害虫取食和机械损伤对菜豆不同部位叶片防御酶活性的影响

【目的】本研究旨在探究菜豆Phaseolus vulgaris植株对不同害虫危害的系统防御机制。【方法】分别以斜纹夜蛾Spodoptera litura、二斑叶螨Tetranychus urticae、西花蓟马Frankliniella occidentalis取食或昆虫针穿刺处理菜豆中部叶片6,24,48,72和96 h后,测定菜豆植株中部处理叶片以及上部和下部未处理叶片的过氧化物酶(POD)、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性的变化。【结果】不同害虫取食后,POD,CAT和SOD活性在受害的菜豆中部叶片发生了明显变化,但不同害虫造成酶活性的变化趋势不同。与未处理的对照植株中部叶片相比,POD活性均是先升高后恢复至对照水平。POD活性在二斑叶螨取食后,于24 h达到最大值,是对照的4.6倍;POD活性在机械损伤和西花蓟马取食后在48 h达到峰值,而斜纹夜蛾取食诱导下POD活性升高最缓慢,直到72 h才达到最大值。中部叶片的CAT活性在机械损伤和3种害虫取食后变化不同,机械损伤24 h后CAT活性明显升高,而3种害虫取食后CAT活性变化较早,在6 h就明显升高,但随时间的延长,CAT活性的变化趋势不同。中部叶片SOD活性在不同处理下变化较大,在机械损伤诱导下仅在96 h明显升高,而二斑叶螨取食24 h以后均明显升高;但斜纹夜蛾及西花蓟马取食后,SOD活性在72 h时受到明显的抑制。在菜豆植株的上部和下部未受害叶片中,3种害虫取食和机械损伤处理后,以上3种酶的活性也发生了明显变化,POD活性在上部未受害叶片不同处理96 h时被抑制,而在下部叶片不同处理下均被激发,但诱导程度不同。机械损伤、斜纹夜蛾、二斑叶螨和西花蓟马处理后,菜豆植株上部和下部未受害叶片CAT活性都分别在24,6,6和24 h被明显诱导。上部和下部未受害叶片SOD活性在机械损伤96 h,斜纹夜蛾和二斑叶螨取食72 h后,均被明显激发;但西花蓟马取食后,SOD活性在48 h和72 h明显被抑制。【结论】斜纹夜蛾、二斑叶螨和西花蓟马取食均能显著诱导菜豆植株受害叶和未受害叶防御酶活性的变化,即引起菜豆植株的系统防御反应,但3种害虫诱导的防御酶活性变化程度不同,表明植物防御反应的时空效应与害虫种类有关。     

韧皮部取食昆虫诱导的植物防御反应

刺吸式昆虫与寄主植物之间具有特殊的生物互作关系。本文对刺吸式昆虫取食韧皮部诱导的植物防御反应类型、 防御物质变化、 信号途径以及植物反应转录组学研究等方面进行综述。韧皮部取食昆虫取食诱导的植物防御反应机制主要包括： (1)改变自身的营养状况; (2)产生有毒的次生化合物; (3)产生防御蛋白。防御反应与植物水杨酸、 茉莉酸、 乙烯等信号分子密切相关。研究表明, 刺吸式昆虫取食诱导的植物防御反应主要引发以水杨酸为主的信号途径, 但相关分子互作机制还有待明确。日益丰富的基因组资源和不断发展的分子生物学技术为揭示植物防御反应中信号分子的作用机制、 找出植物内生抗性的特异因子以及阐明诱导防御机制奠定了基础。了解刺吸式昆虫取食诱导的植物防御反应, 为深入理解植物-昆虫间协同进化关系提供了依据, 为害虫治理和抗虫植物的培育提供了新的思路。     

虫害诱导挥发物的生态调控功能

虫害诱导挥发物（herbivore-induced plant volatiles, HIPVs）是植物受害虫胁迫后释放的挥发性物质,是植物与周围环境进行信息交流的媒介。环境中的天敌、害虫和植物通过感知HIPVs所携带的信息,对各自的行为或生理生化反应做出相应的调整。介绍了挥发物的种类及主要的生物合成途径,概括了影响天敌依据HIPVs搜寻寄主和猎物的主要因素。综述了这类挥发性物质对植食性昆虫寄主选择或产卵行为的影响,介绍了植物地上部分和地下部分受害后对彼此间接防御的影响,讨论了多种害虫加害同种植物后对天敌搜寻猎物或寄主行为的影响。另外,作为损伤信号,HIPVs还能诱导同株植物未受害部位和邻近植株的防御反应。最后,对HIPVs在害虫防治中的应用现状及前景作了介绍和讨论。     

