海拔对高山栎光合气体交换和叶性状的影响

理解影响植物分布的式样及过程是生态学研究的中心内容之一,但对许多物种而言,限制其分布的原因还不清楚。为了认识高山栎分布与生理生态特性的关系,我们在不同海拔的4个观测点研究了帽斗栎的光合气体交换、叶氮含量、叶绿素含量和比叶重。由于高的水气压亏缺和气温,帽斗栎的光合作用和蒸腾作用在午间表现出明显的降低现象。帽斗栎的饱和光合速率、水分利用效率、最大羧化速率、最大电子传递速率和氮利用效率在海拔中部比低海拔或高海拔处的为高。不同海拔的叶氮含量在5月份有差异,8月份则没有明显不同。叶片厚度随海拔增加,但叶绿素含量及光合最适温度随海拔升高而降低。帽斗栎光合作用的海拔变化与叶片的生化效率和氮含量有关,而与比叶重无关。研究结果说明,温度的海拔变化对高山栎的光合作用和叶性状有明显影响,最适宜帽斗栎光合碳获取及生长的海拔范围是3180～3610m。     

Growth and leaf production in the tropical palm Euterpe edulis: Light conditions versus developmental constraints

We studied developmental and environmental constraints on leaf dynamics, morphology and physiology in the monopodial tropical palm of the Atlantic Forest biome, Euterpe edulis. Plastic responses to light environments in terms of photosynthesis, leaf size, leaf life span, patterns of biomass allocation and growth were analysed. Plants were grown during 14 months in a shade house under four different growth irradiances. Plants of Euterpe edulis were able to adjust leaf demography and biomass allocation in the different light treatments. Leaf life span increased by 100 days with decreasing light levels while the rate of leaf production decreased, consistent with lower electron transport rates. At low light levels, adjustments in biomass allocation to leaf components allowed E. edulis to reduce self-shading and increase light interception. At high light plants allocated more biomass to roots, and the plants exhibited small leaf sizes when leaves were compared using an explicit ontogenetic analysis. Ontogeny constrained the maximum size that each consecutive leaf could achieve, while growth irradiance determined the rate of leaf production and other leaf traits. Consequently, there were both, developmental constraints and environmental determinants influencing leaf demography and morphology in E. edulis. The findings of this ecophysiological and demographic study are relevant to palms growing under natural conditions and help to explain the success of E. edulis in the forest understory and its absence from large gap openings. Our results not only confirm that E. edulis is a shade tolerant species, but also show that palms are able to acclimate to different growing condition as well as trees.     

4个花苜蓿居群叶片解剖结构特征及其可塑性对不同水分处理的响应

对经过3种水分处理的4个花苜蓿居群（内蒙古科右中旗、克什克腾旗、陕西南泥湾和甘肃兴隆山）叶片解剖结构特征及它们的可塑性进行了研究。结果表明：除上下表皮细胞厚度外,土壤水分处理对花苜蓿的叶片解剖结构有着显著影响。随着水分减少,大部分花苜蓿居群栅栏组织厚度增加,海绵组织厚度相应减小,叶片厚度增大,叶片组织结构紧密度增加,疏松度减少,叶脉突起度增加。10个解剖指标中,栅栏组织海绵组织厚度比的可塑性指数最大,上表皮细胞厚度次之,叶片厚度最小。4个花苜蓿居群可塑性指数平均值大小排序为：科右中旗〉克什克腾旗〉南泥湾〉兴隆山。综合方差分析和Ducan多重比较,可推测：花苜蓿的抗旱性与其分布的地域有关,分布于典型草原地带的科右中旗和克什克腾旗2个居群的花苜蓿的叶片结构可塑性要较分布于森林草原地带的南泥湾居群和兴隆山居群大。。上述结果有助于了解花苜蓿的生态适应特点,同时也为筛选适应北方干旱、半干旱地区的优良豆科牧草资源提供依据。     

