Changes in mesophyll anatomy and sink–source relationships during leaf development in Quercus glauca, an evergreen tree showing delayed leaf greening

Changes in mesophyll anatomy, gas exchange, and the amounts of nitrogen and cell wall constituents including cellulose, hemicellulose and lignin during leaf development were studied in an evergreen broad‐leaved tree, Quercus glauca, and in an annual herb, Phaseolus vulgaris. The number of chloroplasts per whole leaf in P. vulgaris increased and attained the maximal level around 10 d before full leaf area expansion (FLE), whereas it continued to increase even after FLE in Q. glauca. The increase in the number of palisade tissue cells per whole leaf continued until a few days before FLE in Q. glauca, but it had almost ceased by 10 d before FLE in P. vulgaris. The radius and height of palisade tissue cells in Q. glauca, attained their maximal levels at around FLE whereas the thickness of the mesophyll cell wall and concentrations of the cell wall constituents increased markedly after FLE. These results clearly indicated that, in Q. glauca, chloroplast development proceeded in parallel with the cell wall thickening well after completion of the mesophyll cell division and cell enlargement. The sink–source transition, defined to be the time when the increase in daily carbon exchange rate exceeds the daily increase in leaf carbon content, occurred before FLE in P. vulgaris but after FLE in Q. glauca. During leaf area expansion, the maximum daily increase in nitrogen content on a whole leaf basis (the maximum leaf areas were corrected to be identical for these species) in Q. glauca was similar to that in P. vulgaris. In Q. glauca, however, more than 70% of nitrogen in the mature leaf was invested during its sink phase, whereas in P. vulgaris it was 50%. These results suggest that Q. glauca invests nitrogen for cell division for a considerable period and for chloroplast development during the later stages. We conclude that the competition for nitrogen between cell division and chloroplast development in the area of expanding leaves can explain different greening patterns among plant species.     

皖南亚热带常绿阔叶林林下灌木层主要树种叶片养分特征

对皖南亚热带常绿阔叶林林下灌木层主要树种草珊瑚〔Sarcandra glabra(Thunb.)Nakai〕、乌药〔Lindera aggregata(Sims)Kosterm.〕、香桂(Cinnamomum subavenium Miq.)、红楠(Machilus thunbergii Sieb.et Zucc.)、连蕊茶〔Camellia cuspidata(Kochs)H.J.Veitch〕、甜槠〔Castanopsis eyrei(Champ.ex Benth.)Tutch.〕、矩叶鼠刺(Itea oblonga Hand.-Mazz.)、红淡比(Cleyera japonica Thunb.)和小叶蚊母树〔Distylium buxifolium(Hance)Merr.〕叶片养分(包括C、N、P、K、Ca和Mg)含量、单位叶面积养分含量和比叶面积进行了测定,并分析了比叶面积与养分含量和单位叶面积养分含量的相关性。结果表明:9种树种叶片的C、N、P、K、Ca和Mg含量分别为438.09~492.31、9.79~15.60、0.33~2.06、11.39~32.52、3.84~13.34和2.85~14.05 g·kg-1,单位叶面积C、N、P、K、Ca和Mg含量分别为24.48~47.38、0.66~1.03、0.02~0.21、0.73~1.82、0.22~1.35和0.20~1.05 g·m-2,C/N比、C/P比和N/P比分别为31.40~47.88、227.76~1 495.66和5.26~32.90。9种树种叶片的比叶面积平均值为14.5 m2·kg-1,其中草珊瑚的比叶面积最大(17.90 m2·kg-1)、小叶蚊母树的比叶面积最小(9.89 m2·kg-1)。相关性分析结果表明:供试树种叶片的C/P比与N/P比间呈极显著正相关;比叶面积与叶片N含量呈显著正相关,与单位叶面积C、N和Ca含量分别呈极显著和显著负相关,与其他指标的相关性均不显著。综合分析结果表明:皖南亚热带常绿阔叶林下灌木层主要树种叶片的养分含量及比叶面积差异明显,其中,乌药、草珊瑚、矩叶鼠刺和香桂叶片的养分含量较高,而小叶蚊母树、红淡比和红楠的单位叶面积养分含量较高。     

