星斗山常绿落叶阔叶混交林木本植物叶功能性状及其多样性特征分析

为探究亚热带常绿落叶阔叶混交林中木本植物叶功能性状的变异特征,以及群落功能多样性在海拔梯度下的响应规律。该研究以鄂西南地区的星斗山国家级自然保护区海拔1 200～1 700 m的常绿落叶阔叶混交林为研究对象,对群落内木本植物的叶面积(LA)、比叶面积(SLA)、叶干物质含量(LDMC)、叶厚度(LT)、叶氮含量(LNC)、叶磷含量(LPC)6种叶功能性状的变异特征进行了分析,并分析了群落水平下木本植物叶功能性状和功能多样性对海拔变化的响应。结果表明:(1)星斗山保护区内木本植物叶面积、比叶面积、叶干物质含量、叶厚度、叶氮含量和叶磷含量平均值分别为151.49 cm~2、247.98 cm~2/g、34.08%、0.21 mm、16.59 mg/g和0.04 mg/g,其变异幅度依次为206.96%、57.00%、28.15%、52.38%、24.83%和76.92%。(2)在植物科、叶习性、生活型和树高4个因素中,科类群对6种叶功能性状的影响最大,其次为叶习性。(3)海拔对叶面积、叶干物质含量、叶磷含量影响极显著(P0.001),但对比叶面积、叶厚度和叶氮含量无显著影响(P0.05)。(4)不同海拔梯度上群落生物承载量、功能丰富度、功能分离度和功能离散度均达到显著差异(P0.05),仅功能均匀度在海拔梯度上差异不显著。     

中亚热带樟科3种植物幼苗叶结构型性状的种间差异及其相关性

为了揭示植物叶功能性状对全球气候变化的响应和适应规律,以樟科3种植物幼苗为研究对象,将其人工采集的种子经低温沙藏并于温室培育,然后将幼苗移栽到野外同质园中自然生长,研究中亚热带樟科植物刨花楠(Machilus pauhoi)、香樟(Cinnamomum camphora)和闽楠(Phoebe bournei)两年生幼苗生长季节9种叶结构型性状的种间差异及其相关性。结果显示,(1)在3种植物幼苗中,香樟叶面积、叶厚度、叶体积、叶氮磷比最大,叶氮浓度最高,叶组织密度最小;闽楠叶组织密度、叶干物质含量最大,叶磷浓度最高,叶面积、叶体积、比叶面积、叶氮磷比最小,叶氮浓度最低;刨花楠比叶面积最大,叶厚度、叶干物质含量最小,叶磷浓度最低;3种植物幼苗的叶厚度之间均无显著差异。(2)Pearson相关分析和线性回归分析结果表明,樟科3种植物幼苗的叶面积与叶体积间呈极显著正相关(P0.01)、与叶干物质含量间呈极显著负相关(P0.01)、与叶磷浓度间呈极显著负相关(P0.01)、与叶组织密度间呈显著负相关(P0.05)、与叶氮浓度间呈显著正相关(P0.05);叶厚度与比叶面积间呈显著负相关(P0.05)、与叶干物质含量间呈显著正相关(P0.05);叶体积与叶组织密度间呈极显著负相关(P0.01)、与叶氮浓度间呈极显著正相关(P0.01)、与叶磷浓度间呈显著负相关(P0.05);叶组织密度与叶磷浓度间呈显著正相关(P0.05);比叶面积与叶干物质含量间呈极显著负相关(P0.01)、与叶磷浓度间呈极显著负相关(P0.01);叶干物质含量与叶磷浓度间呈极显著正相关(P0.01)。这表明在同质园中生长的刨花楠、香樟和闽楠幼苗的9种叶结构型性状表现出一定的种间差异,不同物种同一叶结构型性状指标的大小顺序、种间差异及其显著性不同;3种植物幼苗不同叶结构型性状之间的相关性及其显著程度也不同。本研究结果为揭示樟科3种植物幼苗叶功能性状对全球气候变化的响应和适应规律提供了基础数据。     

