冬小麦气孔臭氧通量拟合及通量产量关系的比较分析

基于田间原位开顶箱(Open-Top Chambers,OTCs)实验,研究了不同浓度臭氧(O3)处理下(自然大气处理,AA;箱内大气处理,NF;箱内低浓度O3处理,NF+40 nL/L;箱内中等浓度O3处理,NF+80 nL/L;箱内高浓度O3处理,NF+120 nL/L),冬小麦(Triticum aestivum L.)旗叶气孔运动对不同环境因子的响应,并通过剂量反应分析,比较了冬小麦产量损失与累积气孔O3吸收通量(AFstX)和累积O3暴露浓度(AOT40和SUM06)的相关性差异。结果表明:冬小麦旗叶气孔运动的光饱和点和最适温度分别约为400μmol.m-.2s-1和27℃,水汽压差、土壤含水量和O3剂量的气孔限制临界值分别约为1.4 kPa、-100 kPa和20μL.L-.1h-1,超过此临界值时,气孔导度会明显下降。利用Jarvis气孔导度模型对冬小麦旗叶气孔导度和气孔O3吸收通量进行了预测,结果表明Jarvis模型解释了冬小麦实测气孔导度60%的变异性。由于不同时期植物体气孔导度的差异,冬小麦旗叶生长期内累积气孔O3吸收通量(AFstX)呈非线性增加趋势。O3吸收速率临界值(X)为4 nmol.m-.2s-1时,累积O3吸收通量(AFst4)与冬小麦产量的相关性最高(R2=0.76),该数值介于O3暴露指标AOT40和SUM06的剂量反应决定系数(0.74和0.81)之间。与O3浓度指标(AOT40和SUM06)相比,O3通量指标(AFstX)在本试验冬小麦产量损失评价中未表现出明显优势。     

臭氧胁迫对冬小麦灌浆期光合日变化的影响

利用开顶式气室(OTC)开展了大田实验条件下地表臭氧浓度增加对灌浆期冬小麦光合日变化影响的实验研究.结果表明:13:00-15:00大田环境变量(光合有效辐射、温度、水气压差)对冬小麦光合作用产生了胁迫;与对照组相比,100和150 nl·L-1臭氧熏气下净光合速率平均下降了6.3%和11.1%(P＜O.05);100 nl·L-1臭氧熏气下气孔限制值、蒸腾速率、气孔导度、水分利用率变化趋势与对照组基本一致,但在150 nl·L-1臭氧熏气下,11:00之前蒸腾速率和气孔导度均显著增加,水分利用率显著下降,13:00-15:00,水分利用率显著增高;在无环境胁迫条件下,100和150 nl·L-1臭氧熏气分别对冬小麦光合作用产生了气孔限制和非气孔限制,导致光合速率下降.环境变量胁迫下,100和150nl·L-1臭氧熏气均显著提高了冬小麦的水分利用率,且150 nl·L-1臭氧熏气显著提高了进入气孔用于光合作用的二氧化碳比例.     

大气O3浓度升高对毛竹光合生理的影响

以毛竹(phyllostachys edulis)为试材,运用开顶式气室(OTCs)模拟了4个大气O3浓度情景,分别为CF(背景大气经活性炭过滤后的处理,22～25 nL·L-1)、NF(直接将背景大气输入气室内,40～45 nL·L-1)、T1(O3平均浓度100 nL·L-1,92～106 nL·L-1)、T2(O3平均浓度150 nL· L-1,142 ～160 nL· L-1),分析大气O3浓度对毛竹叶片光合色素、气体交换参数、光合参数的影响.结果表明:不同浓度O3处理的毛竹叶片Pn和Tr日变化均呈单峰型,随着O3浓度的升高,叶片Gs、Ci、Ls日变化规律趋于简单,WUE变化趋于平缓.与环境背景大气比较,高浓度O3(≥100 nL·L-1)条件下叶片Pn、Ls、WUE日均值和Chl、Chl-a、Chl-b和Car含量均显著降低,Gs、Tr日均值显著提高,但对Ci日均值及叶片光合色素组成影响并不明显.T1、T2处理下,毛竹的Pn、Tr与PPED、VpdL、Tair、Ca和RH环境因子间均呈显著或极显著相关,Gs与PPED无显著相关,而与VpdL、Tair、Ca和RH环境因子间均呈显著或极显著相关.研究表明:O3浓度100、150 nL·L-1时分别会造成毛竹叶片发生气孔、非气孔限制,气孔对环境条件的反应变得不敏感,影响了正常的调节反馈机制,增加了水分蒸散,光合色素降解或合成受阻,对毛竹光合作用产生严重的负面效应,不利于毛竹干物质积累.     

