記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER HEIDELBERG  

We observed the formation of latewood tracheids with narrow diameters and thick walls and the disappearance of stored starch around the cambium on the locally heated region of stems in evergreen conifer Chamaecyparis pisifera during winter cambial dormancy.
Wood formation is controlled by cambial cell division, which determines the quantity and quality of wood. We investigated the factors that control cambial activity and the formation of new tracheids in locally heated stems of the evergreen conifer Chamaecyparis pisifera. Electric heating tape was wrapped around one side of the stem, at breast height, of two trees in 2013 and two in 2014. Pairs of stems were locally heated in winter, and small blocks were collected from heated and non-heated regions of stems. Cambial activity and levels of stored starch around the cambium were investigated by microscopy. Cambial reactivation and xylem differentiation occurred earlier in heated than in non-heated regions. New cell plates were formed after 14-18 days of heating. After a few layers of tracheids with large diameters and thin walls had formed, cell division and cell enlargement during differentiation were inhibited. Tracheids with narrow diameters and thick walls, defining those as latewood, were formed near the cambium, and finally, four to six layers of tracheids were induced. After cambial reactivation, amounts of stored starch started to decrease and starch disappeared completely from phloem and xylem cells that were located near the cambium during the differentiation of heated regions. Our results suggest that an increase in temperature induces the conversion of stored starch to soluble sugars for continuous cambial cell division and earlywood formation. By contrast, a shortage of stored starch might be responsible for inhibition of cambial activity and induction of the formation of latewood tracheids.

DOI： 10.1007/s00468-016-1395-4

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Background and Aims In temperate regions, trees undergo annual cycles of cambial growth, with periods of cambial activity and dormancy. Environmental factors might regulate the cambial growth, as well as the development of cambial derivatives. We investigated the effects of low temperature by localized cooling on cambial activity and latewood formation in two conifers, Chamaecyparis obtusa and Cryptomeria japonica.
Methods A plastic rubber tube that contained cooled water was wrapped around a 30-cm-wide portion of the main stem of Chamaecyparis obtusa and Cryptomeria japonica trees during seasons of active cambium. Small blocks were collected from both cooled and non-cooled control portions of the stems for sequential observations of cambial activity and for anatomical measurements of cell morphology by light microscopy and image analysis.
Key Results The effect of localized cooling was first observed on differentiating tracheids. Tracheids narrow in diameter and with significantly decreased cambial activity were evident 5 weeks after the start of cooling in these stems. Eight weeks after the start of cooling, tracheids with clearly diminished diameters and thickened cell walls were observed in these stems. Thus, localized low temperature induced narrow diameters and obvious thickening of secondary cell walls of tracheids, which were identified as latewood tracheids. Two months after the cessation of cooling, a false annual ring was observed and cambium became active again and produced new tracheids. In Cryptomeria japonica, cambial activity ceased earlier in locally cooled portions of stems than in non-cooled stems, indicating that the cambium had entered dormancy sooner in the cooled stems.
Conclusions Artificial cooling of stems induced latewood formation and cessation of cambial activity, indicating that cambium and its derivatives can respond directly to changes in temperature. A decrease in the temperature of the stem is a critical factor in the control of cambial activity and xylem differentiation in trees.

DOI： 10.1093/aob/mcv181

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER HEIDELBERG  

Earlywood width in Quercus crispula increased from 1970 to 2004 without changes of vessel anatomy and ring growth.
The increase in diameter of a tree stem is an important indicator of forest productivity. Xylem traits, such as the number and cross-sectional area of earlywood vessels, are also critical parameters of forest growth because of the physiological and structural contribution of xylem to the growth of the tree stem. Forest productivity appears to be affected by climate change and, indeed, trees might be expected to acclimate to gradual long-term climate change. The aim of this study was to identify long-term changes in increases in stem diameter and in earlywood vessels by examining tree rings of Quercus crispula. Focusing on 20 mature specimens of Q. crispula, we examined annual ring growth from 1970 to 2004 and measured earlywood traits, namely, the width, cross-sectional area (henceforth referred to as area) and number of earlywood vessels, by digital image analysis. We developed a hierarchical Bayesian model for detection of long-term trends in these traits. We found that earlywood width, as well as the total number and area of earlywood vessels, increased during the 35 years under analysis. One possible cause of these changes might be the long-term elevation of temperatures in early spring, which determine the timing of the onset of cambial reactivation from winter dormancy. In contrast to the long-term changes, short-term, yearly changes in earlywood traits fluctuated to a smaller extent than yearly changes in tree ring width. Therefore, the observed long-term changes in earlywood appear to represent acclimation to long-term climate change.

