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  • 1
    Language: English
    In: The New phytologist, 2014-09-01, Vol.203 (4), p.1231-1241
    Description: Conifer tree rings are generally composed of large, thin-walled cells of light earlywood followed by narrow, thick-walled cells of dense latewood. Yet, how wood formation processes and the associated kinetics create this typical pattern remains poorly understood. We monitored tree-ring formation weekly over 3 yr in 45 trees of three conifer species in France. Data were used to model cell development kinetics, and to attribute the relative importance of the duration and rate of cell enlargement and cell wall deposition on tree-ring structure. Cell enlargement duration contributed to 75% of changes in cell diameter along the tree rings. Remarkably, the amount of wall material per cell was quite constant along the rings. Consequently, and in contrast with widespread belief, changes in cell wall thickness were not principally attributed to the duration and rate of wall deposition (33%), but rather to the changes in cell size (67%). Cell enlargement duration, as the main driver of cell size and wall thickness, contributed to 56% of wood density variation along the rings. This mechanistic framework now forms the basis for unraveling how environmental stresses trigger deviations (e.g. false rings) from the normal tree-ring structure.
    Subject(s): Full papers ; Cell growth ; Tracheids ; Cell walls ; Conifers ; Pine trees ; Kinetics ; Wood density ; Growth rings ; Modeling ; Latewood ; xylogenesis ; cambial activity ; conifers ; generalized additive models (GAMs) ; tree‐ring structure ; wood density ; kinetics of tracheid development ; quantitative wood anatomy ; Wood - anatomy & histology ; Coniferophyta - growth & development ; Models, Biological ; Coniferophyta - anatomy & histology ; Xylem - growth & development ; Trees - growth & development ; France ; Wood - growth & development ; Trees - anatomy & histology ; Index Medicus ; Life Sciences ; Agricultural sciences ; Vegetal Biology
    ISSN: 0028-646X
    E-ISSN: 1469-8137
    Source: Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 2
    Language: English
    In: The New phytologist, 2017-11-01, Vol.216 (3), p.728-740
    Description: Interannual variability of wood density – an important plant functional trait and environmental proxy – in conifers is poorly understood. We therefore explored the anatomical basis of density. We hypothesized that earlywood density is determined by tracheid size and latewood density by wall dimensions, reflecting their different functional tasks. To determine general patterns of variability, density parameters from 27 species and 349 sites across the Northern Hemisphere were correlated to tree-ring width parameters and local climate. We performed the same analyses with density and width derived from anatomical data comprising two species and eight sites. The contributions of tracheid size and wall dimensions to density were disentangled with sensitivity analyses. Notably, correlations between density and width shifted from negative to positive moving from earlywood to latewood. Temperature responses of density varied intraseasonally in strength and sign. The sensitivity analyses revealed tracheid size as the main determinant of earlywood density, while wall dimensions become more influential for latewood density. Our novel approach of integrating detailed anatomical data with large-scale tree-ring data allowed us to contribute to an improved understanding of interannual variations of conifer growth and to illustrate how conifers balance investments in the competing xylem functions of hydraulics and mechanical support.
    Subject(s): Full papers ; ring width ; tracheid anatomy ; dendroclimatology ; tree‐ring network ; xylem function ; wood density ; Cell Wall ; Climate ; Temperature ; Wood - anatomy & histology ; Coniferophyta - cytology ; Europe ; Wood - cytology ; Cell Size ; Plant Cells ; Specific gravity ; Paleoclimatology ; Analysis ; Index Medicus ; tree-ring network ; time-series ; tree-ring width ; picea-abies ; climate ; Climate Research ; radial ; Klimatforskning ; pseudotsuga-menziesii mirb ; temperature ; growth ; douglas-fir ; carbon allocation ; Plant Sciences
    ISSN: 0028-646X
    E-ISSN: 1469-8137
    Source: Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 3
    Language: English
    In: Global change biology, 2016-11, Vol.22 (11), p.3804-3813
    Description: The interaction between xylem phenology and climate assesses forest growth and productivity and carbon storage across biomes under changing environmental conditions. We tested the hypothesis that patterns of wood formation are maintained unaltered despite the temperature changes across cold ecosystems. Wood microcores were collected weekly or biweekly throughout the growing season for periods varying between 1 and 13 years during 1998–2014 and cut in transverse sections for assessing the onset and ending of the phases of xylem differentiation. The data set represented 1321 trees belonging to 10 conifer species from 39 sites in the Northern Hemisphere and covering an interval of mean annual temperature exceeding 14 K. The phenological events and mean annual temperature of the sites were related linearly, with spring and autumnal events being separated by constant intervals across the range of temperature analysed. At increasing temperature, first enlarging, wall‐thickening and mature tracheids appeared earlier, and last enlarging and wall‐thickening tracheids occurred later. Overall, the period of wood formation lengthened linearly with the mean annual temperature, from 83.7 days at −2 °C to 178.1 days at 12 °C, at a rate of 6.5 days °C−1. April–May temperatures produced the best models predicting the dates of wood formation. Our findings demonstrated the uniformity of the process of wood formation and the importance of the environmental conditions occurring at the time of growth resumption. Under warming scenarios, the period of wood formation might lengthen synchronously in the cold biomes of the Northern Hemisphere.
