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。     

Involvement of ABA in reduced photosynthesis and stomatal conductance in <Emphasis Type="Italic">Cuscuta campestris — Mikania micrantha</Emphasis> association

We investigated whether changes in abscisic acid (ABA) content in leaves of Mikania micrantha infected by the holoparasite Cuscuta campestris at five growth stages, influenced the host stomatal conductance (g_s), transpiration rate (E) and net photosynthetic rate (P_N). C. campestris infection caused a negative effect on g_s, E and P_N of the host plants. ABA content in host leaves infected by C. campestris was significantly lower at 6 d after parasitization (DAP) and significantly higher at 13 and 33 DAP, relative to uninfected controls. In the parasite, ABA content was lowest at 13 DAP and then sharply increased to the maximum at 26 DAP. Moreover, the ABA content in the parasite was always lower than in the infected host leaves. The results suggest that an increase in host ABA concentration contributes to reduced host g_s, E and P_N in the holoparasitic C. campestris — M. micrantha association.     

Influence of the obligate parasite Cuscuta campestris on growth and biomass allocation of its host Mikania micrantha

As a means of biologically controlling Mikania micrantha H.B.K. in South China, the influence of the obligate parasite Cuscuta campestris Yuncker on its growth and biomass allocation was studied using pot trials. The effect of C. campestris on M. micrantha became greater with time, such that the host biomass was only 1.8% of the control after 60 d of parasitism and by day 72 almost all the aerial parts of the host plants had died. Afterwards, the hosts and the remnant parasite shoots re-grew but the total biomass of the hosts was still significantly lower than that of the controls. The infection by C. campestris greatly increased the shoot:root dry weight ratio and the allocation to stems of the infected plants from 40 to 50 d after parasitization, but decreased their relative growth rate and unit leaf rate starting from 20 d after parasitization and their leaf area ratio from 30 to 60 d after parasitization. Cuscuta campestris significantly reduced the total biomass, changed the biomass allocation patterns, and completely inhibited the flowering of the infected M. micrantha plants. These results indicate that the use of C. campestris could be a potentially effective way of controlling M. micrantha.     

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。     

Effects of virus infection and growth irradiance on fitness components and photosynthetic properties of Eupatorium makinoi (Compositae)

We examined the effects of geminivirus infection on fitness components and on photosynthetic properties of the host plant, Eupatorium makinoi, grown at two irradiance levels in a natural-light greenhouse. Under the low-light condition (13% full sunlight), more than a half of the infected plants died during the 9-mo experiment, while most of uninfected plants survived. Growth rate was also lowered by infection. At high light (50% full sunlight), by contrast, virus infection did not cause mortality despite slight decrease in growth rate. Flowering occurred only at high light, and reproductive outputs of the plants were markedly reduced by the infection. Infected leaves had distinct yellow variegations and, when compared with uninfected leaves, they showed (1) comparable light-saturated photosynthetic rate per unit area, but (2) lower initial slope of light-response curve of photosynthesis on an incident irradiance basis. The lower initial slope was mainly due to reduction of light-harvesting chlorophyll-protein complexes in the variegated parts. Since the differences in plant performance, depending both on infection and on growth irradiance, were largely explained by the differences in growth rate and/or plant size, the reduced photosynthetic production in the infected plants would be a major factor explaining the inferior performance of the host plants.     

薇甘菊可溶性蛋白和抗氧化酶活性对田野菟丝子不同寄生密度的响应

为探求利用寄生植物田野菟丝予对入侵杂草薇甘菊进行生物控制的有效措施,研究了薇甘菊对0、1、2、4和8棵田野菟丝子幼苗寄生在可溶性蛋白和一些抗氧化酶活性方面的响应.寄生后30 d,1棵田野菟丝子/株薇甘菊（以下简称棵/株）以上的寄生密度导致薇甘菊可溶性蛋白含量显著降低.和对照相比,在寄生密度为1棵/株时,超氧物歧化酶(S...     