冬小麦叶片气孔导度模型水分响应函数的参数化

植物气孔导度模型的水分响应函数用来模拟水分胁迫对气孔导度的影响过程, 是模拟缺水环境下植物与大气间水、碳交换过程的关键算法。水分响应函数包括空气湿度响应函数和土壤湿度(或植物水势)响应函数, 该研究基于田间实验观测, 分析了冬小麦(Triticum aestivum)叶片气孔导度对不同空气饱和差和不同土壤体积含水量或叶水势的响应规律。一个土壤水分梯度的田间处理在中国科学院禹城综合试验站实施, 不同水分胁迫下的冬小麦叶片气体交换过程和气孔导度以及其他的温湿度数据被观测, 同时观测了土壤含水量和叶水势。实验数据表明, 冬小麦叶片气孔导度对空气饱和差的响应呈现双曲线规律, 变化趋势显示大约1 kPa空气饱和差是一个有用的阈值, 在小于1 kPa时, 冬小麦气孔导度对空气饱和差变化反应敏感, 而大于1 kPa后则反应缓慢; 分析土壤体积含水量与中午叶片气孔导度的关系发现, 中午叶片气孔导度随土壤含水量增加大致呈现线性增加趋势, 但在平均土壤体积含水量大于大约25%以后, 气孔导度不再明显增加, 而是维持在较高导度值上下波动; 冬小麦中午叶片水势与相应的气孔导度之间, 随着叶水势的增加, 气孔导度呈现增加趋势。根据冬小麦气孔导度对空气湿度、土壤湿度和叶水势的响应规律, 研究分别采用双曲线和幂指数形式拟合了水汽响应函数, 用三段线性方程拟合了土壤湿度响应函数和植物水势响应函数, 得到的参数可以为模型模拟冬小麦的各类水、热、碳交换过程采用。     

青藏高原高寒草甸非生长季温室气体排放特征及其年度贡献

高寒草甸是青藏高原地区的主要植被类型,目前对其温室气体研究多集中于生长季.本文利用静态箱-气相色谱法,对非生长季高寒草甸温室气体排放特征及其与主要环境因子的关系进行了研究.结果表明:非生长季高寒草甸表现为CO2和N2O的源、CH4的汇.其中非生长季CO2通量平均值为89.33 mg·m-2·h-1,累积排放通量为280.01g· m-2;CH4通量平均值为-11.35 μg·m-2·h-1,累积吸收通量为124.74 mg·m-2;N2O通量平均值为8.02 μg·m-2·h-1,累积排放通量为39.51 mg·m-2.非生长季CO2、CH4和N2O累积排放通量分别占全年的13.33％、53.47％和62.67％.冻融期(2012年4月)CH4累积吸收通量较小,只占非生长季的4.5％;而CO2和N2O累积排放通量较大,分别占非生长季的25.8％和20.8％.非生长季CO2通量与温度(气温、5和10 cm土壤温度)和5 cm土壤湿度均存在显著正相关关系,而CH4和N2O通量仅与5 cm土壤湿度存在显著正相关.研究表明,虽然冻融期CH4累积吸收通量在非生长季累积量中比重较小,但非生长季CH4和N2O累积排放量却占全年累积排放量的1/2以上,在温室气体累积通量评估中不容忽视.     

