Effects of ozone and aerosol pollution on photosynthesis of poplar leaves

由于经济的快速发展, 中国大部分地区正面临着严峻的复合型大气污染, 其中臭氧和气溶胶是两种主要污染物。已有的研究表明臭氧对叶片的氧化性伤害能够抑制光合作用, 而气溶胶可通过增加散射辐射比例或缓解高温抑制促进光合作用。但复合污染下, 臭氧和气溶胶如何共同调控叶片光合作用, 仍缺乏研究。该研究利用北京及周边地区之间的污染梯度, 选择加杨(Populus × canadensis)作为实验对象, 于2012-2013年生长季期间对叶片光合速率进行连续观测, 并同时监测臭氧浓度(AOT40)、气溶胶光学厚度(AOD)、空气温度和冠层内外光合有效辐射(PAR)等环境因子, 以期探讨大气复合污染下臭氧和气溶胶变化对植物叶片光合作用的影响及相关机制。结果表明: (1)臭氧浓度与空气温度、气溶胶浓度之间均呈显著正相关关系, 但气溶胶浓度与空气温度没有显著相关关系; (2)臭氧浓度增加显著抑制了阳生叶片的光合作用, 但气溶胶浓度上升促进了阳生叶片的光合作用; 臭氧浓度升高对阴生叶片光合作用的影响较小, 但气溶胶浓度上升促进了阴生叶片的光合作用; (3)标准化后的结果显示, 臭氧对阳生叶片光合作用的影响最大, 此时气溶胶的促进作用一定程度上补偿了臭氧浓度上升所带来的抑制效应。对于阴生叶片光合作用而言, 气溶胶则是最重要的影响因素。该研究发现复合污染下阴生叶和阳生叶光合响应不同, 这表明冠层结构可能通过影响阴生叶和阳生叶的比例, 从而对植物生长产生不同影响。该研究对理解大气复合污染如何影响光合作用提供了的机理支持, 同时也表明, 为了维持生态系统生产力及功能, 需要同时控制气溶胶和臭氧污染。     

环境大气臭氧污染对植物的影响（三）

(六)O_3与环境因素的互作环境中诸多的生物因素和非生物因素(表3) 都可与 O_3发生互作(相互作用),产生相加作用(=单独作用之和)、协同作用(>单独作用之和)和拮抗作用(<单独作用)。在互作的双方中,O_3起主要的作用。但互作可影响植物对 O_3的反应方式和程度。此外,已经证明,与植物 O_3     

施氮肥缓解臭氧对小麦光合作用和产量的影响

以小麦(Triticum aestivum)品种‘扬麦16’为试材, 利用开放式空气臭氧(O₃)浓度升高平台, 研究了增施氮(N)肥对O₃对小麦光合作用和产量影响的缓解作用。结果表明, O₃胁迫下灌浆期小麦的净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)、叶绿素a (Chl a)、叶绿素b (Chl b)、类胡萝卜素(Car)、总叶绿素含量(Chl t)和可溶性蛋白的含量显著降低, 降幅分别为28.95%、31.79%、23.17%、58.89%、68.64%、22.89%、60.31%和32.00%; 胞间CO₂浓度(C_i)变化很小; 成熟期生物量和收获时产量也明显下降, 降幅分别为12.23%和12.63%; 而增施N肥可以增加小麦灌浆期的P_n、Chl a、Chl b、可溶性蛋白的含量, 进而增加小麦生物量和产量, 增幅分别为25.66%、83.05%、121.57%、30.33%、14.94%和10.67%, 而对C_i、G_s、T_r、Car含量无明显影响。O₃和N肥对小麦叶片的P_n、Chl t及可溶性蛋白含量有明显的交互作用。因此, 在大气O₃浓度升高条件下增施N肥对小麦O₃损伤有一定的缓解作用。     

臭氧对冬小麦叶片膜保护系统的影响

通过开顶式气室（ＯＴＣｓ）研究臭氧对冬小麦不同发育时期（抗节期、抽穗期、灌浆期）的叶片膜保护系统的影响。实验结果表明,在自氧胁迫下,小麦叶片叶绿素ａ、ｂ含量明显下降,膜透性增加、丙二醛（ＭＤＡ）含量上升,过氧化氢酶（ＣＡＴ）活性开始上升后转为逐渐下降,过氧化特（ＰＯＤ）活性逐渐或急剧上升。臭氧诱导了活怀氧生成,影响了抗氧化酶的活性,造成活性氧产生和清除之间的不平衡,促进了膜脂过氧化,对叶片膜保护系     

