冬小麦近轴和远轴叶面气孔对土壤水分胁迫反应的敏感性

当根层土壤水分含量不足,作物体内出现水分胁迫时,小麦叶片两面气孔的反应有明显差异。远轴叶面气孔对水分胁迫的反应比近轴叶面气孔敏感。当出现水分胁迫时,远轴叶面气孔首先收缩,且收缩的程度比近轴叶面气孔大。远轴与近轴叶面气孔阻力的比值(r_(ab)/r_(ab))与根层平均土壤水势(Ψ_s)有关,当Ψ_s大于-50 kPa时,r_(ab)/r_(ad)基本稳定在1.5左右,而当Ψ_s小于-50 kPa时,r_(ab )/r_(ab)随Ψ_s降低而明显增加。     

西安市常见绿化植物叶片润湿性能及其影响因素

利用接触角测定仪测定了西安市21种常见绿化植物叶片表面的接触角,探讨了叶片表面特性如蜡质、绒毛、气孔对接触角的影响。结果表明,植物叶片正背面、物种间的接触角差异均显著,叶片正面和背面接触角大小在40°～140°。接触角大小与变异系数呈负相关,可能由于接触角小的润湿叶片在不同的生境和位置下,受到环境条件的影响较大而出现大的变异;接触角较大的非润湿性叶片,环境物质持留时间较短,对叶片形态和组成影响较小,因而出现小的变异。植物叶片表面的接触角随蜡质含量的升高而增大。表皮蜡质去除后大部分叶片接触角明显降低,尤其是疏水性较强的银杏(Ginkgo biloba)、月季(Ro-sa chinensis)和紫叶小檗(Berberis thunbergii)。女贞(Ligustrum lucidum)正背面、加杨(Popu-lus canadensis)背面等亲水型的叶片蜡质去除后接触角反而增大。叶片绒毛的多少及其形态、分布方式对接触角具有重要的影响,不同的作用方式表现出润湿和不润湿的特征,人为将其去除可以增加叶片的润湿性。背面气孔密度与气孔长度、保卫细胞长度呈负相关;接触角则与气孔密度呈负相关,与气孔长度呈正相关。     

植物叶表面的润湿性及其生态学意义

植物叶表面的润湿性是各种生境中常见的一种现象,表现了叶片对水的亲和能力。叶面的润湿性可以通过测定气、固、液界面的接触角大小确定,接触角θ＜110°的为润湿,θ＞130°的为不润湿,表现出斥水性。影响叶片润湿性的主要因素有叶面蜡质含量与形态,叶面绒毛数量、质地、形态和分布方式,气孔和表皮细胞形态和大小,叶水分状况等。叶表面的化学组成和形态是影响叶润湿性的主要内在原因,但外界环境的变化通过影响表面的结构和形态来影响叶润湿性。叶面的润湿性是植物叶片截流降水的微观基础,水分在润湿性强的叶面上铺展呈膜;在不润湿的叶面上形成水珠,容易在风和重力的作用下离开叶面;铺展的水膜,又会对叶的光合作用产生重要的影响。不同润湿性的叶面,滞留、吸附、过滤各种大气污染物数量不同;这些污染物沉降在叶片表面,与叶面发生相互作用,从而改变叶面的润湿性。植物叶含水量的高低对叶感染病菌有重要的影响,在病菌感染期间如果叶表面完全润湿则有利于病菌侵染;一旦病菌侵染,又会对叶面结构造成破坏,需要考虑润湿性能对防治病虫害的农药液滴持留的影响。对于润湿性小、斥水性大的植物,其叶表面表现出一定的自清洁功能;根据这些高疏水性、具有自清洁性的植物叶面特征,可利用或借鉴生物学信息进行仿生设计或制造新的功能材料。润湿性作为固、气、液三相作用的综合结果,是认识植物界面关系的微观基础,对于植物叶面生态功能的认识具有重要的意义。     