丛枝菌根真菌摩西管柄囊霉侵染增强番茄对机械损伤的响应

植食性昆虫取食会给植物造成机械损伤并激活植物的防御反应,而与有益微生物共生是否可以增强植物对机械损伤的响应对植物抗虫有重要意义.本研究在番茄根系被丛枝菌根真菌摩西管柄囊霉侵染后,研究机械损伤对番茄防御反应的影响.结果表明: 预先接种菌根真菌的番茄叶片受到机械损伤处理(FD)后,叶片苯丙氨酸解氨酶(PAL)、超氧化物歧化酶(SOD)、过氧化物酶(POD)、多酚氧化酶(PPO)和过氧化氢酶(CAT)活性,以及叶片和根系苯丙氨酸解氨酶基因(PAL)和β-1,3-葡聚糖酶基因(PR2)的转录水平均显著高于只进行机械损伤的处理(D)、只接种摩西管柄囊霉的处理(F),以及既未接种菌根菌也未进行机械损伤的健康番茄植株(CK).虽然D和 F处理也可诱导部分酶活性及基因转录水平升高,但FD处理诱导的防御反应更迅速和强烈.表明丛枝菌根真菌侵染可以警备(prime)番茄对机械损伤做出更快速和强烈的响应.     

3种不同类型口器的昆虫取食对菜豆叶片PPO和PAL活性的影响

为研究不同口器昆虫取食对菜豆植株系统防御的影响,以斜纹夜蛾(Spodoptera litura)咀嚼取食、二斑叶螨(Tetranychus urticae)刺吸取食和西花蓟马(Frankliniella occidentalis)锉吸取食分别处理菜豆中部叶片6、24、48、72和96 h后,测定菜豆受处理的中部叶片及未处理的上部及下部位叶片多酚氧化酶(PPO)和苯丙氨酸解氨酶(PAL)的活性。结果表明:危害方式、处理时间和叶片部位对菜豆叶片PPO和PAL活性有极显著影响(P0.01),且三者间有极显著的交互作用。不同危害方式诱导后中部处理叶片的PPO活性均是在6 h明显升高(P0.05),但随时间的延长PPO活性在不同处理下变化不同;中部叶片PAL活性在机械损伤处理48 h后才被显著激活,而斜纹夜蛾、二斑叶螨和西花蓟马取食后,PAL活性分别在6、6和24 h明显升高,且达到最大值,分别是对照的2.66、1.75和2.79倍;处理菜豆的上部和下部未受害叶片的PPO和PAL活性对虫害的响应明显比机械损伤迅速;二斑叶螨取食后PAL活性响应最快,上部和下部叶片均在6 h达到最大值,分别为对照的2.72和5.07倍。以上结果说明,害虫取食能引起菜豆植株产生系统防御反应,并且防御的时空效应与害虫的为害方式有关。     

昆虫取食诱导的植物防御反应

植物被昆虫取食后可产生直接防御或间接防御。直接防御通过增加有毒的次生代谢产物或防御蛋白对昆虫生理代谢产生不利的影响,但对植物的消耗较大。间接防御通过释放挥发性化合物吸引天敌昆虫,并以此控制植食性昆虫。特异性的昆虫激发子(insect specific elicitors)能够诱导挥发性化合物的释放。多种信号途径参与昆虫取食诱导的植物防御反应,它们之间的相互作用协同或拮抗。了解昆虫取食诱导的植物防御反应,对于害虫综合治理策略的完善具有重要的意义。     

虫害诱导植物间接防御反应的激发与信号转导途径

植物通过产生和释放挥发性物质增加植食性昆虫的天敌对其寄主或猎物的定位,减少植食性昆虫对植物的取食,从而达到间接防御的目的。植物对植食性昆虫所做出间接防御反应激发因子和信号转导途径的研究,对应用虫害诱导植物挥发物引诱害虫天敌,并进一步从植物、植食性昆虫及其天敌间三级营养关系,研究动植物协同进化机理和病虫害防治具有深远意义。本文根据国内外最新研究进展,对虫害诱导植物间接防御反应的激发因子,昆虫取食信号的转导途径及对植物间接防御相关基因的激活等方面进行了系统地综述。     

