Light and VPD gradients drive foliar nitrogen partitioning and photosynthesis in the canopy of European beech and silver fir

While foliar photosynthetic relationships with light, nitrogen, and water availability have been well described, environmental factors driving vertical gradients of foliar traits within forest canopies are still not well understood. We, therefore, examined how light availability and vapour pressure deficit (VPD) co-determine vertical gradients (between 12 and 42 m and in the understorey) of foliar photosynthetic capacity (Amax), 13C fractionation (∆), specific leaf area (SLA), chlorophyll (Chl), and nitrogen (N) concentrations in canopies of Fagus sylvatica and Abies alba growing in a mixed forest in Switzerland in spring and summer 2017. Both species showed lower Chl/N and lower SLA with higher light availability and VPD at the top canopy. Despite these biochemical and morphological acclimations, Amax during summer remained relatively constant and the photosynthetic N-use efficiency (PNUE) decreased with higher light availability for both species, suggesting suboptimal N allocation within the canopy. ∆ of both species were lower at the canopy top compared to the bottom, indicating high water-use efficiency (WUE). VPD gradients strongly co-determined the vertical distribution of Chl, N, and PNUE in F. sylvatica, suggesting stomatal limitation of photosynthesis in the top canopy, whereas these traits were only related to light availability in A. alba. Lower PNUE in F. sylvatica with higher WUE clearly indicated a trade-off in water vs. N use, limiting foliar acclimation to high light and VPD at the top canopy. Species-specific trade-offs in foliar acclimation to environmental canopy gradients may thus be considered for scaling photosynthesis from leaf to canopy to landscape levels.     

Do higher resource capture ability and utilization efficiency facilitate the successful invasion of native plants?

The great damage caused by native invasive species on natural ecosystems is prompting increasing concern worldwide. Many studies have focused on exotic invasive species. In general, exotic invasive plants have higher resource capture ability and utilization capacity, and lower leaf construction cost (CC) compared to noninvasive plants. However, the physiological mechanisms that determine the invasiveness of native plants are poorly understood. We hypothesized that native invaders, like exotic invaders, may have higher resource capture ability and utilization efficiency compared to native noninvaders. To test this hypothesis, ecophysiological traits including light-saturated photosynthetic rate (A_max), specific leaf area (SLA), photosynthetic nitrogen use-efficiency (PNUE), photosynthetic energy-use efficiency (PEUE), and mass-based and area-based leaf construction cost (CC_mass and CC_area) were measured. We compared the above traits between three pairs of native invasive and noninvasive native species, and between three pairs of exotic invasive and noninvasive species in Guangzhou, southern China. Our results showed that the native invaders had higher A_max, SLA, PNUE, PEUE and lower CC_mass, CC_area, compared to native noninvaders and that these traits were also found in the exotic invaders. PNUE and PEUE in the native invaders were 150.3 and 129.0% higher, respectively, than in noninvasive native species, while these same measures in exotic invaders were 43.0 and 94.2% higher, respectively, than in exotic noninvasive species. The results indicated that native invaders have higher resource capture ability and resource utilization efficiency, suggesting that these traits may be a common biological foundation underlying successful invasion by both native and exotic invasives.     

Specific leaf area relates to the differences in leaf construction cost,photosynthesis, nitrogen allocation,and use efficiencies between invasive and noninvasive alien congeners

Comparisons between invasive and native species may not characterize the traits of invasive species, as native species might be invasive elsewhere if they were introduced. In this study, invasive Oxalis corymbosa and Peperomia pellucida were compared with their respective noninvasive alien congeners. We hypothesized that the invasive species have higher specific leaf (SLA) than their respective noninvasive alien congeners, and analyzed the physiological and ecological consequences of the higher SLA. Higher SLA was indeed the most important trait for the two invaders, which was associated with their lower leaf construction cost, higher nitrogen (N) allocation to photosynthesis and photosynthetic N use efficiency (PNUE). The higher N allocation to photosynthesis of the invaders in turn increased their PNUE, N content in photosynthesis, biochemical capacity for photosynthesis, and therefore light-saturated photosynthetic rate. The above resource capture-, use- and growth-related traits may facilitate the two invaders' invasion, while further comparative studies on a wider range of invasive and noninvasive congeners are needed to understand the generality of this pattern and to fully assess the competitive advantages afforded by these traits.     

