Functional relationship between chlorophyll content and leaf reflectance, and light-capturing efficiency of Japanese forest species

We examined the functional relationship between chlorophyll concentrations and light spectral absorption in 16 species of woody, vine and herbaceous plants in northern Japan. Leaves of each species from under forest shade and in more open sites were measured for chlorophyll, specific leaf area (SLA) and spectral absorption. In all species, SLA increased and the Chl a : b ratio declined in shade- vs open-grown leaves indicating an adaptive adjustment to forest shade in these leaf characters. However, the expected increase in the ratio of 680 to 700 nm absorption in shade leaves did not occur in all species. Light absorption at 680 relative to 700 nm was lower in the shade leaves of Acer japonicum. Kalopanax pictus, Panax japonicus and Petasites japonicus even with a reduced Chl a : b , a commonly accepted indicator of shade adaptation. Therefore, spectral measurements in these species failed to support Chl concentrations that were expected to confer an improvement in the absorption of red light (<680nm) deficient relative to far-red light (>700 nm) in the forest shade. Compared with other species, the absorption pattern of these four 'non-conforming' species is associated with a higher ratio of shade:open leaves in reflectance spectra in the 600–750 nm range. This suggests an increased reflectance in shade leaves caused by changes in leaf surface properties which are not immediately apparent. We conclude that adaptive spectral absorption cannot always be inferred from changes in specific leaf area and chlorophyll a and b concentrations.     

Leaf Physiological Traits and their Importance for Species Success in a Mediterranean Grassland

We related leaf physiological traits of four grassland species (Poa pratensis, Lolium perenne, Festuca valida, and Taraxacum officinale), dominant in a Mediterranean grassland, to their origin and success at community level. From early May to mid-June 1999, four leaf samplings were done. Species originating from poor environments (P. pratensis, F. valida) had low carbon isotope discrimination (), specific leaf area (SLA), leaf water and mineral contents, and net photosynthetic rate on mass basis (P _mass) but high chlorophyll content. The reverse traits were evident for the fast-growing species (L. perenne, T. officinale). Under the resource-limiting conditions (soil nitrogen and water) of the Mediterranean grassland, the physiological traits of P. pratensis and F. valida showed to be more adapted to these conditions leading to high species abundance and dominance.     

Assessment of transpiration efficiency in peanut (Arachis hypogaea L.) under drought using a lysimetric system

Transpiration efficiency (TE) is an important trait for drought tolerance in peanut ( Arachis hypogaea L.). The variation in TE was assessed gravimetrically using a long time interval in nine peanut genotypes (Chico, ICGS 44, ICGV 00350, ICGV 86015, ICGV 86031, ICGV 91114, JL 24, TAG 24 and TMV 2) grown in lysimeters under well-watered or drought conditions. Transpiration was measured by regularly weighing the lysimeters, in which the soil surface was mulched with a 2-cm layer of polythene beads. TE in the nine genotypes used varied from 1.4 to 2.9 g kg⁻¹ under well-watered and 1.7 to 2.9 g kg⁻¹ under drought conditions, showing consistent variation in TE among genotypes. A higher TE was found in ICGV 86031 in both well-watered and drought conditions and lower TE was found in TAG-24 under both water regimes. Although total water extraction differed little across genotypes, the pattern of water extraction from the soil profile varied among genotypes. High water extraction within 24 days following stress imposition was negatively related to pod yield ( r ²   =   0.36), and negatively related to water extraction during a subsequent period of 32 days ( r ²   =   0.73). By contrast, the latter, i.e. water extraction during a period corresponding to grain filling (24 to 56 days after flowering) was positively related to pod yield ( r ²   =   0.36). TE was positively correlated with pod weight ( r ²   =   0.30) under drought condition. Our data show that under an intermittent drought regime, TE and water extraction from the soil profile during a period corresponding to pod filling were the most important components.     

