Relationships between sclerophylly,leaf biomechanical properties and leaf anatomy in some Australian heath and forest species

ABSTRACT

A previous study of 19 south-east Australian heath and forest species with a range of leaf textures showed that they varied considerably in leaf biomechanical properties. By using an index of sclerophylly derived from botanists' rankings (botanists' sclerophylly index, BSI) we determined that leaves considered by botanists to be sclerophyllous generally had both high strength and work to fracture (particularly in punching and tearing tests), both at the level of leaf and per unit leaf thickness. In the current study we have shown that leaves from the same species also varied considerably in leaf specific mass (46–251 g m^-2), neutral detergent fibre concentration (20–59% on a dry weight basis) and in leaf anatomy. Multiple regression indicated a very strong correlation between BSI and the first two components of a principal components analysis (PCA) of leaf anatomy (R ² = 0.91). In addition, there was strong correlation between the first component of a PCA of the mechanical properties (correlated with BSI) and the two axes derived from anatomical characteristics (R ² = 0.66). The anatomical properties contributing most to the significant component axes were thickness of palisade mesophyll and upper cuticle (axis 1) and percentage fibre (neutral detergent fibre) and lower epidermis thickness (axis 2). However, whether these relationships are causal, or reflect correlations with characteristics not measured in this study, such as vascularization and sclerification, is not clear. At a finer scale, however, there is evidence that there are various ways to be sclerophyllous, both in terms of anatomical and mechanical properties. This is illustrated by comparison of two of the sclerophyllous species, Eucalyptus baxteri and Banksia marginata.     

Effects of leaf shape plasticity on leaf surface temperature

干旱区植物叶片形态可塑性是植物适应高温干旱环境的重要生存策略, 但目前仍缺乏直观的数据予以证明。该研究应用热成像技术和图像分析技术, 同步测定真实叶片与模拟叶片的叶温、形态及风速、辐射和温度等环境参数。研究结果显示: 在干旱、高温环境下, 除了蒸腾, 叶片形态变化也是调控叶温的重要因子。干旱区植物叶片变小, 有利于加速叶片与环境的物质及热量交换, 从而达到降低叶温的目的。样地数据显示, 在高温、低风速环境下, 叶片宽度每减少1 cm, 叶片表面温度降低约2.1 ℃, 而模拟叶片叶宽度每减少1 cm, 叶片表面温度降低0.60-0.86 ℃。该研究对深入理解植物生存策略与环境适能力具有重要意义。     

形态变化对叶片表面温度的影响

干旱区植物叶片形态可塑性是植物适应高温干旱环境的重要生存策略, 但目前仍缺乏直观的数据予以证明。该研究应用热成像技术和图像分析技术, 同步测定真实叶片与模拟叶片的叶温、形态及风速、辐射和温度等环境参数。研究结果显示: 在干旱、高温环境下, 除了蒸腾, 叶片形态变化也是调控叶温的重要因子。干旱区植物叶片变小, 有利于加速叶片与环境的物质及热量交换, 从而达到降低叶温的目的。样地数据显示, 在高温、低风速环境下, 叶片宽度每减少1 cm, 叶片表面温度降低约2.1 ℃, 而模拟叶片叶宽度每减少1 cm, 叶片表面温度降低0.60-0.86 ℃。该研究对深入理解植物生存策略与环境适能力具有重要意义。     

Wheat leaf photosynthesis loss due to leaf rust, with respect to lesion development and leaf nitrogen status

In wheat (Triticum aestivum cv. Soissons) plants grown under three different fertilisation treatments, we quantified the effect of leaf rust (Puccinia triticina) on flag leaf photosynthesis during the whole sporulation period. Bastiaans' model: Y = (1 - x)beta was used to characterize the relationship between relative leaf photosynthesis (Y) and disease severity (x). The evolution of the different types of symptoms induced by the pathogen (sporulating, chlorotic and necrosed tissues) was evaluated using image analysis. The beta-values varied from 2 to 11, 1.4-2, and 0.8-1 during the sporulation period, when considering the proportion of sporulating, sporulating + necrotic, and total diseased area, respectively. Leaf nitrogen (N) content did not change the effect of the disease on host photosynthesis. We concluded that leaf rust has no global effect on the photosynthesis of the symptomless parts of the leaves and that the large range in the quantification of leaf rust effect on the host, which is found in the literature, can be accounted for by considering the different symptom types. We discuss how our results could improve disease assessments and damage prediction in a wheat crop.     

