大气CO2浓度升高对植物、植食性昆虫及其天敌的影响研究进展

自世界工业革命以来,化石燃料的大量使用以及人类对自然环境的过度破坏,致使大气CO₂浓度不断升高.研究大气CO₂浓度升高介导的农业生态系统内植物、植食性昆虫及其天敌的适应机制,对于阐明气候变化下农业害虫爆发危害规律,指导防控与减排具有重要意义.本文综述了大气CO₂浓度升高对农业生态系统中植物、植食性昆虫及天敌的影响,主要包括：1)相关研究方法的改进;2)大气CO₂浓度升高介导的寄主植物营养和次生代谢物质的变化;3)大气CO₂浓度升高对以植物为食的昆虫的个体生长发育、种群数量、行为的影响;4)天敌昆虫的生物学及捕食量与寄生率变化.最后对今后的研究方向进行了展望.     

大气CO2浓度升高对植物、植食性昆虫及其天敌的影响研究进展

自世界工业革命以来,化石燃料的大量使用以及人类对自然环境的过度破坏,致使大气CO₂浓度不断升高.研究大气CO₂浓度升高介导的农业生态系统内植物、植食性昆虫及其天敌的适应机制,对于阐明气候变化下农业害虫爆发危害规律,指导防控与减排具有重要意义.本文综述了大气CO₂浓度升高对农业生态系统中植物、植食性昆虫及天敌的影响,主要包括：1)相关研究方法的改进;2)大气CO₂浓度升高介导的寄主植物营养和次生代谢物质的变化;3)大气CO₂浓度升高对以植物为食的昆虫的个体生长发育、种群数量、行为的影响;4)天敌昆虫的生物学及捕食量与寄生率变化.最后对今后的研究方向进行了展望.     

CO2加富与两种供N水平对非洲菊光合生理及生长发育的影响

CO₂加富会促进植物的光合作用和生长发育,但长期的CO₂加富常因植物较低的氮（N）含量而降低这种促进作用。本文在大气CO₂浓度（40 0μmol·mol-1）和CO₂加富（800μmol·mol-1）条件下,研究不同N水平（15 mmol·L-1和30 mmol·L-1）对非洲菊光合生理和生长发育的影响。结果表明,CO₂加富显著提高非洲菊叶片的净光合速率,在整个试验期间CO₂800+N15比CO2400+N 1 5平均增加3 5%;CO₂800+N 3 0平均比CO2400+N 3 0增加了6 5%;在试验末期,CO₂800+N 3 0显著大于CO₂800+N15。非洲菊叶片中可溶性糖和淀粉含量在CO₂加富条件下显著增加,但随着试验处理时间的延长,CO₂800+N30的增加趋势小于CO₂800+N15;CO₂加富降低了非洲菊叶片中蛋白质和N含量,N的增加则缓解了这一下降趋势;在生长发育方面,CO₂加富不但促进了非洲菊的生长,而且提前了非洲菊的花期,增加了非洲菊的花朵数目,增大了花朵直径,增粗了花梗,增加了花朵花色素苷含量,显著提高了非洲菊的观赏品质。同时,增加的N与CO₂互作对非洲菊花部品质也有显著促进作用。以上数据表明,在非洲菊的栽培中,增加CO₂浓度的同时,提高N肥的供给是非常必要的。     

粳稻生育后期剑叶光合日变化和光合色素对大气CO2浓度和温度升高的响应——FACE研究

为研究水稻叶片光合色素和光合日变化对大气CO₂浓度和气温升高的响应,我们采用在开放空气中控制升高CO₂浓度和温度的方法,以常规粳稻南粳9108为试验材料,设置了环境CO₂和高大气CO₂浓度(增加200 μmol·mol^-1)、环境温度和增温(增加1～2 ℃)交互的4个处理,测定了灌浆中期和后期水稻剑叶的光合日变化特征和光合色素含量.结果表明: 水稻剑叶净光合速率(P_n)为双峰曲线,发生了光合“午休”现象;大气CO₂浓度升高提高了剑叶P_n,灌浆中期和后期平均分别增加了47.6%和39.1%;高温有降低P_n的趋势,但相关性未达到显著水平.大气CO₂浓度和温度升高导致水稻剑叶生育后期气孔导度(g_s)平均分别降低了17.0%和11.8%.高CO₂浓度水稻剑叶生育后期蒸腾速率(T_r)、叶绿素a、叶绿素b、类胡萝卜素、总叶绿素和叶绿素a/b值显著降低,平均降幅分别为5.9%、50.4%、21.3%、41.4%、39.4%和21.4%,明显增加了剑叶水分利用率(WUE),平均增幅达47.9%.与之相反,生育后期增温使水稻剑叶T_r增加了10.2%,使WUE平均降低了20.4%.综上所述,大气CO₂浓度升高对粳稻生育后期剑叶P_n、g_s和光合色素含量的影响明显大于增温效应.因此,应重视大气CO₂浓度和温度对水稻光合作用和光合色素的综合效应,减弱增温的负效应.     

