不同施肥措施臭氧浓度升高对不同水稻品种光合特性的影响

近地层臭氧(O₃)已严重威胁到作物生产,而施肥可以调节土壤的养分平衡,进而促进作物生长。以两个水稻品种(徽两优898和南粳9108)为研究对象,利用开顶式气室,设置2个O₃浓度处理(NF:环境大气为对照;NF40:环境大气+40 nmol/mol O₃),每个O₃处理下嵌套设置3个肥料处理(Ino:施无机肥处理,270 kg N hm^-2 a^-1;Red:减施无机肥30%处理,189 kg N hm^-2 a^-1;Com:有机无机肥配施处理,Red+有机肥鸡粪5000 kg hm^-2 a^-1),通过测定不同生育期水稻光合参数,探究不同肥料处理下O₃对水稻不同生育阶段光合生理的影响。结果表明,NF40对水稻营养生长阶段的饱和光合速率(A_sat)没有显著影响,而显著地降低了水稻灌浆期的A_sat。基于两个水稻品种的A_sat和相对叶绿素含量(SPAD)相对减少量与O₃累积剂量关系的斜率,发现杂交稻徽两优898(A_sat和SPAD的斜率:-1.55和-0.98)比常规稻南粳9108(A_sat和SPAD的斜率:-0.92和0.06)对O₃更敏感。此外,基于不同O₃处理下水稻的气孔导度(g_s)和胞间二氧化碳浓度(C_i),可以看出O₃造成南粳9108光合速率降低的主要是非气孔因素,而徽两优898光合的降低是由气孔因素和非气孔因素共同限制。与Ino处理相比,Red处理主要通过降低叶片SPAD进而显著地抑制两种水稻品种的A_sat,但Ino处理和Com处理间A_sat没有显著差异,说明有机无机肥配施能部分缓解减施无机肥造成水稻光合的降低。O₃和肥料处理对两个水稻的所有光合参数都没有显著的交互影响,表明短期有机无机肥配施并不能有效缓解O₃对作物造成的负面影响。在O₃污染背景下,研究结果可以为通过合理的农田氮肥管理措施减缓O₃造成的作物减产提供理论依据。     

高浓度臭氧胁迫两种园林观赏草的逆境生理特征比较

以两种常见园林观赏草：白穗狼尾草（Pennisetum alopecuroides ‘White’）和拂子茅（Calamagrostis epigeios）作为试验材料,利用开顶箱（OTCs）模拟法,研究了不同高浓度臭氧（O₃,EO）：80 nmol/mol（EO-80）、120 nmol/mol（EO-120）和160 nmol/mol（EO-160）下两种观赏草叶片逆境生理特征的变化规律。结果表明：（1）短期（7 d）内随O₃浓度增加,白穗狼尾草叶绿素和类胡萝卜素含量较对照呈下降趋势,拂子茅较对照无显著变化。（2）在EO-120、EO-160下处理7 d时,两种观赏草叶片的净光合速率（P_n）和气孔导度（g_s）较对照显著下降,且白穗狼尾草下降的幅度均大于拂子茅。（3）不同高浓度O₃胁迫下,两种观赏草叶片丙二醛（MDA）含量较对照均有所升高,其中在EO-160下处理21 d时白穗狼尾草和拂子茅叶片MDA含量分别增加30.2%（P<0.05）和13.5%（P>0.05）,表明在EO-160浓度胁迫下白穗狼尾草受到的膜脂过氧化伤害大于拂子茅。（4）在EO-120和EO-160下处理21 d时,白穗狼尾草叶片可溶性蛋白含量较对照分别显著下降24.2%和43.1%,而拂子茅较对照分别下降19.0%和22.9%（P<0.05）。（5）与对照组相比,高浓度O₃下两种观赏草叶片的过氧化物酶（POD）活性随胁迫时间延长呈下降趋势,超氧化物歧化酶（SOD）活性呈先升后降。（6）综合以上生理特征比较及主成成分分析表明,佛子茅比白穗狼尾草更耐O₃,前者在O₃高污染地区可能会有更高的应用价值。     