典型天气下植物叶面滞尘动态变化

在天气变化频繁的春季选择了几种典型天气观测了油松、女贞、珊瑚树和三叶草叶面滞尘动态变化及其与气象因子和空气中颗粒物浓度的关系。研究表明:(1)供试物种的叶面滞尘量(g/m2)由大到小依次为油松(4.57—5.45),珊瑚树(2.23—5.85),女贞(2.14—4.27)和三叶草(0.12—0.38);(2)油松和三叶草叶面滞尘量无明显变化,而天气状况对女贞和珊瑚树叶面滞尘影响明显;(3)连续2d(17.1、14.8 mm)的降雨后,女贞和珊瑚树叶面滞尘量降低了50%以上;极大风速对女贞和珊瑚树叶面滞尘量的影响均呈现先升高后降低,在极大风速为14 m/s时达到峰值;相对湿度大于80%时,女贞和珊瑚树叶面滞尘量明显降低;空气中高浓度的颗粒物可使女贞和珊瑚树叶面滞尘在4—5 d达到饱和。     

Interacting elevated CO2 and tropospheric O3 predisposes aspen (Populus tremuloides Michx.) to infection by rust (Melampsora medusae f. sp. tremuloidae)

We investigated the interaction of elevated CO₂ and/or (Ozone) O₃ on the occurrence and severity of aspen leaf rust (Melampsora medusae Thuem. f. sp. tremuloidae) on trembling aspen (Populus tremuloides Michx.). Furthermore, we examined the role of changes in leaf surface properties induced by elevated CO₂ and/or O₃ in this host–pathogen interaction. Three‐ to five‐fold increases in levels of rust infection index were found in 2 consecutive years following growing‐season‐long exposures with either O₃ alone or CO₂ + O₃ depending on aspen clone. Examination of leaf surface properties (wax appearance, wax amount, wax chemical composition, leaf surface and wettability) suggested significant effects by O₃ and CO₂ + O₃. We conclude that elevated O₃ is altering aspen leaf surfaces in such a way that it is likely predisposing the plants to increased infection by aspen leaf rust.     

Leaf Water Repellency as an Adaptation to Tropical Montane Cloud Forest Environments

Adaptations that reduce water retention on leaf surfaces may increase photosynthetic capacity of cloud forests because carbon dioxide diffuses slower in water than air. Leaf water repellency was examined in three distinct ecosystems to test the hypothesis that tropical montane cloud forest species have a higher degree of leaf water repellency than species from tropical dry forests and species from temperate foothills-grassland vegetation. Leaf water repellency was measured by calculating the contact angle of the leaf surface and the line tangent to a water droplet through the point of contact on the adaxial and the abaxial surface. Leaf water repellency was significantly different between the three study areas. The hypothesis that leaf water repellency is higher in cloud forest species than tropical dry forests and temperate foothills-grassland vegetation was not confirmed in this study. Leaf water repellency was lower for cloud forest species (adaxial surface = 50.8°; abaxial surface = 82.9°) than tropical dry forest species (adaxial surface = 74.5°; abaxial surface = 87.3°) and temperate foothills-grassland species (adaxial surface = 77.6°; abaxial surface = 95.8°). The low values of leaf water repellency in cloud forest species may be influenced by presence of epiphylls and loss of epicuticular wax on the leaf surfaces.     

珍珠菜属植物叶表皮纹饰特征及其系统学意义

利用光学显微镜和扫描电镜对21种珍珠菜属植物叶表皮纹饰特征进行了研究。根据叶表皮外壁纹饰特征,可以明显的划分为两种类型,即黑腺珍珠菜型和细梗香草型。这两种类型与以雄蕊群的构造为主要依据的属下分类系统的对应关系不密切,表明叶表皮纹饰特征在亚属级水平上分类学意义不大。但该属植物叶腺体的有无,颜色和分布以及叶表皮纹饰特征在种内相当稳定,种间差异较大,在种级水平上具有重要的分类学意义。     