薇甘菊叶片对光反射、透射和利用效率及其与同群落植物之比较研究

该文对薇甘菊及其所在群落内19种植物(草本和木本)的叶片透射率、反射率和光合特征指标进行了测定, 结果表明:薇甘菊与其它植物透射和反射图谱的变化趋势都比较相近, 在各个光学特征指标与光合相关指标的相互关系中, 薇甘菊并没有表现出区别于同一群落内其它植物的特征。从平均值来看, 200-800 nm下叶片反射率和透射率由大到小依次为: 薇甘菊>草本植物>木本植物, 薇甘菊各光学植被指标(SR680、SR750和PRI)均低于其它植物的平均值, 但是其光合能力(光利用效率、水分利用效率、电子传递速率和净光合速率)与其它植物接近或稍高。而且, 薇甘菊夏季叶片反射和透射率明显高于冬季, 这有利于散失夏季过多光照和充分利用冬季短缺光照。薇甘菊叶片的上述光学特征, 可能是其生长于其它植物表面强光照环境的一种适应性表现, 有利于其在入侵地快速生长。     

外来入侵植物薇甘菊(Mikania micrantha)对温度升高的响应

为探讨全球变化温度升高对外来入侵植物薇甘菊(Mikania micrantha)化感作用和入侵能力的影响,研究不同温度(22、26和30℃)处理对其种子萌发、幼苗生长、生物量分配、挥发物成分和化感作用的影响。结果表明,薇甘菊种子在温度为22、26和30℃时的萌发率分别为29.2%、52.4%和75.2%。30℃条件下薇甘菊种子萌发率最高,萌发速度快。温度升高显著增加薇甘菊茎的生长、增加对茎的生物量分配。GC-MS和GC测定显示,温度升高改变了薇甘菊挥发物的化学成分。同时,生物测定表明,温度升高增强薇甘菊挥发物对萝卜(Raphanus sativus)和油菜(Brassica campestris)的化感作用。说明温度升高促进了薇甘菊种子的萌发和生长,同时增强了该植物的化感作用,温度升高可能加速薇甘菊的生物入侵。     

Effect of light on in vivo urediniospore germination, lesion development and sporulation of Puccinia hemerocallidis on daylily and Puccinia pelargoniizonalis on geranium

The presence of rusts of daylily and geranium caused respectively by Puccinia hemerocallidis and P. pelargoniizonalis can result in reduced value of these ornamental crops. Experiments were conducted to determine the effects of fluorescent light and sunlight on urediniospore germination, germ tube elongation, lesion development and sporulation of the two fungal pathogens on detached leaves and whole plants. Exposure of dry or hydrated urediniospores of P. hemerocallidis to cool white fluorescent light (600 μmol s(-1) m(-2)) or to sunlight (950-1910 μmol s(-1) m(-2)) for 2 h or 4 h significantly reduced germination and germ tube elongation on detached daylily leaves. Germination but not germ tube elongation of hydrated urediniospores of P. pelargoniizonalis on detached geranium leaves was significantly reduced when exposed to fluorescent light for 2 h or 4 h. A 4 h exposure to either light source significantly reduced lesion development of P. hemerocallidis on detached daylily leaves with fewer lesions developing from hydrated compared to dry urediniospores. Sunlight exposures of 1 h and 2 h of hydrated and dry urediniospores respectively significantly reduced lesion development by either fungus on whole plants. Increasing exposure to fluorescent light negatively affected sporulation of P. hemerocallidis and P. pelargoniizonalis. Complete suppression of sporulation was not observed for either fungus with up to a 24 h exposure to fluorescent light. Light exposure negatively affected disease development by P. hemerocallidis and P. pelargoniizonalis. Exposure to high light intensities may affect spread of rust diseases on ornamental plants.     

薇甘菊叶片对光反射、透射和利用效率及其与同群落植物之比较研究

该文对薇甘菊及其所在群落内19种植物（草本和木本）的叶片透射率、反射率和光合特征指标进行了测定,结果表明：薇甘菊与其它植物透射和反射图谱的变化趋势都比较相近,在各个光学特征指标与光合相关指标的相互关系中,薇甘菊并没有表现出区别于同一群落内其它植物的特征。从平均值来看,200—800nm下叶片反射率和透射率由大到小依次为：薇甘菊〉草本植物〉木本植物,薇甘菊各光学植被指标（SR680、SR750和PRO均低于其它植物的平均值,但是其光合能力（光利用效率、水分利用效率、电子传递速率和净光合速率）与其它植物接近或稍高。而且,薇甘菊夏季叶片反射和透射率明显高于冬季,这有利于散失夏季过多光照和充分利用冬季短缺光照。薇甘菊叶片的上述光学特征,可能是其生长于其它植物表面强光照环境的一种适应性表现,有利于其在入侵地快速生长。     

Phytochrome Control of Chlorophyll Content in Mature Attached Leaves of Petunia axillaris

Petunia axillaris plants were grown under white light (photoperiod10 h). Pulses of end-of-day far-red light, but not red lightat the end of the day slowed down the accumulation of chlorophyllin expanding, greening leaves and reduced chlorophyll contentin mature leaves. The chlorophyll a / b ratio was unaffected.Low phytochrome photoequilibria reduced chlorophyll contentin mature leaves without affecting leaf area or d. wt. Thiseffect occurred even before senescence was triggered in thecontrol plants having high phytochrome photoequilibria     