Leaf stable carbon isotope composition reflects transpiration efficiency in Zea mays

The increasing demand for food production and predicted climate change scenarios highlight the need for improvements in crop sustainability. The efficient use of water will become increasingly important for rain‐fed agricultural crops even in fertile regions that have historically received ample precipitation. Improvements in water‐use efficiency in Zea mays have been limited, and warrant a renewed effort aided by molecular breeding approaches. Progress has been constrained by the difficulty of measuring water‐use in a field environment. The stable carbon isotope composition (δ¹³C) of the leaf has been proposed as an integrated signature of carbon fixation with a link to stomatal conductance. However, additional factors affecting leaf δ¹³C exist, and a limited number of studies have explored this trait in Z. mays. Here we present an extensive characterization of leaf δ¹³C in Z. mays. Significant variation in leaf δ¹³C exists across diverse lines of Z. mays, which we show to be heritable across several environments. Furthermore, we examine temporal and spatial variation in leaf δ¹³C to determine the optimum sampling time to maximize the use of leaf δ¹³C as a trait. Finally, our results demonstrate the relationship between transpiration and leaf δ¹³C in the field and the greenhouse. Decreasing transpiration and soil moisture are associated with decreasing leaf δ¹³C. Taken together these results outline a strategy for using leaf δ¹³C and reveal its usefulness as a measure of transpiration efficiency under well‐watered conditions rather than a predictor of performance under drought.     

基于地理种源的刨花楠苗木比叶面积与叶片化学计量学关系

探讨植物比叶面积(SLA)与叶片碳(C)、氮(N)、磷(P)化学计量学关系,能够反映植物为获取最大光合生产所采取的内部调控机制,共同体现植物的适应策略。利用生长于同一土壤与气候环境中培育的刨花楠(Machilus pauhoi)1年生苗木,对其SLA与叶片C、N、P含量进行测定,并对SLA与叶片C、N、P化学计量学特征及其与种源地环境因子的关系进行分析。结果表明:(1)叶片养分含量的变异系数大小排序为CNP;SLA与叶片N、P含量呈显著的正相关,与叶片C∶N及C∶P呈极显著的负相关。(2)SLA与经度、年均温、年降水量呈显著负相关;叶片C、N、P含量也受种源地环境因子影响,其中以海拔最为重要。研究结果有助于理解刨花楠苗木的生存适应对策,对探究刨花楠对养分的资源利用效率等具有重要意义。     

Elevated CO2 reduces leaf damage by insect herbivores in a forest community

By altering foliage quality, exposure to elevated levels of atmospheric CO(2) potentially affects the amount of herbivore damage experienced by plants. Here, we quantified foliar carbon (C) and nitrogen (N) content, C : N ratio, phenolic levels, specific leaf area (SLA) and the amount of leaf tissue damaged by chewing insects for 12 hardwood tree species grown in plots exposed to elevated CO(2) (ambient plus 200 microl l(-1)) using free-air CO(2) enrichment (FACE) over 3 yr. The effects of elevated CO(2) varied considerably by year and across species. Elevated CO(2) decreased herbivore damage across 12 species in 1 yr but had no detectable effect in others. Decreased damage may have been related to lower average foliar N concentration and SLA and increased C : N ratio and phenolic content for some species under elevated compared with ambient CO(2). It remains unclear how these changes in leaf properties affect herbivory. Damage to the leaves of hardwood trees by herbivorous insects may be reduced in the future as the concentration of CO(2) continues to increase, perhaps altering the trophic structure of forest ecosystems.     

底泥养分富集条件下11种水生植物的光合氮利用效率

为揭示水生植物对富营养化河涌底泥的生理生态适应性及其净化能力,选取11种水生挺水植物(包含6种本土植物和5种外来植物)结合河涌底泥进行试验。通过测定试验一年后植物叶片的光饱和光合速率(P_(sat),μmol m~(-2)s~(-1))、比叶面积(SLA,m~2/kg)、总氮含量(TN,mg/g)和光合作用氮利用效率(PNUE,μmol mol~(-1)s~(-1)),比较分析物种间生理与结构特性及其相互关系。结果表明:种间的SLA层次比较分明,最高的大叶皇冠草(20.31±0.30)与最低的鸢尾草(7.22±0.31)相差近3倍。种间的P_(sat)在(3.76±0.57)(鸢尾草)—(21.53±1.20)(水罂粟)之间,水罂粟比鸢尾草高81.79%。种间的PNUE从42.53±8.42(鸢尾草)至655.8±100.93(天使花),美人蕉、水罂粟、风车草和香蒲的PNUE值均较高,且差异不明显(P0.05),这些植物的PNUE显著高于较低PNUE的种类(包括菖蒲、蓝花草和鸢尾草)(P0.05)。种间SLA分别与PNUE和P_(sat)(μmol kg~(-1)s~(-1))呈显著的正相关,SLA和P_(sat)(μmol m~(-2)s~(-1))分别与TN(mmol/m~2)呈显著负相关(P0.05)。外来植物类群的PNUE、SLA、P_(sat)和TN均显著高于本地植物类群(T-test,P0.05),说明外来水生植物在养分富集化环境下能更有效地利用资源,具有潜在的高生长速率和种间竞争优势。     