臭氧暴露对大豆叶片群体光合作用及产量的影响

臭氧（O₃）已经成为我国许多大中城市夏季的首要污染物,其具有较强的植物毒性,严重威胁农业安全。O₃污染常发生于高温晴天,具有间歇性和累积性的特点,但现有研究多集中于在叶片尺度上探究长期O₃暴露对植物生理过程的影响,而间歇性暴露对植物整株生长和光合生理特性的影响鲜有报道。以大豆为实验对象,依托开顶式气室（OTC）进行间歇性臭氧暴露,探究大豆叶片群体光合作用及产量对间歇性O₃暴露的响应。结果发现（1）间歇性O₃暴露具有累积性和恢复性,在低O₃暴露剂量（AOT40≤2.47μL L^-1 h^-1）处理下,大豆植株的净光合速率降低,但与对照组无显著差异。当AOT40较高时（AOT40≤5.35μL L^-1 h^-1）,大豆植株的净光合速率显著降低,而随着O₃胁迫的消失,大豆植株的净光合速率逐渐回升,并最终恢复。（2）不同的光合参数对间歇性臭氧暴露敏感性不同,其中最大净光合速率最为敏感。在低AOT40下最大净光合速率显著降低,且恢复时间更长。（3） O₃二次暴露后,净光合速率降低幅度较低,且恢复更快,说明间歇性O₃暴露可能会提高大豆的耐受阈值。（4）当AOT40低于5.35μL L^-1 h^-1时,对大豆产量无显著影响,说明间歇性臭氧暴露条件下,大豆减产阈值更高。     

黄河小浪底栓皮栎、刺槐叶片电子传递速率-光响应的模拟

为了比较直角双曲线模型、非直角双曲线模型与叶子飘模型的优缺点, 研究阴生叶和阳生叶电子传递速率的差异, 探讨环境/生物因素对电子传递速率等参数的影响, 该文采用LI-6400XT荧光测定系统对黄河小浪底栓皮栎(Quercus variabilis)、刺槐(Robinia pseudoacacia)叶片电子传递速率-光响应(J-I)曲线进行了测定, 利用直角双曲线模型、非直角双曲线模型和叶子飘模型对J-I曲线进行了拟合。结果表明, 3种模型对叶片J-I曲线拟合的决定系数(R ²)在0.96以上, 叶子飘模型的R ²最高(> 0.99)。直角双曲线模型和非直角双曲线模型无法模拟植物叶片光系统II动力学下调现象, 且不能得出饱和光强(I_sat); 直角双曲线模型对最大电子传递速率(J_max)的模拟明显大于实测值; 叶子飘模型能很好地模拟光系统II动力学下调现象, 得出的J_max和I_sat均最接近实测值。对阴生叶和阳生叶J-I曲线研究发现, 栓皮栎、刺槐阴生叶的J_max分别低于阳生叶25.0%和18.0%, 阳生叶的I_sat分别高于阴生叶26.0%和10.1%。栓皮栎和刺槐J_max与气温显著正相关; 刺槐I_sat与气温、土壤水分含量和净光合速率具有显著的正相关关系; 栓皮栎和刺槐J-I曲线初始斜率α均与净光合速率呈显著负相关关系。     

不同秧苗素质和移栽密度条件下臭氧胁迫对水稻光合作用、物质生产和产量的影响

近地层臭氧浓度升高使水稻生长受抑进而使产量下降,但这种影响是否因不同栽培条件而异尚不清楚。2011年依托先进的稻田臭氧FACE(Free Air gas Concentration Enrichment)技术平台,以汕优63为供试材料,臭氧设置大气臭氧浓度(Ambient)和高臭氧浓度(比Ambient高50%),秧苗素质设置弱苗(移栽时无分蘖)和壮苗(移栽时带两个分蘖),移栽密度设置低密度(16穴/m2)、中密度(24穴/m2)和高密度(32穴/m2),研究不同秧苗素质和移栽密度条件下臭氧胁迫对水稻生长和产量的影响。结果表明:高浓度臭氧使水稻结实期叶片SPAD值、净光合速率、气孔导度和蒸腾速率明显下降,但胞间CO2浓度和叶温无显著变化。高浓度臭氧对水稻拔节前物质生产量没有影响,但使拔节至抽穗期、抽穗至成熟期物质生产量平均分别降低13%和29%,进而使成熟期生物产量和籽粒产量均显著下降。方差分析表明,臭氧与秧苗素质间没有互作效应,但臭氧与移栽密度的互作对最终产量的影响达显著水平。以上结果表明,臭氧胁迫使水稻生长后期光合受阻,导致物质生产和产量显著下降;适当增加移栽密度可能会减少臭氧胁迫下水稻产量的损失。     