壳斗科五树种幼苗叶片结构型性状及其相关关系

通过种子的人工采集、低温沙藏和温室培育后,将幼苗移栽到环境条件相同的同质园中自然生长,研究了中亚热带壳斗科丝栗栲(Castanopsis fargesii)、苦槠(C.sclerophylla)、锥栗(Castanea henryi)、板栗(C.mollissima)和麻栎(Quercus acutissima)2年生幼苗生长季节的叶面积、叶厚度、比叶面积、叶干物质含量、叶氮浓度、叶磷浓度和叶氮磷比7种结构型性状的差异及其相关关系。结果表明:(1)在5树种幼苗中,锥栗幼苗的叶面积和比叶面积最大、叶氮浓度最高,其叶干物质含量最低;丝栗栲幼苗的叶面积最小、叶氮浓度和叶磷浓度最低;苦槠幼苗的叶厚度和比叶面积最小,其叶干物质含量最高;板栗幼苗则是叶厚度最小;同时5树种幼苗叶片的氮磷比均无显著差异(P0.1)。(2)Pearson相关和线性回归分析表明,壳斗科5树种幼苗的叶面积与叶氮浓度极显著正相关(P0.01),并与比叶面积显著正相关(P0.05);叶厚度与比叶面积极显著负相关(P0.01),其与叶干物质含量显著正相关(P0.05);比叶面积与叶干物质含量极显著负相关(P0.01),并与叶氮浓度极显著正相关(P0.01),同时与叶磷浓度显著负相关(P0.05);叶氮浓度与叶干物质含量、叶磷浓度分别为显著负相关(P0.05)和显著正相关(P0.05)。该研究结果表明壳斗科5树种幼苗叶片的7种结构型性状表现出了一定的种间差异性,但同一结构型性状的大小顺序和种间差异的显著性不同;同时所有树种幼苗叶片各结构型性状间的相关性及其显著程度不同。     

Senescence and hyperspectral reflectance of cotton leaves exposed to ultraviolet-B radiation and carbon dioxide

The objectives of this study were to determine the effects of UV-B radiation and atmospheric carbon dioxide concentrations ([CO(2)]) on leaf senescence of cotton by measuring leaf photosynthesis and chlorophyll content and to identify changes in leaf hyperspectral reflectance occurring due to senescence and UV-B radiation. Plants were grown in controlled-environment growth chambers at two [CO(2)] (360 and 720 micro mol mol(-1)) and three levels of UV-B radiation (0, 7.7 and 15.1 kJ m(-2) day(-1)). Photosynthesis, chlorophyll, carotenoids and phenolic compounds along with leaf hyperspectral reflectance were measured on three leaves aged 12, 21 and 30 days in each of the treatments. No interaction was detected between [CO(2)] and UV-B for any of the measured parameters. Significant interactions were observed between UV-B and leaf age for photosynthesis and stomatal conductance. Elevated [CO(2)] enhanced leaf photosynthesis by 32%. On exposure to 0, 7.7 and 15.1 kJ of UV-B, the photosynthetic rates of 30-day-old leaves compared with 12-day-old leaves were reduced by 52, 76 and 86%, respectively. Chlorophyll pigments were not affected by leaf age at UV-B radiation of 0 and 7.7 kJ, but UV-B of 15.1 kJ reduced the chlorophylls by 20, 60 and 80% in 12, 21 and 30-day-old leaves, respectively. The hyperspectral reflectance between 726 and 1142 nm showed interaction for UV-B radiation and leaf age. In cotton, leaf photosynthesis can be used as an indicator of leaf senescence, as it is more sensitive than photosynthetic pigments on exposure to UV-B radiation. This study revealed that, cotton leaves senesced early on exposure to UV-B radiation as indicated by leaf photosynthesis, and leaf hyperspectral reflectance can be used to detect changes caused by UV-B and leaf ageing.     

Anatomical and morphological parameters of leaves and leaf petioles of Actinidia deliciosa

Differences in anatomy and morphology of the kiwifruit leaves and leaf petioles might play a considerable role in the sex-determination. Three months after bud break (June), the kiwifruit leaves of both male and female plants, grown on the vegetative and generative shoots showed different leaf area (128.6 ± 13.45 cm2 in male and 104.5 ± 4.02 cm2 in female plants) and shape. The most frequently leaf shape was determined as "folium cordatum" and "folium rotundato-cordatum". Higher values of total leaf thickness of the female leaves (190 ± 3.84 μm) in comparison to male leaves (174 ± 3.52 μm) were estimated, resulting in the thicker adaxial leaf epidermis and especially in thicker palisade parenchyma in female leaves (136 ± 2.76 μm in comparison to 104 ± 1.61 μm in male leaves). Typically bifacial leaves were observed in both male and female leaves. Anomocytic stomata in hypostomatic leaves were found. The reticulate venation appears to be the main type of leaf venation. Stalked stellate multicellular trichomes on the abaxial leaf side were frequently observed in the leaves of both sexes. No important differences between male and female plants were found in the structures of vascular system in leaves and leaf petioles. Thus leaf thickness and surface morphology of adaxial leaf epidermis can be considered as important structural parameters in the sex determination. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of Benzyladenine and Naphthalene Acetic Acid on Growth and Camptothecin Accumulation in Camptotheca acuminata Seedlings