北京市六种针叶树叶面附着颗粒物的理化特征

对北京市6种针叶树叶面颗粒物附着密度、叶表面微形态、颗粒物矿物与元素组成的研究结果表明：同一树种叶面颗粒物附着密度随大气颗粒物浓度增加而增大;同一地点不同树种叶面颗粒物附着密度存在很大差异,圆柏、侧柏颗粒物附着密度最高,其次为雪松、白皮松,油松、云杉最低;受地面扬尘影响,低矮叶片较高处叶片颗粒物附着密度大;受降雨和新生叶片稀释影响,夏季颗粒物附着密度小于冬季.叶表面粗糙程度越大,颗粒物附着密度越高.SiO₂、CaCO₃、CaMg(CO₃)₂、NaCl、2CaSO₄·H₂O、CaSO₄·2H₂O、Fe₂O₃ 7种主要矿物占叶面颗粒物总质量的10%～30%,其中,SiO₂含量最高,其次为CaMg(CO₃)₂ 、CaSO₄·2H₂O和CaCO₃.此外,还含有蒙脱石、伊利石、高岭石等粘土矿物及长石.21种测定元素占叶面颗粒物总质量的16%～37%,其中Ca、Al、Fe、Mg、K、Na、S 7种元素占测定元素总质量的97%以上,其它痕量污染元素含量很少,并且受采样地点和树种影响较小.     

Detarieae sensu lato (Fabaceae) from the Late Oligocene (27.23 Ma) Guang River flora of north‐western Ethiopia

New species of caesalpinioid legumes, Cynometra sensu lato and Afzelia, are described from the Late Oligocene (27.23 Ma) Guang River flora in north‐western Ethiopia. Both taxa show leaf characteristics that are shared with extant species in the Guineo‐Congolian, Sudanian and/or Zambezian regions of Africa today. The presence of these two species in Ethiopia during the Palaeogene provides further evidence of the importance of the legume tribe Detarieae in northern and north‐eastern Africa throughout much of the Cenozoic, even although the clade is poorly represented in these regions today. The fossil record documents a significant palaeogeographical and evolutionary history of Detarieae in Africa, especially compared with that of Europe and Anatolia. Based on this evidence, it is unlikely that significant diversification of extant African Detarieae took place on the Eurasian landmass. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 163 , 44–54.     

Influence of epiphytic micro-organisms on leaf wettability: wetting of the upper leaf surface of Juglans regia and of model surfaces in relation to colonization by micro-organisms

Wetting of the upper leaf surface of Juglans regia L. and of model surfaces colonized by epiphytic micro-organisms was investigated by measuring contact angles of aqueous solutions buffered at different pH values. During June to October 1995, contact angles of aqueous solutions on the leaf surface of J. regia decreased by angles ranging from 12° (low pH values) to 25° at high pH values. At the end of this vegetation period, wetting was strongly dependent on pH showing significantly lower contact angles with alkaline solutions (pH 9·0) than with acidic solutions (pH 3·0). Contact angle titration measured angles on the leaf surface as a function of the pH of buffered aqueous solutions, covering a pH range from 3·0 to 11·0. Titration curves revealed inflection points around 7·5, indicating the existence of ionizable carboxylic groups at the interface of the phylloplane. Altered leaf-surface wetting properties observed on the intact leaf surface could be simulated in model experiments by measuring contact angles on artificial surfaces colonized by Pseudomonas fluorescens and by epiphytic micro-organisms isolated from the phylloplane of J. regia . Strong evidence is provided that interfacial carboxylic groups derive from epiphytic micro-organisms present on the phylloplane. Results suggest that the age-dependent increase in, and pH dependence of, wetting as leaves mature are related to the presence of epiphytic micro-organisms on the phylloplane. Ecological consequences of increased leaf-surface wetting, concerning the structure of the leaf surface as a microhabitat for epiphytic micro-organisms, are discussed.     

叶面分离苏云金芽孢杆菌的研究进展

苏云金芽孢杆菌是一种在芽孢形成的同时能形成杀虫晶体蛋白的细菌,广泛存在于土壤、昆虫、贮藏物、仓库尘埃、植被等昆虫接触物上.植物叶片作为Bt分离的重要来源,目前对这方面的研究相对较少,国内刚刚起步.本文就叶面分离Bt的研究成果、叶片采样及分离方法进行阐述.     