黄土高原油松和刺槐叶片光合生理适应性比较

以黄土高原地区由南向北分布的杨凌、永寿、富县、安塞、米脂、神木等县为研究地点，研究不同地区油松和刺槐的光合特性与叶结构性状间的关系.结果表明，不同地区油松针叶和刺槐叶片的净光合速率（P_n）、光合氮利用效率（PNUE）、水分利用效率（WUE）、比叶质量（LMA）、氮含量（N_mass）和叶绿素相对含量（Chl）差异均达极显著水平（P＜0.001）,说明不同地区油松和刺槐的光合能力和叶结构性状参数差异很大.由南向北，油松的P_n、WUE和PNUE呈略微增加趋势，而刺槐则呈显著降低趋势，表明油松在干旱生境下仍能维持较高的光合能力，而刺槐光合能力明显受到抑制；油松和刺槐的LMA均呈略微上升趋势，而N_mass和Chl均呈略微下降趋势，且刺槐的变化幅度高于油松，说明油松从生理代谢和叶结构性状上对干旱环境的适应能力均强于刺槐.相关分析表明，不同地区油松和刺槐的LMA与N_mass整体上呈极显著负相关；P_n、PNUE与LMA、N_mass相关不显著，与Chl呈极显著正相关；WUE与LMA呈显著负相关（P＜0.05），与N_mass呈显著正相关.     

Different leaf cost–benefit strategies of ferns distributed in contrasting light habitats of sub-tropical forests

Background and Aims Ferns are abundant in sub-tropical forests in southern China, with some species being restricted to shaded understorey of natural forests, while others are widespread in disturbed, open habitats. To explain this distribution pattern, we hypothesize that ferns that occur in disturbed forests (FDF) have a different leaf cost–benefit strategy compared with ferns that occur in natural forests (FNF), with a quicker return on carbon investment in disturbed habitats compared with old-growth forests.Methods We chose 16 fern species from contrasting light habitats (eight FDF and eight FNF) and studied leaf functional traits, including leaf life span (LLS), specific leaf area (SLA), leaf nitrogen and phosphorus concentrations (N and P), maximum net photosynthetic rates (A), leaf construction cost (CC) and payback time (PBT), to conduct a leaf cost–benefit analysis for the two fern groups.Key Results The two groups, FDF and FNF, did not differ significantly in SLA, leaf N and P, and CC, but FDF had significantly higher A, greater photosynthetic nitrogen- and phosphorus-use efficiencies (PNUE and PPUE), and shorter PBT and LLS compared with FNF. Further, across the 16 fern species, LLS was significantly correlated with A, PNUE, PPUE and PBT, but not with SLA and CC.Conclusions Our results demonstrate that leaf cost–benefit analysis contributes to understanding the distribution pattern of ferns in contrasting light habitats of sub-tropical forests: FDF employing a quick-return strategy can pre-empt resources and rapidly grow in the high-resource environment of open habitats; while a slow-return strategy in FNF allows their persistence in the shaded understorey of old-growth forests.     

