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1.
多花木蓝根系与土体界面摩阻特征 总被引：2，自引：1，他引：1
为研究灌木植物根系的固土护坡力学效应,探讨根系与土体间相互作用的特性。以多花木蓝为供试植物,进行植物根系切片并计算根系的表面凹凸度,选取0~0.5,0.5~1.0,1.0~1.5,1.5~2.0mm 4种粒径的粉质黏土,在不同的土体含水率和根径条件下,制备根土复合体扰动试样,进行单根抗拔摩阻试验和直剪摩阻试验,探讨土体含水率、植物根径以及土体粒径对根土界面摩阻特性的影响。结果表明:多花木蓝根系的表面凹凸度随根径变化无显著性差异,根系的拉拔剪应力集中在17.36~32.76kPa,而根土界面的摩擦系数为0.10~0.20;根系拉拔剪应力和根土界面摩擦系数随土体粒径和土体含水率的增加逐渐下降;土体含水率和土体粒径愈低,根系形态特征对根系的拉拔剪应力和根土界面摩擦系数的影响愈显著。研究结果对分析根土界面摩阻特性的影响因素,以及利用灌木植物提高边坡土体结构稳定和防治水土流失、土壤侵蚀等地质灾害具有重大的指导意义。 相似文献
2.
[目的]研究紫穗槐根系在不同含水率和不同融化时间对土体加固作用,为季冻区紫穗槐固土效应提供设计依据。[方法]以取自西宁市黄土为研究对象,用室内三轴试验方法研究紫穗槐根系根—土复合体的应力应变及强度特性,探讨在不同解冻时间和不同含水率下紫穗槐根—土复合体抗剪强度指标变化规律,并通过SEM电镜扫描试验从微观的角度评价紫穗槐根系的加固机理。[结果]紫穗槐根系在不同含水率时有不同的加筋情况,在低含水率和高含水率加筋作用更加明显;在冻融前后紫穗槐根系的加筋作用体现在当土体受到荷载作用时,紫穗槐根系会束缚土颗粒之间的移动,增大土颗粒之间的咬合以及增大根系和土颗粒之间的接触面,从而增大内摩擦角;通过电镜扫描试验可以看出,紫穗槐根系可以抑制土体中的裂隙产生与发展,从而增大土体的整体性。[结论]紫穗槐根系在不同地区均能起到加筋作用。不同含水率会存在不同的最佳含根量,紫穗槐根系的固土作用体现在增大土体的内摩擦角,增加土体的整体性。 相似文献
3.
草本植物根系对高液限土的加固效应 总被引：2，自引：2，他引：0
[目的]探索草本植物根系对高液限土的加固效应,为工程中合理预估植物根系在高液限土质边坡防护中的作用提供依据。[方法]以高羊茅根系及其与高液限土壤构成的根—土复合体为研究对象,通过一系列室内直剪试验分析高液限土含水率和含根量对抗剪强度的影响。[结果]在土样中掺加根系可以显著提升其黏聚力,小幅提升其内摩擦角。根系对土体的加固效果随着含水率增加呈现先上升后减小的趋势。不同含水率梯度下根—土复合体的最优含根量有所区别,对于20%和25%含水率的土样,其最优含根量大致在0.3%附近,对30%含水率土样在0.4%附近,对35%~45%含水率土样在0.5%附近。[结论]草本植物根系可以有效抑制高液限土的水敏性,且在不同含水率梯度下根系发挥的作用差异显著。 相似文献
4.
裂隙膨胀土细观结构演化试验 总被引：6，自引：4，他引：2
为研究裂隙膨胀土的细观结构特征,对重塑膨胀土进行了干湿循环、三轴浸水和各向等压加载试验。利用CT(computerized tomography)机对试验过程中进行无损实时动态扫描,从细观上分析膨胀土裂隙的产生以及裂隙在水和外力作用下的闭合全过程。将细观扫描数据与宏观物理参数相联系,研究裂隙对膨胀土变形特征的影响。结果表明:无约束情况下对膨胀土进行干湿循环,试样边缘以及孔洞聚集区易形成裂隙;干湿循环造成膨胀土体积收缩存在一个稳定渐近线,体缩会趋于1个稳定值。裂隙膨胀土在浸水初期产生膨胀力并出现湿胀变形;随着浸水量的增加,软化效应产生且膨胀力逐渐减小,在围压和偏应力压缩作用下继而出现体缩现象;浸水后期,在偏应力作用下试样产生剪胀破坏,再次出现轻微剪胀变形。在水和荷载作用下,不规则裂隙和孔洞逐渐演化为较规则的圆形孔洞,且圆形孔洞趋于闭合;仅在外力作用时,裂隙较难完全闭合;水和外力的共同作用使得膨胀土裂隙的闭合效果要优于单纯施加荷载时的闭合效果。裂隙膨胀土在各向等压加载过程中存在明显屈服现象,以屈服点为分界,扫描数据和孔隙比随荷载的增大分为快速体缩段和缓慢体缩段,前者与裂隙在荷载作用下闭合并演化成孔洞有关;后者与加载后期孔洞较难闭合且形成的新结构具备抵御外部荷载的能力有关。研究成果可为进一步认识裂隙对膨胀土力学特性的影响提供参考。 相似文献
5.
