铅、锌及其交互作用对鱼腥草(Houttuynia cordata)叶绿素含量及抗氧化酶系统的影响

采用营养液培养方法研究铅、锌及其交互作用对鱼腥草叶绿素含量及抗氧化酶系统的影响。实验结果显示，随着Pb浓度的增加，鱼腥草叶绿素含量逐渐降低但无显著变化。Zn在一定浓度下能提高鱼腥草叶绿素含量，而在高浓度Zn胁迫下，叶绿素含量急剧下降。鱼腥草叶片中SOD、POD和CAT3种酶活性都是随着Pb浓度的增加先上升后下降。随着Zn浓度的增加，SOD和CAT也是先上升后下降，POD则是逐渐上升。Pb—Zn交互作用增加了鱼腥草叶绿素含量，对SOD和POD活性具有抑制作用，对CAT活性影响不明显。同时研究结果还表明，单一Pb、Zn对鱼腥草叶绿素含量和抗氧化酶系统的影响大于Pb、Zn二者的共同作用，其中高浓度Zn对鱼腥草的伤害作用最大，而当溶液Pb处理浓度达到400mg／L时，鱼腥草仍能正常生长，说明鱼腥草具有较强的耐Pb能力。     

薇甘菊花芽分化前后内源激素及相关基因表达的研究

以云南省瑞丽市勐秀林场扦插种植的薇甘菊为试材,采用液相色谱串联质谱(LC-MS/MS)技术对花芽未分化期和花序原基分化期花芽中的生长素(IAA)、赤霉素(GA)、脱落酸(ABA)、反式玉米素(tZ)、异戊烯腺嘌呤(IP)、1-氨基环丙烷羧酸(ACC)、茉莉酸(JA)和水杨酸(SA)含量进行定量分析,同时基于转录组基因功能注释数据对内源激素合成、代谢及信号转导途径相关基因进行表达分析,以探讨不同内源激素对薇甘菊花芽形成的调控作用,以及内源激素合成和信号转导途径相关基因调控薇甘菊花芽分化的机制,为后期通过外源激素调控薇甘菊内源激素水平的方式来控制薇甘菊的有性繁殖提供理论和技术支持。结果表明：(1)薇甘菊未分化期花芽中GA₁₅、GA₁₉、GA₂₀、GA₂₄、IAA、ABA和ETH含量低于花序原基分化期,而未分化期花芽中两种细胞分裂素tZ和IP含量显著高于花序原基分化期。(2)基于RNA-seq测序结果,在薇甘菊两个花芽分化时期共获得7 116个差异表达基因(DEGs),其中上调3 907个,下调3 209个。(3)在内源激素合成方面,参与GA₁₅、GA₁₉、GA₂₀、GA₂₄、IAA、ABA和ACC合成的大量DEGs在花序原基分化期上调表达,这与它们在薇甘菊花序原基分化期的高含量趋势相一致;参与IAA合成的YUCCA基因家族和ACC合成的ACS基因在花序原基分化期的高表达也可能参与促进薇甘菊花芽分化。(4)在植物激素转导途径中,在花序原基分化期,生长素信号转导途径通过AUX/IAA(gene-E3N88_07743)的下调表达和ARF(gene-E3N88_41119)的上调表达,乙烯信号转导途径通过ERF(gene-E3N88_41547)的上调表达,赤霉素信号转导途径通过GID1(gene-E3N88_19448)基因的上调表达,细胞分裂素信号转导途径通过B-ARR(gene-E3N88_28086)和A-RRR(gene-E3N88_40764)基因的下调表达,脱落酸途径通过AREB(gene-E3N88_18558)基因的上调表达,茉莉酸信号转导途径通过JAZ(gene-E3N88_05628)的上调表达和MYC2(gene-E3N88_32405)的下调表达来调控薇甘菊花芽分化。研究发现,高水平的GA₁₅、GA₁₉、GA₂₀、GA₂₄、IAA、ABA和ACC有利于薇甘菊的花芽分化;薇甘菊在花芽分化过程中通过改变不同种类内源激素合成、代谢基因的表达来调控激素浓度,而激素又通过信号转导途径引起下游基因的表达,进而调控薇甘菊的花芽分化。     

Weak Competition Among Tropical Tree Seedlings: Implications for Species Coexistence