翅果油树及其群落中7种优势木本种类的叶性特征比较

Taking Elaeagnus mollis Diels and seven dominant woody species in its community from Yicheng County of Shanxi Province as research objects, leaf traits including specific leaf area (SLA), nitrogen content in leaf per unit area ( Narea ) , leaf dry matter content ( LDMC ) and photosynthetic nitrogen use efficiency ( PNUE ) were compared, and correlations of SLA value with LDMC and PNUE values were analyzed. The results show that there are different degree variations in four indexes of leaf traits of E. mollis, Vitex negundo var. heterophylla ( Franch.) Rehd., Broussonetia papyrifera ( Linn.) L' Hér. ex Vent., Lespedeza bicolor Turcz., Caragana microphylla Lam., Rosa xanthina Lindl., Amygdalus davidiana ( Carrière) de Vos ex Henry and Periploca sepium Bunge, in which, SLA value with the largest coefficient of variation ( 404%) , and LDMC value with the lowest coefficient of variation ( 103%) . Compared with other tested species, SLA and PNUE values of E. mollis are the lowest ( 103 cm-2 · g-1 and 108 μmol · mol-1 · s-1 , respectively) , while its Narea value is the highest ( 0243 g · m-2 ) , and its LDMC value is also relatively high ( 0380 g·g-1 ) . SLA value of eight tested species show an extremely significant positive correlation ( P<001) with PNUE value, and a significant negative correlation ( P<005 ) with LDMC value, correlation coefficient are 0923 and -0718, respectively, indicating that SLA value is an important parameter of leaf photosynthetic capacity and resource utilization ability. It is suggested that compared with other dominant woody species, E. mollis is more sensitive to environmental change, and has a poor environmental adaptability.     

Spatial patterns of photosynthetic characteristics and leaf physical traits of plants in the Loess Plateau of China

The spatial patterns of photosynthetic characteristics and leaf physical traits of 171 plants belonging to nine life-forms or functional groups (trees, shrubs, herbs, evergreen trees, deciduous trees, C₃ and C₄ herbaceous plants, leguminous and non-leguminous species) and their relationships with environmental factors in seven sites, Yangling, Yongshou, Tongchuan, Fuxian, Ansai, Mizhi and Shenmu, ranging from south to north in the Loess Plateau of China were studied. The results showed that the leaf light-saturated photosynthetic rate (P_max), photosynthetic nitrogen use efficiency (PNUE), chlorophyll content (Chl), and leaf mass per area (LMA) of all the plants in the Loess Plateau varied significantly among three life-form groups, i.e., trees, shrubs and herbs, and two groups, i.e., evergreen trees and deciduous trees, but leaf nitrogen content differed little among different life-form groups. For the 171 plants in the Loess Plateau, leaf P_max was positively correlated with PNUE. The leaf nitrogen content per unit area (N_area) was positively correlated but Chl was negatively correlated with the LMA. When controlling the LMA, the N_area was positively correlated with the Chl (partial r = 0.20, P < 0.05). With regard to relationships between photosynthetic characteristics and leaf physical traits, the P_max was positively correlated with N _area, while the PNUE was positively correlated with the Chl and negatively correlated with the N_area and LMA. For all the species in the Loess Plateau, the PNUE was negatively correlated with the latitude and annual solar radiation (ASR), but positively correlated with the mean annual rainfall (MAR) and mean annual temperature (MAT). With regard to the leaf physical traits, the leaf Chl was negatively correlated with the latitude and ASR, but positively correlated with the MAR and MAT. However, the N_area and LMA were positively correlated with the latitude and ASR, but negatively correlated with the MAR and MAT. In general, leaf N_area and LMA increased, while PNUE and Chl decreased with increases in the latitude and ASR and decreases in MAR and MAT. Electronic supplementary material The online version of this article () contains supplementary material, which is available to authorized users.     

太岳山典型阔叶乔木冠层叶片性状的分布格局

以太岳山4种阔叶乔木不同冠层高度的叶片为研究对象,用LI-3000A叶面积仪和Li-6400便携式光合作用测定系统分别测定了这4种乔木不同冠层高度叶片的叶面积大小和单位面积的叶光饱和速率(Aarea);同时测定了其叶氮含量;计算了其比叶面积(SLA)、单位面积叶氮含量(Narea)、单位重量叶氮含量(Nmass)、单位重量的叶光饱和速率(Amass)和光合氮素利用效率(PNUE),对植株不同冠层高度叶片的SLA、叶氮和光合特性的空间分布格局进行了比较研究,结果表明:Aarea、Amass、Nmass、PNUE、SLA和Narea在树冠上层、中层和下层的差异均达到了极显著水平(P<0.001),表明树冠不同高度的叶片性状参数差异较大;在相同SLA下,Nmass和Narea在冠层中的分布均表现为中层>上层>下层,并出现平行位移现象;Aarea和Nmass都以中层值最大,表明冠层光合能力分布格局以中层相对较高。     