    Subject(s): cell production ; cell differentiation ; secondary wall formation ; cambium ; conifers ; meristem ; growth ; climate change ; Trees ; Cold Temperature ; Plant Development ; Xylem ; Ecosystem ; Coniferophyta ; Seasons ; Biomes ; Environmental aspects ; Global temperature changes ; Cell differentiation ; Ecosystems ; Analysis ; Index Medicus ; Life Sciences ; Vegetal Biology
    ISSN: 1354-1013
    E-ISSN: 1365-2486
    Source: Alma/SFX Local Collection
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 4
    Language: English
    In: Plant, cell and environment, 2016-06, Vol.39 (6), p.1338-1352
    Description: Because of global warming, high‐latitude ecosystems are expected to experience increases in temperature and drought events. Wood formation will have to adjust to these new climatic constraints to maintain tree mechanical stability and long‐distance water transport. The aim of this study is to understand the dynamic processes involved in wood formation under warming and drought. Xylogenesis, gas exchange, water relations and wood anatomy of black spruce [Picea mariana (Mill.) B.S.P.] saplings were monitored during a greenhouse experiment where temperature was increased during daytime or night‐time (+6 °C) combined with a drought period. The kinetics of tracheid development expressed as rate and duration of the xylogenesis sub‐processes were quantified using generalized additive models. Drought and warming had a strong influence on cell production, but little effect on wood anatomy. The increase in cell production rate under warmer temperatures, and especially during the night‐time warming at the end of the growing season, resulted in wider tree‐rings. However, the strong compensation between rates and durations of cell differentiation processes mitigates warming and drought effects on tree‐ring structure. Our results allowed quantification of how wood formation kinetics is regulated when water and heat stress increase, allowing trees to adapt to future environmental conditions. Global warming in high‐latitude ecosystems will affect wood formation. This work focuses on the dynamic processes involved in wood formation under experimental drought and warming treatments. Our study demonstrates that drought and warming have a strong impact on cell production, but a weak influence on xylem anatomy. Using innovative analysis of kinetics of tracheid development, we quantified how the compensation mechanisms between rates and durations of the xylogenesis sub‐processes strongly mitigate negative effects of multistress on wood structure.