The intensity of competition among forest tree seedlings is poorly understood, but has important ramifications for their recruitment and for the maintenance of species diversity. Intense competition among seedlings could allow competitively dominant species to exclude subordinate species. Alternatively, the low density and small stature of forest tree seedlings could preclude intense interseedling competition. In this case, other processes, such as size-asymmetric competition with adults, interactions with consumers, or neutral dynamics would prevail as those structuring the forest understory. We tested the intensity of, and potential for, intraspecific competition among tree seedlings of three species ( Brosimum alicastrum , Matisia cordata , and Pouteria reticulata ) in two Neotropical rain forests. We reduced stem densities by up to 90 percent and monitored individual growth and survival rates for up to 24 mo. Individual growth and survival rates were generally unrelated to stem density. Contrary to the predicted behavior of intensely competing plant populations, the distribution of individual heights did not become more left-skewed with time for any species, regardless of plot density; i.e. , excesses of short, suppressed individuals did not accumulate in high-density plots. We further measured the overlap of zones of influence (ZOIs) to assess the potential for resource competition. Seedling ZOIs overlapped only slightly in extremely dense monodominant plots, and even less in ambient-density plots of mixed composition. Our results thus suggest that interseedling competition was weak. Given the low density of tree seedlings in Neotropical forests, we infer that resource competition among seedlings may be irrelevant to their recruitment.     

山西历山千金榆群落物种多样性研究

在野外调查的基础上,应用Patric丰富度指数（R₀）、Simpson指数（λ）和Shannon-Wiener多样性指数（H'）、Pielou均匀度指数（E₁）和Alatalo均匀度指数（E₅）等对山西历山千金榆群落物种多样性进行了分析研究。结果表明：（1）千金榆群落R₀、H'、E₁和E₅等多样性指数变化趋势基本一致,λ与H'等指数变化趋势相反;综合考虑：千金榆群落的物种多样性顺序为群丛Ⅰ（千金榆-山胡椒-糙苏群丛） > 群丛Ⅲ（千金榆-连翘-糙苏群丛） > 群丛Ⅳ（千金榆-土庄绣线菊+连翘-鹿药群丛） > 群丛Ⅶ（千金榆-接骨木-贝加尔唐松草+淫羊藿群丛） > 群丛Ⅱ（千金榆-小花溲疏-糙苏群丛） > 群丛Ⅵ（千金榆-小花溲疏-香根芹群丛） > 群丛Ⅴ（千金榆-小花溲疏-鹿药群丛）;（2）乔木层多样性与灌木层多样性、草本层多样性呈负相关（P<0.05）,而灌木层多样性与草本层的多样性相关不显著（P>0.05）;（3）千金榆各群丛间多样性指数差异不显著。     

薇甘菊和飞机草抗氧化物和膜脂过氧化物对光照和土壤水分的响应

田间温室控制条件下研究入侵杂草薇甘菊(Mikania micrantha)和飞机草(Chromolaena odoratum)在不同光照(高、中、低光照)和土壤水分(高、中、低水分含量)交互作用下, 叶片超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性, 脯氨酸(Pro)、谷胱甘肽(GSH)以及膜脂过氧化物丙二醛(MDA)含量的变化, 探讨两种杂草对不同光照和土壤水分交互作用的生理适应性。结果表明: 高光下低水处理的两种杂草MDA含量均显著高于全水处理, 表现出明显的胁迫。此胁迫条件下薇甘菊通过迅速提高SOD和CAT活性, 提高Pro和GSH含量来清除活性氧, 维持代谢平衡, 但不能在干旱条件下维持较长时间; 飞机草的SOD活性、Pro和GSH含量也迅速提高, 在高光缺水的适应性响应中起了重要作用, CAT则未能发挥保护作用。相对于其他光照, 低光显著降低了薇甘菊的SOD、CAT活性和MDA含量, 而对飞机草上述指标的影响较小, 说明低光降低了两种杂草尤其是薇甘菊的抗氧化物代谢水平。     

田野菟丝子寄生对薇甘菊气孔行为的影响

田野菟丝子寄生已成为当前控制薇甘菊入侵蔓延的最佳生物防治手段之一。应用扫描电子显微镜技术,观察并统计分析了田野菟丝子寄生对薇甘菊叶片气孔形态参数的影响,为了解寄生对薇甘菊生理特征的影响提供一定的形态学依据。结果表明,田野菟丝子寄生对薇甘菊叶片的气孔长宽比和气孔面积产生显著影响:对照薇甘菊叶片的气孔长宽比和气孔面积表现为双峰日变化动态;而被寄生的薇甘菊的叶片气孔长宽比和气孔面积则表现为单峰日变化规律。对照薇甘菊气孔的长宽比分别在12:00和10:00,气孔面积分别在10:00和14:00达到日变化中的最大值与最小值;在15:00到16:00气孔长宽比和气孔面积再一次达到一个峰值,使气孔长宽比和气孔面积的日波动形成一个双峰曲线。被寄生的薇甘菊的叶片气孔长宽比和气孔面积则表现出单峰曲线,峰值分别出现在12:00和14:00。田野菟丝子寄生对薇甘菊的气孔密度没有产生显著影响。     