大气二氧化碳浓度升高对光合作用的影响（上）

随着工农业生产的发展和人口的迅速增长,人类对能源和木材等的需求量剧增,这便导致化石燃料（煤、石油和天然气等）的大量消耗和森林的不断砍伐。因此,大气中的ＣＯ２浓度正在持续不断地增加,从工业革命前的２７０μｍｏｌ·ｍｏｌ-１（ｐｐｍ）已上升到了目前的３５０μ?..     

Comparative ecophysiology of leaf and canopy photosynthesis

Leaves and herbaceous leaf canopies photosynthesize efficiently although the distribution of light, the ultimate resource of photosynthesis, is very biased in these systems. As has been suggested in theoretical studies, if a photosynthetic system is organized such that every photosynthetic apparatus photosynthesizes in concert, the system as a whole has the sharpest light response curve and is most adaptive. This condition can be approached by (i) homogenization of the light environment and (ii) acclimation of the photosynthetic properties of leaves or chloroplasts to their local light environments. This review examines these two factors in the herbaceous leaf canopy and in the leaf. Changes in the inclination of leaves in the canopy and differentiation of mesophyll into palisade and spongy tissue contribute to the moderation of the light gradient. Leaf and chloroplast movements in the upper parts of these systems under high irradiances also moderate light gradients. Moreover, acclimation of leaves and chloroplasts to the local light environment is substantial. These factors increase the efficiency of photosynthesis considerably. However, the systems appear to be less efficient than the theoretical optimum. When the systems are optically dense, the light gradients may be too great for leaves or chloroplasts to acclimate. The loss of photosynthetic production attributed to the imperfect adjustment of photosynthetic apparatus to the local light environment is most apparent when the photosynthesis of the system is in the transition between the light-limited and light-saturated phases. Although acclimation of the photosynthetic apparatus and moderation of light gradients are imperfect, these markedly raise the efficiency of photosynthesis. Thus more mechanistic studies on these adaptive attributes are needed. The causes and consequences of imperfect adjustment should also be investigated.     

Instantaneous canopy photosynthesis: analytical expressions for sun and shade leaves based on exponential light decay down the canopy and an acclimated non-rectangular hyperbola for leaf photosynthesis

Analytical expressions for the contributions of sun and shade leaves to instantaneous canopy photosynthesis are derived. The analysis is based on four assumptions. First, that the canopy is closed in the sense that it is horizontally uniform. Secondly, that there is an exponential profile of light down the canopy with the same decay constant for light from different parts of the sky. Thirdly, that the leaf photosynthetic response to incident irradiance can be described by a three-parameter non-rectangular hyperbola (NRH). And lastly, that light acclimation at the leaf level occurs in only one parameter of the NRH, that describing the light-saturated photosynthetic rate, which is assumed to be proportional to the local averaged leaf irradiance. These assumptions have been extensively researched empirically and theoretically and their limitations are quite well understood. They have been widely used when appropriate. Combining these four assumptions permits the derivation of algebraic expressions for instantaneous canopy photosynthesis which are computationally efficient because they avoid the necessity for numerical integration down the canopy. These are valuable for modelling plant and crop ecosystems, for which canopy photosynthesis is the primary driver. Ignoring the sun/shade dichotomy can result in overestimates of canopy photosynthesis of up to 20 %, but using a rectangular hyperbola instead of a non-rectangular hyperbola to estimate canopy photosynthesis taking account of sun and shade leaves can lead to a similarly sized underestimate.     

臭氧浓度升高对银杏光合作用的影响

在臭氧浓度升高条件下,采用开顶箱(OTC)方法研究了臭氧浓度升高对沈阳市主要绿化树种银杏光合生理特性的影响.结果表明,与对照相比,高浓度(80±8 nmol·mol-1)臭氧处理下,银杏叶片净光合速率显著降低.处理50 d时,降低幅度为33.90%(P＜0.01),类胡萝卜素含量显著增加(P＜0.05);叶绿素a、叶绿素b与叶绿素(a b)含量变化复杂,叶绿素a/b值则先降低后升高;可溶性糖含量无明显变化,而淀粉含量则随着处理时间的延长显著降低;可溶性蛋白含量低于对照,并随着处理时间延长下降幅度增大;叶片中丙二醛含量随着处理时间显著增加.处理80 d时,丙二醛含量增加了79.53%.光合作用的下降与叶绿素的变化无关,主要与膜脂过氧化有关.光合作用的下降导致了可溶性蛋白质和淀粉的减少,并最终导致生长缓慢.     