柯-青冈常绿阔叶林优势树种叶片性状变异及适应策略

厘清叶片功能性状的变异及性状间的权衡关系,对揭示植物对环境变化的响应及适应策略具有重要意义。以中亚热带柯(Lithocarpus glaber)-青冈(Cyclobalanopsis glauca)常绿阔叶林为对象,测量了1 hm²固定监测样地内6个优势树种的叶面积(LA)、比叶面积(SLA)、干物质含量(LDMC)、叶片厚度(LT)、叶片碳(LC)、叶片氮(LN)、叶片磷(LP)含量和叶片碳氮比(LC ∶ LN)8个功能性状,采用多重比较、主成分分析(PCA)法分析了群落叶片功能性状的生活型、种内和种间变异及性状间关系。结果表明：(1)群落内叶片功能性状种内、种间差异显著,变异中等(CV： 0.02-0.59),其结构性状的可塑性较化学性状保守,变异格局符合"性状空间变异分割假说";针叶树种的LA、SLA显著低于阔叶树种,常绿树种的LC和LDMC最小,而落叶树种的SLA、LN和LP最大以及LT和LC ∶ LN最小。(2)群落叶片功能性状变异主要来源于生活型和种间变异,种内变异亦有显著贡献;生活型对多数性状的贡献率较大,其对LDMC、LC ∶ LN的贡献分别高达93.11%和91.76%;种间变异(LDMC除外)对结构性状的贡献率均高于化学性状;种内变异对LP的贡献率(23.66%)较种间变异高。(3)叶片性状之间多表现出显著相关关系,针叶树和阔叶树在PCA排序图中聚集于不同区域,叶经济型谱在柯-青冈群落中具有适用性。不同树种通过叶片结构、化学性状之间的权衡策略来适应环境变化,从而实现群落物种共存。结果可为理解森林群落物种的环境适应策略、预测群落动态变化和制定植被恢复措施提供科学依据。     

Changes in the photosynthetic light response curve during leaf development of field grown maize with implications for modelling canopy photosynthesis

Changes in the photosynthetic light-response curve during leaf development were determined for the fourth leaf of maize crops sown on 23 April and 10 June. Temperatures were unusually mild during late spring/early summer and neither crop experienced chilling damage. The concept of thermal time was used to take into account the effects of different temperature regimes on developmental stage, thereby enabling photosynthetic light-response data to be combined for both crops to describe the general response. Large variations in the upper asymptote (A_sat) and convexity () of the light-response curve occurred during leaf development, but the maximum quantum yield of CO₂ assimilation remained relatively constant throughout. Dark respiration rates showed a small but significant decrease with leaf age and generally ranged between 5 and 10% of A_sat. A simple mathematical model was developed to assess the sensitivity of daily leaf photosynthesis (A_L) to reductions in the A_sat, and the initial slope () of the light-response curve at different stages of leaf development. On bright sunny days, and at all developmental stages, A_L was ca. twice as sensitive to reductions in A_sat than to reductions in and . In overcast conditions, however, all three parameters contributed significantly to reductions in leaf photosynthesis, although the contribution of was greatest during early leaf growth, while older leaves were most sensitive to depressions in A_sat. The implications of these results for modelling the sensitivity of canopy photosynthesis to chill-induced photoinhibition of the light-response curve are discussed.     

Variations in leaf anatomical characteristics drive the decrease of mesophyll conductance in poplar under elevated ozone

Decline in mesophyll conductance (g_m) plays a key role in limiting photosynthesis in plants exposed to elevated ozone (O₃). Leaf anatomical traits are known to influence g_m, but the potential effects of O₃-induced changes in leaf anatomy on g_m have not yet been clarified. Here, two poplar clones were exposed to elevated O₃. The effects of O₃ on the photosynthetic capacity and anatomical characteristics were assessed to investigate the leaf anatomical properties that potentially affect g_m. We also conducted global meta-analysis to explore the general response patterns of g_m and leaf anatomy to O₃ exposure. We found that the O₃-induced reduction in g_m was critical in limiting leaf photosynthesis. Changes in liquid-phase conductance rather than gas-phase conductance drive the decline in g_m under elevated O_3, and this effect was associated with thicker cell walls and smaller chloroplast sizes. The effects of O₃ on palisade and spongy mesophyll cell traits and their contributions to g_m were highly genotype-dependent. Our results suggest that, while anatomical adjustments under elevated O₃ may contribute to defense against O₃ stress, they also cause declines in g_m and photosynthesis. These results provide the first evidence of anatomical constraints on g_m under elevated O₃.     