寄生植物菟丝子防治外来种薇甘菊研究初探

利用寄生植物田野菟丝子(Cuscuta campestris Yunker)作为外来杂草薇甘菊(Mikania micrantha H．B．k)的生物防治手段,研究了田野菟丝子对薇甘菊的光合作用及生长的影响。结果表明：田野菟丝子寄生于薇甘菊30d左右,薇甘菊单株叶片数、地上茎长度和生物量开始减少,光合速率、蒸腾速率、气孔导度、叶绿素含量以及叶绿素荧光Fv／Fm也开始降低。经过约2个月时间,以上的几个生长指标和生理指标均显著降低。在野外自然状态下,田野菟丝子由最初撒播面积约0．0l辞,很快发展到20m。左右的大块面积,离侵染源中心的最大扩散距离达到5m以上。田野菟丝子寄生可以严重影响薇甘菊茎叶生长及开花结实,可望成为根本上解决薇甘菊危害的一种生物控制技术,而且也可以缓解药用菟丝子资源匮乏的问题。结合国内外最新进展,提出有关田野菟丝子与其寄主相互关系中亟待解决的几个问题。     

Do the capacity and kinetics for modification of xanthophyll cycle pool size depend on growth irradiance in temperate trees?

The present study investigated the interaction of growth irradiance (Q_int) with leaf capacity for and kinetics of adjustment of the pool size of xanthophyll cycle carotenoids (sum of violaxanthin, antheraxanthin and zeaxanthin; VAZ) and photosynthetic electron transport rate (J_max) after changes in leaf light environment. Individual leaves of lower‐canopy/lower photosynthetic capacity species Tilia cordata Mill. and upper canopy/higher photosynthetic capacity species Populus tremula L. were either illuminated by additional light of 500–800 µmol m^?2 s^?1 for 12 h photoperiod or enclosed in shade bags. The extra irradiance increased the total amount of light intercepted by two‐fold for the upper and 10–15‐fold for the lower canopy leaves, whereas the shade bags transmitted 45% of incident irradiance. In control leaves, VAZ/area, VAZ/Chl and J_max were positively associated with leaf growth irradiance (Q_int). After 11 d extra illumination, VAZ/Chl increased in all cases due to a strong reduction in foliar chlorophyll, but VAZ/area increased in the upper canopy leaves of both species, and remained constant or decreased in the lower canopy leaves of T. cordata. The slope for VAZ/area changes with cumulative extra irradiance was positively associated with Q_int only in T. cordata, but not in P. tremula. Nevertheless, all leaves of P. tremula increased VAZ/area more than the most responsive leaves of T. cordata. Shading reduced VAZ content only in P. tremula, but not in T. cordata, again demonstrating that P. tremula is a more responsive species. Compatible with the hypothesis of the role of VAZ in photoprotection, the rates of photosynthetic electron transport declined less in P. tremula than in T. cordata after the extra irradiance treatment. However, foliar chlorophyll contents of the exposed leaves declined significantly more in the upper canopy of P. tremula, which is not consistent with the suggestion that the leaves with the highest VAZ content are more resistant to photoinhibition. This study demonstrates that previous leaf light environment may significantly affect the adaptation capacity of foliage to altered light environment, and also that species differences in photosynthetic capacity and acclimation potentials importantly alter this interaction.     

外来杂草薇甘菊种群分布格局研究

在3个群落中设置样方,采用方差/均值比率法测定了薇甘菊种群的分布格局类型。结果表明,薇甘菊种群的分布格局主要受自身的生物学特征和微环境的影响,呈随机或集群分布。随机分布的种群其聚集强度指标扩散型指数、丛生指数、聚块性指标和平均拥挤度多对1.0没有显著的偏离,负二项参数则较大;而聚集分布的种群其聚集强度指标则符合聚集特征。     

超临界CO2萃取鱼腥草的挥发油成分

从萃取的压力、温度、流量和时间等条件探讨超临界CO2萃取对鱼腥草(Houttuynia cordata Thunb.)挥发油萃取率的影响,确定最佳萃取条件为萃取压力20mPa、温度35℃、CO2流量40kg/h和萃取时间80min,鱼腥草挥发油得率为1．76％。而水蒸气蒸馏提取和石油醚提取的得率分别为0．05％和0．08％。超临界CO2法萃取的鱼腥草挥发油收率高,萃取时间短。