Leaf anatomical structures of <Emphasis Type="Italic">Paphiopedilum</Emphasis> and <Emphasis Type="Italic">Cypripedium</Emphasis> and their adaptive significance

Paphiopedilum and Cypripedium are closely related in phylogeny, but have contrasting leaf traits and habitats. To understand the divergence in leaf traits of Paphiopedilum and Cypripedium and their adaptive significance, we analyzed the leaf anatomical structures, leaf dry mass per area (LMA), leaf lifespan (LL), leaf nitrogen concentration (N _mass), leaf phosphorus concentration (P _mass), mass-based light-saturated photosynthetic rate (A _mass), water use efficiency (WUE), photosynthetic nitrogen use efficiency (PNUE) and leaf construction cost (CC) for six species. Compared with Cypripedium, Paphiopedilum was characterized by drought tolerance derived from its leaf anatomical structures, including fleshy leaves, thick surface cuticles, huge adaxial epidermis cells, lower total stoma area, and sunken stomata. The special leaf structures of Paphiopedilum were accompanied by longer LL; higher LMA, WUE, and CC; and lower N _mass, P _mass, A _mass, and PNUE compared with Cypripedium. Leaf traits in Paphiopedilum helped it adapt to arid and nutrient-poor karst habitats. However, the leaf traits of Cypripedium reflect adaptations to an environment characterized by rich soil, abundant soil water, and significant seasonal fluctuations in temperature and precipitation. The present results contribute to our understanding of the divergent adaptation of leaf traits in slipper orchids, which is beneficial for the conservation of endangered orchids.     

Analysis of relationships among leaf functional traits and economics spectrum of plant species in the desert steppe of Nei Mongol

Aims Grassland desertification is being accelerated because of adverse climate change effects and unsustainable land uses, resulting in several major environmental problems. However, there are few studies on the economics spectrum of different plant functional types in desert steppe. The objectives of the current study are to examine the relationships among leaf functional traits of native plant species, to compare the functional traits among different plant functional types, and to determine whether an economic spectrum exists for the majority of species in the desert steppe of Damao Banner, Nei Mongol, China.
Methods Photosynthetic and chlorophyll fluorescence parameters, specific leaf area (SLA), and leaf nitrogen contents across 24 species of different functional types were measured in situ in the desert steppe ecosystem. Non-parametric tests were used to analyze leaf trait differences in plant species of different functional types. Linear regression analysis was used to determine the relationships among leaf traits in different plant species. Finally, a comprehensive analysis on these leaf traits in different plant species was conducted using the principal component analysis. All data analyses were performed using SPSS 16.0 (SPSS, Chicago, USA).
Important findings Significant differences among plant functional types were found in most of the leaf traits. SLA and mass-based nitrogen concentration (N_mass) in grasses were 2.39 and 1.20 folds, respectively, of that in shrubs; area-based photosynthetic capacity (A_area), SLA, and photosynthetic nitrogen use efficiency (PNUE) in annual species were 1.93, 2.13, and 4.24 folds, respectively, of that in perennial species; and A_area, SLA, and PNUE in C₄ species were 2.25, 1.73, and 3.61 folds, respectively, of that in C₃ species. Almost all relationships significantly differed (p < 0.01) among the leaf traits, with exception of the relationships between A_area and area-based nitrogen concentration (N_area) and between quantum yield of PSII electron transport (Φ_PSII) and SLA, implying that an economic spectrum may exist in the desert steppe ecosystem. The relationships of N_area, mass-based photosynthetic capacity (A_mass), and PNUE with SLA were most significantly strong (R² = 0.54, 0.62, 0.60, respectively; p < 0.01). Results in this study suggest that the annuals, grasses, and C₄ species might be located at the end of the leaf economic spectrum with high area-based photosynthetic rate, high nitrogen concentration on mass basis, short leaf lifespan, and high SLA; whereas the perennials, shrubs, and C₃ species could be located at the another end of the economic spectrum with contrasting traits.     

