Seasonality of insect herbivory on the leaves of Neoboutonia macrocalyx in the Kibale National Park, Uganda

The seasonality of herbivory on the leaves of Neoboutonia macrocalyx Pax. in Kibale Forest National Park, Uganda, was studied. A total of 2929 fallen leaves was collected during 15 months under randomly-selected trees in three different habitats; natural forest and two selectively cut forest sites. The percentage of leaf area eaten and leaf size were estimated. Leaf herbivory was highly seasonal and correlated with rainfall in the previous 2 months, but less than 100 mm monthly rainfall had no effect. There was no correlation between leaf size and rainfall. Although Kibale Forest has two wet seasons, insect feeding on leaves had only one peak during the major rainy season from September to December. Three to four months after peak herbivory, leaves had very low rates of insect damage. Habitat had only a small effect on the amount of insect feeding. The sampling time accounted for 71% of variation in leaf herbivory. New leaves were formed continuously year-round. The constant leaf production by Neoboutonia trees may be an adaptation to escape generalist herbivorous insects which might be synchronized with the major wet season when the leaf flush of the most other deciduous species occurs. Thus, the availability of fresh leaves is not acting as a regulating factor in seasonality of Neoboutonia herbivory.     

A remarkable new species of <Emphasis Type="Italic">Ormosia</Emphasis> (Leguminosae: Papilionoideae: Sophoreae) from Bahian Atlantic Rain Forest,Brazil

Ormosia timboënsis is described and illustrated as a new species based on fruit and leaf material collected in a fragment of Atlantic Rain Forest in central Bahia State, Brazil. This new species can be recognized by possessing the largest seed and hilum of those that have been reported in Ormosia. In addition, O. timboënsis has leaves that in combination with the fruit characters do not match any species currently described in the genus.     

Leaf anatomy in a Venezuelan montane forest

A survey has been made of the leaf anatomy of 43 woody species in three montane vegetation types of Isla Margarita, Venezuela, differing in levels of cloud cover (and hence wetness) and exposure to wind. The only character that varies significantly with increasing probability of periodic drought is specific leaf area, which can be related to the higher proportion of deciduous species in the drier habitat. Leaves become significantly smaller and thicker with increased exposure to wind, and have thicker outer epidermal walls and cuticles. Most characters, including stomatal density, guard cell length, palisade: non-palisade ratios, and the incidence of such features as hypodermis, sclerenchyma, crystals and secretory structures are highly variable and show few or no trends according to habitat. Some of these characters are apparently more constrained by phylogeny than by immediate ecological circumstances. As a contribution to the continuing debate on the significance of xeromorphy in tropical montane forest leaves, it is suggested that low light levels due to cloud cover can be discounted as an important determining factor; in the case of the Isla Margarita vegetation, the need to avoid excessive leaf temperatures may be of greater significance.     

鹿药属植物叶表皮特征及其系统学意义

采用光学显微镜和扫描电镜对鹿药属12种植物的叶表皮进行了观察,首次报道了12种鹿药属(Sm ilaci-na)植物叶表皮的微形态特征。结果表明:气孔器普遍存在于叶的下表皮,少数种的上表皮也有分布,均为不规则形。叶表皮细胞形状为多边形或不规则形,垂周壁式样可区分为近平直、浅波状和波状。在扫描电镜下,叶表皮气孔器外拱盖内缘为近平滑、浅波状或波状;角质膜条纹状,有的条纹隆起,有的条纹上附有颗粒和晶簇。气孔器的分布、气孔器外拱盖内缘形态以及角质膜等特征对该属部分种的区分具有一定的参考价值。     

Variability in leaf optical properties among 26 species from a broad range of habitats