毛竹扩张对亚热带常绿阔叶林主要树种叶结构型性状的影响

毛竹扩张对常绿阔叶林生态系统的影响问题已成为近年国内外关注的热点问题之一。通过对常绿阔叶林和竹阔混交林内甜槠、青冈、枳椇以及青榨槭4树种主要叶结构型性状的调查与测定,分析毛竹扩张对常绿阔叶林主要树种叶结构型性状的影响。结果表明:(1)毛竹扩张不会显著改变乔木层4树种总体叶结构型性状特征。(2)不同生活型阔叶树种对毛竹扩张的响应策略不同。受毛竹扩张影响,常绿阔叶树种叶组织密度(LTD,leaf tissue density)显著减小;落叶阔叶树种叶宽(LW,leaf width)显著减小,叶形态指数(LMI,leaf morphology index)则显著增大。(3)毛竹扩张会使乔木层4树种间部分叶结构型性状差异特征发生改变,竹阔混交林中乔木层4树种间LMI、LTD、比叶面积(SLA,specific leaf area)及叶干物质含量(LDMC,leaf dry matter content)的差异特征不同于常绿阔叶林;毛竹向常绿阔叶林扩张后,甜槠叶长(LL,leaf length)、LW及叶面积(LA,leaf area)显著增大;青冈LMI显著增大,LDMC和LTD显著减小;枳椇的LMI显著增大,LW、LTD显著减小;青榨槭的LW显著减小。(4)毛竹扩张会造成乔木层树种部分叶结构型性状间关系发生改变,使林木的LL与LW、LA与LW间的截距减小,造成林木LL与LW、LA与LW之间的数量关系发生改变。     

亚热带常绿阔叶林木本植物幼树阶段抽枝展叶的权衡关系

亚热带常绿阔叶林植物幼树阶段适应林内生境并开枝散叶是其长成大树的一个重要过程, 植物一年内多次抽枝的现象及其在抽枝展叶过程中小枝伸长、枝茎增粗与叶面积的增加优先顺序及其内在驱动机制还有待进一步研究。该研究对青城山常绿阔叶林木本植物多次抽枝发生比例进行了调查, 并以茶(Camellia sinensis)、细枝柃(Eurya loquaiana)、短刺米槠(Castanopsis carlesii var. spinulosa)、润楠(Machilus nanmu)和大叶山矾(Symplocos grandis) 5种植物的幼树为研究对象, 比较分析了植物在多次抽枝中小枝和叶片生长动态及适应策略的差异。结果显示: 1)一、二次抽枝分别开始于春季(4月)和夏末(8月下旬), 小枝水平上二次抽枝率乔木小于灌木, 常绿植物小于落叶植物。2)一次抽枝小枝枝长、单叶面积, 小枝直径和叶片数量(除大叶山矾外)均高于二次抽枝, 但二次抽枝单叶面积相对生长速率均高于一次抽枝, 二次抽枝叶片比叶质量(LMA)的增长速率高于一次抽枝。3)一次抽枝小枝枝长、叶片数量、小枝直径(除细枝柃和短刺米槠外)和总叶面积(除短刺米槠外)最大相对生长速率均高于二次抽枝, 且大部分物种最大相对生长速率出现在抽枝开始的第一、二周。4)两次抽枝中, 物种先侧重于叶片的生长, 其次是小枝枝长的生长, 最后是小枝直径的增粗。单叶面积和总叶面积皆随着小枝枝长和小枝直径的增加呈显著的异速生长关系, 表明叶片的增长速度大于小枝。单叶面积与叶片数呈显著大于1的异速生长关系, 暗示单叶面积的增长速度大于叶片数的增加速度。小枝枝长与小枝直径也呈显著大于1的异速生长关系, 揭示小枝枝长的增长速度大于小枝直径。综上所述, 两次抽枝过程中, 植物枝叶的优先生长顺序反映了植物为获取更多的资源(尤其是光源)而形成特定的抽枝展叶策略; 二次抽枝单叶面积相对生长速率和LMA增长速率高于一次抽枝, 这可能与植物即将面临的昆虫取食和气温降低压力有关。因此, 了解植物抽枝策略对于理解物种生态适应机制, 揭示物种生活史过程中存在的权衡关系具有重要的理论意义。     