    Subject(s): xylogenesis ; water deficit ; global warming ; tree‐ring structure ; wood anatomy ; Xylem - physiology ; Picea - physiology ; Wood - physiology ; Adaptation, Physiological - physiology ; Trees - growth & development ; Trees - anatomy & histology ; Global Warming ; Trees - physiology ; Wood - anatomy & histology ; Picea - anatomy & histology ; Picea - growth & development ; Xylem - growth & development ; Dehydration - physiopathology ; Wood - growth & development ; Global warming ; Erythromycin ; Droughts ; Analysis ; Index Medicus ; Life Sciences ; Vegetal Biology ; Environmental Sciences ; Global Changes
    ISSN: 0140-7791
    E-ISSN: 1365-3040
    Source: Alma/SFX Local Collection
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 5
    Language: English
    In: Plant, cell and environment, 2019-04, Vol.42 (4), p.1222-1232
    Description: Conifer trees possess a typical anatomical tree‐ring structure characterized by a transition from large and thin‐walled earlywood tracheids to narrow and thick‐walled latewood tracheids. However, little is known on how this characteristic structure is maintained across contrasting environmental conditions, due to its crucial role to ensure sap ascent and mechanical support. In this study, we monitored weekly wood cell formation for up to 7 years in two temperate conifer species (i.e., Picea abies (L.) Karst and Larix decidua Mill.) across an 8°C thermal gradient from 800 to 2,200 m a.s.l. in central Europe to investigate the impact of air temperature on rate and duration of wood cell formation. Results indicated that towards colder sites, forming tracheids compensate a decreased rate of differentiation (cell enlarging and wall thickening) by an extended duration, except for the last cells of the latewood in the wall‐thickening phase. This compensation allows conifer trees to mitigate the influence of air temperature on the final tree‐ring structure, with important implications for the functioning and resilience of the xylem to varying environmental conditions. The disappearing compensation in the thickening latewood cells might also explain the higher climatic sensitivity usually found in maximum latewood density. The structure of conifer wood cells depends on the speed and duration of processes shaping their formation. In this study, we show for the first time that cells growing at colder sites increase their duration of their processes to compensate for a speed reduction. This compensation allows conifers to mitigate the effect of air temperature to maintain a more similar tree‐ring structure despite contrasting conditions.
    Subject(s): temperature response ; xylogenesis ; quantitative wood anatomy ; wood formation dynamics ; tree ring ; conifer ; Temperature ; Picea - physiology ; Wood - cytology ; Wood - anatomy & histology ; Picea - anatomy & histology ; Picea - growth & development ; Larix - physiology ; Xylem - growth & development ; Kinetics ; Larix - growth & development ; Wood - growth & development ; Cell Differentiation - physiology ; Larix - anatomy & histology ; Cell differentiation ; Analysis ; Index Medicus ; Life Sciences
    ISSN: 0140-7791
    E-ISSN: 1365-3040
    Source: Alma/SFX Local Collection
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 6
    Language: English
    In: Annals of botany, 2013-12-01, Vol.112 (9), p.1911-1920
    Description: • Background and Aims Ongoing global warming has been implicated in shifting phenological patterns such as the timing and duration of the growing season across a wide variety of ecosystems. Linear models are routiriely used to extrapolate these observed shifts in phenology into the future and to estimate changes in associated ecosystem properties such as net primary productivity. Yet, in nature, linear relationships may be special cases. Biological processes frequently follow more complex, non-linear patterns according to limiting factors that generate shifts and discontinuities, or contain thresholds beyond which responses change abruptly. This study investigates to what extent cambium phenology is associated with xylem growth and differentiation across conifer species of the northern hemisphere. • Methods Xylem cell production is compared with the periods of cambial activity and cell differentiation assessed on a weekly time scale on histological sections of cambium and wood tissue collected from the stems of nine species in Canada and Europe over 1-9 years per site from 1998 to 2011. • Key Results The dynamics of xylogenesis were surprisingly homogeneous among conifer species, although dispersions from the average were obviously observed. Within the range analysed, the relationships between the phenological timings were linear, with several slopes showing values close to or not statistically different from 1. The relationships between the phenological timings and cell production were distinctly non-linear, and involved an exponential pattern • Conclusions The trees adjust their phenological timings according to linear patterns. Thus, shifts of one phenological phase are associated with synchronous and comparable shifts of the successive phases. However, small increases in the duration of xylogenesis could correspond to a substantial increase in cell production. The findings suggest that the length of the growing season and the resulting amount of growth could respond differently to changes in environmental conditions.