O_3和干旱胁迫对元宝枫叶片气孔特征的复合影响

利用开顶式气室(OTC)研究了O3胁迫(空气O3浓度加118μg·m-3)、干旱胁迫(土壤水分保持在田间持水量的40%~50%)以及O3与干旱复合胁迫(空气O3浓度加118μg·m-3和土壤水分保持在田间持水量的40%~50%)对元宝枫(Acer truncatum Bunge.)叶片气孔特征的影响。结果表明:O3胁迫41 d时气孔密度变化不明显,62和110 d时显著增加(P0.05);干旱胁迫和复合胁迫下气孔密度增加显著(P0.05);O3、干旱及复合胁迫处理110 d气孔面积、周长、长度和宽度明显减小(P0.05),气孔指数明显增加(P0.05);各胁迫气孔开度均明显减小(P0.05),O3和干旱对气孔开度影响存在协同作用,干旱减小了O3胁迫下的气孔开度。O3和干旱胁迫下气孔特征响应不同表明影响气孔的机制不同,O3对气孔影响具有累积效应,干旱可限制O3摄入量从而减小了O3对植物的伤害。     

华北山区侧柏冠层气孔导度特征及其对环境因子的响应

冠层气孔导度(g_s)是衡量冠层-大气界面水汽通量的重要生物学常数,研究其特征及对环境因子的响应,能为开展森林冠层水汽交换过程的机理性研究提供理论依据.于2014年利用SF-L热扩散式探针测定了侧柏的树干液流密度(J_s),同步监测光合有效辐射(PAR)、饱和水汽压差(VPD)、气温(T)等环境因子,计算侧柏的冠层气孔导度特征并分析其对各环境因子的响应.结果表明: 侧柏液流密度的日变化总体呈双峰曲线,生长季高于非生长季,且胸径越大液流密度越大;冠层气孔导度日变化与单位叶面积冠层蒸腾(E_L)趋势相近,均呈双峰曲线,生长季的冠层气孔导度和蒸腾较非生长季略高.侧柏冠层气孔导度与空气温度呈抛物线关系,在10 ℃左右冠层气孔导度达到峰谷;光合有效辐射以400 μmol·m^-2·s^-1为界,小于该阈值两者呈正相关关系,大于该阈值则冠层气孔导度受其影响较小;与饱和水汽压差呈负对数函数关系,随饱和水汽压差增大而逐渐降低.较高的空气温度和光合有效辐射、较低的饱和水汽压差有利于侧柏形成较大的冠层气孔导度,进而促进冠层蒸腾.     

臭氧胁迫下冬小麦物质生产与分配的数值模拟

利用ML9810B型臭氧监测分析仪,测定了浙江嘉兴麦田空气O3浓度,并通过改进的开顶式气室实验确定O3浓度变化对冬小麦叶片光合速率的影响函数.在此基础上,加入O3对叶片生长和穗部光合影响的模拟函数,建立反映O3对冬小麦生长和产量形成影响的作物模型.模型的检验结果表明,该模型较好地反映了O3对冬小麦生长的影响,生物量平均相对误差为10.3%.对冬小麦春后生育期(3—5月)的研究表明,水肥适宜时,由O3影响造成的该地区冬小麦干物质累积总损失量为11.4%,产量损失为17.8%.     