增施CO2对植物修复土壤DEHP污染的影响

修复效率低一直是植物修复技术需要解决的关键问题之一.基于我国的CO₂减排压力和CO₂对植物生长的必要性,选择C3植物绿豆和C4植物玉米作为修复植物,以DEHP为目标污染物,探索增施CO₂对植物修复土壤DEHP污染的影响.结果表明: DEHP对两种植物生长和根际微环境都产生了抑制性影响.增施CO₂后,两种植物地上干质量显著增加,叶片SOD酶活性明显下降,根际土壤碱性磷酸酶活性增加,根际微生物群落结构改变,根际耐DEHP胁迫微生物数量增加,表明增施CO₂对促进植物生长、增强植物抗DEHP胁迫能力、改善根际微环境有积极作用.增施CO₂还促进了两种植物对DEHP的吸收,特别是植物地下部分.这些共同作用导致增施CO₂后的两种植物根际DEHP残留浓度明显下降,土壤污染植物修复效率提高.整体上看,增施CO₂对C3植物绿豆的影响明显大于C4植物玉米.可以将增施CO₂ 作为强化植物修复过程的措施之一.     

CO2浓度倍增影响转Bt水稻非靶标害虫褐飞虱的生长发育及取食行为

近年来,大气CO₂浓度升高等全球气候变化和转Bt作物非靶标害虫抗虫性等问题备受关注.大气CO₂浓度升高直接或间接地影响植食性昆虫,而迄今为止有关大气CO₂浓度升高对刺吸式昆虫(同时也是转Bt作物的非靶标害虫)的影响结论不一,且对其刺吸取食行为的影响研究少有报道.本研究利用智能人工气候箱设置CO₂浓度,研究大气CO₂浓度倍增(800 μL·L^-1)对转Bt水稻的非靶标害虫褐飞虱取食行为及其生长发育和繁殖等的影响.结果表明: 大气CO₂浓度倍增对褐飞虱卵和若虫历期、成虫体质量和寿命,以及4龄和5龄若虫的刺吸取食行为等都具有显著影响,但对其繁殖力影响不显著.与对照CO₂浓度(400 μL·L^-1)相比,倍增CO₂浓度处理下褐飞虱的卵和若虫历期及雌成虫寿命分别显著缩短了4.0%、4.2%和6.6%;长翅型成虫比例显著增加了11.6%;初羽化成虫体质量降低,且雌成虫体质量显著降低了2.2%;此外,倍增CO₂浓度处理下褐飞虱4龄和5龄若虫口针的刺探效率都显著增加;其中,N4b波的持续时间分别显著延长了60.0%和50.1%,频次分别显著增加了230.0%和155.9%.可见,CO₂浓度倍增可通过提高褐飞虱的刺吸取食而促进其生长发育,并缩短其世代历期、提高长翅成虫比例,最终导致大气CO₂浓度升高下转Bt水稻的非靶标害虫褐飞虱发生危害严重,并面临其迁飞扩散为害加重的风险.     

