In response to insect attack,plants use intricate signaling pathways,including phytohormones,such as jasmonate(JA),ethylene(ET),and salicylic acid(SA),to activate defenses.Maize(Zea mays)is one of the most important staple food crops around the world.Previous studies have shown that the JA and ET signaling play important roles in maize defense against insects,but little is known about whether and how SA regulates maize resistance to insect herbivores.In this study,we ectopically expressed the NahG(salicylate hydroxylase)gene in maize plants(NahG maize)to block the accumulation of SA.It was found that compared with the wild-type(WT)maize,the NahG maize exhibited decreased resistance to the generalist insects Spodoptera litura and Spodoptera frugiperda and the specialist Mythimna separata,and the compromised resistance in the NahG maize was associated with decreased levels of defensive me-tabolites benzoxazinoids(Bxs)and chlorogenic acid(CA).Quantification of simulated S.litura feeding-induced JA,JA-isoleucine conjugate(JA-Ile),and ET in the WT and NahG maize indicated that SA does not regulate JA or JA-Ile,but positively controls ET.We provide evidence suggesting that the SA pathway does not crosstalk with the JA or the ET signaling in regulating the accumulation of Bxs and CA.Tran-scriptome analysis revealed that the bHLH,ERF,and WRKY transcription factors might be involved in SA-regulated defenses.This study uncovers a novel and important phytohormone pathway in maize defense against lepidopterous larvae.

叶性状受植株大小的影响,但也会因成年树和幼树所处林冠条件的不同而产生差异.因此植物可通过调整叶性状进而选择不同的生存策略.该研究测量了小兴安岭阔叶红松(Pinus korainesis)林中花楷槭(Acer ukurunduense)、青楷槭(A.tegmentosum)、五角槭(A.pictum subsp.mono)3种槭树的林隙成年树、林隙幼树和林内幼树的叶经济谱性状:比叶面积(SLA)、叶干物质含量(LDMC)、叶片厚度(LT)、叶绿素(Chl)含量、净光合速率(Aarea)和非结构性碳水化合物(NSC)含量及防御性状:总酚(TP)含量和类黄酮(FLA)含量,通过研究植株大小和林冠条件对叶性状变异及相关性的影响,阐述林隙如何通过影响叶性状进而影响林分更新以及不同生境下植株所选生存策略的差异.结果表明:林隙成年树的LDMC、Chl含量、FLA含量和NSC含量显著高于林隙幼树,SLA则显著低于林隙幼树;而林隙幼树的LDMC、LT、Chl含量和Aarea均显著高于林内幼树;成年树SLA和LDMC相关性斜率的绝对值显著大于林隙幼树,林内幼树两者间的斜率的绝对值又显著小于林隙幼树.林隙成年树表现为"保守型"策略,林内幼树表现为"获取型"策略;林隙幼树则表现为两种策略之间的过渡策略.研究结果表明,当幼树不再受到林内环境光照条件限制时,植株大小对叶性状的影响可能发生改变.另外,林隙可以通过提高幼树光合速率,提高对病虫害的抵抗能力等方式促进林分更新.

高阶作用通常指一个物种对另外两个物种之间相互作用强度的影响,对物种共存、群落构建及生物多样性具有重要影响.在集合种群水平上考虑了植食动物对动植物传粉关系造成的高阶作用,以及植食动物对传粉者的间接作用.通过分析基本生态过程,建立植物-传粉者-植食动物的集合群落模型,模型清楚地展示高阶作用和间接作用,可以用来研究它们对集合群落稳定性和续存的影响.结果表明:(1)互惠关系在集合群落尺度上会引起双稳态现象,说明了群落动态对初始条件的依赖性;(2)正高阶作用能够扩大集合群落双稳态的参数范围,负高阶作用和间接作用缩小它的参数范围,但都不会从本质上改变双稳态现象;(3)正高阶作用能够降低集合群落的灭绝阈值,增加集合群落稳定时的占有率,有利于集合群落续存,而负高阶作用和间接作用不利于续存.研究结果说明高阶和间接作用对调节多物种系统动态和物种共存具有重要作用.