臭氧胁迫对冬小麦光响应能力及PSⅡ光能吸收与利用的影响

为准确评价O3胁迫对冬小麦光响应能力和PSⅡ光能吸收、分配与利用的影响,通过OTC设置了活性碳过滤空气(CF,4—28 nL/L)、不通风(5H,15—68 nL/L)、环境空气(NF,7—78 nL/L)、100nL/L O3 (CF100,96—108 nL/L)和150nL/L O3 (CF150,145—160nL/L) 等5种O3熏蒸处理,用IMAGING-PAM测量了冬小麦（丰抗13）扬花期的Fo、Fm及自然光下的快速光曲线。结果表明,O3胁迫显著降低了冬小麦PSⅡ的最大量子效率(Fv/Fm)、最大光合速率(Pm)、半饱和光强(Pm/α)、吸光系数(IA)、调节性热耗散的量子产额(Y(NPQ))和非光化学淬灭系数(NPQ),显著提高了冬小麦的初始光能利用效率(α)、非调节性热耗散的量子产额(Y(NO))和PSⅡ吸收光能的日累计损失（Daily ∑Y(NO)+ Daily ∑Y(NPQ)）;CF处理显著提高了冬小麦的Pm、α、Y(NPQ)、NPQ及PSⅡ日累计利用的光能（Daily ∑Y(Ⅱ)）;当其余4组的Y(NPQ)和NPQ趋于饱和时,NF仍在以较快的速率上升。O3胁迫显著降低了冬小麦吸收、利用光能的能力和光保护能力,改变了PSⅡ吸收光能的分配结构,提高了冬小麦对光强变化的敏感性,加剧了光抑制,致使冬小麦受到O3和过剩光能的双重伤害;CF处理下冬小麦的光合能力和光保护能力显著提高,但对强光的潜在耐受能力低于NF;固城的空气质量已对冬小麦造成一定影响,极可能导致产量损失。     

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.     

Ozone‐induced stomatal sluggishness changes stomatal parameters of Jarvis‐type model in white birch and deciduous oak

• Stomatal ozone flux is closely related to ozone injury to plants. Jarvis‐type multiplicative model has been recommended for estimating stomatal ozone flux in forest trees. Ozone can change stomatal conductance by both stomatal closure and less efficient stomatal control (stomatal sluggishness). However, current Jarvis‐type models do not account for these ozone effects on stomatal conductance in forest trees.
• We examined seasonal course of stomatal conductance in two common deciduous tree species native to northern Japan (white birch: Betula platyphylla var. japonica ; deciduous oak: Quercus mongolica var. crispula ) grown under free‐air ozone exposure. We innovatively considered stomatal sluggishness in the Jarvis‐type model using a simple parameter, s , relating to cumulative ozone uptake (defined as POD : phytotoxic ozone dose).
• We found that ozone decreased stomatal conductance of white birch leaves after full expansion (?28%). However, such a reduction of stomatal conductance by ozone fell in late summer (?10%). At the same time, ozone reduced stomatal sensitivity of white birch to VPD and increased stomatal conductance under low light conditions. In contrast, in deciduous oak, ozone did not clearly change the model parameters.
• The consideration of both ozone‐induced stomatal closure and stomatal sluggishness improved the model performance to estimate stomatal conductance and to explain the dose–response relationship on ozone‐induced decline of photosynthesis of white birch. Our results indicate that ozone effects on stomatal conductance (i.e . stomatal closure and stomatal sluggishness) are crucial for modelling studies to determine stomatal response in deciduous trees, especially in species sensitive to ozone.

     

鲁西北平原冬小麦田臭氧浓度变化特征及对产量的潜在影响和机理分析

近地层高浓度臭氧(O₃)对农作物生长和产量形成有明显的影响。利用在中国科学院禹城综合试验站(山东省)冬小麦(Triticum aestivum)农田生态系统上观测的O₃浓度及微气象资料, 分析了鲁西北平原冬小麦农田生态系统O₃浓度的日变化和季节变化规律, 在此基础上初步分析了O₃浓度与CO₂通量(F_c)的关系, 并用欧洲和美国科学家在实验室得到的O₃浓度-冬小麦产量关系模型估算了O₃对冬小麦产量的潜在影响。结果表明: O₃浓度存在明显的日变化规律, 日最小值和最大值分别出现在7:00和16:00左右。整个观测期间(2011年3-5月)平均O₃浓度为(30.4 ± 20.1) nL·L ^-1(平均值±标准误差); 30 min平均浓度的最大值为93.1 nL·L ^-1。在冬小麦春季生长季节, O₃浓度日平均值呈现逐步增加的趋势, O₃浓度日均增加约为0.17 nL·L ^-1·d ^-1; 白天7 h和12 h平均浓度(M7和M12)分别为45.7和43.1 nL·L ^-1; O₃浓度超过40 nL·L ^-1的3个月累积值(AOT40)为9.8 μL·L ^-1·h; 超过60 nL·L ^-1的O₃浓度累积值(SUM06)为12.6 μL·L ^-1·h; 经过权重修正的O₃污染指标W126为10.1 μL·L ^-1·h。在高浓度O₃ (>60 nL·L ^-1)情况下, CO₂通量与O₃浓度呈现负相关关系, 鲁西北平原O₃对冬小麦光合作用影响的阈值取60 nL·L ^-1比较合适, 该值高于欧洲国家普遍采用的40 nL·L ^-1。基于以上结果, 初步估算得出: 在目前的O₃浓度水平下, 鲁西北平原近地层O₃可能会使冬小麦产量减少5.2%-8.8%。     

