黄土高原植被演替不同阶段植物系数的变化与适应性评价

用4年长期定位试验资料,利用植物系数、蒸散量、土壤含水量和土壤水分对植物的有效性等指标,研究了黄土高原植被群落不同演替阶段(草本群落→灌木群落→早期森林群落→顶级群落)的耗水特性与生态适应性。结果表明:不同演替阶段,群落实际蒸散量主要受降水控制,群落间差异不显著(P＞0.05);土壤含水量是早期森林群落明显高于其它群落,草本群落明显高于灌木群落(P＜0.05);植物系数是灌木群落＞草本群落＞乔木群落,而顶级群落大于早期森林群落;土壤水分对植物的有效性是早期森林和顶级群落明显高于草本和灌木群落(P＜0.05)。因此,进行植被建设不但要考虑植物系数还要考虑土壤水分对不同植物的有效性。     

Consequences of Low Mate Availability in the Rare Self-Incompatible Species Brassica insularis

Abstract:  Self-incompatibility systems prevent self-fertilization in angiosperms. Although numerous S alleles are usually maintained by negative frequency-dependent selection, the number of S alleles can be low in small populations, which limits mate availability and reduces fecundity in endangered populations of self-incompatible plants. Despite the increasing evidence of the negative effect of self-incompatibility in small populations, the direct link between the number and the distribution of S alleles and their reproductive consequences has been rarely reported. Brassica insularis is a rare self-incompatible species with medium to very small populations. Results of a previous study showed that the smallest population has very few S alleles. We investigated whether reduced mate availability affects reproduction in this species. We compared the pollination success and the fruit set in 4 populations differing in population size and number of S alleles. Our results suggest that reproduction may be negatively affected by the low S-allele diversity in the smallest population. Nevertheless, other populations also had reduced fruit set that could not be attributed to self-incompatibility alone.     

Ontogenetic and spatio-temporal patterns of induced volatiles in <Emphasis Type="Italic">Glycine max</Emphasis> in the light of the optimal defence hypothesis

Summary. Plants attacked by herbivorous insects emit a blend of volatile compounds that serve as important host location cues for parasitoid wasps. Variability in the released blend may exist on the whole-plant and withinplant level and can affect the foraging efficiency of parasitoids. We comprehensively assessed the kinetics of herbivore-induced volatiles in soybean in the context of growth stage, plant organ, leaf age, and direction of signal transport. The observed patterns were used to test the predictions of the optimal defence hypothesis (OD). We found that plants in the vegetative stage emitted 10-fold more volatiles per biomass than reproductive plants and young leaves emitted >2.6 times more volatiles than old leaves. Systemic induction in single leaves was stronger and faster by one day in acropetal than in basipetal direction while no systemic induction was found in pods. Herbivore-damaged leaves had a 200-fold higher release rate than pods. To some extent these findings support the OD: i) indirect defence levels were increased in response to herbivory and ii) young leaves, which are more valuable, emitted more volatiles. However, the fact that reproductive structures emitted no constitutive or very few inducible volatiles is in seeming contrast to the OD predictions. We argue that in case of volatile emission the OD can only partially explain the patterns of defence allocation due to the peculiarity that volatiles act as signals not as toxins or repellents.     

Biologically active secondary metabolites in white clover (Trifolium repens L.) – a review focusing on contents in the plant, plant–pest interactions and transformation

Summary.  To exploit biologically active compounds from white clover (Trifolium repens L.) for suppressing weeds and soil-borne diseases, either as isolated products (biopesticides) or through cultivars with enhanced production of these compounds, the biologically active compounds must be identified, plant content measured, and their fate in soil known. The present review summarizes the published knowledge needed for such exploitation; providing essential information on structure and concentration of flavonols, flavones, condensed tannins, isoflavones, isoflavanones, pterocarpans, coumestans, cyanogenic glucosides, and saponins in healthy and stressed white clover plants. Various stresses and particular cultivars affect the concentrations of several of the compounds. Information on biological effects and the degradation/transformation of these compounds in plants or by microorganisms is available. There is no information on the degradation pathway in soil, the mechanisms of exudation and leaching of compounds from plants, and soil sorption properties of the compounds. The clover soil fatigue problem is increasing in grasslands and causes problems especially in organic farming. Research efforts focused on biological elements of clover soil fatigue have not explained it, and the influence of secondary metabolites has not been investigated. There are few investigations into the interaction between beneficial fungi/fungal-diseases and the occurrence of biologically active secondary metabolites in white clover plants. Such studies are critical to better understand beneficial fungi and pathogens.     

具双T-DNA区的大麦黄矮病毒复制酶基因RNAi植物表达载体的构建(英文)

RNAi系双链RNA诱导同源mRNA降解,导致特定基因表达沉默的一种现象.RNAi技术是通过基因工程防治植物病毒病的最佳途径.由大麦黄矮病毒(Barely yellow dwarfvirus,简称BYDV)引起的禾谷类黄矮病发病面积和危害程度在我国呈加重趋势.BYDV-GAV是当前流行的大麦黄矮病毒株系,本文针对BYDV-GAV复制酶基因序列,构建能在细胞内转录形成发卡RNA双链结构的表达盒,并将其置于中间载体pVec8-2b的T-DNA区,pVec8-2b的另一T-DNA区含有hpt选择报告基因表达盒.具双T-DNA区的病毒复制酶基因发卡RNA高效表达载体已导入根癌农杆菌,可用于诱导植物RNAi,创制无选择标记基因的抗大麦黄矮病转基因作物.     