北京植物园不同功能型植物叶经济谱

通过对北京植物园不同功能型植物的叶片光合参数、叶绿素荧光参数、叶面积、叶干质量以及叶氮含量等性状参数进行测定,分析了不同功能型植物的叶经济谱.结果表明: 生活型中草本植物、生活史中一年生植物、光合型中C4植物靠近叶经济谱中快速投资-收益型物种的一端,而生活型中乔木和灌木、生活史中多年生植物、光合型中C3植物位于缓慢投资-收益型物种的一端,表明不同功能型植物通过叶片性状间的权衡采取不同的环境适应策略,验证了不同功能型植物叶经济谱的存在.不同功能型植物叶片性状具有明显差异,其中不同生活型间的叶片比叶面积(SLA)、叶氮含量(N_mass)、最大净光合速率(A_mass)、光合氮利用效率(PNUE)均表现出草本植物>藤本植物>灌木>乔木;不同生活史间一年生植物的SLA、N_mass、A_mass、PNUE均显著高于多年生植物;不同光合型间植物的A_mass、PNUE、PSⅡ实际光化学效率(Φ_PSⅡ)均表现出C4>C3.N_mass、A_mass、SLA两两之间呈显著正相关,而PSⅡ有效光化学量子产量(F_v′/F_m′)与SLA呈显著负相关;PNUE与SLA呈显著正相关.     

Leaf Chemical and Optical Properties of Metrosideros polymorpha Across Environmental Gradients in Hawaii

Leaf chemical, biophysical, and optical properties were measured in 13 populations of Metrosideros polymorpha across gradients of soil fertility and climate in Hawaii. Climate (predominantly temperature) caused large changes in specific leaf area (SLA) and SLA-linked traits, including nitrogen (N) and pigment contents, as did conditions of highest soil fertility on 20 ky old substrates. When averaged by site, chemical constituent ratios containing chlorophyll (Car/Chl, Chl/N) varied more across climate than substrate gradients, while the Chl a/b ratio was similarly influenced by climate and substrate. Variations in Chl a/b ratios and SLA were similar to those found previously in a common garden of M. polymorpha taken from our climate gradient, suggesting strong genetic control over these traits. Optical reflectance indices related to photosynthetic function were closely correlated to pigment changes, varying three times more in response to climate than across substrate ages. Combined, our results suggest that variation in leaf structure, composition, and function of M. polymorpha is a result of genetic and phenotypic adaptation to environmental differences, and that these variations are greater in response to climate (especially temperature) than to soil fertility.     

Plant biodiversity in a larch plantation from the view point of photosynthetic nitrogen use efficiency in northeast China

Forest floor of larch species often provides growth habitat for many kinds of understory species because of relatively sparse structure in a larch canopy. A rich flora of forest understory species may play an essential role in maintaining fertility of a larch stand. An attempt was made to evaluate photosynthetic nitrogen use efficiency (PNUE) of many understory and overstory species according to their Raunkiaer lifeform. By studying 72 perennial deciduous species in a larch plantation in northeast China, marked photosynthetic differences between phanerophytes (Ph) and other three lifeforms of chamaephytes (Ch), hemicryptophytes (He), and cryptophytes (Cr) were found, with marginal differences found among Ch, He, and Cr. Ph species had much lower PNUE, and much lower values of rate of nitrogen allocation to chlorophyll (Chl./N) and nitrogen allocation to carboxylation processes (V _cmax/N) were concurrently observed in Ph compared with the other three lifeforms. Ph had much lower leaf nitrogen per unit of projection area (N _area) and specific leaf area (SLA, cm² g^–1). At lower SLA, for Ph species the change of PNUE with SLA was small, but these changes became very large at higher SLA for Ch, He, and Cr species. Our findings indicate that leaf morphological change is important for clarifying photosynthesis differences among species with different lifeform.     