农田冬小麦生长和产量对臭氧动态暴露的响应

 评估臭氧(O₃)污染对农田冬小麦生长和产量的影响是污染生态学和生理生态学研究的重要内容之一。该研究运用开顶式气室(OTC),对冬小麦‘ 嘉403’(Triticum aestivum cv. Jia 403)进行了O₃动态暴露的田间原位试验。实验设置过滤空气组(CF)、自然大气组(NF)和两个不同浓度的 O₃动态暴露组(DO100和DO150)。结果表明：1) O₃浓度增加,一方面可以改变灌浆期冬小麦叶片气体交换参数的日变化规律;另一方面引起表观 光量子产额、光饱和点和光补偿点等光响应参数的显著降低。这表明灌浆期叶片光合能力的下降是气孔因素和非气孔因素共同作用的结果。2) O₃暴露可以改变小麦形态特征,如植株变矮、叶片衰老加速、 叶面积变小,并最终导致产量大幅下降。     

外源H2O2对盐碱胁迫下苹果矮化砧木幼苗生理特性的影响

以2年生苹果矮化砧木M9 T337为试材,采用盆栽试验法,设置浇灌清水(CK)和盐碱胁迫(0.1 mol/L NaCl+NaHCO₃溶液)+ 喷施5种浓度的H₂O₂ ［0(T₁)、0.2 mmol/L(T₂)、0.4 mmol/L(T₃)、0.6 mmol/L(T₄)、0.8 mmol/L(T₅)］ 处理,测定各处理叶片叶绿素含量、光合气体交换参数、渗透调节物质含量、抗氧化酶活性和细胞膜透性,并利用相关性与主成分分析进行综合评价,以探讨外源过氧化氢(H₂O₂)增强其盐碱耐性的生理机制。结果表明：(1)随着盐碱胁迫(T₁)的时间延长,M9 T337幼苗叶片叶绿素a(Chl a)含量、叶绿素b (Chl b)含量、叶绿素总量(Chl t)、净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)、可溶性蛋白(SP)含量均呈逐渐下降趋势;胞间CO₂浓度(C_i)、可溶性总糖(TSS)含量、脯氨酸(Pro)含量、过氧化氢酶(CAT)活性、抗坏血酸过氧化物酶(APX)活性、相对电导率(REC)、丙二醛(MDA)含量均呈上升趋势;超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性均呈先升后降趋势。(2)与CK相比,盐碱胁迫+外源H₂O₂(T₂- T₅)处理后M9 T337幼苗叶片各指标均呈现不同幅度变化,且存在明显浓度效应,并以T₃(0.4 mmol/L H₂O₂)处理叶片的Chl a、Chl b、Chl t、SP和G_s降幅最小,C_i、REC、MDA升幅最小,TSS、Pro、APX升幅最大。(3)M9 T337幼苗叶片P_n与T_r、G_s、Chl a、Chl b、Chl t、SP、SOD、POD呈显著正相关,与C_i、MDA、CAT、APX、REC呈显著负相关。(4)综合评价表明,各处理对M9 T337幼苗叶片生理特性的效应依次为：CK>T₃>T₄>T₂>T₅>T₁。研究发现,叶面喷施适宜浓度H₂O₂可有效改善盐碱胁迫下M9 T337幼苗光合能力,显著提高抗氧化酶活性和渗透调节物质的含量,降低细胞膜透性,从而达到缓解盐碱胁迫的作用,并以0.4 mmol/L H₂O₂处理效果最佳。     