利用根箱法解析水稻根际土壤中氮的行为

为研究水田土壤中氮的行为,施给15NH4 或15NO3-标记的硝胺(NH415NO3或15NH4NO3)的沙壤土(Shirasu soil)添充在根箱里,对Japonica水稻(品种Hinohikari)进行温室栽培6周.收割后,水稻植株分地上部和根部,对各自的全氮,15N atom％进行测定.根箱各区域的土壤按着鲜土形态进行采取后,对此全氮,NO3-N,水溶性NH4-N,KCl抽出NH4-N和其各自的15N atom％进行测定.研究结果表明,土壤全氮含量与栽培前相比,在非根际明显降低,但在根际比非根际要高,保持了与栽培前相同的水平.土壤NO3-N浓度从非根际到根际递增,但与其栽培前相比显著地降低,在整个根箱里,施给NO3-N的79％为因脱氮而损失.土壤中NO3-N的大部分来自于土壤氮化合物,来自施肥的比例却较低,尤其是在根际.反而,施给NO3-N的残存率约仅为16％左右,但其中有机态氮所占的比率在非根际里55％～86％,在根际却达到了93％.土壤水溶性NH4-N和KCl抽出NH4-N浓度靠近根际逐渐降低,而且在非根际两者匀由1∶10的比例存在,但在根际里水溶性NH4-N没被检索到.在非根际里,土壤KCl抽出NH4-N的35％～66％为来自施肥,但其比例在根际里却降到15％左右.在土壤中残存的来自施给NH4-N的氮化合物之中,有机态氮所占的比例在非根际里约为11％～65％,但在根际却达到了92％.以上结果表明,在水稻根际,氮的无机化和有机化的活性比非根际显著.     

中国北方典型污染城市主要绿化树种的滞尘效应(英文)

为研究城市人工植被的滞尘效应及其对城市生态环境的改善作用,以中国北方典型污染城市--临汾市为例.通过野外典型采样法和室内分析,测定了不同生活型主要绿化植物的滞尘能力,讨论了植物的滞尘量与滞尘时间的关系,并且研究了污染程度及距污染源距离对植物滞尘能力的影响.结果表明,在同一降尘条件下,不同生活型植物滞尘能力差异表现为草本植物的滞尘能力显著高于其它生活型植物(落叶乔木,灌木和藤本植物),而其它生活型植物间的滞尘能力无显著差异性;对针叶林来说,圆柏和雪松的滞尘能力间亦存在显著差异.在不同的污染情况下(污染程度及和污染源的距离不同),同种植物的滞尘能力亦有明显的差异,这与植物的高度和生长特性有关.而且,随时间推移,植物叶片的滞尘量呈现周期变化.而不是一个随时间无限增长的量,也有其饱和量.因此,在进行城市绿化设计时,需要综合考虑绿化树种的滞尘能力、滞尘周期及其生长环境情况等.     

气化熔融处理生活垃圾时灰渣的熔融特性

弄清垃圾灰渣的熔融特性对于保证生活垃圾的气化熔融与液态出渣具有重要作用。针对重庆生活垃圾灰与无烟煤灰形成的灰渣,实验研究了在不同的燃料添加量及添加剂条件下灰渣的熔点与粘度,并结合炉温的变化,分析了不同条件对灰渣熔融及液态出渣的影响。结果表明,灰渣的熔点与粘度均随燃料添加量的增加而升高;向燃料比为10%的灰渣中加入添加剂后,灰渣的熔点降低幅度较小,其粘度却随碱度的增加而增大以至熔渣流动性变差;燃料比为40%时,灰渣熔点与粘度均随添加剂的加入而显著降低,且向渣中加入CaO使得灰渣碱度为1.2时灰渣熔点较低且粘度较小,有利于其熔融与液态出渣。     

人工湿地污水处理对三种植物光合作用及叶绿素荧光特性的影响

人工湿地环境下,湿地植物的光合代谢过程与陆生自然环境有较大的不同.通过对人工湿地三种中生植物即薏米(Coixaquatica Roxb)、文殊兰(Crinum asiaticum)和蜘蛛兰(Hymenocallis Americana)进行污水处理,研究人工湿地对植物的光合作用和叶绿素荧光特性的影响.结果表明:(1)与陆地自然环境相比,在人工湿地环境下,薏米,文殊兰和蜘蛛兰的净光合速率(Pn),蒸腾速率(Tr),气孔导度(Gs),叶绿素含量,最大荧光(Fm)和PSII最大光化学效率(Fv/Fm)均降低,而胞间CO2浓度(Ci)和初始荧光(Fo)升高.其中叶绿素含量,Fo和Fv/Fm在四月份生长旺盛期差异极显著(P<0.01),Gs差异显著(P<0.05).(2)在整个生长期,三种植物的光合参数和荧光参数的变化趋势不是单一的上升或下降,不同植物其变化过程和变化幅度也不一样.蜘蛛兰在生长旺盛期较薏米和文殊兰Pn,Gs,Fv/Fm,Fm,Fo大,而Ci较薏米和文殊兰低.可见人工湿地污水处理对三种植物光合作用和叶绿素荧光特性均有影响,但对各植物影响不一致.综合各项参数,蜘蛛兰耐性强于薏米和文殊兰.     

垃圾焚烧飞灰中重金属的分布与性质

以华东某城市为案例,研究我国城市生活垃圾焚烧飞灰中重金属污染物的分布和性质.结果表明,重金属污染物主要集中于小粒径飞灰中.连续提取实验表明Cd、Pb、Mg、Cu等重金属在环境中具有较强的迁移性,Ag和Sn相对比较稳定.重金属元素的溶出与酸度密切相关,与环境关系较大的Cd、Co、Cu、Mn、Ni、Pb和Zn等元素在酸性条件下表现出最强的溶出能力,但Cr和As则倾向于在碱性条件下溶出.