Leaves from 26 species with growth forms from annual herbs to trees were collected from open, intermediate, and shaded understory habitats in Mississippi and Kansas, USA. Leaf optical properties including reflectance, transmittance, and absorptance in visible and near infrared (NIR) wavelengths were measured along with leaf thickness and specific leaf mass (SLM). These leaf properties and internal light scattering have been reported to vary with light availability in studies that have focused on a limited number of species. Our objective was to determine whether these patterns in leaf optics and light availability were consistent when a greater number of species were evaluated. Leaf thickness and SLM varied by tenfold among species sampled, but within-habitat variance was high. Although there was a strong trend toward thicker leaves in open habitats, only SLM was significantly greater in open vs. understory habitats. In contrast, leaf optical properties were strikingly similar among habitats. Reflectance and reflectance/transmittance in the NIR were used to estimate internal light scattering and there were strong relationships (r1 > 0.65) between these optical properties and leaf thickness. We concluded that leaf thickness, which did not vary consistently among habitats, was the best predictor of NIR reflectance and internal light scattering. However, because carbon allocation to leaves was lower in understory species (low SLM) yet gross optical properties were similar among all habitats, the energy investment by shade leaves required to achieve optical equivalence with sun leaves was lower. Differences in leaf longevity and growth form within a habitat may help explain the lack of consistent patterns in leaf optics as the number of species sampled increases.     

浙江天童国家森林公园主要常绿阔叶树种叶子寿命的研究

用生命表法对天童国家森林公园主要常绿阔叶树种叶子的寿命进行了研究,结果表明：大多数常绿阔叶树种叶子的寿命在１－３年之间,且变化幅度较大,就平均值来看,小乔木及灌木的叶子寿命较长,中乔木叶子的寿命较短;在演替过程中,组成演替早期群落的物种叶子寿命较短,而后期群落的植物叶子的寿命较长。文中还就叶子寿命和常绿阔叶林的结构及动态机理进行了讨论。     

Occurrence of tannins in leaves of beech trees (Fagus sylvatica) along an ecological gradient, detected by histochemical and ultrastructural analyses

Sclerophylly and synthesis of phenolic compounds are active responses of plants subjected to environmental stress (drought, low nutrient supply, u.v.-B radiation, ozone). Here we describe the morphological and histochemical alterations occurring in field-grown leaves of Fagus sylvatica L. from three sites located along an ecological gradient: from a site in cool and protected conditions to one located on a mountain ridge, where the trees grow on a thin layer of soil and are exposed to the wind and to intense solar radiation in summer. The morphological data show that, as the ecological conditions of the stand worsen, individual leaf surface decreases, while the thickness of the leaves and their specific d. wt (i.e. d. wt per unit leaf area) increases. Histochemical and ultrastructural tests show a marked increase of phenolics during the course of the year. These substances, present primarily in the leaves of trees growing in stress conditions, have been identified mainly as tannins. They accumulate in the vacuoles, especially those of the upper epidermal layer and the palisade mesophyll; at a later stage they appear to be solubilized in the cytoplasm and retranslocated, eventually impregnating the outer wall of the epidermal cells amidst the cellulose fibrils, where they cluster together and form an electron-opaque layer between the wall and the cuticle. Observation of the epidermal cells also reveals that the outer cell wall is thicker. The paper discusses the roles of secondary metabolites in protection and detoxification processes; the possible ecological significance of these alterations in the ecophysiology of beech trees.     

USE OF NATIVE PLANTS FOR REMEDIATION OF TRICHLOROETHYLENE: I. DECIDUOUS TREES

Phytoremediation of trichloroethylene (TCE) can be accomplished using fast-growing, deep-rooting trees. The most commonly used tree for phytoremediation of TCE has been the hybrid poplar. This study looks at native southeastern trees of the United States as alternatives to the use of hybrid poplar. The use of native trees for phytoremediation allows for simultaneous restoration of contaminated sites. A 2-mo, greenhouse-based study was conducted to determine if sycamore (Plantanus L.), eastern cottonwood (Populus deltoides), sweetgum (Liquidambar styraciflua L.), and willow (Salix sachalinensis) trees possess the ability to degrade TCE by assessing TCE metabolite formation in the plant tissue. In addition to the metabolic capabilities of each tree species, growth parameters were measured including change in height, water usage, total fresh weight of each tissue type, and calculated total leaf surface area. Willow trees had the greatest increase in height among all trees tested; however, at higher concentrations TCE inhibits growth. Sycamore trees had the highest overall leaf surface area and total biomass, which correlated with sycamore trees also having the highest average water usage over the course of the experiment. Carbon tubes used to sample transpiration gases from sycamore, sweetgum, and cottonwood trees did not contain detectable levels of TCE. Tenex sample collection tubes used to sample willow trees during TCE exposure showed average TCE concentrations of up to 0.354 ng TCE cm^?2 leaf tissue. All exposed trees contained TCE in the root, stem, and leaf tissues. The concentration of TCE remaining in tissues at the conclusion of the experiment varied, with the highest levels found in the roots and the lowest levels found in the leaves. Metabolites were also observed in different tissue types of all trees tested. The highest concentrations of trichloroacetic acid were observed in the leaves of the sycamore trees and cottonwood trees. Based on the growth parameters tested and the ability to metabolize TCE, sycamore and native cottonwood species are the best candidates for phytoremediation from this study.     