遮光对连香树幼苗光合特性及其叶片解剖结构的影响

以2年生连香树实生苗为材料,在田间通过黑色遮阳网设置全光照(L₀)及透光率55%(L₁)、25%(L₂)和10%(L₃)4种光环境,研究遮光对连香树幼苗光合作用及叶片解剖结构的影响。结果表明：(1)连香树幼苗叶片P_n在全光和L₁处理下呈非典型的“乁”形变化,未出现“午休”现象,中午14:00出现极值,而在L₂和L₃处理下变化相对缓和,极值出现在中午12:00;叶片G_s呈现与P_n类似的变化趋势,而C_i则呈基本一致的凹形变化。(2)各处理P_n、G_s和T_r的日均值均表现为L₀＞L₁＞L₂＞L₃,而C_i的日均值则呈相反的顺序;P_n与G_s、T_r、气温和光合有效辐射均呈极显著正相关关系(P＜0.01)。(3)全光照连香树幼苗的光补偿点(LCP)、光饱和点(LSP)、暗呼吸速率(R_d)均显著高于遮光处理,并维持较高的P_n而未出现明显的光抑制;遮光导致幼苗的LCP、LSP、R_d显著降低,有利于充分利用弱光,以满足低光环境下植株的正常生长。(4)与全光照相比,遮光下连香树叶片气孔密度显著变小,但气孔器长度、气孔器宽度、单个气孔器面积显著增加,气孔器面积百分比减少,影响幼苗细胞内外的水分和气体传递。(5)遮光条件下,连香树叶片明显变薄,表皮细胞厚度减小,栅栏组织(PT)厚度降低,排列变得疏松,海绵组织(ST)厚度增加,PT/ST相应减小。(6)与全光照相比,强度遮光下(L₂和L₃)连香树幼苗生长受阻,苗高(H)和基径(D)明显减小,生物量模型D²H下降;而轻度遮光(L₁)下幼苗H和D、H/D和D₂H均未出现显著变化。研究发现,连香树具有一定的光忍耐性和喜光性,对光照条件的生态幅较宽,轻度遮光影响较小,但强度遮光对连香树幼苗气体交换参数和光合响应特征产生了显著影响,同时影响了叶片的解剖结构和气孔分布特征,从而影响连香树幼苗的生长形态。在育苗生产中,适度遮光有利于降低气温、减小蒸腾,但遮光后田间有效辐射强度应保持在自然光强的55%以上。     

信号分子水杨酸减缓干旱胁迫对紫御谷光合和膜脂过氧化的副效应

为研究信号分子水杨酸(SA)对干旱胁迫下紫御谷光合和膜脂过氧化的影响,为SA应用于紫御谷抗旱育苗提供理论依据,测定分析了SA处理对干旱胁迫下紫御谷幼苗叶片光合和膜脂过氧化相关指标的变化。结果表明:(1)干旱胁迫破坏了紫御谷叶绿体的膜结构,使基粒数量明显减少,垛叠不明显,排列比较松散,而SA处理能在一定程度上保护叶绿体的膜结构。(2)干旱胁迫降低了紫御谷幼苗叶片的叶绿素b和总叶绿素含量,而SA处理能提高干旱胁迫下紫御谷幼苗叶片的叶绿素a、叶绿素b、总叶绿素和胡萝卜素含量。(3)干旱胁迫降低了叶片的净光合速率、气孔导度、蒸腾速率、光饱和点和暗呼吸速率,增加了叶片的光补偿点、CO₂饱和点、CO₂补偿点和光呼吸速率,而SA处理则增加了紫御谷幼苗叶片的净光合速率、气孔导度、光饱和点和暗呼吸速率,降低了紫御谷幼苗叶片的光补偿点、CO₂饱和点、CO₂补偿点和光呼吸速率。(4)干旱胁迫降低了紫御谷幼苗叶片的F_v/F_m和Φ_PSⅡ,显著增加了叶片的相对电导率和丙二醛含量,而SA处理则增加了幼苗叶片的F_v/F_m和Φ_PSⅡ,降低了叶片的相对电导率和丙二醛含量。表明:信号分子水杨酸能够有效减缓干旱胁迫对紫御谷光合和膜脂过氧化的影响。     

桂林喀斯特石山50种常见植物叶片光合特性

选取桂林喀斯特石山生境中常见的50种植物为研究对象,分别测定叶片单位面积最大净光合速率（A_area）、单位质量最大净光合速率（A_mass）、气孔导度（Gs）、水分利用效率（WUE）、胞间/环境CO₂浓度比值（Ci/Ca）和蒸腾速率（Tr）等光合特性指标,探讨不同物种光合特性的差异以及光合特性之间的内在联系,以此探究不同植物适应喀斯特石山生境所表现出的光合生理特性。结果表明,50种植物叶片A_area,A_mass,Gs,WUE,Ci/Ca和Tr的平均值分别为8.35 μmol m^-2 s^-1,110.98 nmol g^-1 s^-1,0.10 mol m^-2 s^-1,94.84 μmol/mol,0.57和2.37 mmol m^-2 s^-1;方差分析表明,不同物种之间在A_area,A_mass,Gs,WUE,Ci/Ca和Tr之间存在显著差异。Pearson相关性分析表明,表征50种常见植物叶片光合特性的6个指标相关性除Ci/Ca与A_area和A_mass,WUE与A_mass不一致外,其他指标两两之间相关性均表现为一致性,其中Gs与Ci/Ca呈极显著的正相关。主成分分析表明,在6个光合特性指标中,Gs和Ci/Ca可作为反映喀斯特石山植物适应生境的重要光合指标,主要表征对水分条件的敏感程度以及耐旱性强弱,同时反映了植物叶片光合速率大小,用于衡量植物对喀斯特生境的生理生态适应性。基于Gs和Ci/Ca进行聚类分析表明,50种植物划分为3类：即中等Gs较高Ci/Ca型,较低Gs较高Ci/Ca型和较低Gs,Ci/Ca型。本研究表明,喀斯特生境植物在生理生态方面所表现出的适应策略主要为对资源利用方式及抵御外界不利环境的适应策略,这为后续选择物种加速植被恢复演替进程提供了参考。     