Photosynthetic acclimation to light in woody and herbaceous species: a comparison of leaf structure, pigment content and chlorophyll fluorescence characteristics measured in the field

Acclimation of foliage photosynthetic properties occurs with varying time kinetics, but structural, chemical and physiological factors controlling the kinetics of acclimation are poorly understood, especially in field environments. We measured chlorophyll fluorescence characteristics, leaf total carotenoid (Car), chlorophyll (Chl) and nitrogen (N) content and leaf dry mass per area (LMA) along vertical light gradients in natural canopies of the herb species, Inula salicina and Centaurea jacea, and tree species, Populus tremula and Tilia cordata, in the middle of the growing season. Presence of stress was assessed on the basis of night measurements of chlorophyll fluorescence. Our aim was to compare the light acclimation of leaf traits, which respond to light availability at long (LMA and N), medium (Chl a/b ratio, Car/Chl ratio) and short time scales (fluorescence characteristics). We found that light acclimation of nitrogen content per unit leaf area (N(area)), chlorophyll content per unit dry mass (Chl(mass)) and Chl/N ratio were related to modifications in LMA. The maximum PSII quantum yield (F(v) /F(m)) increased with increasing growth irradiance in I. salicina and P. tremula but decreased in T. cordata. Leaf growth irradiance, N content and plant species explained the majority of variability in chlorophyll fluorescence characteristics, up to 90% for steady-state fluorescence yield, while the contribution of leaf total carotenoid content was generally not significant. Chlorophyll fluorescence characteristics did not differ strongly between growth forms, but differed among species within a given growth form. These data highlight that foliage acclimation to light is driven by interactions between traits with varying time kinetics.     

松嫩草地66种草本植物叶片性状特征

植物叶片功能性状及其相互关系越来越受到关注.以松嫩草地66种草本植物为研究对象,测量叶片干物质含量、比叶面积、叶片厚度、叶片氮含量、叶片磷含量、叶绿素含量和类胡萝卜素含量,检验性状间的相互关系,比较不同功能群(多年生根茎禾草,多年生丛生禾草,多年生杂类草,1年生或2年生草本)间性状的差异性.结果表明,叶片厚度变异系数最大,比叶面积、叶片氮含量、叶片磷含量、叶绿素含量和类胡萝卜素含量之间存在显著的正相关关系;叶片于物质含量与叶片磷含量没有显著的相关关系,与其它叶片性状呈显著的负相关关系;叶片厚度只与叶片干物质含量和比叶面积呈显著的负相关关系,与其它叶片性状不相关.叶片干物质含量、比叶面积、叶片厚度、叶片氮、磷含量在4个功能群间差异显著,叶绿素含量和类胡萝卜素含量在各个功能群间差异不显著;多年生根茎禾草和多年生丛生禾草叶片的7个性状差异不显著;多年生根茎禾草和多年生丛生禾草的叶片干物质含量高于多年生杂类草和1年生或2年生草本,其它性状小于这两个功能群.     