Evolution of leaf developmental mechanisms

Leaves are determinate organs produced by the shoot apical meristem. Land plants demonstrate a large range of variation in leaf form. Here we discuss evolution of leaf form in the context of our current understanding of leaf development, as this has emerged from molecular genetic studies in model organisms. We also discuss specific examples where parallel studies of development in different species have helped understanding how diversification of leaf form may occur in nature.     

干旱区植物叶片大小对叶表面蒸腾及叶温的影响

利用热及物质交换原理, 并结合前人研究成果, 在单叶尺度上建立了简单的叶温和水气蒸腾模型。模型通过预设值驱动, 预设值参照干旱区环境及植物叶片特征设置。模拟结果显示: 随气孔阻力的增加, 叶片蒸腾速率降低, 叶温升高; 同一环境下, 具有低辐射吸收率的叶片蒸腾速率和叶温更低, 并且气孔阻力越大, 这种差异越明显。另外, 叶片宽度及风速是影响叶片蒸腾及叶温的重要因子。干旱地区植物生长季节, 风速小于0.1 m·s ^-1、气孔阻力接近1000 s·m ^-1时, 降低叶片宽度不仅有利于降低叶片温度, 而且能够降低叶片蒸腾速率, 从而实现保持水分, 增强植物适应高温、干旱的能力。     

Detection of sugarcane yellow leaf virus,the causal agent of yellow leaf syndrome in sugarcane by DAS-ELISA

DAS-ELISA studies were conducted on detection of sugarcane yellow leaf virus (SCYLV) causing yellow leaf syndrome (YLS) of sugarcane in leaf and juice antigens. Among the two types of antigen sources used for the virus detection, juice antigen showed high titre for the virus as compared to leaf antigen. Assay with juice samples recorded more number of varieties positive to the virus. Further DAS-ELISA studies revealed that plants raised from disease-infected planting materials recorded high titre for SCYLV as compared to those raised from symptom-free seed canes. Similarly, assaying SCYLV titre in plant and ratoon crop in the field showed that SCYLV infection was partial in plant crop and in the subsequent ratoon crop, all the samples were positive to the virus. ELISA studies also indicated that 33 of 41 cane varieties showing YLS were positive to the virus.     

Determinants of some leaf characteristics of Australian mangroves

Leaf characteristics reflecting the size, lifespan (longevity), moisture content (degree of succulence) and complexity of structure of 20 mangrove species were studied over several years at 13 locations along the tropical and subtropical Australian coast. These characteristics were found to fall generally within the ranges of those for woody species from other ecosystems. With the exception of one species, it was found that leaf longevity was related inversely to leaf moisture content, increasing from nearly 6 months in more succulent species to over 2 years in less succulent species. This suggested that more succulent leaves are less complex in their structure because they have less well‐developed ability to compartmentalize salt. There was a tendency also for leaf longevity to increase in species with larger leaves. These findings were consistent with the general view for land plants that leaf longevity is greater in species that have developed tolerance to environmental stress, salt particularly in the case of mangroves. Leaf tissue in such species is more robust or complex and requires greater metabolic resources in its construction; the plant is then advantaged by retaining the tissue for longer periods. Classification of the species considered here, based on their leaf longevity, moisture content and complexity, identified phylogenetically related species groupings that reflected these leaf longevity effects.     