Morphological and functional traits of herbaceous plants with different functional types in the European Northeast

We aimed to identify marker traits indicating the functional types of plants in the European Northeast. We try to answer the following questions. Which ecological factors make the largest contribution to identifying the functional types of plants in the North and can CO₂-exchange and related traits be used as markers? The data were collected from 1000-km latitudinal gradient across middle, north, and far north boreal forests in the east border of Europe. Comparative analysis of 102 species from 36 plant families enabled us to determine the marker traits indicating plant functional types. Competitor species have maximal plant height, comparatively low leaf dry matter content (LDMC), and accumulate high amounts of nitrogen in leaves. These species also have comparatively high photosynthetic and respiration rates. Ruderal species have low values of LDMC, and maximal photosynthetic rate, respiration rate, and photosynthetic nitrogen-use efficiency (PNUE). Slow-growing stress tolerators have a low photosynthetic rate, low respiration rate, and low levels of nitrogen and PNUE. The specific leaf area (SLA) of these plants shows a highly significant correlation with the light regime. In the boreal zone, SLA was found to be more closely related to light availability than to the plant functional type, indicating that SLA is unsuitable for use as a marker trait. We found strong correlations between plant height, respiration rate, and photosynthetic activity and soil nutrition according to Ellenberg values. Soil mineral element contents and acidity were found to have a significant influence on the functional types of plants.     

翅果油树叶性特征的动态变化

以山西翼城翅果油树(Elaeagnus mollis)自然保护区的翅果油树为研究对象,利用LI-3000A叶面积测定仪测量其单叶面积,用Li-6400便携式光合作用测定系统测定单位叶面积饱和光合速率(Aaraa),用H2SO4-H2O2消煮法测定叶氮含量,计算叶性参数比叶面积(SLA)、单位叶重量饱和光合速率(Amass)、光合氮利用率(PNUE)和单位重量叶氮含量(Nmass)的值,并研究它们与径级之间的关系.结果表明:随着翅果油树径级的增加,SLA、Nmass、Aarea、Amass和PNUE值先下降后上升,当翅果油树径级为7.5 cm左右时,SLA、Nmass、Aarea、Amass和PNUE值均降到最小值,表明径级为7.5 cm左右的翅果油树其光合能力最弱、光合氮利用率较低且生存压力较大.翅果油树叶性参数是研究翅果油树种群动态变化的有效指标,可为研究翅果油树种群动态提供更为便捷的方法.     

Comparisons of plastic responses to irradiance and physiological traits by invasive Eupatorium adenophorum and its native congeners

To explore the traits contributing to invasiveness of Eupatorium adenophorum and to test the relationship between plasticity of these traits and invasiveness, we compared E. adenophorum with its two native congeners at four irradiances (10%, 23%, 40%, and 100%). The invader showed constantly higher performance (relative growth rate and total biomass) across irradiances than its native congeners. Higher light-saturated photosynthetic rate (P(max)), respiration efficiency (RE), and nitrogen (PNUE) and water (WUE, at 40% and 100% irradiances only) use efficiencies contributed directly to the higher performance of the invader. Higher nitrogen allocation to, stomatal conductance, and the higher contents of leaf nitrogen and pigments contributed to the higher performance of the invader indirectly through increasing P(max), RE, PNUE and WUE. The invader had consistently higher plasticity only in carotenoid content than its native congeners in ranges of low (10-40%), high (40-100%) and total (10-100%) irradiances, contributing to invasion success in high irradiance by photo protection. In the range of low irradiances, the invader had higher plasticity in some physiological traits (leaf nitrogen content, nitrogen contents in bioenergetics, carboxylation and in light-harvesting components, and contents of leaf chlorophylls and carotenoids) but not in performance, while in the ranges of high or total irradiances, the invader did not show higher plasticity in any variable (except Car). The results indicated that the relationship between invasiveness and plasticity of a specific trait was complex, and that a universal generalization about the relationship might be too simplistic.     