DOI： 10.1007/s00468-015-1206-3

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：BOTANICAL SOC AMER INC  

Premise of the study: Differences in leaf size are expected to be coordinated with various shoot traits and branching intensity because these relationships will influence light capture efficiency, water use, and biomechanics. Previous studies have mainly focused on interspecific patterns of these trait relationships, but not on intraspecific patterns at the geographic scale. We investigated intraspecific variation in shoot traits and branching intensity of Fagus crenata in Japan.
Methods: Allometric relationships between the traits of current-year shoots and branching intensity per branch unit of 1-m length on the main axis (BI) and its coordination with latitude were investigated using trees from 10 provenances in a common garden.
Key results: Individual trees originating from lower latitudes have smaller leaves with greater leaf mass per area and nitrogen content per area, greater Huber value (stem cross-sectional area per total leaf area [A(TL)]) of current-year shoots, and greater BI. Notably, the slope of the log-log relationship between BI and A(TL) was close to -1.0 across the trees from different source sites, implying that branching in this species occurs to control leaf area.
Conclusions: Shoot traits and branching intensity were apparently coordinated with leaf size to control leaf area deployment in this species. Such patterns probably reflect differences in competition for hydraulic conductance among nearby shoots within crowns, as a consequence of different meteorological conditions across the source sites.

DOI： 10.3732/ajb.1400559

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

The networks of vessel elements play a vital role in the transport of water from roots to leaves, and the continuous formation of earlywood vessels is crucial for the growth of ring-porous hardwoods. The differentiation of earlywood vessels is controlled by external and internal factors. The present study was designed to identify the limiting factors in the induction of cambial reactivation and the differentiation of earlywood vessels, using localized heating and disbudding of dormant stems of seedlings of a deciduous ring-porous hardwood, Quercus serrata.
Localized heating was achieved by wrapping an electric heating ribbon around stems. Disbudding involved removal of all buds. Three treatments were initiated on 1 February 2012, namely heating, disbudding and a combination of heating and disbudding, with untreated dormant stems as controls. Cambial reactivation and differentiation of vessel elements were monitored by light and polarized-light microscopy, and the growth of buds was followed.
Cambial reactivation and differentiation of vessel elements occurred sooner in heated seedlings than in non-heated seedlings before bud break. The combination of heating and disbudding of seedlings also resulted in earlier cambial reactivation and differentiation of first vessel elements than in non-heated seedlings. A few narrow vessel elements were formed during heating after disbudding, while many large earlywood vessel elements were formed in heated seedlings with buds.
The results suggested that, in seedlings of the deciduous ring-porous hardwood Quercus serrata, elevated temperature was a direct trigger for cambial reactivation and differentiation of first vessel elements. Bud growth was not essential for cambial reactivation and differentiation of first vessel elements, but might be important for the continuous formation of wide vessel elements.

DOI： 10.1093/aob/mcu026

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER JAPAN KK  

Because of their overwhelming size over other organisms, trees define the structural and energetic properties of forest ecosystems. From grasslands to forests, leaf area index, which determines the amount of light energy intercepted for photosynthesis, increases with increasing canopy height across the various terrestrial ecosystems of the world. In vertically well-developed forests, niche differentiation along the vertical gradient of light availability may promote species coexistence. In addition, spatial and temporal differentiation of photosynthetic traits among the coexisting tree species (functional diversity) may promote complementary use of light energy, resulting in higher biomass and productivity in multi-species forests. Trees have evolved retaining high phenotypic plasticity because the spatial/temporal distribution of resources in forest ecosystems is highly heterogeneous and trees modify their own environment as they increase nearly 1,000 times in size through ontogeny. High phenotypic plasticity may enable coexistence of tree species through divergence in resource-rich environments, as well as through convergence in resource-limited environments. We propose that the breadth of individual-level phenotypic plasticity, expressed at the metamer level (leaves and shoots), is an important factor that promotes species coexistence and resource-use complementarity in forest ecosystems. A cross-biome comparison of the link between plasticity of photosynthesis-related traits and stand productivity will provide a functional explanation for the relationship between species assemblages and productivity of forest ecosystems.