Resistance in sorghum to shoot fly Atherigona soccata: Evidence for the source of leaf surface wetness

Leaf surface wetness (LSW) of the central whorl leaf of sorghum seedlings has been associated with susceptibility to shoot fly. Previous physical and physiological evidence suggested that LSW originates from the plant. This was confirmed by radioactive labelling methods using tritium and carbon-14. Tritiated water applied to the soil of potted seedlings was translocated to the surface of the whorl leaf. There were significant differences in the amount of tritiated water collected from susceptible (CSH 5) and resistant (IS 18551) genotypes. Studies with carbon-14 labelling of sorghum seedlings indicated the presence of (small amounts of) solutes in the surface water that may affect larval movement and survival.     

The influence of leaf thickness on the CO2 transfer conductance and leaf stable carbon isotope ratio for some evergreen tree species in Japanese warm-temperate forests

1. The influence of leaf thickness on internal conductance for CO₂ transfer from substomatal cavity to chloroplast stroma ( g _i) and carbon isotope ratio (δ¹³C) of leaf dry matter was investigated for some evergreen tree species from Japanese temperate forests. g _i was estimated based on the combined measurements of gas exchange and concurrent carbon isotope discrimination.
2. Leaves with thicker mesophyll tended to have larger leaf dry mass per area (LMA), larger surface area of mesophyll cells exposed to intercellular air spaces per unit leaf area ( S _mes) and smaller volume ratio of intercellular spaces to the whole mesophyll (mesophyll porosity).
3. g _i of these leaves was correlated positively to S _mes but negatively to mesophyll porosity. The variation in g _i among these species would be therefore primarily determined by variation of the conductance in liquid phase rather than that in gas phase.
4. δ¹³C was positively correlated to mesophyll thickness and leaf nitrogen content on an area basis. However, g _i values did not correlate to δ¹³C. These results suggest that difference in δ¹³C among the species was not caused by the variation in g _i, but mainly by the difference in long-term photosynthetic capacity.
5. Comparison of our results with those of previous studies showed that the correlation between leaf thickness and g _i differed depending on leaf functional types (evergreen, deciduous or annual). Differences in leaf properties among these functional types were discussed.     

A micromorphological study of some representative genera in the tribe Saturejeae (Lamia ceae)

HUSAIN, S. Z., MARIN, P. D., ŠILIĆ, Č., QAISER, M. & PETCOVIĆ, B., 1990. A micromorphological study of some representative genera in the tribe Saturejeae (Lamiaceae). The Old World genera in the tribe Saturejeae are usually distributed either in Europe and North Africa or in the temperate parts of Asia. The centres of distribution of investigated genera are mainly in the Mediterranean region. In taxonomic revisions very little reference is made to micromorphological characters, in particular, to nutlets and leaf indumentum, in spite of the stability of these characters. Scanning electron microscopy of nutlet surface and patterns of leaf indumentum show a wide range of variation, not only among genera, but also at lower levels of classification. In view of this, nutlet surface and leaf indumentum structure, as seen with the SEM, of representative species of eight genera in the tribe Saturejeae provides useful additional character combinations in delimiting these closely related genera. This study also supports Boissier's delimitation of sections Micromeria and Pseudomelissa.     

Leaf surface properties of Norway spruce needles exposed to sulphur dioxide and ozone in an open-air fumigation system at Liphook

Samples of current-year and 1-year-old foliage were taken from Norway spruce (Picea abies (L.) Karst.) trees in April 1991, 4 months after a 3–4 year controlled fumigation with O₃ and SO₂ in the open at Liphook, south-east England. Trees were grown in seven plots, and treated in a factorial design with three levels of SO₂ and two levels of O₃ (ambient and c. 1.3 × ambient), with an extra ambient air plot. All statistical analyses were made on plot means. Leaf wettability, as measured by the contact angle of water droplets, was significantly affected by needle age and by SO₂ treatment (P≤0–05. in older needles, decreasing with increasing SO₂ concentration. There was no effect of O₃ on wettability, and no effect of any treatment on amounts of surface wax extracted by immersion of needles in chloroform. Electrolyte leakage rates from detached current-year needles were not affected by prior exposure to O₃, but decreased significantly (P= 0.034) with increasing exposure to SO₂. There was no detectable effect of fumigation on the rate of water loss from detached needles. Similarly, there was no effect of fumigation on the dry weight/fresh weight ratio of needles. The total sulphur content of needles increased significantly (P≤0.0001) with exposure to SO₂ and with needle age. Amounts of water-extractable sulphate, however, varied greatly among plots, but with no pattern with respect to fumigation treatment. It is concluded that leaf wettability and electrolyte leakage rates may be good indicators of the persistent effects of SO₂ on Norway spruce growing in the open air, and that the observed changes in leaf surface properties in response to SO₂ fumigation have implications for the processes, both biotic and abiotic, that occur on leaf surfaces.     