Up to 40％of global crops are destroyed by arthropod pests,either prior to harvest or during storage(Gullino et al.,2021).This problem is exacerbated by current and anticipated climate changes that will allow the long-term survival of pest populations in new habitats,as well as by the introduction of new pest species into areas where they were not previously present.For instance,the recent introduction of Spodoptera frugiperda(fall armyworm),which previously was a major pest of Zea mays(maize)only in the Americas,led to the expansion of this species throughout the maize-growing regions of Africa and Asia in less than 5 years(Tay et al.,2022).

Soil microbes have important effects on the interactions of plants with their environment,by promoting plant growth,inducing resistance to pests or by conferring tolerance to abiotic stress.However,their effects are variable and the factors responsible for this variation are mainly unknown.Our aim was to assess how drought stress modifies the effect of the nonpathogenic rhizobacterium Pseudomonas simiae WCS417r on plant growth and resistance against the generalist leaf-chewing caterpillar Mamestra brassicae.We studied Arabidopsis thaliana Col-0 plants,as well as mutants altered in the biosynthesis of the phytohormones jasmonic acid (JA) and abscisic acid (ABA).Caterpillars did not prefer rhizobacteria-treated plants,independently of drought stress.Rhizobacteria colonization had a variable effect on caterpillar performance,which ranged from positive in one experiment to neutral in a second one.Drought had a consistent negative effect on herbivore performance;however,it did not modify the effect ofrhizobacteria on herbivore performance.The effect of drought on herbivore performance was JA-mediated (confirmed with the use of the dde2-2 mutant),but it was still present in the ABA-deficient mutant aba2-1.Plant biomass was reduced by both drought and herbivory but it was enhanced by rhizobacterial colonization.Pseudomonas simiae WCS417r is able to promote plant growth even when plants are suffering herbivory.Nevertheless,the microbial effect on the herbivore is variable,independently of drought stress.To get the best possible outcome from the rhizobacteria-plant mutualism it is important to understand which other factors may be responsible for its context-dependency.

植食性动物取食植物(植食作用)一直是生物多样性和生态系统功能研究的热点问题.植食作用能够显著影响植物幼苗的生长,从而决定种群更新动态.以往的研究较少讨论植物的不同性状对幼苗植食作用差异的重要性,也较少将之与物种相对多度对植食作用的影响进行比较.该文以千岛湖地区的16种常见木本被子植物幼苗为研究对象,调查植物的11种功能性状和相对多度,并运用回归模型和方差分解方法.研究植物功能性状和物种相对多度对幼苗叶片受昆虫植食损伤(虫食率)的相对重要性,探讨虫食率对植物功能性状的依赖性以及物种相对多度对虫食率的影响.结果表明叶片功能性状(即叶片碳氮比、叶片厚度)和物种相对多度对虫食率有重要影响,二者共解释了种间虫食率变异的54％.在这些性状中,有更高的防御能力、更低的营养成分和更高相对多度的物种虫食率更低.我们建议在未来的植食作用研究中,应考虑基于个体水平的功能性状和基于群落水平的相对多度.

竞争力增强进化假说(Evolution of Increased Competitive Ability,EICA)认为入侵植物在入侵地由于天敌逃逸导致对天敌防御投入降低而增加生长和繁殖等投入.然而,EICA假说所预测防御能力的进化主要集中在防御的组成抗性方面,而从诱导抗性和耐受性的角度进行的验证还很有限,并且忽视了生境资源可利用性对植物防御策略的影响.本研究采用同质园实验比较了喜旱莲子草(Alternanthera philoxeroides)原产地(阿根廷)和入侵地(美国)各9个种群,在高、低养分和有、无专食性天敌取食处理下的防御相关功能性状(比茎长、根冠比)及其对天敌取食的诱导反应,以及它们与植物适合度相关指标的关系.结果表明:入侵地种群具有较高的总生物量(+14.7％)、较低的比茎长(防御钻茎化蛹天敌的重要指标,-27.5％),暗示其个体大小增加而防御投入降低,符合EICA假说的预测.入侵地种群耐受性与原产地种群没有显著差异.在高养分下,入侵地种群的比茎长对专食性天敌取食的诱导反应显著增加,且与总生物量呈显著正相关.这些结果表明,相比原产地种群,入侵地种群具有更高的生物量,对专食性天敌的组成抗性降低,且在高养分下对专食性天敌的诱导抗性增加,推测生境的养分富集可能会降低喜旱莲子草的生物防治效果.