    Subject(s): Climate change ; Cell growth ; Xylem ; Tracheids ; Phenology ; Cell walls ; Conifers ; Cambium ; Cellular differentiation ; Species ; Cambium - growth & development ; Canada ; Xylem - cytology ; Climate Change ; Coniferophyta - growth & development ; Europe ; Xylem - growth & development ; Cell Differentiation ; Index Medicus ; Life Sciences ; xylogenesis ; cell production ; cell differentiation ; secondary wall formation ; conifers ; meristem ; productivity ; phenology ; growth ; Original ; climate change
    ISSN: 0305-7364
    E-ISSN: 1095-8290
    Source: Academic Search Ultimate
    Source: PubMed Central
    Source: Alma/SFX Local Collection
    Source: Oxford Journals 2016 Current and Archive A-Z Collection
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 7
    Language: English
    In: Journal of experimental botany, 2013-01-01, Vol.64 (7), p.1983-1994
    Description: The intra-annual dynamics of wood formation, which involves the passage of newly produced cells through three successive differentiation phases (division, enlargement, and wall thickening) to reach the final functional mature state, has traditionally been described in conifers as three delayed bell-shaped curves followed by an S-shaped curve. Here the classical view represented by the 'Gompertz function (GF) approach' was challenged using two novel approaches based on parametric generalized linear models (GLMs) and 'data-driven' generalized additive models (GAMs). These three approaches (GFs, GLMs, and GAMs) were used to describe seasonal changes in cell numbers in each of the xylem differentiation phases and to calculate the timing of cell development in three conifer species [Picea abies (L.), Pinus sylvestris L., and Abies alba Mill.]. GAMs outperformed GFs and GLMs in describing intra-annual wood formation dynamics, showing two left-skewed bell-shaped curves for division and enlargement, and a right-skewed bimodal curve for thickening. Cell residence times progressively decreased through the season for enlargement, whilst increasing late but rapidly for thickening. These patterns match changes in cell anatomical features within a tree ring, which allows the separation of earlywood and latewood into two distinct cell populations. A novel statistical approach is presented which renews our understanding of xylogenesis, a dynamic biological process in which the rate of cell production interplays with cell residence times in each developmental phase to create complex seasonal patterns.
    Subject(s): Growing seasons ; Xylem ; Tracheids ; Cell walls ; Conifers ; Wood anatomy ; Growth rings ; Parametric models ; Latewood ; Species ; RESEARCH PAPER ; Fundamental and applied biological sciences. Psychology ; Biological and medical sciences ; Plant physiology and development ; Models, Theoretical ; Pinus - growth & development ; Pinus - metabolism ; Picea - growth & development ; Abies - growth & development ; Abies - metabolism ; Wood - metabolism ; Picea - metabolism ; Wood - growth & development ; Index Medicus ; Life Sciences ; Cambial activity, Conifers, Generalized linear and additive models (GLMs and GAMs), Gompertz functions (GFs), Timing of cell development, Tree ring, Wood formation, Xylogenesis ; xylogenesis ; generalized linear and additive models (GLMs and GAMs) ; timing of cell development ; conifers ; wood formation ; Gompertz functions (GFs) ; Research Paper ; tree ring ; Cambial activity
    ISSN: 0022-0957
    E-ISSN: 1460-2431
    Source: Alma/SFX Local Collection
    Source: Oxford Journals 2016 Current and Archive A-Z Collection
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  • 8
    Language: English
    In: Plant physiology (Bethesda), 2016-05-01, Vol.171 (1), p.306-317
    Description: The complex inner mechanisms that create typical conifer tree-ring structure (i.e. the transition from large, thin-walled earlywood cells to narrow, thick-walled latewood cells) were recently unraveled. However, what physiological or environmental factors drive xylogenesis key processes remain unclear. Here, we aim to quantify the influence of seasonal variations in climatic factors on the spectacular changes in the kinetics of wood cell differentiation and in the resulting tree-ring structure. Wood formation was monitored in three sites over 3 years for three coniferous species (Norway spruce [ ], Scots pine [ ], and silver fir [ ]). Cell differentiation rates and durations were calculated and related to tracheid final dimensions and corresponding climatic conditions. On the one hand, we found that the kinetics of cell enlargement and the final size of the tracheids were not explained by the seasonal changes in climatic factors. On the other hand, decreasing temperatures strongly constrained cell wall deposition rates during latewood formation. However, the influence of temperature was permanently written into tree-ring structure only for the very last latewood cells, when the collapse of the rate of wall deposition was no longer counterbalanced by the increase of its duration. Our results show that the formation of the typical conifer tree-ring structure, in normal climatic conditions, is only marginally driven by climate, suggesting strong developmental control of xylogenesis. The late breakage of the compensatory mechanism at work in the wall deposition process appears as a clue to understand the capacity of the maximum latewood density to record past temperature conditions.