Low stomatal and internal conductance to CO2 versus Rubisco deactivation as determinants of the photosynthetic decline of ageing evergreen leaves

A novel A-Ci curve (net CO2 assimilation rate of a leaf -An- as a function of its intercellular CO2 concentration -Ci) analysis method (Plant, Cell & Environment 27, 137-153, 2004) was used to estimate the CO2 transfer conductance (gi) and the maximal carboxylation (Vcmax) and electron transport (Jmax) potentials of ageing, non-senescing Pseudotsuga menziesii leaves in relation to their nitrogen (N) content and protein and pigment composition. Both gi and the stomatal conductance (gsc) of leaves were closely coupled to Vcmax, Jmax and An with all variables decreasing with increasing leaf age. Consequently, both Ci and Cc (chloroplastic CO2 concentration) remained largely conserved through successive growing seasons. The N content of leaves, as well as the amount of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and other sodium dodecyl sulfate-soluble proteins, increased during the first three growing seasons, then stabilized or decreased only slightly afterwards. Thus, the age-related photosynthetic nitrogen use efficiency (PNUE) decline of leaves was not a consequence of decreased allocation of N towards Rubisco and other proteins involved in bioenergetics and light harvesting. Rather, loss of photosynthetic capacity was the result of the decreased activation state of Rubisco and proportional down-regulation of electron transport towards the photosynthetic carbon reduction (PCR) and photorespiratory (PCO) cycles in response to a reduction of CO2 supply to the chloroplasts' stroma. This study emphasizes the regulatory potential and homeostaticity of Cc- rather than photosynthetic metabolites or Ci- in relation to the commonly observed correlation between photosynthesis and gsc.     

A model explaining genotypic and ontogenetic variation of leaf photosynthetic rate in rice (Oryza sativa) based on leaf nitrogen content and stomatal conductance

BACKGROUNDS AND AIMS: Identification of physiological traits associated with leaf photosynthetic rate (Pn) is important for improving potential productivity of rice (Oryza sativa). The objectives of this study were to develop a model which can explain genotypic variation and ontogenetic change of Pn in rice under optimal conditions as a function of leaf nitrogen content per unit area (N) and stomatal conductance (g(s)), and to quantify the effects of interaction between N and g(s) on the variation of Pn. METHODS: Pn, N and g(s) were measured at different developmental stages for the topmost fully expanded leaves in ten rice genotypes with diverse backgrounds grown in pots (2002) and in the field (2001 and 2002). A model of Pn that accounts for carboxylation and CO diffusion processes, and assumes that the ratio of internal conductance to g(s) is constant, was constructed, and its goodness of fit was examined. KEY RESULTS: Considerable genotypic differences in Pn were evident for rice throughout development in both the pot and field experiments. The genotypic variation of Pn was correlated with that of g(s) at a given stage, and the change of Pn with plant development was closely related to the change of N. The variation of g(s) among genotypes was independent of that of N. The model explained well the variation in Pn of the ten genotypes grown under different conditions at different developmental stages. Conclusions The response of Pn to increased N differs with g(s), and the increase in Pn of genotypes with low g(s) is smaller than that of genotypes with high g(s). Therefore, simultaneous improvements of these two traits are essential for an effective breeding of rice genotypes with increased Pn.     

十万大山山地常绿阔叶林群落物种组成与结构特征

十万大山是广西生物多样性热点区域之一,其主要植被类型是山地常绿阔叶林。为了解区域内山地常绿阔叶林的群落现状及优势种群结构的发展现状,该文以十万大山山地常绿阔叶林1 hm²固定监测样地中胸径(DBH)≥1 cm的木本植物为研究对象,分析其物种组成、径级结构、树高结构并用g(r)函数分析优势种的空间分布格局。结果表明:(1)群落中DBH≥1 cm的木本植物共计7 517株,隶属52科108属153种; 群落的优势种有云南桤叶树(Clethra delavayi)、银木荷(Schima argentea)、毛折柄茶(Hartia villosa)、红锥(Castanopsis hystrix)、黄杞(Engelhardtia roxburghiana)、罗伞树(Ardisia quinquegona)、鼠刺(Itea chinensis)、腺叶山矾(Symplocos adenophylla)、假杨桐(Eurya subintegra)、毛冬青(Ilex pubescens),但优势种的优势地位不明显。(2)群落整体平均DBH为5.51 cm,径级、树高分布呈近似倒“J”型; 优势种的径级分布多呈倒“J”型或“L”型,群落有较强的更新能力。(3)群落优势种稳定共存; 优势种在样地中呈聚集分布,但优势种间聚集分布的位置有差异。总体而言,群落目前更新状态良好,群落中已有顶极群落优势种的存在,但群落具有一定的次生性特征,还未到达稳定的顶极群落状态,优势种间能稳定共存,有向稳定顶极群落演替的潜力,应继续加强管护,促进十万大山山地常绿阔叶林群落的更新与生存。     

