叶际微生物诱发气孔免疫的机制及其应用前景北大核心CSCD

植物叶际微生物通过自身代谢活动影响植物功能的正常运行。而植物则可感应叶际微生物的存在,在诱发气孔免疫关闭以抵御病原菌入侵的同时,也降低了植物蒸腾作用,提高了其水分利用效率。对气孔免疫相关理论的研究有利于开发新型生物抗蒸腾剂,并对开发节水农业新技术具有重要意义。该文综述了叶际微生物与植物间的互作关系、气孔免疫及其免疫机制等方面的研究进展,并探讨了相关机制在节水农业方面的应用前景和重点研究方向。     

气孔免疫的研究进展及展望

气孔长期以来被认为是植物病原菌入侵植物体内的被动通道,而最新的研究则表明气孔作为植物先天免疫的重要环节,在限制细菌入侵方面起到主动作用。这一发现也带动了植物免疫学,即植物气孔开合调控和植物免疫学交叉学科的快速发展。基于此,本文对气孔免疫的机制研究展开综述并对其对植物水分利用效率的影响进行展望。     

植物的气孔振荡及其应用前景

介绍了植物气孔振荡的发现及其研究进展,并分析了气孔振荡发生的机制及在干旱农业区的应用前景。     

叶际微生物及其与外界互作的研究进展

叶际微生物及其生存环境共同形成了一个复杂的生态系统。建立在纯种分离和纯培养技术基础之上的传统研究方法只能了解其中部分叶际微生物,但对物种组成、种群结构和生态学作用等方面的认识都比较片面。近年来随着分子生物学和生物信息学的进步,人们对叶际微生物总群落的分析逐渐揭示了叶际微生物组成的多样性及其特点,以及与外界互相作用的复杂性。研究表明,植物种类、地理位置和季节差异等都不同程度地影响着叶际微生物群落的构成。本文综述了近年来国内外叶际微生物群落结构组成及其与外界互作方面的研究进展,有利于加深对叶际微生物的了解,也有助于深入理解叶际微生物与植物生长和植物病虫害防治的关联关系。     

玉米与叶际微生物组的互作遗传机制

为了解玉米(Zeamays)和其定植微生物组之间的相互作用,探究玉米与叶际微生物组之间的互作遗传机制,该研究采用数学模型量化微生物之间相互作用的4种方式:互利共生、拮抗、侵略、利他,分析230份玉米叶际微生物组数据,利用网络作图研究玉米与叶际微生物组之间的互作遗传机制。结果表明:在微生物互作网络中确定了67个中心节点微生物,通过网络作图筛选到玉米405个显著单核苷酸多态性(SNPs)位点,最终定位到23个枢纽基因,发现其在促进植物生长、抵御病原菌侵染、耐受非生物胁迫方面起到重要作用。研究结果有助于在作物遗传育种以及构建新型菌剂促进植物生长方面提供思路。     

叶际微生物对马尾松凋落针叶分解的影响

叶际微生物作为最先定殖在凋落叶上的微生物类群,可能直接参与凋落叶的分解。为验证此猜想,该研究通过扩增子高通量测序技术和室内分解实验,探究了马尾松(Pinusmassoniana)叶际微生物多样性及叶际微生物对马尾松凋落物的分解影响。结果表明:(1)马尾松的叶际存在着丰富而多样的微生物群体,针叶在凋亡后,叶际微生物群落发生变化。成熟针叶、凋落针叶、分解层针叶共有大量可操作分类单元(OTUs)。(2)马尾松针叶分解过程可分为两个阶段:快速分解期(前8个月)和缓慢分解期(8个月以后)。衰亡针叶(刚凋落但未接触土壤)叶际微生物可直接参与马尾松凋落针叶分解,且分解速率表现为叶际微生物+土壤微生物处理>叶际微生物处理>土壤微生物处理。在马尾松针叶分解过程中叶际微生物与土壤微生物存在协同作用。(3)凋落针叶分解速率与木质素和纤维素分解速率呈极显著正相关关系,但与木质素和纤维素分解酶活性无显著相关关系。木质素分解酶——多酚氧化酶与过氧化物酶活性极显著负相关,纤维素分解酶——β葡萄糖苷酶活性与纤维二糖苷酶活性则呈极显著正相关关系。综上,该研究结果表明叶际微生物可直接参与凋落针叶的分解,且其对...     