Changes in crown development patterns and current-year shoot structure with light environment and tree height in Fagus crenata (Fagaceae)

The relative effects of light and tree height on the architecture of leader crowns (i.e., the leading section of the main trunk, 100 cm in length) and current-year shoots for a canopy species, Fagus crenata, occupying both the ridge top and the valley bottom in a cool-temperate forest in Japan were investigated. For leader crowns, the number of current-year shoots and leaves increased with increasing tree height, whereas the mean length of current-year shoots increased with increasing relative photon flux density (PFD). The leader crown area decreased, and the depth and leaf area index of leader crowns increased, with increasing relative PFD. The mass of current-year shoots increased with relative PFD. However, this total mass was allocated differently between stems and leaves depending on tree height, such that the relative allocation to stems increased with increasing tree height. Furthermore, stem structures within current-year shoots also changed with height, such that taller trees produced thicker and shorter stems of the same volume. In contrast, leaf structure and leaf biomass allocations changed with relative PFD. Specific leaf area decreased with increasing relative PFD. In addition, leaf number increased more rapidly with increasing individual leaf mass for trees exposed to greater relative PFD. Consequently, the total leaf area supported by a stem of a given diameter decreased with increasing tree height and relative PFD. Thus, the architecture of leader crowns and current-year shoots were related differently to light and tree height, which are considered important for efficient light capture and the growth of small and tall trees in different environments.     

Leaf morphology of 40 evergreen and deciduous broadleaved subtropical tree species and relationships to functional ecophysiological traits

We explored potential of morphological and anatomical leaf traits for predicting ecophysiological key functions in subtropical trees. We asked whether the ecophysiological parameters stomatal conductance and xylem cavitation vulnerability could be predicted from microscopy leaf traits. We investigated 21 deciduous and 19 evergreen subtropical tree species, using individuals of the same age and from the same environment in the Biodiversity‐Ecosystem Functioning experiment at Jiangxi (BEF‐China). Information‐theoretic linear model selection was used to identify the best combination of morphological and anatomical predictors for ecophysiological functions. Leaf anatomy and morphology strongly depended on leaf habit. Evergreen species tended to have thicker leaves, thicker spongy and palisade mesophyll, more palisade mesophyll layers and a thicker subepidermis. Over 50% of all evergreen species had leaves with multi‐layered palisade parenchyma, while only one deciduous species (Koelreuteria bipinnata) had this. Interactions with leaf habit were also included in best multi‐predictor models for stomatal conductance (g_s) and xylem cavitation vulnerability. In addition, maximum g_s was positively related to log ratio of palisade to spongy mesophyll thickness. Vapour pressure deficit (vpd) for maximum g_s increased with the log ratio of palisade to spongy mesophyll thickness in species having leaves with papillae. In contrast, maximum specific hydraulic conductivity and xylem pressure at which 50% loss of maximum specific xylem hydraulic conductivity occurred (Ψ₅₀) were best predicted by leaf habit and density of spongy parenchyma. Evergreen species had lower Ψ₅₀ values and lower maximum xylem hydraulic conductivities. As hydraulic leaf and wood characteristics were reflected in structural leaf traits, there is high potential for identifying further linkages between morphological and anatomical leaf traits and ecophysiological responses.     