Susceptibility of Tobacco Leaves to Photoinhibition following Infection with Two Strains of Tobacco Mosaic Virus under Different Light and Nitrogen Nutrition Regimes

Sensitivity to photoinhibition under high light stress (2000 [mu]mol photons m-2 s-1 for 2 h in air) and recovery from this stress were examined in leaves of control, uninfected tobacco (Nicotiana tabacum cv Xanthi) leaves and in leaves in tobacco plants infected with tobacco mosaic virus (TMV) when grown under low light (150-200 [mu]mol photons m-2 s-1) or high light (1200 [mu]mol photons m-2 s-1) with high (8.0 mM) or low (0.5 mM) nitrate supply. Photoinhibition was monitored using the dark-adapted fluorescence parameters variable fluorescence/maximum fluorescence, an indicator of photosynthetic efficiency that correlated well with the quantum yield of photosynthetic oxygen evolution, and initial fluorescence, potentially an indicator of photoinhibitory damage. Susceptibility to photoinhibition was greater in low light- and low nitrogen-grown control plants than in high light- or high nitrogen-treated plants. Compared with uninfected controls, infection with the masked strain PV42 increased susceptibility to photoinhibition only in plants grown under low light/low nitrogen conditions. In expanding leaves, infection with severe strain TMV PV230 markedly accelerated photoinhibition under these conditions and under high light/low nitrogen conditions, even before visible symptoms were evident. High nitrogen levels during growth protected against this accelerated photoinhibitory response to virus infection during light stress and generally promoted recovery, at least prior to symptom development. As symptoms developed, the yellow regions provided evidence for chronic photoinhibitory damage, prior to and during the stress treatment, irrespective of growth conditions. Green regions of leaves showing visible symptoms were generally indistinguishable from control, uninfected plants during photoinhibitory stress and recovery. In developed leaves that remained free of visible symptoms during the experiments, in spite of the accumulation of about the same amounts of virus protein (S. Balachandran, C.B. Osmond, A. Makino [1994] Plant Physiol 104: 1043-1050) infection led to an acceleration of photoinhibition during stress treatments, especially in low light/low nitrogen treatments, in which chronic photoinhibitory damage was evident. These studies suggest a role for photoinhibitory damage in the acceleration of visible symptom development following TMV PV230 infection of expanding leaves, as well as in acceleration of senescence in developed leaves without visible symptoms.     

Host plant mediation of diapause induction in the cabbage beetle, Colaphellus bowringi Baly （Coleoptera： Chrysomelidae）

The cabbage beetle, Colaphellus bowringiBaly （Coleoptera： Chrysomelidae）, is a serious pest of crucifers in China, undergoing an imaginal summer and winter diapause in the soil. The effects of host plants on diapause incidence were tested in the beetle. The ratio of adults entering diapause was significantly low when they fed on the mature leaves of Chinese cabbage Shanghaiqin （Brassica chinesis var communis） than those feeding on Chinese cabbage Suzhouqin （Brassica chinesis var communis）, radish （Raphanus sativus var longipinnatus） and stem mustard （Brassicajuncea vat tumida） at 25℃ combined with 13：11 （L： D） h. Fewer adults entered diapause on young leaves compared to physiologically aged and mature radish leaves at 25℃ combined with 13：11 （L： D） h. The effect of host plant species on diapause induction was also evident under continuously dark rearing conditions or at different photoperiods. These experimental results demonstrate that host plant mediation of diapause induction exists in the cabbage beetle. However, at temperatures ≤20℃ or photoperiods of 16：8 （L： D） h combined with 25℃, all individuals entered diapause regardless of the host plants, indicating that the effects of host plants on diapause induction could be expressed only within a limited range of temperatures and photoperiods.     

Striga hermonthica reduces photosynthesis in sorghum: the importance of stomatal limitations and a potential role for ABA?