Effects of altitudinal gradient on Salix atopantha foliar delta13C

In 2010, measurements were conducted on the foliar delta13C, photosynthesis, CO2 diffusive conductivity, nitrogen content, photosynthetic nitrogen use efficiency (PNUE), and special leaf area (SLA) of Salix atopantha at different altitudes (2350 m, 2700 m, 3150 m, and 3530 m) in Wolong Natural Reserve. With the increase of altitude, the foliar nitrogen content (especially the nitrogen content per unit leaf area, N(area)) and the PNUE increased, and the foliar delta13C had a significant increase, with an increment of 1.4 per thousand per 1000 m altitude. The stomatal and mesophyll CO2 diffusion conductance also increased with increasing altitude, which had definite negative effect on the increase of foliar delta13C, but the effect was not strong enough. Comparing with CO2 diffusion conductance, carboxylation capacity was a more important factor limiting the P(c)/P(a), and even, the foliar delta13C. At altitude 2350-2700 m, air temperature was the main factor affecting the allocation of nitrogen in S. atopantha photosynthetic system, whereas at altitude 2700-3530 m, light could be the main affecting factor. No significant difference was observed in the SLA at different altitudes.     

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.     

Genetic variation in leaf pigment,optical and photosynthetic function among diverse phenotypes of <Emphasis Type="Italic">Metrosideros polymorpha</Emphasis> grown in a common garden

Coordinated variation has been reported for leaf structure, composition and function, across and within species, and theoretically should occur across populations of a species that span an extensive environmental range. We focused on Hawaiian keystone tree species Metrosideros polymorpha, specifically, 13-year old trees grown (2–4 m tall) in a common garden (approximately 1 ha field with 2–3 m between trees) from seeds collected from 14 populations along an altitude–soil age gradient. We determined the genetic component of relationships among specific leaf area (SLA), the concentrations of nitrogen (N) and pigments (chlorophylls, carotenoids, and anthocyanins), and photosynthetic light-use efficiency. These traits showed strong ecotypic variation; SLA declined 35% with increasing source elevation, and area-based concentrations of N, Chl a + b and Car increased by 50, 109 and 96%, respectively. Concentrations expressed on a mass basis were not well related to source elevation. Pigment ratios expressed covariation that suggested an increased capacity for light harvesting at higher source elevation; Chl/N and Car/Chl increased with source elevation, whereas Chl a/b declined; Chl a/b was higher for populations on younger soil, suggesting optimization for low N supply. Parallel trends were found for the photosynthetic reactions; light-saturated quantum yield of photosystem II (Φ _PSII) and electron transport rate (ETR) increased with source elevation. Correlations of the concentrations of photosynthetic pigments, pigment ratios, and photosynthetic function across the ecotypes indicated a stoichiometric coordination of the components of the light-harvesting antennae and reaction centers. The constellation of coordinated morphological, biochemical and physiological properties was expressed in the leaf reflectance and transmittance properties in the visible and near-infrared wavelength region (400–950 nm), providing an integrated metric of leaf status among and between plant phenotypes.     

Flexible and reversible responses to different irradiance levels during photosynthetic acclimation of Cypripedium guttatum

Cypripedium guttatum can be found both in open and shady habitats. Photosynthetic acclimation of C. guttatum to different light availabilities was detected using measurements of chlorophyll fluorescence, photosynthesis and leaf traits. When growing under low light conditions, C. guttatum exhibited a greater efficiency in photochemical utilization of absorbed light energy, and a lower ability for non-photochemical dissipation of excess light energy, as compared to the plants growing under high light conditions. Under intermediate light conditions, C. guttatum exhibited higher photosynthetic capacity (A(max)) than those under both low light or high light conditions. The differences in A(max) among three light environments was linked to the differences in biochemical efficiency, leaf N content (LNC) and leaf dry mass per unit area (LMA), but not to the differences of chlorophyll content. However, there were no significant differences in the light compensation points (LCP) and light saturation points (LSP) for photosynthesis for the plants growing under the three light conditions. These results indicate that the photosynthetic capacity of C. guttatum leaves allows for flexible and reversible responses to different irradiance levels. Photosynthetic acclimation in C. guttatum was affected by biochemical changes, the changes in LMA and ratio of Chl a/b. Successful acclimation of C. guttatum to a broad range of light levels likely allows for its wide geographical distribution. A level of about 45% sunlight appears to be optimal for photosynthesis.