寒旱环境灌木根系增强边坡土体抗剪强度特征 总被引：1，自引：0，他引：1
为深入研究根系与剪切面呈不同夹角α条件下,边坡土体中根系对土体抗剪强度的影响,以及定量分析评价植物根系对边坡土体抗剪强度的增强作用,该项研究以生长期为150 d的柠条锦鸡儿、霸王根系及其组成的柠条锦鸡儿根-土复合体、霸王根-土复合体为研究对象分别进行室内单根拉伸试验和复合体剪切试验。通过对2灌木根系进行单根拉伸试验,得到2种灌木根系单根的抗拉强度,并对根系与剪切面夹角α分别为45°、60°、75°、90°等4种条件下的根-土复合体进行剪切试验,得到4种α角度条件下的根-土复合体试样抗剪强度;在此基础上,分析探讨了单根抗拉强度与根-土复合体试样粘聚力值之间的关系。结果表明:柠条锦鸡儿根系的单根抗拉强度较霸王根系的单根抗拉强度略高;柠条锦鸡儿根-土复合体、霸王根-土复合体试样,在4种不同α角度条件下的黏聚力均显著大于素土黏聚力;当α角由45°增大至90°时,2种灌木根-土复合体的黏聚力值呈逐渐增大的趋势,且黏聚力的增长率亦表现出一致性变化规律,即2种灌木根-土复合体试样的黏聚力的增长率均随着α角的增大而呈增大趋势;根-土复合体黏聚力值与单根抗拉强度存在正相关关系。由上述复合体黏聚力值的变化规律反映出,试验区2种灌木根系对边坡土体抗剪强度具有显著增强作用,同时亦反映出随根系的单根抗拉强度的增大,根系对土体粘聚力值的增强效果相对愈加显著,且随根系与剪切面间夹角不同,根系增强边坡土体抗剪强度贡献具有不同的变化规律,即表现在根系与剪切面之间的夹角趋于垂直时,根系具有相对最大限度地增强土体抗剪强度的作用。该研究结果为定量评价植物根系增强边坡土体抗剪强度的贡献,提供了试验方面的数据支撑,这为进一步深入探讨植物根系增强边坡土体抗剪强机理提供参考。 相似文献
6.
以大柴旦盐湖区及其周边地区作为试验区,选取海韭菜、芦苇2种优势盐生植物作为供试种,通过对2种盐生植物根—土复合体试样和素土试样进行剪切试验,探讨了盐生植物根系对土体抗剪强度增强作用以及土体抗剪强度的影响因素。结果表明:2种植物根—土复合体试样粘聚力值为13.48~21.87kPa,不含根系素土试样粘聚力值为8.45kPa,与不含根系素土相比,根—土复合体的粘聚力值增长量为5.03~13.42kPa,其增长幅度为59.53%~158.82%;海韭菜根—土复合体试样粘聚力值大于芦苇,2种盐生植物根—土复合体试样粘聚力值与2种盐生植物在一定范围内的根系含量之间呈正相关关系,同时一定程度上表明了试验区2种植物根系增强土体强剪强度的机制表现为,在一定范围内根—土复合体中根系密度和数量愈高则其对土体抗剪强度增强程度相对愈显著,且海韭菜对土体粘聚力的增强作用显著大于芦苇。该研究成果对研究区以及与该区地质条件相类似的其他地区利用盐生植物增强土体抗剪强度,以实现有效地防治地表水土流失、浅层滑坡等地质灾害具有理论研究价值和实际指导意义。 相似文献
7.
为研究草本和灌木根系在护坡中的力学机理,以西宁盆地为例,对青藏高原黄土区生长2年的草本芨芨草和灌木柠条锦鸡儿进行了野外观测和现场力学试验。结合研究区现场观察、试验和分析得出：芨芨草和柠条锦鸡儿根系的生长特征及力学特征均较其他乡土植物显著,护坡力学效应较强;试验区草本植物根系在土体中主要起加筋作用,灌木植物水平根系起牵引作用、垂直根系起锚固作用。通过建立根-土相互作用的力学模型得出：草本植物根系对边坡的加筋作用大小与根系数量、根系抗拉力以及根系在土体中的延伸方向均有关;灌木根系对土体的牵引效应与根系数量、直径和抗拉强度呈正相关,根系锚固力的大小主要取决于根系与土体间的摩擦力,且根系所受的摩擦力与根系半径、土层深度和土体重度呈正相关。对于坡度为40°的土质边坡,选择芨芨草、柠条锦鸡儿等根系发达的灌草植物进行护坡,其防护效果较好。 相似文献
8.