Leaf dynamics and insect herbivory in a Eucalyptus camaldulensis forest under moisture stress

Abstract The influence of soil moisture content on leaf dynamics and insect herbivory was examined between September 1991 and March 1992 in a river red gum (Eucalyptus camaldulensis) forest in southern central New South Wales. Long-term observations of leaves were made in trees standing either within intermittently flooded waterways or at an average of 37. 5m from the edge of the waterways. The mean soil moisture content was significantly (P≤0.05) greater in the waterways than in the non-flooded areas. Trees in the higher soil moisture regime produced significantly larger basal area increments and increased canopy leaf area. This increase in canopy leaf area was achieved, in part, through a significant increase in leaf longevity and mean leaf size. Although a greater number of leaves was initiated and abscissed per shoot from the non-flooded trees, more leaves were collected from litter traps beneath the denser canopies of the flooded trees. Consumption of foliage by insects on the trees subjected to flooding compared to the non-flooded trees was not significantly different. However, the relative impact of insect herbivory was significantly greater on the non-flooded trees. Leaf chewing was the most common form of damage by insects, particularly Chryso-melidae and Curculionidae. No species was present in outbreak during this study. Leaf survival decreased as the per cent area eaten per leaf increased. In addition, irrespective of the level of herbivory, leaf abscission tended to be higher in E. camaldulensis under moisture deficit. The influence of soil moisture content on the balance between river red gum growth and insect herbivory is discussed.     

Didymodon mesopapillosus sp. nov. (Pottiaceae) from Tibet,China

Didymodon mesopapillosus J. Kou, X.‐M. Shao & C. Feng is described and illustrated as a new species from Tibet, China. It is characterized mainly by its ovate to ovate‐lanceolate leaves appressed to weakly erect when dry, margins recurved from leaf base to apex, laminal cell superficial walls markedly thicker than the internal walls, laminal papillae present only on both sides of costa, short‐excurrent costa, undifferentiated basal cells and differentiated perichaetial leaves. This species is compared with similar species and its ecology is discussed.     

桂北岩溶区青冈栎-青檀群落植物叶片比叶面积研究

为揭示岩溶地区植物叶片比叶面积变化规律和叶片形态之间的相关关系,研究了桂北岩溶区青冈栎-青檀群落的叶片长/宽(LL/LW)、叶片厚度(LT)和比叶面积(SLA)及其之间的关系。结果表明:群落中常绿树种的LL/LW和LT显著高于落叶树种,而常绿树种的SLA显著低于落叶树种;乔木和灌木之间的LL/LW存在显著差异,但SLA和LT不存在显著差异。总体上看,SLA与LL/LW、LT之间是显著负相关关系,SLA随着LL/LW、LT的变大而逐渐减小。但LT与SLA负相关趋势比LL/LW与SLA的明显。因此,LT比LL/LW对叶片SLA的影响大,其明显影响了叶片的SLA。SLA的大小是衡量叶片获取光照能力的指标,因此岩溶区植物较厚的叶片对光照的获取能力具有较大的影响,并可导致光合作用效率的降低。     

POPULATION STRUCTURE IN ZAMIA DEBILIS (ZAMIACEAE) I. SIZE CLASSES,LEAF PHENOLOGY,AND LEAF TURNOVER

Population structure, leaf phenology and leaf turnover were followed over a 29-month period in Zamia debilis L.f. ex Aiton (Zamiaceae), an understory species in the Cambalache Forest in northern Puerto Rico. It was not possible to determine plant age or to measure the subterranean stems; size classes based on leaf number and leaf × leaflet number indices were used to determine population structure. Despite seasonal and year to year fluctuations in leaf number at the individual and population level, population profiles remained relatively constant. At any one time, over 50% of the population was composed of unbranched individuals with one or two leaves. Only 7% of the plants were branched. Plants with seven or more leaves comprised at a maximum 8% of the population, but accounted for 28% of the total foliage. Size classes based on leaf number and on a leaf × leaflet index gave approximately reverse J-shaped curves typical of trees with shade tolerant seedlings and saplings. New leaves emerged throughout the year, with a peak at the beginning of the rainy season in May or June and lowest production during the dry months of February through April. Average leaf life expectancy was approximately 2.3 years. Leaf death occurred over an extended period of time by the loss of individual leaflets. Patterns in leaf production and loss differed between few- and many-leaved plants. On the average, as the number of mature leaves on a plant increased, time between emergence of new leaves decreased. In many-leaved plants more than one event of new leaf emergence per year was common. Individuals with one to three mature leaves and individuals with four or more mature leaves differed in their response to water stress: few-leaved plants generally reduced the rate of new leaf production and retained old leaves longer. Plants with more than three leaves continued to produce new leaves, but the rate of leaf mortality increased so that most had a net leaf loss. There was no evidence that leaf emergence or retention were affected by cone production or seed maturation.     