The effects of the cytokinin benzyladenine (BA) and the auxin naphthalene acetic acid (NAA) on Camptotheca acuminata Decaisne growth and camptothecin (CPT) accumulation (leaf CPT concentration and total leaf CPT yield) were studied in a hydroponic culture system for three weeks. Increasing BA concentrations from 0 to 3 mg l^–1 in growth medium decreased plant height, stem weight, and leaf weight but increased root weight. High BA levels (1 and 3 mg l^–1) increased leaf CPT concentration (% of dry weight), whereas BA applications had no effect on total leaf CPT yield, the product of leaf CPT concentration and total leaf dry weight per seedling. There was a positive correlation between root weight and leaf CPT concentration under BA treatments. NAA supplementations (from 0.5 to 4 mg l^–1) to growth medium reduced plant height, leaf number, leaf length, specific leaf weight, plant weight, stem weight, and leaf weight compared with the NAA control. Meanwhile, there were no differences in plant height, leaf length, and specific leaf weight among the NAA supplementations. NAA applications had no effect on leaf CPT concentration and NAA applications decreased total leaf CPT yield. There were negative correlations between leaf number and leaf CPT concentration, leaf length and leaf CPT concentration under NAA treatments. Our results suggest that BA applications from 0.3 to 3 mg l^–1 are not helpful for achieving high total leaf CPT yield and NAA applications from 0.5 to 4 mg l^–1 decrease total leaf CPT yield.     

不同林龄刺槐叶功能性状差异及其与土壤养分的关系

对不同林龄刺槐群落叶功能性状差异及其与土壤养分的关系进行研究,分析刺槐对黄土丘陵区土壤环境的适应策略.结果表明: 随林龄的增大,刺槐比叶面积、叶面积、叶片含水量、叶全氮含量及叶有机碳含量呈先增大后减小的变化趋势,且在30年林龄时达到最大值,分别为279.18 cm²·g^-1、12.33 cm²、0.09%、33.01 g·kg^-1、523.08 g·kg^-1.随林龄的增大,叶组织密度、叶全磷含量、叶厚度及气孔密度呈增大趋势,气孔长度及气孔宽度呈减小趋势.主成分分析表明,叶面积、比叶面积、叶全磷含量、叶片含水量、叶厚度及气孔密度均为刺槐叶功能性状随林龄变化的主要指标.各指标间呈一定的相关性,这表明刺槐能改变自身的形态结构,形成最佳功能组合以适应环境的变化.影响叶面积、叶片含水量、比叶面积及气孔长度的主要土壤因子是土壤全氮含量,影响气孔宽度、叶组织密度、叶厚度、叶全磷含量、叶全氮含量及气孔密度的主要土壤因子是土壤有机碳含量,这表明土壤全氮含量和有机碳含量是影响不同林龄刺槐叶功能性状的主要土壤因子.随林龄的增大,刺槐群落土壤养分得到改善,进而影响刺槐叶功能性状.不同林龄刺槐叶功能性状的差异反映出刺槐具有较强的叶片形态可塑性,有利于其适应黄土丘陵区的土壤环境.     