DOI： 10.1007/s11284-012-1025-6

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s00425-013-1839-7

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Background and Aims Morphology of crown shoots changes with tree height. The height of forest trees is usually correlated with the light environment and this makes it difficult to separate the effects of tree size and of light conditions on the morphological plasticity of crown shoots. This paper addresses the tree-height dependence of shoot traits under full-light conditions where a tree crown is not shaded by other crowns.
Methods Focus is given to relationships between tree height and top-shoot traits, which include the shoot's leaf-blades and non-leafy mass, its total leaf-blade area and the length and basal diameter of the shoot's stem. We examine the allometric characteristics of open-grown current-year leader shoots at the tops of forest tree crowns up to 24 m high and quantify their responses to tree height in 13 co-occurring deciduous hardwood species in a cool-temperate forest in northern Japan.
Key Results Dry mass allocated to leaf blades in a leader shoot increased with tree height in all 13 species. Specific leaf area decreased with tree height. Stem basal area was almost proportional to total leaf area in a leader shoot, where the proportionality constant did not depend on tree height, irrespective of species. Stem length for a given stem diameter decreased with tree height.
Conclusions In the 13 species observed, height-dependent changes in allometry of leader shoots were convergent. This finding suggests that there is a common functional constraint in tree-height development. Under full-light conditions, leader shoots of tall trees naturally experience more severe water stress than those of short trees. We hypothesize that the height dependence of shoot allometry detected reflects an integrated response to height-associated water stress, which contributes to successful crown expansion and height gain.

DOI： 10.1093/aob/mcr228

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

The diameter growth of trees may vary depending on the tree size, species and other tree-related factors. However, such variation is challenging to consider while estimating the growth response to weather conditions. This study investigated the effects of the weather conditions and variations in tree factors on diameter growth in a mature forest. In particular, we focused on diameter growth in June, the month of active diameter growth. We recorded the monthly diameter growth of 6 tree species for 7 years and constructed a generalized linear mixed model in which the mean growth was dependant on tree size, weather conditions, and the interaction between tree size and weather.
The estimated growth responses to weather factors were different among species. but their interaction to tree size was unclear in all species. Sensitivity analysis of growth rate to weather conditions, such as temperature and precipitation, showed that the sensitivity to weather depended both on tree size and tree species. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.foreco.2009.12.012

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS  

Within a canopy, spatial variation in leaf traits may be determined by light and nutrient availabilities. Such environmentally caused changes in leaf traits may be an important cause of changes in leaf palatability to herbivores. We conducted a factorial experiment with fertilization and selective cutting in a northern Japanese forest dominated by oak (Quercus crispula Blume). Fertilization increased the nitrogen content of upper canopy leaves. Leaf mass per area (LMA) was greater in the upper canopy than in the lower canopy. Selective cutting and all interactions had significant effects oil LMA. Total phenolics mid condensed tannin in leaves were also greater in the upper canopy than in the lower canopy. The interaction of selective cutting X position in the canopy (upper or lower) had a significant effect oil total phenolics: a similar trend was seen for condensed tannin. Herbivory was greater in the lower canopy than ill file upper canopy. Also. fertilization increased herbivory, whereas selective Cutting decreased it. These results imply that human activities, such IS logging and nitrogen deposition, may strongly influence spatial variation in herbivory through changes in leaf traits.

DOI： 10.1139/X08-006

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER TOKYO  

Recent studies suggest that physiological traits can be affected by tree size due to stronger hydraulic limitation in taller trees. As trees vary greatly in size, both within and among species, the adaptive responses to hydraulic limitation may be different among species with different maximum sizes. To investigate this, we explored size-dependency in photosynthetic and hydraulic parameters of three Acer species (Acer mono Maxim., Acer amoenum Carr and Acer japonicum Thunb.) using trees of various sizes under well-lit conditions. Leaf stomatal conductance of the Acer species decreased with tree size, implying that water supply to leaves decreases as trees grow. In contrast, content of nitrogen increased with tree size, which may compensate for the decrease in stomatal conductance to maintain the photosynthetic rate. Although the increase in nitrogen and leaf mass per area were larger in species with larger statures, the size-dependency in stomatal conductance was not different among species, and photosynthetic rate and hydraulic conductance were maintained in the three Acer species. Therefore, we suggest that hydraulic limitation on gas exchange does not necessarily depend on the maximum height of the species and that maintenance of photosynthesis and hydraulic properties is a fundamental physiological process during tree growth.