Uncovering hidden genetic variation in photosynthesis of field‐grown maize under ozone pollution

Ozone is the most damaging air pollutant to crops, currently reducing Midwest US maize production by up to 10%, yet there has been very little effort to adapt germplasm for ozone tolerance. Ozone enters plants through stomata, reacts to form reactive oxygen species in the apoplast and ultimately decreases photosynthetic C gain. In this study, 10 diverse inbred parents were crossed in a half‐diallel design to create 45 F₁ hybrids, which were tested for ozone response in the field using free air concentration enrichment (FACE). Ozone stress increased the heritability of photosynthetic traits and altered genetic correlations among traits. Hybrids from parents Hp301 and NC338 showed greater sensitivity to ozone stress, and disrupted relationships among photosynthetic traits. The physiological responses underlying sensitivity to ozone differed in hybrids from the two parents, suggesting multiple mechanisms of response to oxidative stress. FACE technology was essential to this evaluation because genetic variation in photosynthesis under elevated ozone was not predictable based on performance at ambient ozone. These findings suggest that selection under elevated ozone is needed to identify deleterious alleles in the world's largest commodity crop.     

Effects of low-level ozone exposure under ambient conditions on photosynthesis and stomatal control of Vicia faba L.

Abstract. Gas exchange rates of 4-week-old faba bean plants were measured after exposure to ozonc (120 μg m³) in an open top chamber for 8 h per day over a period of 2 weeks. The exchange rates were compared with those of control plants. Plants exposed between mid-May and the end of July 1987 showed a minor negative effect on stomatal conductance, while there was no effect on photosynthesis and respiration. Plants exposed between the end of August and early October showed a negative effect on both stomatal conductance and photosynthesis. In addition, the dark respiration rate was slightly increased. It is concluded that ozone can have a direct effect on the stomata as well as on the photosynthetic system and that the stomata are more sensitive than the photosynthetic system.     

适度高温胁迫对亚热带森林3种建群树种幼树光合作用的影响

利用Licor-6400光合作用测定系统和叶室荧光仪（Licor-6400LCF）测定适度高温（42℃）胁迫下阳生树种荷木（Schima superba）、耐荫树种黄果厚壳桂（Cryptocarya concinna）和中生性树种红锥（Castanopsis hystrix）在全日光和遮阴（20％全日光）生长下的叶片光合速率和叶绿素a荧光。适度高温胁迫引起全日光和遮阴叶片PSII原初最大光化量子产率（Fv/Tm）降低,反映适度高温胁迫引起PSII功能的部分抑制。其中适度高温对阴生树种黄果厚壳桂和遮阴下生长叶片的PSII抑制较阳生树种荷木在全日光下生长的叶片大。除在全日光下生长的黄果壳桂外,适度高温胁迫能增高全日光或遮阴下生长的荷木和红锥叶片的光合速率。同时亦表现较高的耐高光强抑制的能力。适度高温胁迫降低全日光下生长荷木和红锥叶片的PSII量子产率（ФPSII）,但对具有低西ФPSII的阴生树种黄果厚壳桂或在遮阴下生长的阳生树种荷木或中生性树种红锥叶片则影响较小。适度高温胁迫引起生长在全日光下的阳生树种荷木或中生性树种红锥叶片的CO2同化量子需要量降低,但甚少影响阴生树种黄果厚壳桂或遮阴下生长叶片CO2同化量子需要量。适度高温对亚热带森林建群种幼树光合作用的影响依赖于植物种类和叶类型（阳生和阴生叶）。     

Effects of moderate high-temperature stress on photosynthesis in three saplings of the constructive tree species of subtropical forest