散孔材与环孔材树种枝干、叶水力学特性的比较研究

为揭示散孔材与环孔材树种树木水分生理特性的差异,选取了常见的3种散孔材落叶树种(毛白杨、法国梧桐和樱花)和3种环孔材落叶树种(刺槐、合欢和白蜡),研究了其枝干与叶水力学性质的差异及其协调性。结果表明:3种环孔材树种枝干横截面积基础上的最大比导水率(Ks-max)大于3种散孔材树种,但其木质部对空穴化的脆弱性(P50branch)高于散孔材树种,6种树木枝干的水分传输能力和抵抗空穴化能力之间存在一种相互制约的权衡关系。3种散孔材与3种环孔材树种的叶最大水力导度(Kl-max)和水力脆弱性(P50leaf)并无显著差异;对于3种散孔材树种,叶的水力脆弱性要高于枝干,但对3种环孔材树种而言,枝干的水力脆弱性要高于叶。6种树木枝干和叶的水力学性质(Kmax、P50)之间并无相关关系。这些结果表明:散孔材与环孔材树种的枝干水力学特性有明显差异,但叶水力学特性无差异;枝干与叶水力学性质之间是相互独立的。     

Leaf traits and water relations of 12 evergreen species in Costa Rican wet and dry forests: patterns of intra-specific variation across forests and seasons

This study examined variation in leaf traits and water relations in 12 evergreen and semideciduous woody species that occur in both seasonal wet and dry forests in Costa Rica and compared intra-specific leaf–trait correlations to those found in inter-specific global studies. The following traits were measured in both forests across seasons for 2 years: leaf nitrogen (N), leaf carbon (C), specific leaf area (SLA), toughness, cuticle thickness, leaf thickness, and leaf lifespan (LLS). Leaf water potential (LWP) and water content (LWC) were measured as indices of plant available water. Canopy openness, soil moisture, and herbivory were also measured to compare environmental variation across sites. Although species contributed the greatest amount to variation in traits, season, forest, and their interaction had a large influence on patterns of intra-specific leaf–trait variation. Leaf traits that contributed most to variation across sites were C, LWP, leaf thickness, and SLA. Traits that contributed most to variation across seasons were leaf toughness, LWP, and LWC. Furthermore, leaf traits were more correlated (i.e., number and strength of correlations) in the dry than in the wet forest. In contrast to results from global literature syntheses, there was no correlation between LLS and N, or LLS and SLA. Both light and water availability vary seasonally and may be causing variation in a number of leaf traits, specifically those that relate to water relations and leaf economics. Strong seasonality may cause leaf–trait relationships at the local scale to differ from those documented in continental and global-scale studies.     

南天竹不同叶色与若干生理生化指标关系的研究

本文研究南天竹不同叶色的叶片叶绿素、花青素、可溶性糖含量和气孔密度、POD、CAT活性的变化。结果表明,南天竹叶色差异与花青素、叶绿素含量有关,绿叶花青素含量低、叶绿素含量高;红叶则相反。此外,红叶下表皮气孔数目少,气孔小;绿叶气孔数目多,气孔大。红叶的可溶性糖含量明显高于绿叶,而POD和CAT活性低于绿叶。     

Habitat structure and fish predation: effects on invertebrate colonisation and breakdown of stream leaf packs

1. We investigated the effects of two features of leaf‐pack habitat structure (i.e. mass of a leaf pack and surface area of leaves comprising a leaf pack) and fish predation on colonisation of shredders and leaf breakdown rates in a coldwater stream. Packs were constructed of red maple (Acer rubrum) leaves. 2. A 2 × 3 × 3 factorial experiment was used to manipulate fish predation (exclusion and control cage), leaf‐pack mass (1, 3 and 5 g dry mass) and leaf surface area (small: approx. 17.9 cm², medium: approx. 34.6 cm², large: approx. 65.6 cm²). Exclusion cages had mesh on all sides, whereas control cages lacked mesh on two sides to provide access to fish. 3. Common shredders were Gammarus pseudolimnaeus, Pycnopsyche and Lepidostoma. Shredder biomass per leaf pack increased with the mass of a leaf pack (P < 0.001), but biomass per unit mass of leaf pack did not differ with leaf‐pack mass (P = 0.506). Shredder densities did not respond to the exclusion of fish (P > 0.7) or leaf surface area (P > 0.7), and interactions among treatment factors were not significant (P > 0.2). 4. Breakdown rates were lower for leaf packs comprised of small leaves (P < 0.001) and leaf packs with high mass (P = 0.001). Excluding fish did not significantly affect leaf breakdown rates (P = 0.293), and interactions among treatment factors were not significant (P > 0.3). Breakdown rates were highest when packs consisted of few leaves (i.e. leaf packs with large leaves and low mass) and were colonised by many shredders. 5. Fish predation was not an important factor controlling shredder densities in leaf packs over the spatiotemporal scale of our experiment. Nevertheless, we found shredder colonisation was proportional to leaf‐pack mass and breakdown rates were affected by leaf‐pack size (i.e. number of leaves in a pack). We suspect that fragmentation is the primary mechanism causing the breakdown rates to be dependent on leaf‐pack size.     