DOI： 10.1007/s11284-007-0374-z

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：HERON PUBLISHING  

Understanding seasonal changes in photosynthetic characteristics of canopy leaves is indispensable for modeling the carbon balance in forests. We studied seasonal changes in gas exchange characteristics that are related to the temperature dependence of photosynthesis in canopy leaves of Quercus crispula Blume, one of the most abundant species in cool-temperate forests in Japan. Photosynthetic rate and ribulose- 1,5-bisphosphate (RuBP) carboxylation capacity (V-cmax) at 20 degrees C increased from June to August and then decreased in September. The activation energy of V-cmax a measure of the temperature dependence of V-cmax, was highest in summer, indicating that V-cmax was most sensitive to leaf temperature at this time. The activation energy of V-cmax was significantly correlated with growth temperature. Other parameters related to the temperature dependence of photosynthesis, such as intercellular CO2 partial pressure and temperature dependence of RuBP regeneration capacity, showed no clear seasonal trend. It was suggested that leaf senescence affected the balance between carboxylation and regeneration of RuBP. The model simulation showed that photosynthetic rate and its optimal temperature were highest in summer.

DOI： 10.1093/treephys/27.7.1035

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：HERON PUBLISHING  

We examined open-grown Acer mono Maxim. trees of different sizes to test the hypotheses that (1) hydraulic limitation increases with tree size, thereby reducing photosynthesis, and (2) photosynthetic water- and nitrogen-use efficiencies change with tree size. Maximum net assimilation rate per unit dry mass was significantly lower in large trees than in small trees, whereas leaf nitrogen concentration increased with tree size. As a consequence, photosynthetic nitrogen-use efficiency decreased with increase in tree size. Photosynthetic water-use efficiency, however, increased with tree size, partly as a result of reduced stomatal conductance. Neither root-to-leaf hydraulic conductance nor minimum leaf water potential changed with tree size.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER-VERLAG TOKYO  

Understanding the induced resistance to herbivory in plants is important in elucidating plant life-history traits. Resistance to herbivory takes two basic forms: defense and tolerance. Induced defense plays an important role in the ecology and evolution of plant-herbivore interactions. It has become increasingly clear that induced defenses to herbivory are complex traits involving the interaction of intrinsic and extrinsic factors. In this study, we investigated the effects of herbivory and the availability of light on induced resistance in Quercus crispula saplings, and the relation between defense and tolerance involving photosynthesis and growth. We conducted field experiments with herbivorous insects under two light conditions. As an induced defense, the leaf mass per area increased with herbivory regardless of the amount of light available, and the concentration of condensed tannin was significantly higher when light was plentiful. On the other hand, as induced tolerance, the photosynthetic rate decreased with herbivory under conditions of ample light. In conclusion, we found that both the availability of light and herbivory affected defense and tolerance in Q. crispula. In addition, we suggest that the interaction between defense and tolerance was noticeable when much light was available because of the photosynthetic reduction caused by herbivory.

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記述言語：日本語   出版者・発行元：日本分析化学会  

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記述言語：日本語   出版者・発行元：日本生態学会暫定事務局  

本特集の基となった第55回日本生態学会福岡大会における生理生態学企画集会は、主に地上部を見て植物の生態を研究している研究者が地下部のどのような性質に注意をして研究をすすめていく必要があるのか、勉強する機会を設けるというコンセプトで開かれた。地下部の水透過性は環境に合わせて、アクアポリンを代表とするタンパク質の性質に依存し数十分のオーダーですばやく変化するとともに植物全体の水透過性に大きく影響する事、地上部の活動(蒸散)が地下部の活動(呼吸)と相関を持ち、地上部を見ているだけでは気づく事ができないコストが地下で発生している事、共生を介した栄養塩獲得能力が地上部と地下部を結ぶシグナルによって制御されている事、地下部にも地上部以上に機能分化したモジュールがありその機能ごとに場合分けが必要である事、これらの企画集会で紹介された研究結果は、地上部の研究者達にとって地下部は無視できないものである事を改めて認識させるに充分なインパクトがあったと思われる。本総括論文では、前半でまずこれらの研究成果について生態学的視点から振り返る。そして、後半では本特集によって見えて来た「地上部と地下部のつながりの理解のために必要な研究とはなにか」について、細根系の機能的ユニット、栄養塩吸収と水吸収のコスト、根の水分生理というトピックに分け、現状と展望を紹介していきたい。