We report the effects of the root hemiparasite Striga hermonthica (Del.) Benth. on the growth and photosynthesis of two cultivars of sorghum: CSH-1, a susceptible variety, and Ochuti, which shows some tolerance to S. hermonthica in the field. Within 4 d of parasite attachment to the host roots, infected plants of both cultivars were significantly shorter than uninfected controls. At 55 d, infected plants of both cultivars had significantly less shoot and root biomass, and significantly smaller leaf areas than uninfected controls. The dry weight of S. hermonthica attached to host roots was insufficient at this stage to explain the decreased growth in terms of a competing sink for carbon and nitrogen. Leaf chlorophyll and nitrogen per unit area were greater in infected plants of both cultivars compared with control plants. However, whereas photosynthesis and transpiration in young leaves of infected CSH-1 plants declined with time when compared with controls, the rates in infected Ochuti plants were similar to those in uninfected controls throughout the time course of observation. In both cultivars, a strong correlation was observed between the rate of photosynthesis and stomatal conductance during photosynthetic induction, but infection resulted in a much slower induction than in controls. In CSH-1 plants, both steady-state photosynthesis and stomatal conductance were lower than in controls, whereas in leaves of Ochuti steady-state photosynthesis and stomatal conductance eventually reached the same values as in the control leaves. Results from AlC_i analysis and also from determination of ¹³C isotope discrimination were consistent with a stomatal limitation to photosynthesis in the leaves of Striga-infected plants. The concentration of the plant growth regulator abscisic acid (ABA) was measured in the xylem sap of infected CSH-1 plants only, and was found to be twice that of uninfected plants. A possible role of ABA in determining host response to infection by S. hermonthica is discussed.     

Physiology of the parasitic association between maize and witchweed (Striga hermonthica): is ABA involved?

Striga hermonthica (Del.) Benth. is an obligate hemiparasiticangiosperm which can cause severe losses of yield in cerealcrops in the semi-arid tropics. The effects of this parasiteon the growth and stomatal conductance of three varieties ofmaize (Zea mays L.) during the first 6 weeks of the associationhave been studied. From 24 d after planting (DAP), infectedplants were significantly shorter than uninfected controls.When the plants were harvested 45 DAP, infected plants had fewerfully expanded leaves, less leaf biomass and less pseudo-stembiomass than uninfected controls. However, the parasitized plantshad more root biomass and hence a higher root:shoot ratio thanuninfected controls. The stomatal conductance of infected hostswas severely inhibited by comparison with that in uninfectedplants. The possibility that abscisic acid (ABA) may be involved inthe regulation of the parasitic association was investigated.ABA concentrations in leaf tissue of maize (cv. Cargimontana)and S. hermonthica were determined by radioimmunoassay. Whilethere was a difference between cultivars in the extent of theresponse, the concentrations of ABA were significantly higherin infected maize plants than in the uninfected controls. InS. hermonthica, leaf tissue ABA concentration was found to bean order of magnitude higher than in the host leaf tissue. Detachedleaves of S. hermonthica which were dehydrated at room temperatureuntil they had lost 10–20% of their fresh weight containedthree times the ABA concentration of control leaves. This suggeststhat leaves of S. hermonthica can synthesize or re-mobilizeABA in response to water deficit. It is not yet known whetherthis contributes to the higher concentration in infected hosts,but the results suggest that ABA has a role in this parasiticassociation. Key words: Striga hermonthica, abscisic acid, growth, parasitic angiosperm, stomatal conductance     

Survival and persistence of bioluminescent Xanthomonas campestris pv. campestris on host and non-host plants in the field environment

Dispersal and persistence of a pathogenic strain of Xanthomonas campestris pv. campestris , genetically engineered to bioluminesce, was followed in and on host and non-host plants in the field environment. Black rot susceptible cabbage plants were mist inoculated with the bioluminescent strain only, or were mist inoculated with X. campestris pv. vesicatoria or a weakly pathogenic strain of X. c. campestris 1 week before challenge inoculation with the bioluminescent strain. Growth of the bioluminescent strain was detected with a low-light, charge-coupled device camera or through bioluminescence measurements of broth-enrichment cultures of leaf disk samples. Bioluminescent X. c. campestris could often be observed as populations on symptomless leaves or in lesions, and persisted as a vascular endophyte for more than 6 months throughout the winter growing season. Dispersal to cruciferous and non-cruciferous weeds was frequently detected. Pre-inoculation with X. c. vesicatoria or the weakly pathogenic X. c. campestris did not significantly affect the movement and persistence of the bioluminescent strain nor reduce the incidence of black rot disease.     