植物地下部与地上部远端相互调控研究进展

植物作为一个有机整体,已进化出复杂的机制来协调地下部与地上部的生长与发育,以应对环境的变化。本文从地下部与地上部之间远端调控的物质交换、信号传导、应用调控三方面综述了近年来的最新进展,以期对地下部与地上部远端相互调控机制有深入的了解,为植物生产过程的调控提供思路。     

水稻防御信号NO对褐飞虱产卵刺激的响应

植物对昆虫产卵刺激产生的防御反应不仅可以直接抑制卵的发育,还可以为防御下一步若虫/幼虫带来的危害做准备。对褐飞虱产卵处理后水稻植株内一氧化氮(NO)合成的关键酶-硝酸还原酶基因的表达量和NO含量进行测定,对比褐飞虱取食和机械损伤处理,结果显示褐飞虱产卵能够诱导水稻硝酸还原酶基因的表达和NO的生成。处理后12 h,水稻硝酸还原酶基因表达量显著高于取食和和机械损伤处理;12-24 h产卵诱导的NO含量显著高于对照和机械损伤组水稻。褐飞虱产卵诱导水稻启动NO合成关键基因的表达和物质合成表明,与取食危害类似,水稻同样会对褐飞虱产卵刺激产生响应,诱导NO升高,启动相应的植物防御体系。     

植物地上部信息化合物在植物一害虫一天敌关系中的生态学功能及在害虫治理中的应用前景

本文综述了近年来有关地上部植物信息化合物在植物一害虫一天敌三营养级关系中的信息联系,分析地上部植物信息化合物在植物一害虫、植物一天敌、植物个体内和个体间信号传递的生态学功能,阐明地上部植物信息化合物在害虫治理中的应用潜力,包括害虫诱捕和诱杀、昆虫种群监测、植物拒避剂、干扰害虫对寄主搜索、“推一拉”策略和植物内源激发子的应用等,讨论了地上部植物信息化合物与其他控害手段的协同作用,以及在生产实践中可能存在的相关问题,旨在为地上部植物信息化合物在害虫持续治理中的应用提供科学指导。     

Effects of simulated root herbivory and fertilizer application on growth and biomass allocation in the clonal perennialSolidago canadensis

Summary Compensatory growth in response to simulated belowground herbivory was studied in the old-field clonal perennialSolidago canadensis. We grew rootpruned plants and plants with intact root systems in soil with or without fertilizer. For individual current shoots (aerial shoot with rhizome and roots) and for whole clones the following predictions were tested: a) root removal is compensated by increased root growth, b) fertilizer application leads to increased allocation to aboveground plant organs and increased leaf turnover, c) effects of fertilizer application are reduced in rootpruned plants. When most roots (90%) were removed current shoots quickly restored equilibrium between above-and belowground parts by compensatory belowground growth whereas the whole clone responded with reduced aboveground growth. This suggests that parts of a clone which are shared by actively growing shoots act as a buffer that can be used as source of material for compensatory growth in response to herbivory. Current shoots increased aboveground mass and whole clones reduced belowground mass in response to fertilizer application, both leading to increased allocation to aboverground parts. Also with fertilizer application both root-pruned and not root-pruned plants increased leaf and shoot turnover. Unfertilized plants, whether rootpruned or not, showed practically no aboveground growth and very little leaf and shoot turnover. Effects of root removal were as severe or more severe under conditions of high as under conditions of low nutrients, suggesting that negative effects of belowground herbivory are not ameliorated by abundant nutrients. Root removal may negate some effects of fertilizer application on the growth of current shoots and whole clones.     

First insights into specificity of belowground tritrophic interactions

Tritrophic interactions involving plants, herbivores and parasites have been only recently documented for belowground systems, where entomopathogenic nematodes can exploit root herbivore induced volatile compounds to locate their hosts. Little is known, however, about whether the specificity of such interactions rivals that of the remarkable interactions found in aboveground studies. Using a belowground six-arm olfactometer that allows recording of nematode attraction, specificity of nine economically important species of different trophic levels, including plants, root feeders and entomopathogenic nematodes, was tested. We found that belowground tritrophic interactions are variable at the level of plant volatiles that are induced, elicitation by herbivores, as well as behavior of nematodes. We argue that studies on specificity and variability of belowground responses should be included in plant defense theories and in efforts to exploit tritrophic interactions to improve biological control practices.     