CO2浓度倍增影响转Bt水稻非靶标害虫褐飞虱的生长发育及取食行为

近年来,大气CO₂浓度升高等全球气候变化和转Bt作物非靶标害虫抗虫性等问题备受关注.大气CO₂浓度升高直接或间接地影响植食性昆虫,而迄今为止有关大气CO₂浓度升高对刺吸式昆虫(同时也是转Bt作物的非靶标害虫)的影响结论不一,且对其刺吸取食行为的影响研究少有报道.本研究利用智能人工气候箱设置CO₂浓度,研究大气CO₂浓度倍增(800 μL·L^-1)对转Bt水稻的非靶标害虫褐飞虱取食行为及其生长发育和繁殖等的影响.结果表明: 大气CO₂浓度倍增对褐飞虱卵和若虫历期、成虫体质量和寿命,以及4龄和5龄若虫的刺吸取食行为等都具有显著影响,但对其繁殖力影响不显著.与对照CO₂浓度(400 μL·L^-1)相比,倍增CO₂浓度处理下褐飞虱的卵和若虫历期及雌成虫寿命分别显著缩短了4.0%、4.2%和6.6%;长翅型成虫比例显著增加了11.6%;初羽化成虫体质量降低,且雌成虫体质量显著降低了2.2%;此外,倍增CO₂浓度处理下褐飞虱4龄和5龄若虫口针的刺探效率都显著增加;其中,N4b波的持续时间分别显著延长了60.0%和50.1%,频次分别显著增加了230.0%和155.9%.可见,CO₂浓度倍增可通过提高褐飞虱的刺吸取食而促进其生长发育,并缩短其世代历期、提高长翅成虫比例,最终导致大气CO₂浓度升高下转Bt水稻的非靶标害虫褐飞虱发生危害严重,并面临其迁飞扩散为害加重的风险.     

根际CO2浓度富集对番茄光合生理的影响

本文采用气雾法栽培方式,研究了60 d根际CO₂浓度富集处理对番茄光合生理的影响.结果表明： 2500 μL·L^–1及以上CO₂浓度处理下,番茄植株叶片叶绿素含量、叶面积显著降低,叶片Mg²⁺ ATPase、Ca²⁺ ATPase和磷酸烯醇式丙酮酸羧化酶(PEPC)活性显著减少,而根系PEPC活性显著增加,叶片净光合速率、气孔导度和胞间CO₂浓度均显著降低.表明根际高CO₂浓度条件下,根系PEPC活性增强、叶片固定CO₂的能力减弱、叶片Mg^2+ ATPase和Ca²⁺ ATPase活性显著降低,根际长期高CO₂浓度处理可能是导致植株光合生理指标下降的原因之一.
     

柚树叶片CO2驯化的光合参数变化

柚树(Citrus grandis)幼树生长在砂和石至石的生长介质.每周供给0.05mmol P(正常P,P)和0.1mmol P(高磷,2P)的营养液.植株分别生长在空气CO₂分压(约39Pa)和倍增CO₂分压(81±5Pa)下45d.利用CI-301PS(CID,Inc)光合作用测定系统在较高光强(1150μmol·m^-2·s^-1)下测定叶片光合速率并得出的Pn-Pi关系曲线和在较高CO₂分压(PCO₂,56Pa)下得出Pn-PAR关系曲线计算有关光合参数.结果表明,大气CO₂分压下2P植株最大光合速率较P植株高13.3%,倍增CO₂分压下,无论P或2P植株最大光合速率较大气CO₂分压下相应植株低,但在倍增CO₂分压下2P植株较P植株高.且2P植株有较P植株高的表观量子产率和光能利用效率(P<0.05),但并不改变Γ^*、Rd和Rubisco羧化速率(Vc)和氧速率的比率(P>0.05).在大气CO₂分压下2P植株的V_cmax和J_max较P植株分别高8.3%和12.5%.在倍增CO₂分压下2P植株的V_cmax和J_max均较P植株高.柚树在高CO₂驯化中改变叶N在Rubisco和捕光组分分配系数,但不改变叶N在光合电子传递链的分配系数,结果表明,增加P供给可以促进高CO₂分压下光合碳循环中P的周转,提高倍增CO₂分压下植株的光合速率.调节柚树叶片的CO₂驯化的光合参数.     