青杨雌雄株叶际微生物群落多样性和结构的差异

【目的】本论文探究了青杨雌雄株的叶际微生物的群落结构差异及其主要环境影响因素。【方法】以河北小五台山的天然青杨林为研究对象,采用基于16S rRNA/ITS1基因的MiSeq高通量测序技术,分析了青杨雌雄株叶际细菌和真菌的群落结构,并耦合分析其与叶片理化性质的相关性。【结果】测序结果表明细菌和真菌的多样性指数ACE、Chao1、Shannon、Simpson在雌雄株间都无显著性差异(P>0.05)。Metastats组间群落显著性差异分析表明,在门水平,青杨雌雄株叶际细菌和真菌都无显著差异。而在属水平,青杨雌雄株的叶际细菌Amnibacterium和Spingomonas及真菌Aureobasidium、Elmerina、Exobasidium、Endoconidioma、Monilinia和Rhodotorula的相对丰度在雌雄株叶际有显著差异(P<0.05)。基于OTUs的菌群分析表明,青杨雌株和雄株的叶际环境上都有其各自的特有菌群,如雌株的特有真菌Pringsheimia(0.15%)和细菌Chitinophaga(0.04%)。RDA冗余分析表明,叶片含水量与青杨叶际真菌的群落结构有显著相关性(P<0.05),而未发现青杨细菌群落结构与测定的叶片理化性质有显著相关。【结论】青杨雌雄株叶际微生物在属水平有显著分异的菌属,且可能受叶片理化性质影响,该结果为揭示雌雄异株植物的叶际微生物差异有重要借鉴意义。     

弱光下生长的葡萄叶片蒸腾速率和气孔结构的变化

 植物能够对生长环境产生生态适应性,这种适应性可从气孔导度、光合速率、水分利用效率等生态指标上反映出来。为了研究葡萄蒸腾特性对弱光环境的适应性变化,本试验以‘京玉’葡萄幼苗（Vitis vinefera cv. Jingyu）为试验材料,通过遮光处理（2个处理,分别遮光65%和85%）营造弱光环境,测定了在弱光环境下生长的葡萄叶片蒸腾速率、气孔导度、水分利用效率对光照强度的响应,同时用扫描电镜技术观察了气孔的发育。结果表明,弱光环境下生长的葡萄幼苗,叶片的水势较高,但水分利用效率较低,叶片蒸腾速率和气孔导度变化对光照强度的响应缓慢,而自然光下生长的葡萄叶片则反应较迅速。通过对气孔结构的研究发现,与自然光照环境下生长的植株相比,在弱光环境下生长的葡萄幼苗,叶片下表皮的气孔横轴变宽,大小气孔之间差异减少,气孔外突,表皮细胞变大甚至扭曲,角质层变薄。说明葡萄幼苗能够对弱光环境产生适应性变化,其蒸腾特性的变化与其气孔结构的变化相关,具有一致性。     

拟南芥与叶际微生物组的互作遗传机制——基于网络作图理论

叶际微生物组对植物的生长发育至关重要,但植物与其定殖微生物组相互作用机制尚不明确。目前植物与微生物互作研究多集中于根际微生物组,对叶际微生物组的研究较少,且这些研究未能从微生物互作的角度探究植物与微生物的相互作用机理。基于网络作图理论,将拟南芥基因组SNP （Single Nucleotide Polymorphisms）分子标记数据与微生物组网络特征值相关联,挖掘影响叶际微生物组网络结构的枢纽基因,以探究拟南芥塑造叶际微生物组网络结构的遗传机制。通过对188株拟南芥及其叶际微生物组数据的分析,识别出四种关系下的中心节点微生物,筛选到622个显著SNP位点。进一步构建了贝叶斯遗传网络,获得26个枢纽基因,这些基因可能参与了植物抗病、激素分泌和生长发育相关的分子途径。本研究从全基因组角度探究植物调控自身微生物组的遗传机制,揭示植物与微生物组如何互作促进植物健康,将为精准分子育种提供理论基础和遗传资源,并为合成菌群用于创制新型菌剂提供数据支持,具有重要的科学意义和应用价值。     