冬小麦光合特征及叶绿素含量对保水剂和氮肥的响应

以不施保水剂和氮（N）肥为对照,测定了保水剂（60 kg·hm^-2）与不同N肥水平（0、225、450 kg·hm^-2）及其配施条件下大田小麦的光合特征、叶绿素含量和水分利用效率等指标,研究了冬小麦拔节期和灌浆期光合生理特征、叶绿素含量及水分利用对保水剂和N肥的响应.结果表明：灌浆期各处理的光合速率、气孔导度、胞间CO₂浓度、叶片水分利用效率及叶绿素含量均大于拔节期.在拔节期,单施N肥条件下,随施N量的增加,单叶水分利用效率提高,光合速率、气孔导度、胞间CO₂浓度及蒸腾速率均先增后减;225 kg·hm^-2 N肥处理的叶绿素含量最高.施用保水剂后,随施N量的增加,胞间CO₂浓度降低,而光合速率等均提高;单施保水剂及其与N肥配施提高了叶绿素含量,而过多N肥效果不显著在灌浆期,单施N肥显著提高了小麦的光合速率及水分利用效率,降低了气孔导度、胞间CO₂浓度及蒸腾速率;叶绿素含量随N肥用量的增加而增加.施用保水剂后,随N肥用量的增加,光合速率和叶片水分利用效率均先增后减,而胞间CO₂浓度和蒸腾速率先减后增,但均低于对照,气孔导度随施N量的增加而提高.单施保水剂的叶绿素含量显著提高,但其与N肥配施叶绿素含量有所降低.保水剂与N肥配合施用显著提高了小麦的千粒重、产量及水分生产效率.其中,保水剂与225 kg·hm^-2N肥配施处理的产量及水分生产效率均最高.     

中国西北干旱区树木蒸腾对气象因子的响应

应用数值方法 ,对中国西北干旱区 5个主要树种 (樟子松、榆树、二白杨、胡杨和沙枣 )的叶面蒸腾及气孔导度对气象因子的响应进行了探讨 ,时间尺度为日。两套综合环境观测系统分别安置在黑河中游的临泽和下游的额济纳旗 ,每半小时自动记录微气象因子、土壤水分和树汁流量。应用日平均树汁流量、饱和差、总辐射、平均气温和土壤含水量拟合树木叶面蒸腾及气孔导度的经验公式。气孔导度和单个气象因子之间具有很高的相关性。应用多个气象因子所建立的经验公式能够很好的模拟气孔导度 ,模拟效果比气孔导度与单一因子的相关性高。气孔导度总体上和饱和差和气温呈指数关系 ,与总辐射的关系多种多样 ,与土壤含水量的关系较复杂。在中游地区 ,二白杨气孔导度、叶面蒸腾量和单株树木树汁流量最大。试验期间下游试验点土壤水分充足 ,耐旱树种胡杨及沙枣树汁流量较大 ,但其气孔导度及叶面蒸腾量均较小。本次研究没有发现树木叶面蒸腾量和单一环境因子之间具有明显的相关性。叶面蒸腾模拟效果没有气孔导度模拟效果好 ,原因是叶面蒸腾是气孔导度和饱和差的函数。     

Genotypic variations in carbon isotope discrimination, transpiration efficiency, and biomass production in rice as affected by soil water conditions and N

Genotypic and environmental (soil water regime and N level) variation in carbon isotope discrimination (CID) in relation to the gas exchange, transpiration efficiency (A/T), and biomass production were investigated in field experiments using eleven rice (Oryza sativa L.) genotypes. The results showed that genotype was more dominant for variation in CID than in total biomass. Genotypic ranking in CID was consistent across environments because of small genotype × environment interactions. Japonica genotypes tended to have lower CID than indica genotypes. Higher soil water and lower N rate significantly increased CID. Variation in CID was slightly smaller for water regime than for genotype. There was a negative correlation between CID andA/T among genotypes within water regimes. Genotypic variation in CID was associated mainly with variation in stomatal conductance under all soil water regimes and with photosynthetic capacity in late growth stages under aerobic soil conditions. The decrease in CID at higher N was probably due to lower stomatal conductance under aerobic soil conditions and to higher photosynthetic rates under submerged soil conditions. The correlation between biomass and CID was not clear in aerobic soil, whereas it was positive in submerged soil, which indicated that the significance of lower or higher CID for improving biomass productivity may differ under different soil water regimes. Overall, the results implied a possible use of CID as a selection criterion for genotypic improvement inA/T and productivity in rice.     

毛竹叶片衰老过程的叶重量、叶面积及元素内吸收率的动态

对福建永春毛竹(Phyllostachyspubescens Mazel ex H.de Lehaie)叶片衰老过程的叶重量、叶面积及元素内吸收率的动态进行了研究,并对元素内吸收率RE1(以元素的干重含量为计算单位,mg/g)、RE2(以单位叶片的元素含量为计算单位,mg/leaf)以及RE3(以单位叶面积的元素含量为计算单位,mg/cm2)进行了比较.叶片衰老过程中,平均叶重量、叶面积及比叶重分别下降了19.55%、15.16%和5.07%.叶重量与叶面积下降百分率的季节变化趋势一致,说明毛竹叶片存在一定的重量与面积比率.在不同的元素内吸收率比较中,N和K的元素内吸收率均为正,Ca均为负,表明叶片衰老过程中N和K的元素含量从衰老叶片中转移至植株的其他部位,而Ca在老叶中累积.N、P、K、Ca和Mg5种元素平均的元素内吸收率高低顺序均为RE2＞RE3＞RE1,反映出以元素的干重含量为计算单位和以单位叶面积的元素含量为计算单位的元素内吸收率偏低.     