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。     

盐胁迫下赤霉素对黄瓜种子萌发及幼苗生长的影响

研究外源GA₃对盐胁迫下黄瓜种子萌发和幼苗生长的影响。结果表明,添加不同质量浓度GA₃的各处理,其发芽率、发芽势和发芽指数均显著高于NaCl胁迫处理,其中以100 mg/L GA₃处理的发芽势、发芽率和发芽指数最高,幼苗的叶面积、根长、根冠比也最大,同时叶片中叶绿素含量最高,幼苗叶片的光合速率(P_n)、气孔导度(G_s)、胞间CO₂摩尔分数(C_i)及蒸腾速率(T_r)等均达到最大;而当赤霉素的质量浓度为50 mg/L时,叶片中的POD活性为2 005 U/(g·min）,达最大值。     

遮荫对闽楠幼苗光合及其叶片解剖特性的影响

以2年生闽楠幼苗为材料,探讨不同遮荫处理［0(CK,全光照) 和30%、50%、70%遮荫］对闽楠［Phoebe bournei (Hemsl.) Yang］幼苗光合作用及其叶片解剖结构的影响,为闽楠的合理栽培及人工林混交树种的配置提供理论依据。结果表明：(1)与全光照处理(CK)相比,闽楠幼苗叶片净光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)、最大净光合速率(P_nmax) 、光饱和点(LSP)、光补偿点(LCP)及暗呼吸速率(Rd)均随遮荫强度的增加而显著下降;在30%和50%遮荫下,幼苗能通过提高水分利用效率(WUE)和表观量子效率(AQY),增加叶绿素含量来充分利用弱光环境;70%遮荫处理则影响闽楠幼苗的正常生长。(2)遮荫降低了闽楠幼苗叶片的气孔密度,但单个气孔器的面积显著增加;遮荫处理下,闽楠叶片和主脉明显变薄;栅栏组织和海绵组织厚度降低,排列稀疏,栅海比减小,有利于提高对光能的利用效率。(3)闽楠幼苗根、茎、叶及总生物量均在全光照下最大,遮荫抑制了植株生物量的积累。研究发现,闽楠幼苗在遮荫处理下生物量积累和光合效率降低,但同时在叶片解剖结构和功能上表现出对遮荫的适应性,从而表现出一定的耐荫性。     

Similar Effects of Ozone on Four Cultivars of Lettuce in Open Top Chambers During Winter

Ozone is the major phytotoxic air pollutant that reduces the yield of several agricultural crops in the Spanish Mediterranean area. We studied four lettuce cultivars (Lactuca sativa L.) for the effects of different O₃ concentrations during the winter on chlorophyll (Chl) a fluorescence, lipid peroxidation, and root length in outdoor open-top chambers. Under O₃ the photosynthetic quantum conversion declined while heat emissions increased in all cultivars; these results provide more evidence of non-filtered air with additional ozone (NFA+O₃) treatment compared with non-filtered air (NFA) and charcoal filtered ozone-free air (CFA). Changes in the Chl a fluorescence may be associated with an increase in membrane lipid peroxidation as well as with observed reduction of root length under O₃ stress.     