水杨酸对黄瓜子叶表皮气孔开度的调节作用

以黄瓜品种中农203(Cucumis sativus L.cv.Zhongnong 203)幼苗为试材,采用SA溶液根部施用和子叶表皮浸泡两种方式,显微观测了不同外源水杨酸(Salicylic acid,SA)溶液处理对其子叶表皮气孔开度的影响,以探讨SA与气孔运动的关系.结果表明:SA子叶表皮浸泡或根部施用后,气孔运动的趋势是随着SA浓度增加而孔径逐渐变小,且SA磷酸缓冲液的作用效果与SA水溶液相似.随着处理时间的延长,气孔开度逐渐变小,且气孔开度与SA处理时间达极显著(r=-0.962**)或显著(r=-0.914*)负相关.溶液低pH值,增强了SA对气孔开度的抑制作用,且SA浓度越高作用越明显;0.1 mmol/L SA处理后,pH为8、7、6溶液的气孔开度抑制率分别为90.2%、93.8%和96.3%,即SA溶液对气孔开度的抑制率随着溶液pH降低而升高.可见,外源SA能够促进气孔关闭,其作用随着SA浓度升高、处理时间延长和溶液pH值降低而增强,相对于磷酸缓冲液,以蒸馏水作为溶剂的SA溶液促进气孔关闭的作用更大.     

假瘤蕨属 (水龙骨科) 植物叶表皮特征的比较研究

在光镜和扫描电镜下观察了假瘤蕨属2系、5亚系的24种植物的叶表皮。结果表明,叶表皮细胞形状不规则,垂周壁波曲状。下生气孔,气孔类型有极细胞型、共环极细胞型、腋下细胞型、聚腋下细胞型和不规则型,常伴生出现。在扫描电镜下,叶表皮气孔器外拱盖内缘为浅波状、少平滑;一些种的保卫细胞两端有“T”型加厚;角质膜波状有条纹,有时附有颗粒。叶表皮的一些特征对该属部分种的区分有一定的参考价值。叶表皮的微形态特征,如气孔器类型和垂周壁类型特征不能用来界定假瘤蕨属的系和亚系。     

Leaf attributes and tree growth in a tropical dry forest

Questions: How are leaf attributes and relative growth rate (RGR) of the dominant tree species of tropical deciduous forest (TDF) affected by seasonal changes in soil moisture content (SMC)? What is the relationship of functional attributes with each other? Can leaf attributes singly or in combination predict the growth rate of tree species of TDF? Location: Sonebhadra district of Uttar Pradesh, India. Methods: Eight leaf attributes, specific leaf area (SLA); leaf carbon concentration (LCC); leaf nitrogen concentration (LNC); leaf phosphorus concentration (LPC); chlorophyll concentration (Chl), mass‐based stomatal conductance (Gs_mass); mass based photosynthetic rate (A_mass); intrinsic water use efficiency (WUEi); and relative growth rate (RGR), of six dominant tree species of a dry tropical forest on four sites were analysed for species, site and season effects over a 2‐year period. Step‐wise multiple regression was performed for predicting RGR from mean values of SMC and leaf attributes. Path analysis was used to determine which leaf attributes influence RGR directly and which indirectly. Results: Species differed significantly in terms of all leaf attributes and RGR. The response of species varied across sites and seasons. The attributes were positively interrelated, except for WUEi, which was negatively related to all other attributes. The positive correlation was strongest between Gs_mass and A_mass and the negative correlation was strongest between Gs_mass and WUEi. Differences in RGR due to site were not significant when soil moisture was controlled, but differences due to season remained significant. The attributes showed plasticity across moisture gradients, which differed among attributes and species. Gs_mass was the most plastic attribute. Among the six species, Terminalia tomentosa exhibited the greatest plasticity in six functional attributes. In the step‐wise multiple regression, A_mass, SLA and Chl among leaf attributes and SMC among environmental factors influenced the RGR of tree species. Path analysis indicated the importance of SLA, LNC, Chl and A_mass in determining RGR. Conclusion: A _mass, SMC, SLA and Chl in combination can be used to predict RGR but could explain only three‐quarters of the variability in RGR, indicating that other traits/factors, not studied here, are also important in modulating growth of tropical trees. RGR of tree species in the dry tropical environment is determined by soil moisture, whereas the response of mature trees of different species is modulated by alterations in key functional attributes such as SLA, LNC and Chl.     