大气CO2浓度升高对香蕉光合作用及光合碳循环过程中叶氮分配的影响

生长在高CO₂浓度(700±5μl·L^-1)1周的香蕉叶片,其光合速率(Pn,μmol·m^-2·s^-1)为5.14±0.32,较生长在大气CO₂浓度(356±301μl·L^-1)的高22.1%,而生长在较高CO₂浓度下8周,叶片Pn较生长在大气CO₂浓度的低18.1%,表现香蕉叶片对较长期高CO₂浓度的驯化和光合作用抑制.生长在高CO₂浓度的香蕉叶片有较低光下呼吸速率(R_d),而不包括光下呼吸的CO₂补偿点则变幅较小.最大羧化速率(Vcmax)和电子传递速率(J)分别较生长在大气CO₂浓度的低30.5%和14.8%,根据气体交换速率计算的表观量子产率(α,mol CO₂·mol^-1光量子),生长在较高CO₂浓度下8周的叶片为0.014±0.01,而生长在大气CO₂浓度下的为0.025±0.005.较高CO₂浓度下叶片的表观量子产率降低44%.光能转换效率electrons·quanta^-1)亦从0.203降低至0.136.生长在较高CO₂浓度下香蕉叶片的叶氮在Rubicos分配系数(PR)、叶氮在生物力能学组分分配系数(P_B)和叶氮在光捕组分的分配系数(P_L)均较生长在大气CO₂浓度低,表明在高CO₂浓度下较长期生长(8周)的香蕉叶片多个光合过程受抑制,光合活性明显降低.     

Evidence for spatial niche partitioning in predaceous aphidophaga: Use of plant colour as a cue

A field experiment involving aphid-free control and nutrient-stressed plants of 5 maize (Zea mays L.) genotypes was conducted to determine if predaceous aphidophaga use plant cues, such as colour, to select plants on which to forage. Nutrient stress resulted in plants lighter in colour (Yellow) than control plants in all the maize genotypes. Coccinellids were significantly more abundant on yellow plants than on greener control plants whereas chrysopids were significantly more numerous on controls in 3 out of 5 maize genotypes. These two groups of predators may use plant colour to partition habitat spatially and exploit their aphid prey while minimizing intraguild interactions.     

Plant and fungal identity determines pathogen protection of plant roots by arbuscular mycorrhizas

1.  A major benefit of the mycorrhizal symbiosis is that it can protect plants from below-ground enemies, such as pathogens. Previous studies have indicated that plant identity (particularly plants that differ in root system architecture) or fungal identity (fungi from different families within the Glomeromycota) can determine the degree of protection from infection by pathogens. Here, we test the combined effects of plant and fungal identity to assess if there is a strong interaction between these two factors.
2.  We paired one of two plants ( Setaria glauca , a plant with a finely branched root system and Allium cepa , which has a simple root system) with one of six different fungal species from two families within the Glomeromycota. We assessed the degree to which plant identity, fungal identity and their interaction determined infection by Fusarium oxysporum , a common plant pathogen.
3.  Our results show that the interaction between plant and fungal identity can be an important determinant of root infection by the pathogen. Infection by Fusarium was less severe in Allium (simple root system) or when Setaria (complex root system) was associated with a fungus from the family Glomeraceae. We also detected significant plant growth responses to the treatments; the fine-rooted Setaria benefited more from associating with a member of the family Glomeraceae, while Allium benefited more from associating with a member of the family Gigasporaceae.
4.   Synthesis . This study supports previous claims that plants with complex root systems are more susceptible to infection by pathogens, and that the arbuscular mycorrhizal symbiosis can reduce infection in such plants – provided that the plant is colonized by a mycorrhizal fungus that can offer protection, such as the isolates of Glomus used here.     

Allelopathy of a native grassland community as a potential mechanism of resistance against invasion by introduced plants

Successful plant invasions depend, at least partly, on interactions between introduced plants and native plant communities. While allelopathic effects of introduced invaders on native resident species have received much attention, the reverse, i.e. allelopathic effects of native residents on introduced plants, have been largely neglected. Therefore, we tested whether allelopathy of native plant communities decreases their invasibility to introduced plant species. In addition, we tested among the introduced species whether the invasive ones are more tolerant to allelopathy of native plant communities than the non-invasive ones. To test these hypotheses, we grew nine pairs of related (congeneric or confamilial) invasive and non-invasive introduced plant species (i.e. 18 species) in the presence or absence of a native grassland community, which consisted of three common forbs and three common grasses, with or without activated carbon in the soil. Activated carbon reduced the survival percentage and growth of introduced plants in the absence of the native plant community. However, its net effect on the introduced plants was neutral or even slightly positive in the presence of the native community. This might suggest that the native plant community imposed allelopathic effects on the introduced plants, and that these effects were neutralized or reduced by activated carbon. The invasive and non-invasive introduced plants, however, did not differ in their tolerance to such allelopathic effects of the native plant community. Thus, although allelopathy of native plant communities might increase their resistance against introduced plants, there was no evidence that tolerance to allelopathy of native plant communities contributes to the degree of invasiveness of introduced plants.     