黄龙山林区不同演替时期典型树种光诱导的气孔动力学研究

光诱导的气孔动力学响应快慢是影响植物叶水分利用效率的重要因素,为探索黄土高原不同演替阶段树种水分利用效率差异的生理机制,该研究以黄龙山林区典型树种(演替早期种山杨和白桦、演替后期种辽东栎)的幼龄实生苗为材料,采用盆栽试验,研究了叶片光诱导的气孔导度动力学参数差异及其与气孔特征、叶长期水分利用效率的关系。结果表明：(1)山杨和白桦气孔开放过程中气孔导度(g_s)增加的时间常数(K_i)小于辽东栎,但气孔关闭过程中气孔导度降低的时间常数(K_d)则大于辽东栎,表明山杨和白桦气孔开放更快,而辽东栎的气孔关闭更快。同时,气孔开放过程中山杨和白桦的g_s响应幅度均大于辽东栎,气孔关闭过程中山杨的g_s响应幅度亦大于辽东栎。(2)3种树种中,辽东栎的气孔密度最大,气孔最小,气孔指数最大,辽东栎气孔特征无法解释其慢速的气孔开放过程。 (3)山杨和白桦具有高的光合速率、最大羧化效率和最大电子传递速率,3种树种碳同位素比率(δ¹³C)表征的长期水分利用效率表现为山杨>白桦>辽东栎。研究认为,演替早期种山杨和白桦的高水分利用效率与其快速的气孔开放有关,而演替后期种辽东栎快速的气孔关闭并未增加其水分利用效率,且长期水分利用效率低于山杨和白桦,可能与辽东栎慢速的气孔开放限制了其光合速率有关。     

Effects of Drought Stress Induced by Polyethylene Glycol on Pigment Content and Photosynthetic Gas Exchange of Pistacia Khinjuk and P. Mutica

The effects of drought stress induced by polyethylene glycol, PEG (molecular mass 6000) on some ecophysiological characteristics of two wild pistachio species, Mastic and Khinjuk (P. mutica and P. khinjuk) selected as root stocks for production of edible pistachio trees (P. vera) in Iran and Turkey, were studied. Net photosynthetic rate (P _N), stomatal conductance (g _s), chlorophyll (Chl) fluorescence parameters, leaf water potential (Ψ₁), leaf osmotic potential (Ψ_π), leaf osmotic adjustment (ΔΨ_π), and Chl a and b were measured. All parameters were influenced by increase in concentra-tion of PEG in the nutrient solutions. P _N, g _s, and Chl a were significantly higher in P. mutica than in P. khinjuk but, compared to the control treatment, P. khinjuk showed a higher resistance to drought stress than P. mutica. This revised version was published online in August 2006 with corrections to the Cover Date.     

Stomatal limitation of photosynthesis as affected by water stress and CO2 concentration

A water stress effect on photosynthesis and transpiration of wheat seedlings at 50-500 µmol(CO2) mol-1 was measured in an open gas exchange system. The limitation of photosynthesis by stomatal conductance was quantified by a stomatal control coefficient of the net photosynthetic rate. The stomatal control coefficient increased linearly as the water potential of root media decreased to -1 MPa, and it decreased with increasing CO2 concentration.     

Compensatory effects of elevated CO<Subscript>2</Subscript> concentration on the inhibitory effects of high temperature and irradiance on photosynthetic gas exchange in carrots

We determined the interactive effects of irradiance, elevated CO₂ concentration (EC), and temperature in carrot (Daucus carota var. sativus). Plants of the cv. Red Core Chantenay (RCC) were grown in a controlled environmental plant growth room and exposed to 3 levels of photosynthetically active radiation (PAR) (400, 800, 1 200 μmol m⁻² s⁻¹), 3 leaf chamber temperatures (15, 20, 30 °C), and 2 external CO₂ concentrations (C _a), AC and EC (350 and 750 μmol mol⁻¹, respectively). Rates of net photosynthesis (P _N) and transpiration (E) and stomatal conductance (g _s ) were measured, along with water use efficiency (WUE) and ratio of internal and external CO₂ concentrations (C _i/C _a). P _N revealed an interactive effect between PAR and C _a. As PAR increased so did P _N under both C _a regimes. The g _s showed no interactive effects between the three parameters but had singular effects of temperature and PAR. E was strongly influenced by the combination of PAR and temperature. WUE was interactively affected by all three parameters. Maximum WUE occurred at 15 °C and 1 200 μmol m⁻² s^{− 1} PAR under EC. The C _i /C _a was influenced independently by temperature and C _a. Hence photosynthetic responses are interactively affected by changes in irradiance, external CO₂ concentration, and temperature. EC significantly compensates the inhibitory effects of high temperature and irradiance on P _N and WUE.     