Seasonal changes of leaf surface contamination in beech, oak, and ginkgo in relation to leaf micromorphology and wettability

The leaf surfaces of beech, oak and ginkgo have been investigated with respect to contamination with particles during one growing season. Based on the observation that particles are removed from water-repellent leaves by rain (Lotus effect) the three species were selected because they differ in leaf surface micromorphology and wettability. Leaves of beech are smooth, lacked wax crystals and were ±wettable. Those of ginkgo were rough because their cells were convex and were densely covered by wax crystals, resulting in permanent water repellency. Leaves of oak were covered by waxes and were water repellent when young, but, a few weeks after leaf expansion had ceased the waxes were rapidly eroded. These differences in wettability resulted in different amounts of contamination. Ginkgo collected a very small number of particles during the whole vegetation period. In beech the contamination was significantly higher, but fairly constant, whereas oak leaves accumulated particles with age.     

The role of leaf surface wetness in larval behaviour of the sorghum shoot fly, Atherigona soccata

The susceptibility of sorghum to the shoot fly Atherigona soccata Rondani, (Diptera: Muscidae) is affected by seedling age and is highest when seedlings are 8–12 days old. This corresponds with high moisture accumulation on the central leaf which is the path of newly hatched larva as it moves downwards from the oviposition site, towards the growing apex. Studies showed that leaf surface wetness (LSW) of the central shoot leaf was higher in 10-day old seedlings than in seedlings of other ages. Similarly, LSW was much higher in the susceptible sorghum genotype CSH 1 than in the resistant genotype IS 2146. Larvae moved faster towards the growing point and produced deadhearts much earlier in CSH 1 than in IS 2146. They also moved faster in 10-day old seedlings than in seedlings of other ages. It was also shown that the leaf surface wetness of the central shoot leaf is a more reliable parameter of resistance than the glossy leaf trait or trichome density.

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L'influence de la humidité de la surface foliaire sur le comportement de la mouche des pousses du sorgho

Résumé La sensibilité du sorgho à la mouche des pousses du sorgho, Atherigona soccata Rondani, est liée à l'âge de la plantule. Elle est plus forte lorsque la plantule est âgée de 8 à 12 jours et la sensibilité est maximale à 10 jours. A ce stade de croissance on observe une forte accumulation d'humidité sur la feuille centrale de la tige. Les jeunes larves traversent cette zone humide lorsqu'elles descendent vers la zone de croissance à partir des pontes déposées sur la face ventrale des feuilles déroulées.Des études ont été menées à l'ICRISAT (Inde) sur la relation entre l'humidité de la feuille centrale de la tige des plantules du sorgho et les dégâts provoqués par la mouche des pousses. L'humidité de la surface des feuilles (HSF) a été estimée grâce à une échelle visuelle graduée 1 à 5 où, 1 = pas d'humidité apparente et 5 = surface de la feuille recouverte de gouttes d'eau. La HSF est plus élevée sur des pousses de sorgho âgées de 10 j que sur les pousses appartenant à d'autres classes d'âge. Les valeurs observées sont également plus fortes pour les variétés non résistantes à ce ravageur (CSH 1,4.8) que pour les variétés résistantes (IS 2146, (2)). La vitesse du déplacement larvaire entre le cornet et la zone de la croissance varie en fonction de l'âge de la plante et des cultivars. Les larves migrent plus rapidement vers la zone de croissance et provoquent la mort du coeur du sorgho plus tôt dans la variété CSH 1 que dans IS 2146. Les larves se déplacent plus rapidement dans les pousses âgées de 10 j que dans les pousses appartenant à d'autres classes d'âge.Des études ont également démontré que la HSF n'est pas directement liée au caractère feuille lisse où à la densité des trichomes. La HSF est faible pour les génotypes résistants présentent où non le caractère feuille lisse. Par contre la HSF est élevée pour les génotypes non résistants présentant le caractère feuille lisse ou non. Aucune relation directe entre la densité des trichomes et les dégâts provoqués par la mouche des pousses n'a pu être mise en évidence. L'analyse des correlations établie pour les caractères de surface des feuilles avec la mort du cur des sorghos indique que les correlations sont faibles et non-significatives pour le caractère feuille lisse (0.49) et la densité des trichomes (0.39 et 0.2). Par contre les correlations sont fortes et significatives pour la HSF (0.82).On conclue que la HSF de la feuille centrale de la tige est un facteur important dans le déterminisme de la résistance du sorgho vis à vis de la mouche des pousses. Les relations entre les processus physiologiques de la plante et les facteurs impliquées dans l'accumulation d'eau sur la surface des feuilles font actuellement l'objet d'études détaillées.