毛竹叶片衰老过程的叶重量、叶面积及元素内吸收率的动态

对福建永春毛竹(Phyllostachys pubescens Mazel ex H.de Lehaie)叶片衰老过程的叶重量、叶面积及元素内吸收率的动态进行了研究,并对元素内吸收率RE_1(以元素的干重含量为计算单位,mg/g)、RE_2(以单位叶片的元素含量为计算单位,mg/leaf)以及RE_3(以单位叶面积的元素含量为计算单位,mg/cm~2)进行了比较。叶片衰老过程中,平均叶重量、叶面积及比叶重分别下降了19.55％、15.16％和5.07％。叶重量与叶面积下降百分率的季节变化趋势一致,说明毛竹叶片存在一定的重量与面积比率。在不同的元素内吸收率比较中,N和K的元素内吸收率均为正,Ca均为负,表明叶片衰老过程中N和K的元素含量从衰老叶片中转移至植株的其他部位,而Ca在老叶中累积。N、P、K、Ca和Mg 5种元素平均的元素内吸收率高低顺序均为RE_2>RE_3>RE_1,反映出以元素的干重含量为计算单位和以单位叶面积的元素含量为计算单位的元素内吸收率偏低。     

Productivity, leaf traits and carbon isotope discrimination in 29 Populus deltoides x P. nigra clones

Here we tested whether some leaf traits could be used as predictors for productivity in a range of Populus deltoides x P. nigra clones. These traits were assessed in 3-yr-old rooted cuttings from 29 clones growing in an open field trial, in a five randomized complete block design, under optimal irrigation. Variables were assigned to four groups describing productivity (above-ground biomass, total leaf area), leaf growth (total number of leaves increment rate), leaf structure (area of the largest leaf, specific leaf area, carbon and nitrogen contents), and carbon isotope discrimination in the leaves (Delta). High-yielding clones displayed larger total leaf area and individual leaf area, while no correlation could be detected between productivity and either leaf structure or Delta. By contrast, Delta was negatively correlated with number of leaves increment rate and leaf N content. Our study shows that there is a potential to improve water-use efficiency in poplar without necessarily reducing the overall productivity.     

Carbon gain in a multispecies canopy: the role of specific leaf area and photosynthetic nitrogen-use efficiency in the tragedy of the commons

Models have been formulated for monospecific stands in which canopy photosynthesis is determined by the vertical distribution of leaf area, nitrogen and light. In such stands, resident plants can maximize canopy photosynthesis by distributing their nitrogen parallel to the light gradient, with high contents per unit leaf area at the top of the vegetation and low contents at the bottom. Using principles from game theory, we expanded these models by introducing a second species into the vegetation, with the same vertical distribution of biomass and nitrogen as the resident plants but with the ability to adjust its specific leaf area (SLA, leaf area:leaf mass). The rule of the game is that invaders replace the resident plants if they have a higher plant carbon gain than those of the resident plants. We showed that such invaders induce major changes in the vegetation. By increasing their SLA, invading plants could increase their light interception as well as their photosynthetic nitrogen-use efficiency (PNUE, the rate of photosynthesis per unit organic nitrogen). By comparison with stands in which canopy photosynthesis is maximized, those invaded by species of high SLA have the following characteristics: (1) the leaf area index is higher; (2) the vertical distribution of nitrogen is skewed less; (3) as a result of the supra-optimal leaf area index and the more uniform distribution of nitrogen, total canopy photosynthesis is lower. Thus, in dense canopies we face a classical tragedy of the commons: plants that have a strategy to maximize canopy carbon gain cannot compete with those that maximize their own carbon gain. However, because of this strategy, individual as well as total canopy carbon gain are eventually lower. We showed that it is an evolutionarily stable strategy to increase SLA up to the point where the PNUE of each leaf is maximized.