薇苷菊乙醇提取物对桔全爪螨种群的控制作用

研究薇苷菊(Mikaniamicrantha)乙醇提取物对桔全爪螨(Panonychuscitri)种群的控制作用,并比较其与常用杀螨剂哒螨灵的效果.在实验室用0.1、0.2、0.4g·L^-13个浓度提取物分别喷布桔全爪螨卵、幼螨和若螨,除了01g·L^-1浓度处理对卵没有效果外,该处理幼螨、若螨存活率以及另2个浓度处理3个螨态的存活率都显著下降.在非选择性试验条件下,用这3个浓度的提取物处理叶片饲养的桔全爪螨雌螨繁殖量显著减少,寿命也显著缩短.在田间用这3个浓度的提取物在20d内连喷2次,桔全爪螨卵、幼螨和若螨的存活率都低于对照,干扰作用控制指数分别为0518、0.292、0.277,即对种群增长控制的效果分别为4.82%、70.8%、72.3%,比15%哒螨灵乳油2000倍处理更有效控制桔全爪螨的田间种群.田间试验结果还表明,提取物处理的叶片比对照和哒螨灵处理的浓绿,而且对桔全爪螨的天敌较安全     

Crude Exopolysaccharides (EPS) from Xanthomonas campestris pv. manihotis, Xanthomonas campestris pv. Campestris and Commercial Xanthan Gum as Inducers of Protection in Coffee Plants against Hemileia vastatrix

Foliar-applied exopolysaccharides, obtained from bacterial cells of either Xanthomonas campestris pv. manihotis (EPS-Xcm) or Xanthomonas campestris pv. campestris (EPS-Xcc), isolate NRRL B-1459, were tested for their ability to induce local and systemic protection against coffee leaf rust caused by Hemileia vastatrix. Both preparations of EPS were effective in inducing local and systemic protection when applied 72 h before challenge with the pathogen. Protection was also observed when plants were treated with different concentrations of a commercially available preparation of xanthan gum (CXG).
Systemic protection was induced by EPS-Xcm, EPS-Xcc and CXG even after the removal of the treated leaves immediately before the challenge. Local protection lasted at least 5 weeks, when EPS-Xcm was applied at the concentration of 100 μg equivalents of glucose/ml. Fluorescent microscopic studies of pathogen development in protected and control leaves indicated that neither the germination, appressoria formation nor the number of infection sites were affected by treatment with EPS-Xcm.     

Cardinium infection alters cotton defense and detoxification metabolism of its whitefly host

Field monitoring revealed that the infection ratio of the bacterial symbiont Cardinium in the whitefly (Bemisia tabaci MED) was relatively low in northern China. However, the role of this symbiont and the symbiont–whitefly–host plant interaction mechanism are poorly understood. We investigated the influence of Cardinium on the competitiveness of the host whitefly and the physiological interaction between the host plants and host whiteflies. Cardinium-infected whiteflies were displaced by uninfected whiteflies after 5 generations, which showed that Cardinium infection reduced whitefly competitiveness. The defense response genes of cotton significantly decreased under infestation by infected whiteflies compared to uninfected whiteflies. The expression of detoxification metabolism genes, especially the uridine 5ʹ-diphospho-glucuronyltransferase and P450 genes, in infected whiteflies significantly decreased. These results demonstrated that Cardinium could inhibit the defense response of the host plant and decrease the detoxification metabolism ability of the host whitefly. The reduced competitiveness of infected whiteflies may be associated with the inhibition of the whitefly detoxification metabolism by Cardinium, resulting in the reduced performance of infected whiteflies. However, Cardinium infection can suppress plant defenses, which may benefit both infected and uninfected whiteflies when they coexist. This research illustrates the symbiont–whitefly–host plant interaction mechanism and the population dynamics of the whitefly.     

Growth and hare, Lepus timidus, resistance of white birch, Betula pendula, clones grown in different soil types

Many plant species have the ability to expand laterally through space by clonal growth. Plant pathogens can affect clonal growth characteristics thereby altering the success of host plants within populations and of clonal species within communities. We conducted a greenhouse experiment to determine the effects of the systemic fungal pathogen, Epichloë glyceriae , on clonal growth patterns of its host grass, Glyceria striata . We found that infected and uninfected plants produced similar total biomass and numbers of tillers plus primary stolons per mother ramet. However, biomass allocation to tillering (vegetative growth) vs stolon production (clonal growth) was significantly affected by pathogen infection. Infected plants produced more stolons and clonal growth biomass than uninfected plants while mother ramets of uninfected plants produced more tillers and biomass than infected plants. Stolon architecture of infected and uninfected plants also differed. In two of three populations, infected plants produced stolons with greater biomass and shorter spacer lengths, even though mean stolon lengths were similar for infected and uninfected plants. These results contrast strongly with most other clonal plant-pathogen systems where infected plants are less vigorous and have reduced clonal growth compared to uninfected plants. Greater clonal growth may be an effective mechanism for host genotypes to persist and spread when seed production is prevented, as is the case with castrating pathogens like Epichloë glyceriae .