Low nutritive quality as a plant defence: Effects of herbivore-mediated interactions

Summary A plant may lower its nutritive quality, for herbivores, by using secondary compounds, morphological characters and/or having a lowered nutrient content. If such traits decrease the amount of resources lost through herbivory, then they act as antiherbivore defences. However, if herbivores compensate for the lowered nutrient availability, by increasing their intake rates or by prolonging their feeding periods, then this may render the defence useless. I analyse the conditions for evolution of this type of plant defences in a game theoretical model. The predictions of the model depend on the amount of compensatory feeding performed by the herbivores and on the herbivores' mobility in relation to the spatial structure of the plant population. When herbivores cannot compensate for a lowered nutritive quality, the defence can evolve irrespective of the type of herbivore. When herbivores can compensate for such defences, the outcome depends on how the herbivores compensate. In situations where herbivores compensate only on defended plants, which could correspond to immobile herbivores, this type of defence can evolve only if the level of compensation is lower than a certain critical value. When herbivores compensate more on defended than on undefended plants, e.g. because of low mobility, the outcome depends on the level of compensation performed on defended plants. If this level of compensation is high, then the model predicts a stable coexistence of defended and undefended plants and, if it is low, then the populations can consist of only defended plants. When herbivores compensate more on undefended plants than on defended ones, e.g. highly mobile herbivores, the result is populations consisting of either only defended plants, or only undefended plants. Consequently, the fact that herbivores may compensate for lowered nutrient quality does not, as such, nullify the notion of low nutrient quality as a plant defence. However, compensatory feeding may restrict the conditions for the evolution of such defences.     

You get what you pay for: reward-specific trade-offs among direct and ant-mediated defences in plants

Plant defences against herbivores include direct defences such as secondary metabolites or physical structures (e.g. trichomes) as well as indirect defences mediated via mutualistic interactions with other organisms including ants. Production of both direct defences and rewards for mutualistic ants may be costly for a plant, and it has been suggested that trade-offs may exist between direct and ant-mediated defences. We have conducted a meta-analysis of 25 studies testing the above hypothesis and found a significant negative correlation between plant allocation to direct and ant-mediated defences. The strength of correlation was similar for across- and within-species comparisons, and for chemical and physical direct defences. However, trade-offs with direct defences were significant only in plants which offered to ants more costly rewards such as food bodies and/or domatia, but not in plants which attracted ants with relatively cheap extrafloral nectaries. Our results therefore support the hypothesis that plant investment in ant-mediated defences may reduce the requirement for direct chemical and physical defences, but only in plants which offer more costly rewards to their bodyguards.     

Integrated view of plant metabolic defense with particular focus on chewing herbivores

Success of plants largely depends on their ability to defend against herbivores. Since emergence of the first voracious consumers, plants maintained adapting their structures and chemistry to escape from extinction. The constant pressure was further accelerated by adaptation of herbivores to plant defenses, which all together sparked the rise of a chemical empire comprised of thousands of specialized metabolites currently found in plants. Metabolic diversity in the plant kingdom is truly amazing, and although many plant metabolites have already been identified, a large number of potentially useful chemicals remain unexplored in plant bio-resources. Similarly, biosynthetic routes for plant metabolites involve many enzymes, some of which still wait for identification and biochemical characterization. Moreover, regulatory mechanisms that control gene expression and enzyme activities in specialized metabolism of plants are scarcely known. Finally, understanding of how plant defense chemicals exert their toxicity and/or repellency against herbivores remains limited to typical examples, such as proteinase inhibitors, cyanogenic compounds and nicotine. In this review, we attempt summarizing the current status quo in metabolic defense of plants that is predominantly based on the survey of ubiquitous examples of plant interactions with chewing herbivores.     