Acceleration of leaf senescence inFagus sylvatica L. by low levels of tropospheric ozone demonstrated by leaf colour,chlorophyll fluorescence and chloroplast ultrastructure

From April 1988 to October 1991 3-year-old seed propagated beech (Fagus sylvatica L.) trees were exposed in open-top chambers to four different levels of air pollution: (1) charcoal filtered air, (2) ambient air, (3) ambient air plus 30 nl 1^-1 ozone during the summer, and (4) ambient air plus 30 nl 1^-1 ozone during the summer and 20 nl 1^-1 SO₂ and NO₂ during the winter. Leaf colour was studied in the autumns of 1989 and 1991 and a close relationship between ozone dose and premature senescence was found. A correlation also exists between the colour groups and chlorophyll fluorescence (F_v/F_m). Ozone fumigation increases the size and speeds up the development of the plastoglobules. This is described using an index based on the volume of plastoglobules as a percentage of chloroplast volume. The index was significantly higher for ozone fumigated plants than for control plants during August to November 1989. According to all three methods it is concluded that low levels of ozone accelerate leaf senescence processes inF. sylvatica. There are indications that leaves of the first and the second flush react differently to the ozone treatment. Irrespective of the ozone treatment a special cell wall structure, probably a local suberization, is confined to the subsidiary cells in leaves of the first flush.     

Ethylene production by different age class ponderosa and Jeffery pine needles as related to ozone exposure and visible injury

Summary Ethylene produced by different needle age classes representing natural populations of two ponderosa pine varieties [Pinus ponderosa var. arizonica (Engelm.) Shaw and var. ponderosa Dougl. ex Laws.] and Jeffery pine (Pinus jeffreyi Grev. and Balf.) was characterized using mercuric perchlorate traps. All populations contained individual trees which were either symptomatic or asymptomatic with respect to visible ozone injury. Ethylene production by different needle age classes was also characterized in P. ponderosa var. ponderosa seedlings grown in open top ozone fumigation chambers. Older age class needles produce significantly (P>0.05) more ethylene than younger age class needles. Needles of both P. ponderosa var. ponderosa and P. jeffreyi exhibiting ozone injury in the field produced significantly (P>0.05) higher levels of ethylene than asymptomatic conspecific trees. Seedlings exposed to the highest level of ozone in the fumigation study produced the highest levels of ethylene, followed by fumigation with medium and low ozone concentrations and carbon filtered air. These data indicate that the measurement of ethylene in conifer needles, as a measure of stress, needs to be calibrated for needle age class. It also suggests that the sensitivity of a tree to ozone injury may be regulated by the inherent ability of the individual to produce ethylene.     

Effects of Ozone Fumigation on Photosynthesis and Membrane Permeability in Leaves of Spring Barley, Meadow Fescue, and Winter Rape

Seedlings of spring barley, meadow fescue, and winter rape were fumigated with 180 μg kg⁻¹ of ozone for 12 d, and effect of O₃ on photosynthesis and cell membrane permeability of fumigated plants was determined. Electrolyte leakage and chlorophyll fluorescence were measured after 6, 9, and 12 d of fumigation, while net photosynthetic rate (P _N) and stomatal conductance (g _s) were measured 9 d after the start of ozone exposure. O₃ treatment did not change membrane permeability in fescue and barley leaves, while in rape a significant decrease in ion leakage was noted within the whole experiment. O₃ did not change the photochemical efficiency of photosystem 2 (PS2), i.e., F_v/F_m, and the initial fluorescence (F₀). The values of half-rise time (t_1/2) from F₀ to maximal fluorescence (F_m) decreased in fescue and barley after 6 and 9 d of fumigation. P _N decreased significantly in ozonated plants, in the three species. The greatest decrease in P _N was observed in ozonated barley plants (17 % of the control). The ozone-induced decrease in P _N was due to the closure of stomata. Rape was more resistant to ozone than fescue or barley. Apparently, the rape plants show a large adaptation to ozone and prevent loss of membrane integrity leading to ion leakage. This revised version was published online in August 2006 with corrections to the Cover Date.     