Spatial and temporal effects of free-air CO2 enrichment (POPFACE) on leaf growth,cell expansion,and cell production in a closed canopy of poplar

Leaf expansion in the fast-growing tree, Populus x euramericana was stimulated by elevated [CO(2)] in a closed-canopy forest plantation, exposed using a free air CO(2) enrichment technique enabling long-term experimentation in field conditions. The effects of elevated [CO(2)] over time were characterized and related to the leaf plastochron index (LPI), and showed that leaf expansion was stimulated at very early (LPI, 0-3) and late (LPI, 6-8) stages in development. Early and late effects of elevated [CO(2)] were largely the result of increased cell expansion and increased cell production, respectively. Spatial effects of elevated [CO(2)] were also marked and increased final leaf size resulted from an effect on leaf area, but not leaf length, demonstrating changed leaf shape in response to [CO(2)]. Leaves exhibited a basipetal gradient of leaf development, investigated by defining seven interveinal areas, with growth ceasing first at the leaf tip. Interestingly, and in contrast to other reports, no spatial differences in epidermal cell size were apparent across the lamina, whereas a clear basipetal gradient in cell production rate was found. These data suggest that the rate and timing of cell production was more important in determining leaf shape, given the constant cell size across the leaf lamina. The effect of elevated [CO(2)] imposed on this developmental gradient suggested that leaf cell production continued longer in elevated [CO(2)] and that basal increases in cell production rate were also more important than altered cell expansion for increased final leaf size and altered leaf shape in elevated [CO(2)].     

神木天坑不同小生境木本植物叶功能性状的差异与关联

为进一步探讨天坑生境下木本植物的生存策略，该研究以神木天坑不同小生境(底部、坑腰和边缘)的木本植物为对象，选取叶厚度、叶组织密度、叶面积等10个叶功能性状指标，运用单因素方差分析和相关性分析等方法，分析了天坑木本植物叶功能性状的变异特征以及小生境对木本植物叶功能性状的影响。结果表明：(1)在神木天坑木本植物10个叶功能性状中，叶面积变异系数最大(113.9%),叶碳含量变异系数最小(10.5%)。(2)天坑边缘、坑腰的乔木叶组织密度显著高于底部(P<0.05),天坑底部乔木、灌木的叶钾含量显著高于边缘(P<0.05),3种小生境中木质藤本未出现显著差异(P>0.05)。(3)不同小生境叶功能性状相关性存在一定差异，从天坑底部到边缘小生境，叶厚度与叶面积逐渐呈极显著正相关；主成分分析结果显示叶组织密度(-0.833)、叶钾含量(0.782)、叶干物质含量(-0.647)贡献较大，是神木天坑不同小生境木本植物叶功能性状的主要指标。综上认为，叶功能性状之间普遍关联，天坑木本植物通过对叶功能性状的权衡来适应不同小生境。该研究结果为了解植物对特殊生境的适应机制以及天坑植被的保护...     

Identification of Nitrogen,Phosphorus, and Potassium Deficiencies in Rice Based on Static Scanning Technology and Hierarchical Identification Method

Establishing an accurate, fast, and operable method for diagnosing crop nutrition is very important for crop nutrient management. In this study, static scanning technology was used to collect images of a rice sample''s fully expanded top three leaves and corresponding sheathes. From these images, 32 spectral and shape characteristic parameters were extracted using an RGB mean value function and using the Regionprops function in MATLAB. Hierarchical identification was used to identify NPK deficiencies. First, the normal samples and non-normal (NPK deficiencies) samples were identified. Then, N deficiency and PK deficiencies were identified. Finally, P deficiency and K deficiency were identified. In the identification of every hierarchy, SVFS was used to select the optimal characteristic set for different deficiencies in a targeted manner, and Fisher discriminant analysis was used to build the diagnosis model. In the first hierarchy, the selected characteristics were the leaf sheath R, leaf sheath G, leaf sheath B, leaf sheath length, leaf tip R, leaf tip G, leaf area and leaf G. In the second hierarchy, the selected characteristics were the leaf sheath G, leaf sheath B, white region of the leaf sheath, leaf B, and leaf G. In the third hierarchy the selected characteristics were the leaf G, leaf sheath length, leaf area/leaf length, leaf tip G, difference between the 2^nd and 3^rd leaf lengths, leaf sheath G, and leaf lightness. The results showed that the overall identification accuracies of NPK deficiencies were 86.15, 87.69, 90.00 and 89.23% for the four growth stages. Data from multiple years were used for validation, and the identification accuracies were 83.08, 83.08, 89.23 and 90.77%.     