Leaf size and leaf display of thirty-eight tropical tree species

Trees forage for light through optimal leaf display. Effective leaf display is determined by metamer traits (i.e., the internode, petiole, and corresponding leaf), and thus these traits strongly co-determine carbon gain and as a result competitive advantage in a light-limited environment. We examined 11 metamer traits of sun and shade trees of 38 coexisting moist forest tree species and determined the relative strengths of intra- and interspecific variation. Species-specific metamer traits were related to two variables that represent important life history variation; the regeneration light requirements and average leaf size of the species. Metamer traits varied strongly across species and, in contrast to our expectation, showed only modest changes in response to light. Intra- and interspecific responses to light were only congruent for a third of the traits evaluated. Four traits, amongst which leaf size, specific leaf area (SLA), and leaf area ratio at the metamer level (LAR) showed even opposite intra- and interspecific responses to light. Strikingly, these are classic traits that are thought to be of paramount importance for plant performance but that have completely different consequences within and across species. Sun trees of a given species had small leaves to reduce the heat load, but light-demanding species had large leaves compared to shade-tolerants, probably to outcompete their neighbors. Shade trees of a given species had a high SLA and LAR to capture more light in a light-limited environment, whereas shade-tolerant species have well-protected leaves with a low SLA compared to light-demanding species, probably to deter herbivores and enhance leaf lifespan. There was a leaf-size-mediated trade-off between biomechanical and hydraulic safety, and the efficiency with which species can space their leaves and forage for light. Unexpectedly, metamer traits were more closely linked to leaf size than to regeneration light requirements, probably because leaf-size-related biomechanical and vascular constraints limit the trait combinations that are physically possible. This suggests that the leaf size spectrum overrules more subtle variation caused by the leaf economics spectrum, and that leaf size represents a more important strategy axis than previously thought. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Leaf biomechanics, morphology, and anatomy of the deciduous mesophyte Prunus serrulata (Rosaceae) and the evergreen sclerophyllous shrub Heteromeles arbutifolia (Rosaceae)

Leaf tensile properties were compared between the mesic deciduous tree Prunus serrulata (var. "Kwanzan") and the xeric and sclerophyllous chaparral evergreen shrub Heteromeles arbutifolia (M. Roem). All values for biomechanical parameters for H. arbutifolia were significantly greater than those of P. serrulata. The fracture planes also differed between the two species with P. serrulata fracturing along the secondary veins, while H. arbutifolia most often fractured across the leaf irrespective of the vein or mesophyll position, thus yielding qualitative differences in the stress-strain curves of the two species. Anatomically, P. serrulata exhibits features typical for a deciduous mesophytic leaf such as a thin cuticle, a single layer of palisade mesophyll, isodiametric spongy mesophyll, and extensive reticulation of the laminar veins. Heteromeles arbutifolia leaves, however, are typically two- to three-fold thicker with a 35% higher dry mass/fresh mass ratio. The vascular tissue is restricted to the interface of the palisade and spongy mesophyll near the center of the leaf. Both epidermal layers have a thick cuticle. The palisade mesophyll is tightly packed and two to three layers thick. The spongy mesophyll cells are ameboid in shape and tightly interlinked both to other spongy cells as well as to the overlying palisade layer. We conclude that the qualitative and quantitative biomechanical differences between the leaves of these two species are likely due to a complex interaction of internal architectural arrangement and the physical/chemical differences in the properties of their respective cell walls. These studies illustrate the importance that morphological and anatomical correlates play with mechanical behavior in plant material and ultimately reflect adaptations present in the leaves of chaparral shrubs that are conducive to surviving in arid environments.     