Net photosynthetic and transpiration rates in a chlorophyll-deficient isoline of soybean under well-watered and drought conditions

The gas exchange traits of wild type soybeans (cv. Clark) and a near-isogenic, chlorophyll-deficient line homozygous for the recessive allele y9 (y9y9) were compared under either well-watered or water-stress conditions. Mature leaves of y9 had a 65% lower chlorophyll content than wild type. However, the net photosynthetic rate (PN) of y9 leaves was only 20% lower than in the wild type, irrespective of water availability. Transpiration rates (E) were significantly higher in leaves of y9, compared to the wild type, either under well-watered or stress conditions. The higher E of y9 correlated with increased stomatal conductance, particularly in the abaxial epidermis, where more than 70% of the stomata were located. The combination of lower PN and increased E resulted in a significant decrease of water use efficiency in y9, at both water availability levels. The relative water content decreased in stressed leaves, much more in y9 than in wild type leaves, probably because of the higher E of the mutant line. This revised version was published online in June 2006 with corrections to the Cover Date.     

Photosynthesis and Water Use Efficiency in Twenty Tropical Tree Species of Differing Succession Status in a Brazilian Reforestation

Leaf gas exchange characteristics were measured in twenty woody species that differ in succession status ranging from pioneer species (PS) to late succession species (LS) in a Brazilian rain-reforestation ecosystem. Photon-saturated photosynthetic rate, calculated per either a leaf area (P _NA) or a dry mass (P _NM) basis, differed among species. P _NA and P _NM were highest in PS and lowest in LS. Variation among species was 3-fold (from 7 to 23 mol m^–2 s^–1) for P _NA, and 5-fold (from 50 to 275 mol kg^–2 s^–1) for P _NM. The highest P _NA (23 mol m^–2 s^–1) and P _NM (275 mol kg^–2 s^–1) values were recorded in PS Croton urucurana, while the lowest P _NA (7 mol m^–2 s^–1) and P _NM (50 mol kg^–2 s^–1) values were recorded in LS Aspidosperma cylindrocarpon. A considerable overlap was recorded between PS and LS in values of stomatal conductance (g _s), transpiration rate (E), and leaf mass to area ratio (ALM). However, C. urucurana also showed highest g _s and E. P _NM was highly correlated with ALM in both PS and LS (r=–0.75 and –0.90, respectively). The high values of instantaneous transpiration efficiency (ITE) and intrinsic water use efficiency (WUE_i) were also observed in the PS when compared with the LS.     

Stomatal and photosynthetic responses to shade in sorghum, soybean and eastern gamagrass

We studied photosynthetic and stomatal responses of grain sorghum ( Sorghum bicolor [L.] Moench cv. Pioneer 8500), soybean ( Glycine max L. cv. Flyer) and eastern gamagrass ( Tripsacum dactyloides L.) during experimental sun and shade periods simulating summer cloud cover. Leaf gas exchange measurements of field plants showed that short-term (5 min) shading of leaves to 300–400 μmol m⁻² s⁻¹ photosynthetic photon flux density reduced photosynthesis, leaf temperature, stomatal conductance, transpiration and water use efficiency and increased intercellular CO₂ partial pressure. In all species, photosynthetic recovery was delayed when leaves were reilluminated, apparently by stomatal closure. The strongest stomatal response was in soybean. Photosynthetic recovery was studied further with soybeans grown indoors (maximum photosynthetic photon flux density 1 200 μmol m⁻² s⁻¹). Plants grown indoors had responses to shade similar to those of field plants, except for brief nonstomatal limitation immediately after reillumination. These responses indicated the importance of the light environment during leaf development on assimilation responses to variable light, and suggested different limitations on carbon assimilation in different parts of the soybean canopy. Photosynthetic oxygen evolution recovered immediately upon reillumination, indicating that the light reactions did not limit soybean photosynthetic recovery. While shade periods caused stomatal closure and reduced carbon gain and water loss in all species, the consequences for carbon gain/water loss were greatest in soybean. The occurrence of stomatal closure in all three species may arise from their shared phenologies and herbaceous growth forms.     