The effects of leaf size,leaf habit,and leaf form on leaf/stem relationships in plant twigs of temperate woody species

Question: Do thick‐twigged/large‐leaf species have an advantage in leaf display over their counterparts, and what are the effects of leaf habit and leaf form on the leaf‐stem relationship in plant twigs of temperature broadleaf woody species? Location: Gongga Mountain, southwest China. Methods: (1) We investigated stem cross‐sectional area and stem mass, leaf area and leaf/lamina mass of plant twigs (terminal branches of current‐year shoots) of 89 species belonging to 55 genera in 31 families. (2) Data were analyzed to determine leaf‐stem scaling relationships using both the Model type II regression method and the phylogenetically independent comparative (PIC) method. Results: (1) Significant, positive allometric relationships were found between twig cross‐sectional area and total leaf area supported by the twig, and between the cross‐sectional area and individual leaf area, suggesting that species with large leaves and thick twigs could support a disproportionately greater leaf area for a given twig cross‐sectional area. (2) However, the scaling relationships between twig stem mass and total leaf area and between stem mass and total lamina mass were approximately isometric, which indicates that the efficiency of deploying leaf area and lamina mass was independent of leaf size and twig size. The results of PIC were consistent with these correlations. (3) The evergreen species were usually smaller in total leaf area for a given twig stem investment in terms of both cross‐sectional area and stem mass, compared to deciduous species. Leaf mass per area (LMA) was negatively associated with the stem efficiency in deploying leaf area. (4) Compound leaf species could usually support a larger leaf area for a given twig stem mass and were usually larger in both leaf size and twig size than simple leaf species. Conclusions: Generally, thick‐twigged/large‐leaf species do not have an advantage over their counterparts in deploying photosynthetic compartments for a given twig stem investment. Leaf habit and leaf form types can modify leaf‐stem scaling relationships, possibly because of contrasting leaf properties. The leaf size‐twig size spectrum is related to the LMA‐leaf life span dimension of plant life history strategies.     

珍稀濒危植物长苞铁杉群落的植物生活型及叶特征分析

根据Raunkiaer的分类系统,对福建省天宝岩国家级自然保护区长苞铁杉(Tsuga longibracteata Cheng)群落的维管植物生活型及叶特征进行了分析,结果表明该群落以高位芽植物占优势,且以小、矮高位芽植物占优势,并有较大比例的藤本高位芽植物.叶级以中型叶植物所占比率最大,为51.5%,小型叶、大型叶、微型叶和细型叶分别占37.7%、5.4%、3.1%和2.3%;叶型以单叶为主,占92.9%;叶质以厚革质叶和革质叶所占比率最大,为66.4%,纸质叶占32.1%,薄叶占1.4%;全缘叶占43.6%.此外,对群落中植物生活型、叶型与层次结构、外貌的关系进行了分析.群落内阴性植物所占比例较大,为总种数的49.3%,并伴有一定数量的阳性植物.     

Correlations between leaf constituent levels and the densities of herbivorous insect guilds in an Australian forest