9种芦荟属植物叶的结构和芦荟素含量的比较研究

9种芦荟属植物叶的比较解剖研究结果表明,它们都具有明显的旱生叶的结构特征,其维管束的韧皮部内都有大型薄壁细胞,但其表皮角质膜的厚度,表面纹饰,气孔上,下腔的形状和大小,同化组织 导 ,细胞分化情况,维管束的大小,分布密度和其大型薄壁细胞占维管束的比例,中央贮水组织占叶横切面的比例等特征,在各种间存在差异,且性状稳定,可以作为该属内种间分类的解剖学指标,植物化学分析结果表明,9种植物叶内蒽醌类物质的主要种类和含量不同,其含量高,低与叶内维管束密度,大型薄壁细胞占维管束的比例以及同化组织的厚度密度切相关,从而为芦荟属植物选育商业用良种提供了植物解剖学依据。     

Chloroplast avoidance movement is not functional in plants grown under strong sunlight

Chloroplast movement in nine climbing plant species was investigated. It is thought that chloroplasts generally escape from strong light to avoid photodamage but accumulate towards weak light to perform photosynthesis effectively. Unexpectedly, however, the leaves of climbing plants grown under strong sunlight showed very low or no chloroplast photorelocation responses to either weak or strong blue light when detected by red light transmittance through leaves. Direct observations of Cayratia japonica leaves, for example, revealed that the average number of chloroplasts in upper periclinal walls of palisade tissue cells was only 1.2 after weak blue‐light irradiation and almost all of the chloroplasts remained at the anticlinal wall, the state of chloroplast avoidance response. The leaves grown under strong light have thin and columnar palisade tissue cells comparing with the leaves grown under low light. Depending on our analyses and our schematic model, the thinner cells in a unit leaf area have a wider total plasma membrane area, such that more chloroplasts can exist on the plasma membrane in the thinner cells than in the thicker cells in a unit leaf‐area basis. The same strategy might be used in other plant leaves grown under direct sunlight.     

元江干热河谷植物叶片解剖和养分含量特征

研究了元江干热河谷旱田植物(旱季可浇灌,水分较好)和山坡半萨王纳植被中(自然状况,水分较差)共20种的叶片形态解剖特征,以及7种山坡植物叶片养分含量特征.结果表明,山坡植物叶片比叶重大,气孔密度大,气孔长度小,海绵组织/栅栏组织的值小等.元江干热河谷山坡植物叶片养分含量低,1.3%＞Ca＞N＞K＞1%＞Mg＞P＞S.除氮元素外,其它元素种间差别1～3倍.与热带植物群落叶片养元素含量相比,热带雨林＞元江山坡植物＞东南亚沙地旱生林和巴西矮卡廷加群落,表明元江干热河谷植物叶片具有明显的旱生性形态解剖特征,且叶片养分含量也较低.     

浙江天童常绿植物当年生与往年生叶片性状的变异与关联

植物叶片性状随叶龄的变化是植物生活史策略的体现, 反映了植物叶片的物质投资和分配方式。该研究通过在个体和物种2个水平, 比较浙江天童1 hm ²样地内常绿阔叶树种的平均叶面积(MLA)、比叶面积(SLA)和叶片干物质含量(LDMC)在当年生和往年生叶片间的差异和关联, 探究叶片物质分配策略在异龄叶间的变化, 并分析叶龄对植物叶片性状, 特别是叶片面积建成消耗的影响。结果显示: 1)在个体和物种水平上, MLA变异系数最大(个体: 79.5%; 物种: 66.5%), SLA次之(个体: 28.1%; 物种: 24.7%), LDMC较低(个体: 17.0%, 物种: 14.1%); 当年生叶片MLA、LDMC和SLA的变异系数均高于往年生叶片; 2)往年生叶MLA显著大于当年生叶(t = -38.53, p < 0.001), 往年生叶SLA显著小于当年生叶(t = 45.30, p < 0.001), 往年生叶LDMC显著大于当年生叶(t = -9.71, p < 0.001); 3)在个体水平, 当年生叶片MLA、SLA和LDMC值分别解释了往年生叶片MLA、SLA和LDMC变异的86%、48%和41%; 在物种水平, 当年生叶片MLA、SLA和LDMC值分别解释了往年生叶片MLA、SLA和LDMC变异的97%、83%和85%; 4) SLA在异龄叶间的变化表明, 与往年生叶片相比, 投资相同干物质, 当年生叶片可形成较大的叶面积, 其叶片面积建成消耗较小。研究认为, 植物叶性状在异龄叶间具有较大的变异性和关联性, 叶面积形成过程中生物量建成与消耗的协调可能影响植物叶片的发育。