Leaf age and season influence the relationships between leaf nitrogen, leaf mass per area and photosynthesis in maple and oak trees

Abstract. Seasonal changes in photosynthesis, leaf nitrogen (N) contents and leaf mass per area (LMA) were observed over three growing seasons in open-grown sun-lit leaves of red maple ( Acer rubrum ), sugar maple ( A. sacchamm ) and northern pin oak ( Quereus ellipsoidalis ) trees in southern Wisconsin. Net photosynthesis and leaf N were highly linearly correlated on both mass and area bases within all species from late spring until leaf senescence in fall. Very early in the growing season leaves had high N concentrations, but low photosynthetic rates per unit leaf N, suggesting that leaves were not fully functionally developed at that time. Leaf N per unit area and LMA had nonparallel seasonal patterns, resulting in differing relationships between leaf N/area and LMA in the "early versus late growing season. As a result of differences in seasonal patterns between leaf N/area and LMA, net photosynthesis/area was higher for a given LMA in the spring than fall, and the overall relationships between these two parameters were poor.     

Complex adjustments of photosynthetic potentials and internal diffusion conductance to current and previous light availabilities and leaf age in Mediterranean evergreen species Quercus ilex

Mature non-senescent leaves of evergreen species become gradually shaded as new foliage develops and canopy expands, but the interactive effects of integrated light during leaf formation (Q(int)G), current light (Q(int)C) and leaf age on foliage photosynthetic competence are poorly understood. In Quercus ilex L., we measured the responses of leaf structural and physiological variables to Q(int)C and Q(int)G for four leaf age classes. Leaf aging resulted in increases in leaf dry mass per unit area (M(A)), and leaf dry to fresh mass ratio (D(F)) and decreases in N content per dry mass (N(M)). N content per area (N(A)) was independent of age, indicating that decreases in N(M) reflected dilution of leaf N because of accumulation of dry mass (NA = N(M) M(A)). M(A), D(F) and N(A) scaled positively with irradiance, whereas these age-specific correlations were stronger with leaf growth light than with current leaf light. Area-based maximum ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylase activity (V(cmax)A), capacity for photosynthetic electron transport (J(max)A) and the rate of non-photorespiratory respiration in light (R(d)A) were also positively associated with irradiance. Differently from leaf structural characteristics, for all data pooled, these relationships were stronger with current light with little differences among leaves of different age. Acclimation to current leaf light environment was achieved by light-dependent partitioning of N in rate-limiting proteins. Mass-based physiological activities decreased with increasing leaf age, reflecting dilution of leaf N and a larger fraction of non-photosynthetic N in older leaves. This resulted in age-dependent modification of leaf photosynthetic potentials versus N relationships. Internal diffusion conductance (g(m)) per unit area (g(m)A) increased curvilinearly with increasing irradiance for two youngest leaf age classes and was independent of light for older leaves. In contrast, g(m) per dry mass (g(m)M) was negatively associated with light in current-year leaves. Greater photosynthetic potentials and moderate changes in diffusion conductance resulted in greater internal diffusion limitations of photosynthesis in higher light. Both area- and mass-based g(m) decreased with increasing leaf age. The decrease in diffusion conductance was larger than changes in photosynthetic potentials, leading to larger CO2 drawdown from leaf internal air space to chloroplasts (delta(c)) in older leaves. The increases in diffusion limitations in older leaves and at higher light scaled with age- and light-dependent increases in MA and D(F). Overall, our study demonstrates a large potential of foliage photosynthetic acclimation to changes in leaf light environment, but also highlights enhanced structural diffusion limitations in older leaves that result from leaf structural acclimation to previous rather than to current light environment and accumulation of structural compounds with leaf age.     