Abstract Significant correlations were found between herbivorous insect densities and leaf constituent levels across 18 species of understorey shrub in an Australian forest. In general, insect densities were positively correlated with nitrogen and water and negatively correlated with fibre and its constituents (cellulose and lignin), but not all insect guilds were significantly correlated with all leaf constituents. When mature leaf traits were considered, total herbivore density among plant species was most strongly correlated with levels of nitrogen and water. However, when insects were divided into functional guilds, only densities of sucking insects were significantly correlated with mature leaf nitrogen and water, whereas chewing insect densities were significantly correlated with mature leaf fibre and lignin. Low leaf nitrogen levels were recorded for all plants surveyed (among the lowest reported for woody angiosperms), and many plant species also had high levels of leaf fibre. These features are characteristic of Australian forests and have been linked to the generally nutrient‐poor soils of this continent. Levels of new leaf nitrogen (% fresh weight) were generally less than or equal to levels of mature leaf nitrogen (% fresh weight). Hence the new leaf preference of several herbivore guilds could not be explained by higher levels of leaf nitrogen. However, significant negative correlations were found between chewer densities and levels of leaf fibre, cellulose and lignin for new and mature leaves, suggesting that higher levels of fibre, cellulose and lignin in mature leaves may be contributing more strongly to the new leaf preference of chewers than leaf nitrogen levels. Despite the significant correlations between leaf constituent levels and the densities of individual guilds, multivariate analyses found no significant relationship between leaf constituent levels and the taxonomic or guild composition of herbivorous insect assemblages.     

红松和紫椴叶片暗呼吸及其光抑制性在幼、成树间的差异

叶片暗呼吸是森林碳循环的重要组分,深入分析幼、成树的叶片暗呼吸及其光抑制性的差异,对生态系统总生产力(GPP)的准确估算具有重要意义.本研究以长白山阔叶红松林主要树种(红松和紫椴)的幼树和成树为研究对象,分别测算不同光照下叶片暗呼吸与无光暗呼吸,比较叶片暗呼吸及其光抑制性在幼、成树间的差异,结合幼、成树叶片生理生态参数的对比,对幼、成树叶片暗呼吸及其光抑制性差异的原因进行探讨.结果表明: 两个树种幼树叶片光下暗呼吸的值高于成树,在生长季(6—9月),幼树的值比成树高6.8%～39.6%;两个树种幼树叶片暗呼吸光抑制程度低于成树,幼树叶片暗呼吸光抑制性的值比成树低2.5%～14.1%;红松幼、成树间叶片暗呼吸光抑制性的差异总体高于紫椴幼、成树间叶片暗呼吸光抑制性的差异,差值最高可达18.6%;幼树中较高的光下暗呼吸值和较低的光抑制程度可能与最大净光合速率、比叶面积、气孔导度的变化有关,与叶片氮含量的变化无关.     

不同叶位整形模式对白肋烟生长及烟叶多酚物质含量的影响

叶位整形是一项促进烟叶生长和品质提高的栽培管理措施,为明确不同叶位整形模式对白肋烟生长及多酚物质含量的影响,我们在白肋烟主产区—湖北省恩施州研究了不同叶位整形模式下不同生育期白肋烟的叶面积、叶绿素含量(CCI值)、各器官生物量和上下位叶片中多酚物质含量。结果表明:叶位整形显著影响了白肋烟生长和烟叶多酚物质含量,不但增大了不同叶位烟叶的叶面积及CCI值,还协调了各器官生物量、营养物质的合理分配以及不同叶位烟叶中多酚物质的含量;但不同叶位整形模式对白肋烟的生长影响不同,即旺长期整形(WZ)处理对白肋烟整株的促进作用较好,而团棵后期整形(TH)处理仅对上位叶效果较好。本研究采用的叶位整形栽培管理技术在保证白肋烟产量的同时,可在一定程度上促进白肋烟生长及烟叶品质的提高。     

Leaf Lateral Asymmetry in Morphological and Physiological Traits of Rice Plant

Leaf lateral asymmetry in width and thickness has been reported previously in rice. However, the differences between the wide and narrow sides of leaf blade in other leaf morphological and physiological traits were not known. This study was conducted to quantify leaf lateral asymmetry in leaf width, leaf thickness, specific leaf weight (SLW), leaf nitrogen (N) concentration based on dry weight (Nw) and leaf area (Na), and chlorophyll meter reading (SPAD). Leaf morphological and physiological traits of the two lateral halves of the top three leaves at heading stage were measured on 23 rice varieties grown in three growing seasons in two locations. Leaf lateral asymmetry was observed in leaf width, leaf thickness, Nw, Na, and SPAD, but not in SLW. On average, the leaf width of the wide side was about 17% higher than that of the narrow side. The wide side had higher leaf thickness than the narrow side whereas the narrow side had higher Nw, Na, and SPAD than the wide side. We conclude that the narrow side of leaf blade maintained higher leaf N status than the wide side based on all N-related parameters, which implies a possibility of leaf lateral asymmetry in photosynthetic rate in rice plant.