Relationship of antioxidant enzymes to ozone tolerance in branches of mature ponderosa pine (Pinus ponderosa) trees exposed to long-term, low concentration, ozone fumigation and acid precipitation

Seasonal activity of superoxide dismutase (SOD, EC 1.15.1.1). ascorbate peroxidase (APOD, EC 1.11.1.11) and guaiacol-oxidizing enzymes (GPODs, EC 1.11.1.7) was examined in needles of 12- to 15-year-old ponderosa pine (Pinus ponderosa Laws.) trees which received ozone (O₃) and acid precipitation treatment. Individual branches were enclosed in branch exposure chambers delivering either charcoal-filtered (O₃-reduced) air, ambient air, or air with twice ambient (2 x ambient) concentrations of O₃. Acid precipitation treatments were rain of pH 3.0 or 5.1 or no rain. Changes in antioxidant enzyme activity were not a consistent response to O₃ fumigation or acid precipitation, but when observed, they occurred most often in the O₃-sensitive clone and in symptomatic, fumigated branches. In the second year of fumigation. O₃ fleck symptoms appeared on needles of the sensitive clone as early as July and APOD activities were significantly increased by O₃ at all sampling dates. In the tolerant clone, antioxidant enzyme activities were not significantly changed by O₃ in the first season of fumigation (March to December 1990), not even during an episode when ambient O₃ concentrations reached 125 nl 1^?1 (240 nl 1^?1 in 2x ambient chambers). No foliar symptoms were observed on needles of the tolerant clone during this year. However, in the second year of fumigation (1992), O₃ fleck symptoms were observed on the tolerant clone and APOD activities were significantly increased in previous-year needles. The tolerant clone had SOD, APOD, and GPOD activities at least 40% higher than those of the sensitive clone before fumigation and 65, 178, and 119% higher, respectively, during both years of fumigation. The higher constitutive levels of these enzymes may have protected against foliar injury in 1990, however in 1992 we concluded that the stimulations in antioxidant enzyme activities observed in symptomatic branches of both clones were a consequence of O₃ injury. Total (intra- and extracellular) activities of the antioxidant enzymes did not appear to be good indicators of O₃ tolerance. Phenotypically, the O₃-tolerant clone was much more vigorous and in both years of fumigation, gas exchange rates were 30 to 71% higher than in the sensitive clone (P. D. Anderson, unpublished data). The greater vigor of the tolerant clone may allow more carbon allocation to protective and repair processes which include, but are not restricted to, the turnover of antioxidant enzymes and metabolites.     

O3浓度升高和太阳辐射减弱对小麦根际土壤微生物功能多样性的影响

采用开顶箱(OTC)法和遮光网技术,设置100 n L/L臭氧熏气与3个辐射减弱梯度结合,模拟臭氧浓度升高和太阳辐射减弱的复合大气背景。用BIOLOG生态测试板,采用孔平均颜色变化率法(AWCD)测定冬小麦根际土壤微生物利用不同碳源的能力,计算微生物群落多样性指数,对不同碳源的利用率进行了主成分分析。两年试验结果显示,臭氧熏气与太阳辐射减弱复合作用,降低了土壤微生物对碳源的利用速度和利用总量;除了聚合物以外其它碳源利用率显著降低;对土壤微生物多样性没有直接的影响;对碳源降解的抑制效应大于增强的O3与减弱的太阳辐射两因素各自的单独作用。太阳辐射减弱20%,一定程度上增加了对聚合物类的分解。O3熏气条件下太阳辐射减弱,糖类、胺类代谢变异度较高,受环境影响较大。     

毛竹对大气臭氧胁迫的生理响应变化

以毛竹1年生盆栽苗为材料,运用开顶式气室(OTCs)模拟环境背景大气O3浓度(AA,40～45 nL·L-1)和高O3浓度(EO,92～106 nL·L-1)情景,分析毛竹叶片光合生理、脂质过氧化及抗氧化酶等主要生理指标的变化,为气候变化背景下的竹林培育应对策略提供理论依据.结果显示:(1)EO较AA在同一处理时间的毛竹叶片O3通量均显著升高,且二处理的叶片O3通量均随着处理时间的延长呈升高趋势.(2) EO较AA的光合速率(Pn)、气孔导度(Gs)和可溶性糖含量均显著下降,且叶片叶绿素(ChD含量、胞间CO2浓度(Ci)显著下降的时间点分别出现在EO处理的60 d和92 d,可溶性蛋白在处理60 d后显著升高;随处理时间的延长,EO的叶片Pn、Ci、Chl含量均呈下降趋势,可溶性糖和可溶性蛋白含量呈先升高后降低的趋势;Pn下降由气孔限制因素引起.(3)超氧自由基(O2)含量、丙二醛(MDA)含量、相对电导率分别在处理29 d、60 d、60 d后均显著升高,且随着处理时间的延长呈升高趋势.(4)超氧化物歧化酶(SOD)活性在高浓度O3处理60 d时显著升高,后显著下降,而POD活性均显著升高,且SOD和POD活性均随着处理时间呈先升高后降低的趋势.研究表明,毛竹对大气高O3胁迫存在着短时间的主动生理生化适应,但长期高O3胁迫会对毛竹造成严重的过氧化伤害,从而影响毛竹的正常生长.     