Linking aboveground and belowground interactions via induced plant defenses

Plants have a variety of chemical defenses that often increase in concentration following attack by herbivores. Such induced plant responses can occur aboveground, in the leaves, and also belowground in the roots. We show here that belowground organisms can also induce defense responses aboveground and vice versa. Indirect defenses are particularly sensitive to interference by induced feeding activities in the other compartment, and this can disrupt multitrophic interactions. Unravelling the involvement of induced plant responses in the interactions between aboveground and belowground communities associated with plants is likely to benefit from comprehensive metabolomic analyses. Such analyses are likely to contribute to a better understanding of the costs and benefits involved in the selection for induced responses in plants.     

Physiological integration of roots and shoots in plant defense strategies links above- and belowground herbivory

Roots play a critical, but largely unappreciated, role in aboveground anti-herbivore plant defense (e.g. resistance and tolerance) and root–leaf connections may therefore result in unexpected coupling between above- and belowground consumers. Using the tobacco ( Nicotiana tabacum ) system we highlight two examples of this phenomenon. First, the secondary metabolite nicotine is produced in roots, yet translocated aboveground for use as a foliar resistance trait. We demonstrate that nematode root herbivory interferes with foliar nicotine dynamics, resulting in positive effects on aboveground phytophagous insects. Notably, nematode-induced facilitation only occurred on nicotine-producing plants, and not on nicotine-deficient mutants. In the second case, we use stable isotope and invertase enzyme analyses to demonstrate that foliar herbivory elicits a putative tolerance response whereby aboveground nutritional reserves are allocated to roots, resulting in facilitation of phytoparasitic nematodes. Thus, plants integrate roots in resistance and tolerance mechanisms for leaf defense, and such root–leaf connections inherently link the dynamics of above- and belowground consumers.     

Sequential effects of root and foliar herbivory on aboveground and belowground induced plant defense responses and insect performance

Plants are often simultaneously or sequentially attacked by multiple herbivores and changes in host plants induced by one herbivore can influence the performance of other herbivores. We examined how sequential feeding on the plant Plantago lanceolata by the aboveground herbivore Spodoptera exigua and the belowground herbivore Agriotes lineatus influences plant defense and the performance of both insects. Belowground herbivory caused a reduction in the food consumption by the aboveground herbivore independent of whether it was initiated before, at the same time, or after that of the aboveground herbivore. By contrast, aboveground herbivory did not significantly affect belowground herbivore performance, but significantly reduced the performance of later arriving aboveground conspecifics. Interestingly, belowground herbivores negated negative effects of aboveground herbivores on consumption efficiency of their later arriving conspecifics, but only if the belowground herbivores were introduced simultaneously with the early arriving aboveground herbivores. Aboveground–belowground interactions could only partly be explained by induced changes in an important class of defense compounds, iridoid glycosides (IGs). Belowground herbivory caused a reduction in IGs in roots without affecting shoot levels, while aboveground herbivory increased IG levels in roots in the short term (4 days) but only in the shoots in the longer term (17 days). We conclude that the sequence of aboveground and belowground herbivory is important in interactions between aboveground and belowground herbivores and that knowledge on the timing of exposure is essential to predict outcomes of aboveground–belowground interactions.     

The importance of belowground mineral element stores in cattails (Typha latifolia L.)

We measured the amount of N, P, K, Ca, Mg, Fe, B, Mn, Na, Sr, Cu and Zn in above- and belowground parts of cattails (Typha latifolia L.) every 2 weeks during the growing season (April–October) in plants growing in a marsh on the shore of Lake Mendota, Wisconsin. Elements differed considerably in their distribution between above- and belowground parts and the amount of apparent exchange between parts. The ratio of the amount of an element in aboveground plant parts to that belowground (A:B) was between 1:1 and 2:1 for most elements, as compared with the 2.2:1 ratio of biomass. The maximum amounts of Fe and Zn belowground exceeded their aboveground maxima, while K, Ca and Mn had A:B ratios greater than 2:1. N, P and K in belowground plant parts decreased considerably during the spring, and belowground decreases were large enough to be potentially important sources of these elements for shoot growth. Belowground stores of Ca, Mg, Mn, Na and Sr decreased little in the spring and do not function as reserves.     