When herbivores attack, plants specifically reconfigure their metabolism. Herbivory on the wild tobacco Nicotiana attenuata strongly induces the R2R3 MYB transcriptional activator MYB8, which was re-ported to specifically regulate the accumulation of phenolamides (Pas). We discovered that transcriptional regulation of trypsin protease inhibitors (TPIs) and a threonine deaminase (TD) also depend on MYB8 expression. Induced distributions of Pas, TD and TPIs all meet predictions of optimal defense theory: their leaf concentrations increase with the fitness value and the probability of attack of the tissue. Therefore, we suggest that these defensive compounds have evolved to be co-regulated by MYB8.

外来植物往往可以入侵多种生境并受到多种昆虫的采食,而不同生境条件将可能会影响这些入侵植物对昆虫采食的防御策略.以入侵我国的克隆植物——空心莲子草为研究对象,分别选择生长在水生生境、水陆两栖生境和陆生生境中的无性个体(分株),通过50％去叶处理模拟昆虫采食,分析不同生境下空心莲子草对模拟昆虫采食处理的生长及化学防御响应的差异.模拟昆虫采食处理显著抑制了陆生生境、水陆两栖生境以及水生生境下空心莲子草的根、茎、叶和总生物量,但对3种生境下空心莲子草的生物量分配(根冠比、根生物量分配、茎生物量分配和叶生物量分配)均无显著影响.陆生生境下空心莲子草根、茎和总生物量显著高于水陆两栖生境和水生生境,根冠比显著低于水陆两栖生境和水生生境.模拟昆虫采食处理显著降低了空心莲子草的木质素含量,而对单宁和总酚含量影响不显著.生境对木质素含量无显著影响,但陆生生境下空心莲子草单宁含量显著高于水陆两栖生境和水生生境,且总酚含量显著高于水陆两栖生境,表明陆生生境中空心莲子草具有更强的防御能力.空心莲子草木质素含量与总生物量无显著相关性,但在模拟采食情况下,其总酚含量与总生物量呈显著负相关,而无论模拟昆虫采食处理存在与否,空心莲子草单宁含量与总生物量均呈显著正相关.因此,空心莲子草存在昆虫介导的生长和化学防御之间的权衡,在昆虫采食的情况下可通过减少生长来增加对化学防御物质的投入,但生境对空心莲子草这种生长-防御权衡的影响十分有限.

上行因子、下行因子和种内种间作用均会影响盐沼植物的生长繁殖,然而上行效应的研究较多,而下行效应的研究则较少.芦苇(Phragmites australis)是黄河三角洲湿地的主要植被类型,而潮水芦苇则是重要和独特的芦苇种群.本研究旨在探讨下行效应对黄河三角洲潮水芦苇幼苗生长的影响.本研究于芦苇幼苗期在黄河三角洲自然保护区潮水芦苇区域设置24个2 m×2 m样方调查天津厚蟹取食对芦苇幼苗生长的影响.结果表明:潮水芦苇幼苗受了天津厚蟹的严重取食和破坏;24个样方中共有1139株芦苇幼苗,其中被轻度取食的芦苇幼苗有308株(占27.04％),被重度取食的芦苇幼苗有234株(占20.54％),未被取食的芦苇幼苗有597株(占52.41％);黄河三角洲潮水芦苇幼苗生长指标受到天津厚蟹取食的显著影响,天津厚蟹重度取食显著减少芦苇幼苗高度生长、减少幼苗叶片数和幼苗叶片长度.因此,在黄河三角洲潮水芦苇保护和管理时应该考虑下行因子对芦苇生长的影响.