为了系统性研究灌木植物根系的固土力学效应,探讨土体对根系的摩阻特性,以4种不同土壤粒径（原级配,1.0~2.0,0.5~1.0,<0.5 mm）和3年生的典型护坡植物种火棘及紫穗槐为研究对象,采用室内直剪的方式对根系进行根—土界面直剪摩擦试验。结果表明：（1）根—土及土—土界面的摩阻强度与垂直荷载呈明显的正线性关系;随土体粒径的增加,根—土及土—土界面的摩阻强度、摩擦系数、黏聚力和摩擦角均呈现下降趋势,且在相同粒径范围内,火棘根—土界面摩阻特性显著优于紫穗槐和素土;（2）根—土界面与素土界面的剪应力随位移的增长速率呈现先增大后减小的趋势;根—土界面剪应力与位移关系曲线呈现曲折蜿蜒式上升,而素土曲线表现为平缓式上升;（3）土体粒径越小,根土间接触面的比表面积越大,细小的土壤颗粒与根表面发生镶嵌,加大接触面的咬合力,使摩阻能力加大。研究结果对进一步探讨灌木植物根—土相互作用力学机制,以及利用灌木植物提高试验区边坡土体稳定性、防治坡面浅层滑落具有一定的理论指导意义。 相似文献
9.
青藏高原东北部黄土区草本植物根系加筋土的抗剪特性 总被引：6，自引：3，他引：3
为了分析草本植物根系加筋土的抗剪特性,以青藏高原东北部黄土区生长时间为1a的芨芨草根系作为加筋土的筋材,通过将根系加筋土试样制成9组不同含根量的扰动试样,进行了直剪摩擦试验。结果表明,当含根量与含水量一定时,根系加筋土的抗剪强度与剪切面上的法向压力呈正比,抗剪强度随垂直压力的增加基本呈线性增大;当根系加筋土含水量与垂直压力一定时,抗剪强度随含根量的增加而呈增大趋势,其黏聚力c和内摩擦角φ均有不同程度的提高,c值明显增加,且c值与含根量之间呈指数函数关系,φ值变化不大;在20.5,61.5,102.5,和143.5kPa这4种垂直压力下,根系加筋土抗剪强度和含根量之间均呈指数函数关系。说明供试种芨芨草根系可以显著提高试验区土体的抗剪强度,同时有助于增强坡体稳定性。 相似文献
10.
把植物防护后的边坡土体看作由土和根系组成的根-土复合体,建立根-土相互作用力学模型,定量分析植物根系的加筋作用,从而增强边坡土体的抗剪强度,减小水土流失和边坡病害的发生。为边坡工程的设计计算提供一定的参考。 相似文献
11.
低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响 总被引：2，自引：2，他引：0
【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。 相似文献
12.
Kyle Devey Michael Mucalo Gordon Rajendram Joseph Lane 《Communications in Soil Science and Plant Analysis》2015,46(4):72-80
Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing. 相似文献
13.
《中国生态农业学报》2014,(8)
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology, 相似文献
14.
I.L. Boyd 《Biological conservation》2010,143(7):1664-1674
“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options. 相似文献
15.
Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage 总被引：1，自引：0，他引：1
Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate. 相似文献
16.
M.A. Callaham Jr. J.M. BlairT.C. Todd D.J. KitchenM.R. Whiles 《Soil biology & biochemistry》2003,35(8):1079-1093
The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils. 相似文献
17.
Grete Skrede Berit Karoline Martinsen Anne-Berit Wold Stein-Erik Birkeland Kjersti Aaby 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(3):193-208
Abstract A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species. 相似文献
18.
Yoav Bashan Bernardo Salazar Ma. Esther Puente Macario Bacilio Robert Linderman 《Biology and Fertility of Soils》2009,45(6):585-594
To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse
trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus
were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB;
the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons
reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened
later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons
growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants,
no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi,
enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant.
In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after
30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination
only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity
to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as
compost or PGPB can either amplify the effect or else attenuate it. 相似文献
19.
Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value. 相似文献
20.
《Communications in Soil Science and Plant Analysis》2012,43(7):865-877
Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L?1 nitric acid (HNO3) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L?1 ammonium acetate (NH4OAc) and 1.0 mol L?1 HNO3 extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils. 相似文献