浙江天童常绿阔叶林栲树种子雨的时空格局

在浙江天童常绿阔叶林中选择5株栲树,通过种子筐和地表取样,分析了栲树种子雨的时空格局特征.结果表明,栲树种子雨从11月3日到12月16日,持续45d,存在散落的高峰期(11月18日～27日);散落在地表的种子雨主要集中在离母株树干1.5～5.5m区段内,占总数的85.6%,最远不超过8m,空间格局符合二次分布;整个种子雨期间,单株平均落果数为112.8个·m^-2(70个·m^-2～239.5个·m^-2),东南向较多(135.6个·m^-2)、西北向较少(86.8个·m^-2),但无显著差异;种子雨中有活力的坚果占总数的27.3%、未成熟的占25.7%,昆虫幼虫侵害的占42%,松鼠啃食的占5%.     

Mesophyll conductance in land surface models: effects on photosynthesis and transpiration

The CO₂ transfer conductance within plant leaves (mesophyll conductance, g_m) is currently not considered explicitly in most land surface models (LSMs), but instead treated implicitly as an intrinsic property of the photosynthetic machinery. Here, we review approaches to overcome this model deficiency by explicitly accounting for g_m, which comprises the re‐adjustment of photosynthetic parameters and a model describing the variation of g_m in dependence of environmental conditions. An explicit representation of g_m causes changes in the response of photosynthesis to environmental factors, foremost leaf temperature, and ambient CO₂ concentration, which are most pronounced when g_m is small. These changes in leaf‐level photosynthesis translate into a stronger climate and CO₂ response of gross primary productivity (GPP) and transpiration at the global scale. The results from two independent studies show consistent latitudinal patterns of these effects with biggest differences in GPP in the boreal zone (up to ~15%). Transpiration and evapotranspiration show spatially similar, but attenuated, changes compared with GPP. These changes are indirect effects of g_m caused by the assumed strong coupling between stomatal conductance and photosynthesis in current LSMs. Key uncertainties in these simulations are the variation of g_m with light and the robustness of its temperature response across plant types and growth conditions. Future research activities focusing on the response of g_m to environmental factors and its relation to other plant traits have the potential to improve the representation of photosynthesis in LSMs and to better understand its present and future role in the Earth system.     

金华北山常绿阔叶林群落结构及优势乔木树种更新类型

以金华北山常绿阔叶林为对象,对群落的结构特征和优势乔木树种的更新进行调查研究。根据调查统计,群落共有维管植物66科115属144种,木本植物中的常绿阔叶树种以壳斗科、樟科、山茶科为主,达到62.96%,体现了亚热带常绿阔叶林的特点。该群落可划分为乔木层、灌木层、草本层和层间4个层次,其物种多样性表现出灌木层乔木层层间草本层的特点。根据径级频率分布形状,将各树种的种群结构归纳为4种类型,并结合各种群的生物学和生态学特性,分别讨论其更新类型,同时对群落所处的演替阶段进行诊断。结果为:(1)群落的建群种为木荷、苦槠,枫香、马尾松等也占有一定优势。(2)种群结构为逆-J字型的木荷、苦槠、香樟,耐荫性强,可以通过实生和萌生两种方式实现种群的更新,是顶极群落的优势种;L型的木、女贞、格药柃等均为常绿阔叶小乔木或者大灌木,是顶极群落亚乔木层和灌木层的主要组成种;间歇型的枫香、麻栎、锥栗等,种群结构具有机会性和波动性,体现出顶级性先锋种的特性;纺锤型的白栎、马尾松和杉木为高大阳性树种,是演替序列中的先锋种,在此群落中种群更新不足,已表现出衰退的迹象。(3)该群落正处于顶级演替的前期,并未达到最终阶段,将进一步向以木荷、苦槠为优势种的方向发展。     

The effect of growth irradiance on leaf anatomy and photosynthesis in Acer species differing in light demand

Variation in light demand is a major factor in determining the growth and survival of trees in a forest. There is strong relation between the light‐demand and the effect of growth irradiance on leaf morphology and photosynthesis in three Acer species: A. rufinerve (light‐demanding), A. mono (intermediate) and A. palmatum (shade‐tolerant). The increase in mesophyll thickness and surface area of chloroplasts facing the intercellular airspaces (S_c) with growth irradiance was highest in A. rufinerve. Although the increase in light‐saturated photosynthesis (A_max) was similar among the species, the increase in water use efficiency (WUE) was much higher in A. rufinerve than that in the other species, indicating that the response to water limitation plays an important role in leaf photosynthetic acclimation to high light in A. rufinerve. The low CO₂ partial pressure at the carboxylation site (C_c) in A. rufinerve (130 µmol mol^?1) at high irradiance was caused by low stomatal and internal conductance to CO₂ diffusion, which minimized the increase in A_max in A. rufinerve despite its high Rubisco content. Under shade conditions, interspecific differences in leaf features were relatively small. Thus, difference in light demand related to leaf acclimation to high light rather than that to low light in the Acer species.     