The Effect of Elevated Ozone Concentrations with Varying Shading on Dry Matter Loss in a Winter Wheat-Producing Region in China

Surface-level ozone pollution causes crop production loss by directly reducing healthy green leaf area available for carbon fixation. Ozone and its precursors also affect crop photosynthesis indirectly by decreasing solar irradiance. Pollutants are reported to have become even more severe in Eastern China over the last ten years. In this study, we investigated the effect of a combination of elevated ozone concentrations and reduced solar irradiance on a popular winter wheat Yangmai13 (Triticum aestivum L.) at field and regional levels in China. Winter wheat was grown in artificial shading and open-top-chamber environments. Treatment 1 (T1, i.e., 60% shading with an enhanced ozone of 100±9 ppb), Treatment 2 (T2, i.e., 20% shading with an enhanced ozone of 100±9 ppb), and Control Check Treatment (CK, i.e., no shading with an enhanced ozone of 100±9 ppb), with two plots under each, were established to investigate the response of winter wheat under elevated ozone concentrations and varying solar irradiance. At the field level, linear temporal relationships between dry matter loss and cumulative stomatal ozone uptake were first established through a parameterized stomatal-flux model. At the regional level, ozone concentrations and meteorological variables, including solar irradiance, were simulated using the WRF-CMAQ model (i.e., a meteorology and air quality modeling system). These variables were then used to estimate cumulative stomatal ozone uptake for the four major winter wheat-growing provinces. The regional-level cumulative ozone uptake was then used as the independent variable in field data-based regression models to predict dry matter loss over space and time. Field-level results showed that over 85% (T1: R² = 0.85 & T2: R² = 0.89) of variation in dry matter loss was explained by cumulative ozone uptake. Dry matter was reduced by 3.8% in T1 and 2.2% in T2 for each mmol O₃·m^-2 of cumulative ozone uptake. At the regional level, dry matter loss in winter wheat would reach 50% under elevated ozone concentrations and reduced solar irradiance as determined in T1, and 30% under conditions as determined in T2. Results from this study suggest that a combination of elevated ozone concentrations and reduced solar irradiance could result in substantial dry matter loss in the Chinese wheat-growing regions.     

Influence of atmospheric vapour pressure deficit on ozone responses of snap bean (Phaseolus vulgaris L.) genotypes