    Subject(s): ECOPHYSIOLOGY AND SUSTAINABILITY ; Climate ; Forests ; Trees - cytology ; Abies - physiology ; Signal Transduction ; Picea - physiology ; Plant Cells ; Coniferophyta - physiology ; Pinus sylvestris - physiology ; Abies - cytology ; Xylem - cytology ; Trees - physiology ; Coniferophyta - cytology ; Cell Differentiation ; Pinus sylvestris - cytology ; Seasons ; Picea - cytology ; Botanical research ; Plant physiological ecology ; Tree-rings ; Conifers ; Environmental aspects ; Physiological aspects ; Research ; Index Medicus ; Life Sciences
    ISSN: 0032-0889
    E-ISSN: 1532-2548
    Source: American Society of Plant Biologists
    Source: HighWire Press (Free Journals)
    Source: Hellenic Academic Libraries Link
    Source: PubMed Central
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 9
    Language: English
    In: The New phytologist, 2021-01, Vol.229 (1), p.213-229
    Description: Summary A valid representation of intra‐annual wood formation processes in global vegetation models is vital for assessing climate change impacts on the forest carbon stock. Yet, wood formation is generally modelled with photosynthesis, despite mounting evidence that cambial activity is rather directly constrained by limiting environmental factors. Here, we apply a state‐of‐the‐art turgor‐driven growth model to simulate 4 yr of hourly stem radial increment from Picea abies (L.) Karst. and Larix decidua Mill. growing along an elevational gradient. For the first time, wood formation observations were used to validate weekly to annual stem radial increment simulations, while environmental measurements were used to assess the climatic constraints on turgor‐driven growth. Model simulations matched the observed timing and dynamics of wood formation. Using the detailed model outputs, we identified a strict environmental regulation on stem growth (air temperature 〉 2°C and soil water potential 〉 −0.6 MPa). Warmer and drier summers reduced the growth rate as a result of turgor limitation despite warmer temperatures being favourable for cambial activity. These findings suggest that turgor is a central driver of the forest carbon sink and should be considered in next‐generation vegetation models, particularly in the context of global warming and increasing frequency of droughts.
    Subject(s): process‐based model ; tree hydraulics ; wood formation ; tree rings ; radial stem growth ; climate change ; Analysis ; Global warming ; Models
    ISSN: 0028-646X
    E-ISSN: 1469-8137
    Source: Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals
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  • 10
    Language: English
    In: Frontiers in plant science, 2016, Vol.7, p.734-734
    Description: Wood is of crucial importance for man and biosphere. In this mini review, we present the fundamental processes involved in tree-ring formation and intra-annual dynamics of cambial activity, along with the influences of the environmental factors. During wood formation, new xylem cells produced by the cambium are undergoing profound transformations, passing through successive differentiation stages, which enable them to perform their functions in trees. Xylem cell formation can be divided in five major phases: (1) the division of a cambial mother cell that creates a new cell; (2) the enlargement of this newly formed cell; (3) the deposition of its secondary wall; (4) the lignification of its cell wall; and finally, (5) its programmed cell death. In most regions of the world cambial activity follows a seasonal cycle. At the beginning of the growing season, when temperature increases, the cambium resumes activity, producing new xylem cells. These cells are disposed along radial files, and start their differentiation program according to their birth date, creating typical developmental strips in the forming xylem. The width of these strips smoothly changes along the growing season. Finally, when climatic conditions deteriorate (temperature or water availability in particular), cambial activity stops, soon followed by cell enlargement, and later on by secondary wall deposition. Without a clear understanding of the xylem formation process, it is not possible to comprehend how annual growth rings and typical wood structures are formed, recording normal seasonal variations of the environment as well as extreme climatic events.
    Subject(s): Life Sciences ; Vegetal Biology ; xylem ; Plant Science ; tree-ring structure ; cambial activity ; cellulose ; tree growth ; lignin ; quantitative wood anatomy ; climatic factors ; Quantitative wood anatomy ; Lignin ; Xylem ; Cellulose
    ISSN: 1664-462X
    E-ISSN: 1664-462X
    Source: PubMed Central
    Source: Directory of Open Access Journals
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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