     

Size fractions of dust and amount of associated metals on leaf surface and inner wax of 15 plant species at Beijing roadside

To provide more insight into the removal ability of urban air dust and associated metals by plant leaves, and thus guide urban green planning to improve air quality, 15 plant species leaves collected from Beijing roadside were analyzed for size fractions of leaf surface dust (SD) and inner wax dust (WD). Seven associated metals Cd, Cr, Cu, Fe, Mn, Pb and Zn were also measured. Metal Accumulation Index (MAI) was calculated for different species leaves at various dust sizes and soluble forms, respectively. Cluster analysis was used for the plant species and correlations between dust and metal concentrations and for inter-metal concentrations were calculated for both surface and inner wax dust. Mean leaf total dust TD (SD?+?WD), SD and WD were measured as 1159, 817 and 342?mg m^?2, respectively, with the highest values observed all in Euonymus japonicus. Most species leaves collected larger ratios of SD than WD except Salix babylonica and Robinia pseudoacacia. While SD was presented at all particle size fractions for all plants, nearly all species leaves collected higher proportions of WD >10?µm. Mean metal levels of leaf TD of all species ranged from high to low as Fe?>?Cr?>?Zn?>?Pb?>?Cu?>?Mn?>?Cd, but with different orders for individual species. Metals were observed in all sizes of SD/WD, although the size distributions were various for certain metals. Intercorrelations of metal concentrations in leaf SD/WD were positively significant except Pb, which may have different emission sources. Species Prunus cerasifera f. atropurpurea, Syringa oblata, Malus micromalu, Koelreuteria paniculata and Robinia pseudoacacia may possess better overall metal collection ability due to their relatively higher MAI values, but species Euonymus japonicus, Malus micromalu, Ligustrum x vicaryi and Koelreuteria paniculata were identified as the best choices in removing air dust based on cluster analysis and suggested to be planted at heavy trafficked road site for air quality improvement.     

The dynamics of leaf surface wetness of sorghum seedlings in relation to resistance to the shoot fly, Atherigona soccata

In quantitative measurements of leaf surface wetness (LSW) of the central whorl leaf of sorghum seedlings in August (rainy season) and November (post-rainy season), the highest amount (6.29 mg of water) was recorded in August in the shoot fly Atherigona soccata (Diptera: Muscidae), susceptible sorghum genotype CSH 1, while the lowest (0.07 mg) was recorded in November in the resistant genotype IS 18551. Studies on diurnal fluctuation revealed that LSW was lowest at sunset, was highest between 02.00 and 04.00 h (closely corresponding with hatching of shoot fly eggs) and dropped before sunrise. This fluctuation was associated with the evaporation of water from the plant during the night. More LSW accumulation occurred during the main crop season (June-October) than in the post-rainy season (November-April). Annual fluctuation of LSW followed trends similar to the population dynamics of shoot fly and crop infestation and were correlated with rainfall, temperature and relative humidity. Measurements of leaf temperature and the vapour pressure gradient between the leaf and the air indicated that leaf surface water originates from the plant. This was further supported by the different amounts of LSW on susceptible and resistant cultivars with similar microclimatic conditions.