纳米二氧化钛对生菜的生长效应分析

为了阐明纳米二氧化钛颗粒(TiO₂NPs)对生菜(Lactuca sativa)生长的影响，采用自行设计的水培装置探究不同浓度TiO₂NPs (300~1 200 mg/L)下，生菜生长和生理生化指标的变化。结果表明，300 mg/L TiO₂NPs能促进生菜幼苗的根长、茎长、叶表面积、鲜重和干重；随着TiO₂ NPs浓度增大，生菜的生长指标呈现下降趋势，但仍优于对照组。生菜体内的抗氧化酶(SOD、POD)在低TiO₂ NPs浓度(300 mg/L)时，活性明显下降；随着TiO₂ NPs浓度增大，这两种抗氧化酶活性逐渐增强。因此，生菜对TiO₂NPs胁迫具有浓度依赖性，表现为“低促高抑”，且能够通过抗氧化酶系统来减轻TiO₂NPs伤害。     

Interactions between nitrogen fertilization and ozone in watermelon cultivar Reina de Corazones in open-top chambers. Effects on chlorophyll a fluorescence, lipid peroxidation, and yield

Watermelon (Citrillus lanatus) plants were grown for two consecutive years in open-top chambers with three different ozone concentrations (O₃-free air, O₃ ambient, and air with additional O₃; CFA, NFA, and NFA+O₃) and three nitrogen fertilizer concentrations [0, 14.0, and 29.6 g N per pot; N0, N1, and N2). There was an interaction between ozone and N fertilizer for the major parameters studied. O₃ and N2 treatments led to a significant decrease in maximum efficiency of photosystem 2 (PS2) photochemistry (F_v/F_m), and induced a significant decrease in the actual quantum yield of PS2 (Φ_PS2), due mainly to the increased closure of PS2 reaction centres (q_P) and to an increase in the non-photochemical quenching (NPQ). On the other hand, these plants exhibited an increased susceptibility to photoinhibition, which could be associated with an increased fraction of reduced Q_A. An increase in lipid peroxidation indicated that damage was occurring at the membrane levels. High N concentration enhanced the detrimental effects of ozone on the fluorescence parameter induction and lipid peroxidation. All these negative alterations led to a decreased yield.     

Response of gas exchange and yield components of field-grown Triticum aestivum L. to elevated ozone in China

To assess photosynthesis and yield components’ response of field-grown wheat to increasing ozone (O₃) concentration (based on diurnal pattern of ambient O₃) in China, winter wheat (Triticum aestivum L.) cv. Jia 403 was planted in open top chambers and exposed to three different O₃ concentrations: O₃-free air (CF), ambient air (NF), and O₃-free air with additional O₃ (CF+O₃). Diurnal changes of gas exchange and net photosynthetic rate (P _N) in response to photosynthetic photon flux density (PPFD) of flag leaves were measured at the filling grain stage, and yield components were investigated at harvest. High O₃ concentration altered diurnal course of gas exchange [P _N, stomatal conductance (g _s), and intercellular CO₂ concentration (C _i)] and decreased significantly their values except for C _i. Apparent quantum yield (AQY), compensation irradiance (CI), and saturation irradiance (SI) were significantly decreased, suggesting photosynthetic capacity was also altered, characterized as reduced photon-saturated photosynthetic rate (P _Nmax). The limit of photosynthetic activity was probably dominated by non-stomatal factors in combination with stomatal closure. The significant reduction in yield was observed in CF+O₃ treatment as a result of a marked decrease in the ear length and the number of grains per ear, and a significant increase in the number of infertile florets per ear. Even though similar responses were also observed in plants exposed to ambient O₃ concentration, no statistical difference was observed at current ambient O₃ concentration in China.