Hierarchical plant responses and diversity loss after nitrogen addition: testing three functionally-based hypotheses in the Inner Mongolia grassland

Background

Numerous studies have shown that nitrogen (N) deposition decreases biodiversity in terrestrial ecosystems. To explain the N-induced species loss, three functionally based hypotheses have been proposed: the aboveground competition hypothesis, the belowground competition hypothesis, and the total competition hypothesis. However, none of them is supported sufficiently by field experiments. A main challenge to testing these hypotheses is to ascertain the role of shoot and root competition in controlling plant responses to N enrichment. Simultaneously examining both aboveground and belowground responses in natural ecosystems is logistically complex, and has rarely been done.

Methodology/Principal Findings

In a two-year N addition experiment conducted in a natural grassland ecosystem, we investigated both above- and belowground responses of plants at the individual, species, and community levels. Plants differed significantly in their responses to N addition across the different organizational levels. The community-level species loss was mainly due to the loss of perennial grasses and forbs, while the relative abundance of plant species was dependent mainly on individual-level responses. Plasticity in biomass allocation was much smaller within a species than between species, providing a biological basis for explaining the functionally based species loss. All species increased biomass allocation to aboveground parts, but species with high belowground allocations were replaced by those with high aboveground allocations, indicating that the increased aboveground competition was the key process responsible for the observed diversity loss after N addition in this grassland ecosystem.

Conclusions/Significance

Our findings shed new light on the validity of the three competing hypotheses concerning species loss in response to N enrichment. They also have important implications for predicting the future impacts of N deposition on the structure and functioning of terrestrial ecosystems. In addition, we have developed a new technique for ascertaining the roles of aboveground and belowground competition in determining plant responses to N fertilization.     

植物种间和种内的化学作用

植物间相互作用是生态学基础科学问题之一,植物能感受和识别共存同种或异种植物,进而调整生长、繁殖和防御策略。植物种间和种内的感受和识别大多是由植物产生释放的次生物质所介导,这类化学识别通讯可以启动相应的植物化感作用机制。近年发现,植物亲属间也存在着化学识别、地下根系通讯调控地上开花繁殖等植物种间和种内的化学作用关系。目前植物通过地上挥发物介导的植物化学作用已基本澄清,但根分泌物介导的植物地下化学作用机制及其信号物质还所知甚少。地下化学作用不仅决定根系侵入(接近)和躲避(排斥)行为,也能调控地上开花时间和花期。这样,植物间的化学作用还涉及植物地下和地上的协调互作。本文以植物化感作用和植物化学识别通讯及相应的化感物质和信号物质为基点,从植物亲属识别、根系化学识别和行为模式、地下化学作用调控地上开花繁殖3个方面综述植物种间和种内化学作用的研究进展,为全面理解植物间相互作用提供新视野。     

Legacy effects of aboveground-belowground interactions

Root herbivory can greatly affect the performance of aboveground insects via changes in plant chemistry. These interactions have been studied extensively in experiments where aboveground and belowground insects were feeding on the same plant. However, little is known about how aboveground and belowground organisms interact when they feed on plant individuals that grow after each other in the same soil. We show that feeding by aboveground and belowground insect herbivores on ragwort (Jacobaea vulgaris) plants exert unique soil legacy effects, via herbivore-induced changes in the composition of soil fungi. These changes in the soil biota induced by aboveground and belowground herbivores of preceding plants greatly influenced the pyrrolizidine alkaloid content, biomass and aboveground multitrophic interactions of succeeding plants. We conclude that plant-mediated interactions between aboveground and belowground insects are also important when they do not feed simultaneously on the same plant.     

The difference between above- and below-ground self-thinning lines in forest communities

Quantifying the self-thinning process in various plant communities has been a long-standing issue in both theoretical and empirical studies. Most studies on plant self-thinning have centered only on aboveground parts, and rarely on belowground parts. There is still a general lack of comparison between above- and belowground self-thinning processes, especially for forest communities. The fundamental mechanistic difference and the functional association between above- and belowground competition indicate that the self-thinning process of belowground parts may be different from that of aboveground parts. We investigated the self-thinning lines for above-ground (M _A), below-ground (M _B), and total biomass (M _T), respectively, across forest communities in China. The results showed that neither the classical self-thinning rule (−3/2 exponent) nor the universal scaling rule (−4/3 exponent) can apply to all the self-thinning relationships across these forest communities and that the self-thinning lines for belowground biomass were flatter and lower than those for aboveground biomass across most of these forest communities.