三峡水库消落带植物叶片光合与营养性状特征

自2007年三峡大坝试运行以来,其独特的人工水位调度节律给当地的水库消落带生态系统带来了巨大的负面影响。植物功能性状可以反映某一特殊生境植物的生理生态过程特殊性,是指示生态系统结构与功能的有效指标。因此,在三峡水库消落带形成2a后,于2009年调查了消落带的42种适生植物以及对照带33种植物的6个叶片功能性状:最大净光合速率(Amax)、叶片气孔导度(Gs)、比叶重(LMA)、叶片全氮含量(Nmass)、全磷含量(Pmass)和全钾含量(Kmass)。运用标准化主轴回归分析对消落带植物叶片各功能性状之间关系进行分析,并对照全球尺度叶片功能性状数据库,旨在说明反季节淹水对消落带植物叶片功能性状之间关系与全球尺度对比发生了哪些变化。同时,运用成对方差t检验的分析方法,对比了在消落带和对照带都存在的33个种的叶片光合与营养性状之间的差异,以阐明消落带植物对消落带特殊生境的生理响应。结果表明:(1)消落带植物叶片各性状关系呈现出与全球尺度基本一致的格局,表现出植物叶性状之间关系的趋同性;(2)消落带植物Amass、Nmass、Pmass和Kmass显著高于全球尺度,而LMA则显著低于全球尺度。处于驯化阶段的消落带植物各叶片性状处在全球叶片经济型谱"低投入-快速回收"的一端。(3)消落带植物叶片Amass与对照带相比,有显著提高。表明三峡水库消落带植物叶片光合能力得到显著提高,这可能是其适应消落带特殊生境的关键生理生态对策之一。     

Effects of leaf age,elevation and light conditions on photosynthesis and leaf traits in saplings of two evergreen conifers,Abies veitchii and A. mariesii

亚高山的针叶树物种分布在广泛的海拔范围内,因此它们必须具备抵抗严酷自然条件(如高海拔和长期的黑暗)的能力。 在日本中部的亚高山地带,两种常绿的针叶树冷杉(Abies veitchii)和马尾冷杉(Abies mariesii)分别在低海拔和高海拔地区占据优势。本研究的目的是探讨叶龄、海拔和光照条件对两个物种叶片形态和生理性状的影响。我们以两种针叶树的幼树为样本,分别在两种针叶树下部 (1600米)和上部(2300米)的林下层和冠层间隙中取样,并分析叶龄、海拔和光照条件对冷杉和马尾冷杉的光合作用和叶片性状的影响。研究结果表明,两种针叶树的光合作用和叶片性状对叶龄呈现相似的响应,但其对海拔和光照条件则表现出不同的响应。冷杉最大光合速率与单位叶面积质量和非结构性碳水化合物浓度呈负相关。两种树木的单位叶面积质量在高海拔处均增加,而非结构性碳水化合物浓度仅在冷杉中增加。因此,冷杉的最大光合速率在高海拔时降低。此外,两个物种的最大光合速率均与氮浓度呈正相关。在林下层,叶片氮浓度在冷杉中下降,而在马尾冷杉中上升。在林下条件下,只有马尾冷杉的单位叶面积质量下降、叶绿素-氮比增加,表明在黑暗条件下,马尾冷杉比冷杉有更高的捕光效率。本研究表明,与冷杉相比,马尾冷杉的光合和叶片特性具有更强的耐阴性,光合速率受海拔的影响较小,从而使马尾冷杉在林下植被中生存,并在高海拔地区占据优势。     

Screening of mulberry germplasm lines against Powdery mildew,Myrothecium leaf spot and Pseudocercospora leaf spot disease complex

Abstract

Fifty-six indigenous and 29 exotic mulberry varieties were screened against powdery mildew, Myrothecium leaf spot, Pseudocercospora leaf spot for a period of three years under field conditions. The percent disease index (PDI) was recorded during the peak season of the diseases. Out of 85 germplasm lines studied four-germplasm lines viz. Thailand lobed (0.43), M. multicaulis (2.63), Italian (2.83) and M. australis (4.56) were found highly resistant; nine lines were resistant; 43 lines were moderately resistant and 29 were susceptible to the disease complex. Powdery mildew showed significant positive correlation with Pseudocercospora leaf spot. Highly resistant varieties may be utilized for future disease resistance breeding programme to evolve multiple disease resistant mulberry varieties.     