Enhanced contact allergen- and UVB-induced keratinocyte apoptosis in the absence of CD95/Fas/Apo-1

FAS/CD95/Apo-1 is a ubiquitously expressed cell-surface receptor involved in the initiation of programmed cell death. Its function in epidermal keratinocytes has been incompletely defined. Available evidence from in vitro studies points to important roles of Fas in the pathogenesis of contact dermatitis and in keratinocyte apoptosis induced by ultraviolet light. To define functions of Fas in the epidermis in vivo, we have generated mice with epidermis-specific deletion of the fas gene and tested its requirement for 2,4-dinitrofluorobenzene-induced contact dermatitis and for ultraviolet light B (UVB)-induced keratinocyte apoptosis. We report here our unexpected finding that keratinocyte apoptosis induced by both a contact allergen and UVB irradiation was significantly enhanced in Fas-negative epidermis. Expression of Fas by epidermal keratinocytes was neither necessary for the normal development of contact hypersensitivity of the skin, nor required for keratinocyte apoptosis following UVB irradiation. Our study results thus show that in the epidermis in vivo Fas exerts antiapoptotic effects that outweigh its proapoptotic role in contact hypersensitivity responses of the skin and in the tissue response of the epidermis to UVB irradiation.     

中国卫矛属植物叶表皮微形态特征及其分类学意义

利用光学显微镜和扫描电子显微镜对中国卫矛属(Euonymus L.)24种以及沟瓣属（Glyptopetalum Thw.）3种植物的叶表皮微形态特征进行了观察研究,测量并统计了气孔器长宽比、密度和气孔指数。结果显示,两属植物叶表皮微形态特征基本一致：叶上、下表皮细胞形状多为多边形,垂周壁平直-弓形;气孔器通常仅分布在叶下表皮;均具有无规则型气孔器,部分种还具环列型气孔器。扫描电镜下角质膜纹饰、表皮细胞界限及气孔特征在一些种间存在差异,可以作为区分部分近缘种类的参考依据。     

燕山山脉野生欧李群体叶表皮微形态特征研究

利用扫描电子显微镜对同一生境条件下自然生长的燕山山脉野生欧李实生群体（含嫁接类型）叶片表面微形态特征进行观测。结果表明：欧李叶表皮细胞形态存在两种类型,一类是上下表皮细胞向下凹陷相互连接形成蜂窝状,另一类是上下表皮细胞向上隆起近圆形,且上表皮细胞均具条纹状的角质层;叶片上表皮仅有表皮毛而无气孔分布,叶片下表皮仅有气孔分布;气孔突出于表皮细胞,属无规则型,气孔平均长度8.22±1.30 μm,宽度2.55±0.65 μm,大小21.64±8.60μm²,密度836.23±197.16 个/mm²;欧李群体中不同株系间、叶表皮细胞形态不同类别间气孔特征变异程度较大,可作为欧李优异种质选育和抗干旱胁迫研究的指标之一。     

Mouse genetics identifies unique and overlapping functions of fibroblast growth factor receptors in keratinocytes

Fibroblast growth factors (FGFs) are key regulators of tissue development, homeostasis and repair, and abnormal FGF signalling is associated with various human diseases. In human and murine epidermis, FGF receptor 3 (FGFR3) activation causes benign skin tumours, but the consequences of FGFR3 deficiency in this tissue have not been determined. Here, we show that FGFR3 in keratinocytes is dispensable for mouse skin development, homeostasis and wound repair. However, the defect in the epidermal barrier and the resulting inflammatory skin disease that develops in mice lacking FGFR1 and FGFR2 in keratinocytes were further aggravated upon additional loss of FGFR3. This caused fibroblast activation and fibrosis in the FGFR1/FGFR2 double‐knockout mice and even more in mice lacking all three FGFRs, revealing functional redundancy of FGFR3 with FGFR1 and FGFR2 for maintaining the epidermal barrier. Taken together, our study demonstrates that FGFR1, FGFR2 and FGFR3 act together to maintain epidermal integrity and cutaneous homeostasis, with FGFR2 being the dominant receptor.