Environmental conditions influence plant responses to ozone (O(3)), but few studies have evaluated individual factors directly. In this study, the effect of O(3) at high and low atmospheric vapour pressure deficit (VPD) was evaluated in two genotypes of snap bean (Phaseolus vulgaris L.) (R123 and S156) used as O(3) bioindicator plants. Plants were grown in outdoor controlled-environment chambers in charcoal-filtered air containing 0 or 60 nl l(-1) O(3) (12 h average) at two VPDs (1.26 and 1.96 kPa) and sampled for biomass, leaf area, daily water loss, and seed yield. VPD clearly influenced O(3) effects. At low VPD, O(3) reduced biomass, leaf area, and seed yield substantially in both genotypes, while at high VPD, O(3) had no significant effect on these components. In clean air, high VPD reduced biomass and yield by similar fractions in both genotypes compared with low VPD. Data suggest that a stomatal response to VPD per se may be lacking in both genotypes and it is hypothesized that the high VPD resulted in unsustainable transpiration and water deficits that resulted in reduced growth and yield. High VPD- and water-stress-induced stomatal responses may have reduced the O(3) flux into the leaves, which contributed to a higher yield compared to the low VPD treatment in both genotypes. At low VPD, transpiration increased in the O(3) treatment relative to the clean air treatment, suggesting that whole-plant conductance was increased by O(3) exposure. Ozone-related biomass reductions at low VPD were proportionally higher in S156 than in R123, indicating that differential O(3) sensitivity of these bioindicator plants remained evident when environmental conditions were conducive for O(3) effects. Assessments of potential O(3) impacts on vegetation should incorporate interacting factors such as VPD.     

Ozone effects in a drier climate: implications for stomatal fluxes of reduced stomatal sensitivity to soil drying in a typical grassland species

The widely distributed temperate grassland species Dactylis glomerata was grown in competition with Ranunculus acris at two different watering regimes and exposed for 20 weeks to eight ozone treatments with mean concentrations ranging from 16.2 to 89.5 ppb, representing pre‐industrial to predicted post‐2100 ozone climates. Measurements of stomatal conductance were used to parameterize ozone flux models for D. glomerata. For the first time, a modification was made to the standard flux model to account for the observed decrease in sensitivity of stomatal conductance to reduced water availability with increasing ozone. Comparison of calculated cumulative ozone flux between the two versions of the model demonstrated that exclusion of the ozone effect on stomatal conductance in the standard flux model led to a large underestimation of ozone fluxes at mid‐ to high‐ozone concentrations. For example, at a mean ozone concentration of 55 ppb (as predicted for many temperate areas in the next few decades), the standard flux model underestimated ozone fluxes in D. glomerata by 30–40% under reduced water availability. Although the modified flux model does not markedly change the flux‐based critical level for D. glomerata, this study indicates that use of the standard flux model to quantify the risk of ozone damage to a widely distributed grassland species such as D. glomerata in areas where high ozone concentrations and reduced soil moisture coincide could lead to an underestimation of effects. Thus, this study has shown that under predicted future climate change and ozone scenarios, ozone effects on vegetation may be even greater than previously predicted in the drier areas of the world.     

光合作用-蒸腾作用-气孔导度的耦合模型及C_3植物叶片对环境因子的生理响应(英文)

以叶片的气体传输过程为基础,将蒸腾作用包括在以往光合作用气孔导度的耦合模型中,建立了光合作用蒸腾作用气孔导度的耦合模型。该模型可以模拟边界层导度对生理过程的影响。模拟了Ｃ３植物叶片对环境因子,如光照、温度、湿度、边界层导度和ＣＯ２浓度等的生理响应（光合作用、蒸腾作用、气孔导度）以及Ｃｉ和水分利用效率的变化。在环境因子变化于较大范围的情况下,模拟结果符合许多实验结论。     

Effect of Growth Irradiance on Photosynthesis and Transpiration inPhaseolus vulgaris L.

In comparison with primary leaves of French bean plants grown under a photon flux density of 100 μeinstein m-2 s-1 (LP), leaves grown under 400 μeinstein m-2 s-1 (HP) were thicker (contained 82 to 104% more dry matter per blade area), had 44 to 48% higher stomatal frequency, 18 to 26% more chlorophyll (a + b) per leaf area unit and 31 to 42% less chlorophyll (a + b) per dry matter unit, 41% higher photosynthetic and 38% higher transpiration rates at light saturation, 33% higher stomatal conductance and 40% higher Photosystem 2 (H2O → K3[Fe(CN)6]) activity of isolated chloroplasts. There were no significant differences in the Photosystem 1 (TMPD/Ascorbate → MV) activity per unit amount of chlorophyll. Higher growth irradiance increased the ratio of frequencies of stomata in the upper/lower epidermes.