During the exposition to moderate high-temperature stress, photosynthetic rates and fluorescence of chlorophyll a were measured with a photosynthetic measurement system (Li-Cor 6400) and leaf chamber fluorometer (Li-Cor6400 LCF), respectively, in leaves of saplings, sun-adapted species (Schima superba), shade-adapted species (Cryptocarya concinna), and in mesophytic plant (Castanopsis hystrix) (42°C). The results showed that moderate high-temperature stress led to a decrease in F_v/F_m, namely the primary photochemical quantum efficiency, indicating that moderate high-temperature stress causes a partial inhibition of PSII. It also showed that such an effect was more severe in the shade-adapted plant C. concinna than in the sun-adapted species S. superba. However, except for the sun-grown leaves of C. concinna, the moderate high-temperature stress increased the photosynthetic rate of leaves at high light intensity. Simultaneously, less photoinhibition was found to occur under high-light intensity, suggesting that the capacity of resistant-photoinhibition was stimulated by moderate high-temperature stress. The quantum yield of PSII (ϕ_PSII) decreased in the sun-grown leaves of S. superba and C. hystrix but did not show any significant change in leaves of the shade plant C. concinna and shade-grown leaves of sun plant S. superba or the mesophytic plant C. hystrix because they already had a very low ϕ_PSII under this condition. Moderate high-temperature stress led to a decrease in ϕ_PSII/ϕ_CO2 ratios, an estimate of the quantum requirement for CO₂ assimilation, in the sun plant S. superba and the mesophytic plant C. hystrix because they were associated with the dissipation of a lower fraction of excitation energy. However, no significant changes were found in shade plant C. concinna and in shade-grown leaves of the other examined plants. The effect of moderate high-temperature (42°C) on photosynthesis depends on species and leaf type (sun and shade leaves) in the saplings of subtropical broad-leaved trees.     

Effects of moderate high-temperature stress on photosynthesis in three saplings of the constructive tree species of subtropical forest

During the exposition to moderate high-temperature stress, photosynthetic rates and fluorescence of chlorophyll a were measured with a photosynthetic measurement system (Li-Cor 6400) and leaf chamber fluorometer (Li-Cor6400 LCF), respectively, in leaves of saplings, sun-adapted species (Schima superba), shade-adapted species (Cryptocarya concinna), and in mesophytic plant (Castanopsis hystrix) (42°C). The results showed that moderate high-temperature stress led to a decrease in F_v/F_>m, namely the primary photochemical quantum efficiency, indicating that moderate high-temperature stress causes a partial inhibition of PSII. It also showed that such an effect was more severe in the shade-adapted plant C. concinna than in the sun-adapted species S. superba. However, except for the sun-grown leaves of C. concinna, the moderate high-temperature stress increased the photosynthetic rate of leaves at high light intensity. Simultaneously, less photoinhibition was found to occur under high-light intensity, suggesting that the capacity of resistant-photoinhibition was stimulated by moderate high-temperature stress. The quantum yield of PSII (?_PSII) decreased in the sun-grown leaves of S. superba and C. hystrix but did not show any significant change in leaves of the shade plant C. concinna and shade-grown leaves of sun plant S. superba or the mesophytic plant C. hystrix because they already had a very low ?_PSII under this condition. Moderate high-temperature stress led to a decrease in ?_PSII/?_CO2 ratios, an estimate of the quantum requirement for CO2 assimilation, in the sun plant S. superba and the mesophytic plant C. hystrix because they were associated with the dissipation of a lower fraction of excitation energy. However, no significant changes were found in shade plant C. concinna and in shade-grown leaves of the other examined plants. The effect of moderate high-temperature (42°C) on photosynthesis depends on species and leaf type (sun and shade leaves) in the saplings of subtropical broad-leaved trees.     

Variations in leaf anatomical characteristics drive the decrease of mesophyll conductance in poplar under elevated ozone

Decline in mesophyll conductance (g_m) plays a key role in limiting photosynthesis in plants exposed to elevated ozone (O₃). Leaf anatomical traits are known to influence g_m, but the potential effects of O₃-induced changes in leaf anatomy on g_m have not yet been clarified. Here, two poplar clones were exposed to elevated O₃. The effects of O₃ on the photosynthetic capacity and anatomical characteristics were assessed to investigate the leaf anatomical properties that potentially affect g_m. We also conducted global meta-analysis to explore the general response patterns of g_m and leaf anatomy to O₃ exposure. We found that the O₃-induced reduction in g_m was critical in limiting leaf photosynthesis. Changes in liquid-phase conductance rather than gas-phase conductance drive the decline in g_m under elevated O_3, and this effect was associated with thicker cell walls and smaller chloroplast sizes. The effects of O₃ on palisade and spongy mesophyll cell traits and their contributions to g_m were highly genotype-dependent. Our results suggest that, while anatomical adjustments under elevated O₃ may contribute to defense against O₃ stress, they also cause declines in g_m and photosynthesis. These results provide the first evidence of anatomical constraints on g_m under elevated O₃.