasing drop size from 5 to 50?µL. The drop size at lowest θ _A for hydrophobized silica sand with 1?g?kg^–1 stearic acid (SA) and the acryl surfaces was 20?µL, whereas that for hydrophobized silica sand with 5?g?kg^–1 SA and siliconed paper was 30?µL. The decrease in θ _A with increasing drop size was explained as a result of the line tension effect using the modified Young's equation. Despite the surface heterogeneity, all the surfaces tested in this study showed positive line tensions on the order of 10?µJ?m^–1. Irrespective of the heterogeneity of the surfaces, the θ _A in this experiment agreed with the modified Young's equation for drop sizes up to about 20–30?µL, where the θ _A and θ _G were also in good agreement. Drop size dependence of contact angle was independent of the level of surface hydrophobicity. The θ _A on all the examined surfaces started to increase with increasing drop size when the deformation index, I _d, exceeded 5%, where the wetting radius, R exceeded the capillary length. The increase in θ _A with increasing drop size was attributed to the deformations of water drops due to the effect of gravity.  相似文献   

Fractionation of soil humic acids by preparative polyacrylamide gel electrophoresis in the presence of concentrated urea     

Saiful Karim 《Soil Science and Plant Nutrition》2013,59(6):827-839

To separate soil humic acids (HAs) into their constituents and characterize them, polyacrylamide gel electrophoresis (PAGE) was carried out in the presence of 7 M urea using a preparative electrophoresis system. Two types of soil HAs were fractionated into nine fractions by PAGE. The dark-colored constituents were recovered from the electrophoretic fractions by precipitation on acidification, and the brown-colored constituents dissolved in the acidic solution of fast-moving fractions were recovered by adsorption onto DAX-8 resin. High-performance size-exclusion chromatography (HPSEC) confirmed that the constituents of the HAs were separated based on their molecular size by PAGE. The dark-colored constituents exhibited higher degrees of humification than did the corresponding unfractionated HAs, except for the constituents remaining in the electrophoretic gels at the end of electrophoresis. Diffuse reflectance infrared spectroscopy revealed that the chemical properties of the dark-colored constituents changed regularly: the content of carboxyl groups decreased and the proportions of proteinous, aliphatic and polysaccharide moieties increased with increasing molecular size. The humification degrees of the constituents adsorbed onto DAX-8 resin were considerably lower than those of the corresponding unfractionated HAs. The chemical properties of the DAX-8-adsorbed constituents were different from those of the dark-colored constituents. Observation of electrophoretic fractions under blue light (470 nm) and HPSEC with fluorescence detection at an excitation wavelength of 460 nm and an emission wavelength of 520 nm showed that green fluorescent substances were largely concentrated in the smallest molecular size fractions and were partitioned into both the dark-colored precipitates and DAX-8-adsorbed fractions. The proportion of organic carbon recovered by precipitation and adsorption onto DAX-8 resin was 45–63%, indicating that substantial parts of the HA constituents were missing. The unrecovered constituents were considered to be acid-soluble, nearly colorless substances. The dissociation of the acid-soluble constituents from the acid-insoluble dark-colored constituents during the preparative PAGE of soil HAs was ascribed to disruption of hydrogen bonding and hydrophobic interactions caused by concentrated urea.  相似文献   

Spatial variability of water retention parameters and saturated hydraulic conductivity in a calcareous Inceptisols (Khuzestan province of Iran) under sugarcane cropping     

Farzad Moradi  Bijan Khalili Moghaddam 《Archives of Agronomy and Soil Science》2016,62(12):1686-1699

The objective of this study was to quantify inherent spatial variability and spatial cross-correlation of the van Genuchten retention parameters and saturated hydraulic conductivity (K_s) of surface and subsurface layers in a calcareous Inceptisols (Khuzestan province, Iran) under sugarcane cropping. Measurements were performed on 100-cm³ undisturbed soil cores collected at 94 locations along a 30-m-long transect with horizontal sampling distance intervals of 0.3 and 1 m at soil depths of 0–40 and 40–80 cm, respectively. Spatial variability was investigated using conventional statistics and geostatistical techniques. Coefficient of variation (CV) varied from 8.2% (for shape parameter, n at 40–80 cm depth) to 256.7% (for K_s at 0–40 cm depth). The n parameter and saturated water content, θ_s, showed a small-scale spatial heterogeneity with a maximum CV of 11.3% for the first depth and 9.2% for the second depth. Most of the hydraulic parameters at both depths showed a spatial structure and convex experimental semivariograms with dominant spherical models with the influence range of 3.2–41 m. In most cases, the extent of spatial correlation scales of cross-semivariograms for pairs of cross-correlated hydraulic variables was found to be different with reference to those relating to the direct semivariograms of correlated variables.  相似文献