不同品种茶花在干旱胁迫下叶 片气孔和蜡质的差异化表现

摘要：以茶花品种?十八学士''和?情人节''为研究对象，在塑料大棚室温15～25℃下，采用盆栽控水法进行干旱胁迫，利用扫描电子显微镜观测叶片的表皮结构。研究不同品种在干旱胁迫下，叶片表皮结构的差异对抗旱性的影响，为茶花的栽植管护推广和造景应用提供基础性的理论依据。 结果表明，茶花叶片仅有下表皮具有气孔，上、下表皮都有不同程度量的蜡质附着物。随干旱胁迫程度的加重，气孔开合及蜡质积累出现差异性变化。抗旱性较差的品种，主要通过利用蜡质的合成、堆积来堵塞气孔，降低蒸腾作用。抗旱性较强的品种，气孔的保卫细胞在干旱早期就启动闭合响应机制，叶片上表面的蜡质堆积程度更强，能更好的保护叶片免受光照和有害物质的伤害，说明叶片表皮结构对于茶花抗旱性强弱的决定作用较大。     

冬小麦叶片和冠层尺度的光合-蒸腾模拟

利用气孔导度-光合-蒸腾耦合模型(SMPT-SB),选取冬小麦关键生育期的典型日，模拟了冬小麦叶片和冠层尺度的光合与蒸腾速率日变化，并借助光合仪和涡度相关系统获得的观测数据进行了验证。研究结果表明：模型模拟的叶片和冠层尺度光合及蒸腾速率与实测值变化趋势具有较好的一致性，光合速率日均绝对误差不超过1μmol·m^-2·s^-1,蒸腾速率日均绝对误差不超过0.41 mmol·m^-2·s^-1;叶片尺度光合和蒸腾速率模拟值与实测值的决定系数R²均在0.90以上，冠层尺度也分别达到了0.96、0.88。此外，模型中水汽响应函数以f(D_s)=RH表示时，相对湿度(RH)变化较大会导致参数m值不能准确量化气孔导度(g_s)的变化，从而降低模拟效果；若分时期率定m值，会大幅提高模拟精度。该模型适用于冬小麦叶片及冠层尺度的土壤-植物-大气之间水碳交换的模拟。     

干旱-复水对构树叶片水势和气孔开闭的影响

为探究干旱-复水对构树(Broussonetia papyrifera L.)叶片水势和气孔导度及其相关关系的影响，本研究以贵州贞丰(GZ)、河南周口(HN)、山东菏泽(SD)3个种源构树2年生幼苗为研究对象，研究不同干旱胁迫强度下构树叶片水势和气孔导度的变化特征。结果表明：干旱强度、干旱时间、种源及三者的交互作用均对构树叶片水势和气孔导度有显著影响。随着干旱胁迫强度的增强，GZ种源构树叶片水势显著降低，干旱胁迫指数明显增大，相较于对照(CK),轻度干旱(LS)、重度干旱(SS)处理下HN和SD种源构树叶片水势呈现先下降后上升的趋势。SS处理下各种源构树气孔导度显著低于CK。复水后，3个种源构树叶片水势和气孔导度均能恢复到CK水平。因此，干旱尤其是重度干旱显著降低了各种源构树水势和气孔导度，复水后均可恢复至正常供水水平，甚至出现超补偿生长。     

Air pollution removal through deposition on urban vegetation: The importance of vegetation characteristics

Urban vegetation has the potential to improve air quality as it promotes pollutant deposition and retention. Urban air quality models often include the effect vegetation have on pollution dispersion, however, processes involved in pollution removal by vegetation are often excluded or simplified and does not consider different vegetation characteristics. In this systematic review, we analyze the influence of the large interspecies variation in vegetation characteristics to identify the key factors affecting the removal of the major urban pollutants, particulate matter (PM) and nitrogen dioxide (NO₂) from the air through vegetation deposition. The aim is to identify key processes needed to represent vegetation characteristics in urban air quality modelling assessments.We show that PM is mainly deposited to the leaf surface, and thus representation of characteristics affecting the aerodynamics from canopy down to leaf surface are important, such as branch/shoot complexity and leaf size, leaf surface roughness and hairiness. In addition, characteristics affecting PM retention capacity, resuspension and wash-off, include leaf surface roughness, hairiness and wax content. NO₂ is mainly deposited through stomatal uptake, and thus stomatal conductance and its responses to environmental conditions are key factors. These include response to solar radiation, vapour pressure deficit and soil moisture.Representation of these vegetation characteristics in urban air quality models could greatly improve our ability to optimize the type and species of urban vegetation from an air quality perspective.