Intrinsic changes in photosynthetic parameters of carrot leaves under increasing CO<Subscript>2</Subscript> concentrations and soil moisture regimes

A controlled growth chamber experiment was conducted to investigate the short-term water use and photosynthetic responses of 30-d-old carrot seedlings to the combined effects of CO₂ concentration (50–1 050 μmol mol⁻¹) and moisture deficits (−5, −30, −55, and −70 kPa). The photosynthetic response data was fitted to a non-rectangular hyperbola model. The estimated parameters were compared for effects of moisture deficit and elevated CO₂ concentration (EC). The carboxylation efficiency (α) increased in response to mild moisture stress (−30 kPa) under EC when compared to the unstressed control. However, moderate (−55 kPa) and extreme (−70 kPa) moisture deficits reduced α under EC. Maximum net photosynthetic rate (P _Nmax) did not differ between mild water deficit and unstressed controls under EC. Moderate and extreme moisture deficits reduced P _Nmax by nearly 85 % compared to controls. Dark respiration rate (R _D) showed no consistent response to moisture deficit. The CO₂ compensation concentration (Γ) was 324 μmol mol⁻¹ for −75 kPa and ranged 63–93 μmol mol⁻¹ for other moisture regimes. Interaction between moisture deficit and EC was noticed for P _N, ratio of intercellular and ambient CO₂ concentration (C _i/C _a), stomatal conductance (g _s ), and transpiration rate (E). P _N was maximum and C _i/C _a was minimum at −30 kPa moisture deficit and at C _a of 350 μmol mol⁻¹. The g _s and E showed an inverse relationship at all moisture deficit regimes and EC. Water use efficiency (WUE) increased with moisture deficit up to −55 kPa and declined thereafter. EC showed a positive influence towards sustaining P _N and increasing WUE only under mild moisture stress, and no beneficial effects of EC were noticed at moderate or extreme moisture deficits.     

An attempt to establish a synthetic model of photosynthesis-transpiration based on stomatal behavior for maize and soybean plants grown in field

A synthetic model of photosynthesis-transpiration was established based on a comprehensive consideration of models of CO₂ and H₂O fluxes controlled by stomata of plant leaves.The synthetic model was developed by introducing the internal conductance to CO₂ assimilation, g_ic, and the general equation of stomatal conductance model to H₂O diffusion, g_sw = g₀+a₁A_mf(D_s)/(C_s-Γ), into models of CO₂ and H₂O diffusion through the plant leaves stomata. In the above expression, g₀ and a₁ are coefficients, C_s ambient CO₂ concentration at leaf surface, Γ CO₂ compensation point, and f(D_s) the general function describing the response of stomatal conductance to humidity. Using the data observed in maize (Zea mays L.) and soybean (Glycine max Merr.) plants grown in the field, the parameters in the model were identified, and the applicability of the model was examined. The verification indicated that the developed model could be used to estimate net assimilation rate, transpiration rate, and water use efficiency with a high enough level of precision. The examination also showed that when f(D_s) = h_s or f(D_s) = (1+D_s/D₀)⁻¹ was employed, the estimation precision of the synthetic model was highest. In the study, the parameter g_ic was estimated by means of a linear function of Q_P because it was shown to be mostly correlated with photosynthetic photon flux, Q_P, among various environmental factors.     

Evidence of changing intrinsic water‐use efficiency under rising atmospheric CO2 concentrations in Boreal Fennoscandia from subfossil leaves and tree ring δ13C ratios

Investigating the many internal feedbacks within the climate system is a vital component of the effort to quantify the full effects of future anthropogenic climate change. The stomatal apertures of plants tend to close and decrease in number under elevated CO₂ concentrations, increasing water‐use efficiency (WUE) and reducing canopy evapotranspiration. Experimental and modelling studies reveal huge variations in these changes such that the warming associated with reduced evapotranspiration (known as physiological forcing) is neither well understood or constrained. Palaeo‐observations of changes in stomatal response and plant WUE under rising CO₂ might be used to better understand the processes underlying the physiological forcing feedback and to link measured changes in plant WUE to a specific physiological change in stomata. Here we use time series of tree ring (Pinus sylvestris L.) δ¹³C and subfossil leaf (Betula nana L.) measurements of stomatal density and geometry to derive records of changes in intrinsic water‐use efficiency (iWUE) and maximum stomatal conductance in the Boreal zone of northern Finland and Sweden. We investigate the rate of change in both proxies, over the recent past. The independent lines of evidence from these two different Boreal species indicate increased iWUE and reduced maximum stomatal conductance of similar magnitude from preindustrial times (ca. ad 1850) to around ad 1970. After this maximum stomatal conductance continues to decrease to ad 2000 in B. nana but iWUE in P. sylvestris reaches a plateau. We suggest that northern boreal P. sylvestris might have reached a threshold in its ability to increase WUE as CO₂ rises.