哀牢山中山湿性常绿阔叶林木径向生长季节动态及其对气候因子的响应

研究采用树木生长环在哀牢山中山湿性常绿阔叶林持续9年(2009—2017年)监测了2个常绿树种(厚皮香,Ternstroemia gymnanthera;南亚枇杷,Eriobotrya bengalensis)和2个落叶树种(西桦,Betula alnoides;珍珠花,Lyonia ovalifolia)的树干月生长量,采用逻辑斯蒂生长模型(Logistic model)模拟树木径向生长量和物候参数,并分析了年、季尺度上径向生长与主要气候因子的关系。结果表明:1)4个树种年平均生长量为6.3 mm,落叶树种年平均生长量(10.6 mm/a)显著高于常绿树种(3.0 mm/a);2)雨季(5—10月)是哀牢山中山湿性常绿阔叶林树木生长的主要时期,4个树种雨季平均生长量为5.9 mm,占全年总生长量的93%,其中落叶树种雨季生长量占全年的96%,而常绿树种雨季生长量占全年的86%;3)常绿树种生长季长度为169天,长于落叶树种(137天),而落叶树种最大生长速率(0.14 mm/d)显著高于常绿树种(0.03 mm/d),最大径向生长速率能很好地预测树种年生长量;4)低温、雾日和光合有效...     

不同干扰背景下栲树（Castanopsis fargesii）幼苗幼树的生理生态特性比较——以浙江天童常绿阔叶林为例

浙江天童国家森林公园的常绿阔叶林在我国东南沿海地区具有代表性,在研究区内设置不同干扰方式下的5块样地,借助LI-6400型便携式光合测定系统对研究区内不同干扰背景下5块样地常绿阔叶林主要优势种之一的栲树幼苗、幼树的光合生理生态特性进行了测定。比较了不同干扰背景下栲树幼苗、幼树的净光合作用速率、蒸腾作用速率、水分利用效率、表观量子效率等生理生态指标。结果表明,去除乔木层的样地1,2,3中栲树幼苗、幼树的净光合速率与蒸腾速率要高于仅保留乔木层的样地4和对照样地5,水分利用效率和表观量子效率则低于样地5和样地4。应用统计分析软件对净光合作用速率与诸生理生态影响因子的相关性进行分析,同时使用逐步回归的方法建立光合速率和诸影响因子之间的回归方程模型,栲树幼苗:Pn=-2.399 0.205Ta 43.209Gs,栲树幼树:Pn=-2.265 0.006PAR-3.915Vpdl 0.364Ta 38.121Gs,在α=0.05水平上,两个方程均有显著性意义,有良好的预测性。     

常绿阔叶林外生、内生菌根树种细根化学计量学性状对N添加的响应

为揭示不同菌根类型树种细根化学计量学性状对N添加的塑性响应,在福建省建瓯市万木林自然保护区常绿阔叶林内选择外生菌根树种罗浮栲(Castanopsis faberi)和内生菌根树种木荷(Schima superba)为研究对象,采用根袋法开展N添加试验,细根在根袋内生长半年后测定化学计量学指标(C、N、P、C/N、N/P、C/P)。结果表明:根序对细根化学计量学性状有显著影响,随着根序的增加,罗浮栲与木荷细根C浓度、C/N、C/P明显增加,N浓度与P浓度明显下降。N添加对细根C、N浓度均有极显著的促进作用,但对细根P浓度影响不显著,从而导致细根C/N维持稳定,但N/P、C/P升高,细根受P限制增加。细根化学计量学性状对N添加的塑性响应在不同序级间以及在外生菌根树种罗浮栲和内生菌根树种木荷之间均无显著差异。结论表明,研究所选内生、外生菌根树种细根化学计量学性状对N添加具有基本相似的响应。