Non-native plants rarely provide suitable habitat for native gall-inducing species

For insect herbivores, a critical niche requirement—possibly the critical niche requirement—is the presence of suitable host plants. Current research suggests that non-native plants are not as suitable as native plants for native herbivores, resulting in decreases in insect abundance and richness on non-native plants. Like herbivores, gall-forming insects engage in complex, species-specific interactions with host plants. Galls are plant tissue tumors (including bulbous or spindle-shaped protrusions on leaves, stems and other plant organs) that are induced by insects through physical or chemical damage (prompting plants to grow a protective tissue shell around the insect eggs and larvae). As such, we hypothesized that gall-inducing insect species richness would be higher on native than non-native plants. We also predicted higher gall-inducing insect species richness on woody than herbaceous plants. We used an extensive literature review in which we compiled gall host plant species by genus, and we assigned native or non-native (or mixed) status to each genus. We found that native plants host far more gall-inducing insect species than non-native plants; woody plants host more gall-inducing species than herbaceous plants; and native woody plants host the most gall-inducing species of all. Gall-inducing species generally are a very cryptic group, even for experts, and hence do not elicit the conservation efforts of more charismatic insects such as plant pollinators. Our results suggest that non-native plants, particularly non-native woody species, diminish suitable habitat for gall-inducing species in parallel with similar results found for other herbivores, such as Lepidopterans. Hence, the landscape-level replacement of native with non-native species, particularly woody ones, degrades taxonomically diverse gall-inducing species (and their inquilines and parasitoids), removing multiple layers of diversity from forest ecosystems.

     

Mycorrhizal networks: des liaisons dangereuses?

Mycorrhizal associations, by which most land plants receive mineral nutrition, are diffuse and often non-specific. A common mycorrhizal network is formed when fungal mycelia colonize and link together the roots of two or more plants, sometimes of different species. Here, we discuss recent work showing how, under realistic ecological conditions, such networks can affect the physiology and ecology of plants by facilitating interplant nutrient exchange, acting as inoculum reservoirs for seedlings and altering plant competitive abilities. Although mechanisms for their evolutionary emergence remain unclear, investigating mycorrhizal networks profoundly modifies our understanding of plant communities.     

Transgenerational consequences of plant responses to herbivory: an adaptive maternal effect?

Herbivory has many effects on plants, ranging from shifts in primary processes such as photosynthesis, growth, and phenology to effects on defense against subsequent herbivores and other species interactions. In this study, I investigated the effects of herbivory on seed and seedling characteristics of several families of wild radish (Raphanus raphanistrum) to test the hypothesis that herbivory may affect the quality of offspring and the resistance of offspring to plant parasites. Transgenerational effects of herbivory may represent adaptive maternal effects or factors that constrain or amplify natural selection on progeny. Caterpillar (Pieris rapae) herbivory to greenhouse-grown plants caused plants in some families to produce smaller seeds and those in other families to produce larger seeds compared with undamaged controls. Seed mass was positively associated with probability of emergence in the field. The number of setose trichomes, a putative plant defense, was higher in the progeny of damaged plants in some families and lower in the progeny of damaged plants in other families. In a field experiment, plant families varied in their resistance to several herbivores and pathogens as well as in growth rate and time to flowering. Seeds from damaged parent plants were more likely to become infested with a plant virus. Although herbivory on maternal plants did not directly affect interactions of offspring with other plant parasites, seed mass influenced plant resistance to several attackers. Thus, herbivory affected seed characters, which mediated interactions between plants and their parasites. Finally, irrespective of seed mass, herbivory on maternal plants influenced components of progeny fitness, which was dependent on plant family. Natural selection may act on plant responses to herbivory that affect seedling-parasite interactions and, ultimately, fitness.     

Acquired immunity to herbivory and allelopathy caused by airborne plant emissions

Numerous plant species respond to volatile cues to adjust their defenses against herbivores. Some volatile chemicals, such as terpenoids and green leaf volatiles, that are responsible for communication between plants and arthropods are also required for intraspecific communication between plants and for coordination among branches within a single plant. We are now aware that some ‘receiver’ plants are able to eavesdrop on their neighbors and tailor their defenses to their current and expected risks caused by herbivores. By contrast, a suite of volatiles also serve as natural herbicides (allelochemicals) that are detrimental for receiver plants. Since various molecular and ecological mechanisms underlying these phenomena have been clarified, it is time to ask whether more plants eavesdrop on infochemical cues, and if these cues that allow them to adjust their defenses to suit their risk also increase their fitness as a result.