观察植物叶迹、叶隙立体结构的实验方法

通过实验研究提出了观察植物叶迹、叶隙立体结构的方法。对观察节处维管组织的变化, 有重要意义。     

Relationships of leaf dark respiration to leaf nitrogen, specific leaf area and leaf life-span: a test across biomes and functional groups

Based on prior evidence of coordinated multiple leaf trait scaling, we hypothesized that variation among species in leaf dark respiration rate (R _d) should scale with variation in traits such as leaf nitrogen (N), leaf life-span, specific leaf area (SLA), and net photosynthetic capacity (A _max). However, it is not known whether such scaling, if it exists, is similar among disparate biomes and plant functional types. We tested this idea by examining the interspecific relationships between R _d measured at a standard temperature and leaf life-span, N, SLA and A _max for 69 species from four functional groups (forbs, broad-leafed trees and shrubs, and needle-leafed conifers) in six biomes traversing the Americas: alpine tundra/subalpine forest, Colorado; cold temperate forest/grassland, Wisconsin; cool temperate forest, North Carolina; desert/shrubland, New Mexico; subtropical forest, South Carolina; and tropical rain forest, Amazonas, Venezuela. Area-based R _d was positively related to area-based leaf N within functional groups and for all species pooled, but not when comparing among species within any site. At all sites, mass-based R _d (R _d-mass) decreased sharply with increasing leaf life-span and was positively related to SLA and mass-based A _max and leaf N (leaf N _mass). These intra-biome relationships were similar in shape and slope among sites, where in each case we compared species belonging to different plant functional groups. Significant R _d-mass−N _mass relationships were observed in all functional groups (pooled across sites), but the relationships differed, with higher R _d at any given leaf N in functional groups (such as forbs) with higher SLA and shorter leaf life-span. Regardless of biome or functional group, R _d-mass was well predicted by all combinations of leaf life-span, N _mass and/or SLA (r ²≥ 0.79, P < 0.0001). At any given SLA, R _d-mass rises with increasing N _mass and/or decreasing leaf life-span; and at any level of N _mass, R _d-mass rises with increasing SLA and/or decreasing leaf life-span. The relationships between R _d and leaf traits observed in this study support the idea of a global set of predictable interrelationships between key leaf morphological, chemical and metabolic traits. Received: 23 May 1997 / Accepted: 16 December 1997     

Ammonium, calcium, and leaf senescence in rice

The possible involvement of calcium in the regulation of ammonium-promoted senescence of detached rice leaves was investigated. Calcium effectively reduced ammonium-promoted senescence of detached rice leaves. The effect of ammonium on the senescence was also significantly reduced by the calcium ionophore A23187. Ammonium-promoted senescence of detached rice leaves may be mediated through blocking the entrance of calcium ions into the cytosol.     

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。     

西藏紫花针茅叶功能性状沿降水梯度的变化

植物叶功能性状与环境因子的关系是近10年来植物生态学的研究热点。该文以广泛分布于青藏高原干旱、半干旱草地的优势植物种紫花针茅(Stipa purpurea)为研究对象, 沿降水梯度(69-479 mm)系统测定了日土、改则、珠峰、当雄和纳木错5个调查地点紫花针茅比叶面积(SLA)、单位重量和单位面积叶氮含量(N_mass, N_area)、叶密度和厚度等叶功能性状以及土壤全氮含量等因子, 试图验证干旱胁迫地区同一物种内SLA-N_mass关系沿降水梯度的策略位移现象是否具有普遍性, 并对是否出现策略位移现象提出可能的解释。研究结果表明: 1) SLA和N_mass与生长季温度和降水以及土壤全氮含量均没有显著关系, SLA与N_mass的关系在干旱半干旱区(年降水/蒸发比< 0.11)与半湿润区(年降水/蒸发比> 0.11)之间并没有出现典型的位移现象; 2)叶密度是决定半湿润区SLA变化的主导因子, 而叶厚度则是干旱半干旱区SLA变化的控制因子, 两者与SLA均呈负相关, 随着温度增加或降水减少, 叶厚度增加而叶密度降低, 导致SLA随温度和降水变化不明显; 3)半湿润区的叶密度增加引起N_area增加, 而干旱半干旱区的叶厚度增加并没有造成N_area的显著变化, 导致N_area沿降水梯度没有显著变化; 4)紫花针茅地上生物量与N_area具有显著正相关关系, 表明N_area的增加有助于提高植被生产力。结果表明, 在干旱胁迫下, 植物通过增加叶厚度来维持不变的N_area可能有助于保持与较湿润地区相似的光合生产和水分利用效率。叶厚度和叶密度对比叶面积的相对影响在干旱半干旱区与半湿润区之间发生转变, 这为进一步检测高寒草地植被的水分限制阈值提供了新思路。