DOI： 10.18960/seitai.59.1_71

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記述言語：日本語   出版者・発行元：日本生態学会  

本特集の基となった第55回日本生態学会福岡大会における生理生態学企画集会は、主に地上部を見て植物の生態を研究している研究者が地下部のどのような性質に注意をして研究をすすめていく必要があるのか、勉強する機会を設けるというコンセプトで開かれた。地下部の水透過性は環境に合わせて、アクアポリンを代表とするタンパク質の性質に依存し数十分のオーダーですばやく変化するとともに植物全体の水透過性に大きく影響する事、地上部の活動(蒸散)が地下部の活動(呼吸)と相関を持ち、地上部を見ているだけでは気づく事ができないコストが地下で発生している事、共生を介した栄養塩獲得能力が地上部と地下部を結ぶシグナルによって制御されている事、地下部にも地上部以上に機能分化したモジュールがありその機能ごとに場合分けが必要である事、これらの企画集会で紹介された研究結果は、地上部の研究者達にとって地下部は無視できないものである事を改めて認識させるに充分なインパクトがあったと思われる。本総括論文では、前半でまずこれらの研究成果について生態学的視点から振り返る。そして、後半では本特集によって見えて来た「地上部と地下部のつながりの理解のために必要な研究とはなにか」について、細根系の機能的ユニット、栄養塩吸収と水吸収のコスト、根の水分生理というトピックに分け、現状と展望を紹介していきたい。

DOI： 10.18960/seitai.59.1_71

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記述言語：日本語   出版者・発行元：一般社団法人日本森林学会  

樹高成長は,樹種や立地条件に依存して変化し,ある高さ以上になると停止する。決定された最大樹高は,光をめぐる資源獲得競争での優位性や群落の階層構造の発達,森林の生産性を規定する要因として重要である。近年,樹冠へアクセスするシステムや技術が発達し,数十メートルにも及ぶ高木の樹冠における生理学的測定が可能となった。その結果,土壌からの水輸送の限界による個葉光合成速度の低下や,重力による水ポテンシャルの低下によるシュートや葉における細胞の伸長抑制などといった生理学的要因によって樹高成長が制限される可能性が示された。また理論研究や操作実験などから,自重や風圧に対する力学的支持機能や老化による遺伝的な変化に関しては,樹高成長の制限要因としての寄与は低いことが示唆されている。今後は樹高成長制限が天然林での遷移過程や個体間の相互作用,群落の発達機構などにどのように影響しているかを明らかにすることで,樹高成長の包括的な理解と森林の生産性予測などへの応用が可能になると考えられる。

DOI： 10.4005/jjfs.90.420

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記述言語：日本語   出版者・発行元：日本生態学会  

光合成速度の温度依存性は同じC3植物でも種や生育温度によって異なる。光合成の生化学モデルに基づけば、光合成速度の温度依存性は（１）葉内二酸化炭素濃度、（２）RuBP（リブロース二リン酸）カルボキシレーション最大速度（Vcmax）の温度依存性、（３）RuBP再生最大速度（Jmax）の温度依存性、（４）カルボキシレーションと再生のバランス、の4つのパラメータに帰することができる。本研究ではミズナラの林冠葉においてこれらの要因がどのように季節変化をするのかを調べた。北大苫小牧研究林の落葉広葉樹林において、林冠クレーンを用い葉群最上部の葉の光合成速度を様々な温度・二酸化炭素濃度で測定した。測定は2001年・2002年にそれぞれ3回行った。20度で測定した光合成速度、気孔コンダクタンス、Vcmaxは春と秋に低く、夏に高かった。20度で測定したJmaxは春から夏にかけて上昇し、秋の低下は見られなかった。Vcmaxの温度依存性は春と秋に低く、夏に高い傾向を示し、生育温度と正の相関が見られた。一方その他のパラメータには明確な季節応答・生育温度応答は見られなかった。夏季にVcmaxの温度依存性が増加することにより光合成速度の最適温度が若干上昇していることが示唆された。

DOI： 10.14848/esj.ESJ52.0.540.0

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