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  • 1
    Language: English
    In: Oecologia, 2007-05-01, Vol.152 (1), p.1-12
    Description: Temperature is the most important factor affecting growth at high altitudes. As trees use much of the allocated carbon gained from photosynthesis to produce branches and stems, information on the timing and dynamics of secondary wood growth is crucial to assessing temperature thresholds for xylogenesis. We have carried out histological analyses to determine cambial activity and xylem cell differentiation in conifers growing at the treeline on the eastern Alps in two sites during 2002- 2004 with the aim of linking the growth process with temperature and, consequently, of defining thresholds for xylogenesis. Cambial activity occurred from May to July-August and cell differentiation from May-June to September-October. The earliest start of radial enlargement was observed in stone pine in mid-May, while Norway spruce was the last species to begin tracheid differentiation. The duration of wood formation varied from 90 to 137 days, depending on year and site, with no difference between species. Longer durations were observed in trees on the south-facing site because of the earlier onset and later ending of cell production and differentiation. The threshold temperatures at which xylogenesis had a 0.5 probability of being active were calculated by logistic regressions. Xylogenesis was active when the mean daily air temperature was 5.6-8.5°C and mean stem temperature was 7.2-9°C. The similar thresholds among all trees suggested the existence of thermal limits in wood formation that correspond with temperatures of 6-8°C that are supposed to limit growth at the treeline. Different soil temperature thresholds between sites indicated that soil temperature may not be the main factor limiting xylogenesis. This study represents the first attempt to define a threshold through comparative assessment of xylem growth and tissue temperatures in stem meristems at high altitudes.
    Subject(s): Trees ; Cell growth ; Xylem ; Tree growth ; Tracheids ; Timberlines ; Cell differentiation ; Ecophysiology ; Stems ; Growth rings ; Soil temperature ; Life Sciences ; Alps ; Tree ring ; Treeline ; Ecology ; Plant Sciences ; Cambial activity ; Fundamental and applied biological sciences. Psychology ; Biological and medical sciences ; General aspects ; Animal and plant ecology ; Animal, plant and microbial ecology ; Temperature ; Xylem - cytology ; Coniferophyta - growth & development ; Periodicity ; Xylem - growth & development ; Cell Differentiation ; Seasons ; Wood - growth & development ; Altitude ; Index Medicus
    ISSN: 0029-8549
    E-ISSN: 1432-1939
    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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  • 2
    Language: English
    In: Plant cell reports, 2013-06, Vol.32 (6), p.885-898
    Description: The radial growth of plant stem is based on the development of cribro-vascular cambium tissues. It affects the transport efficiency of water, mineral nutrients and photoassimilates and, ultimately, also plant height. The rate of cambial cell divisions for the assembly of new xylem and phloem tissue primordia and the rate of differentiation of the primordia into mature tissues determine the amount of biomass produced and, in the case of woody species, the wood quality. These complex physiological processes proceed at a rate which depends on several factors, acting at various levels: growth regulators, resource availability and environmental factors. Several hormonal signals and, more recently, further regulatory molecules, have been shown to be involved in the induction and maintenance of cambium and the formation of secondary vascular tissues. The control of xylem cell patterning is of particular interest, because it determines the diameter of xylem vessels, which is central to the efficiency of water and nutrient transport from roots to leaves through the stem and may strongly influence the growth in height of the tree. Increasing scientific evidence have proved the role of other hormones in cambial cell activities and the study of the hormonal signals and their crosstalking in cambial cells may foster our understanding of the dynamics of xylogenesis and of the mechanism of vessel size control along the stem. In this article, the role of the hormonal signals involved in the control of cambium and xylem development in trees and their crosstalking are reviewed.
    Subject(s): Biotechnology ; Auxin ; Crosstalking ; Ethylene ; Brassinosteroids ; Gibberellin ; Cytokinin ; Cell Biology ; Abscisic_acid ; Life Sciences ; Plant Biochemistry ; Peptide_hormones ; Plant Sciences ; Trees - cytology ; Xylem - physiology ; Trees - growth & development ; Lactones - metabolism ; Plant Stems - physiology ; Polyamines - metabolism ; Peptide Hormones - metabolism ; Cambium - growth & development ; Xylem - cytology ; Trees - physiology ; Body Patterning ; Plant Stems - cytology ; Xylem - growth & development ; Cell Differentiation ; Cambium - cytology ; Cambium - physiology ; Plant Stems - growth & development ; Peptides ; Physiological aspects ; Abscisic acid ; Index Medicus
    ISSN: 0721-7714
    E-ISSN: 1432-203X
    Source: Springer Online Journal Archives (DFG Nationallizenzen)
    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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  • 3
    Language: English
    In: Sensors (Basel, Switzerland), 2019-05-27, Vol.19 (10), p.2419
    Description: Thermal dissipation probe (TDP) method (Granier, 1985) is widely used to estimate tree transpiration (i.e., the water evaporated from the leaves) because it is simple to build, easy to install, and relatively inexpensive. However, the universality of the original calibration has been questioned and, in many cases, proved to be inaccurate. Thus, when the TDP is used in a new species, specific tests should be carried out. Our aim was to propose a new method for improving the accuracy of TDP on trees in the field. Small hazelnut trees (diameter at breast height 5 cm) were used for the experiment. The response of TDP sensors was compared with a reference water uptake measured with an electronic potometer system provided with a high precision liquid flow meter. We equipped three stems where we measured the sap flow density, the sapwood area (by using fuchsine), the total tree water uptake (reference), and the main meteorological parameters during summer 2018. Results confirmed that the original Granier's calibration underestimated the effective tree transpiration (relative error about -60%). We proposed a new equation for improving the measurement accuracy within an error of about 4%. The system proposed appeared an easier solution compared to potted trees and particularly suitable for orchards, thus contributing to improve the irrigation management worldwide.
    Subject(s): trees ; hazelnut ; water management
    ISSN: 1424-8220
    E-ISSN: 1424-8220
    Source: Academic Search Ultimate
    Source: PubMed Central
    Source: Directory of Open Access Journals
    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: Ecology letters, 2014-08, Vol.17 (8), p.988-997
    Description: Angiosperm hydraulic performance is crucially affected by the diameters of vessels, the water conducting conduits in the wood. Hydraulic optimality models suggest that vessels should widen predictably from stem tip to base, buffering hydrodynamic resistance accruing as stems, and therefore conductive path, increase in length. Data from 257 species (609 samples) show that vessels widen as predicted with distance from the stem apex across angiosperm orders, habits and habitats. Standardising for stem length, vessels are only slightly wider in warm/moist climates and in lianas, showing that, rather than climate or habit, plant size is by far the main driver of global variation in mean vessel diameter. Terminal twig vessels become wider as plant height increases, while vessel density decreases slightly less than expected tip to base. These patterns lead to testable predictions regarding evolutionary strategies allowing plants to minimise carbon costs per unit leaf area even as height increases.
    Subject(s): xylem ; allometry ; convergence ; hydraulic architecture ; lianas ; linear models ; optimality models ; vessel taper ; vessel density ; Adaptation ; Fundamental and applied biological sciences. Psychology ; Biological and medical sciences ; General aspects ; Animal and plant ecology ; Animal, plant and microbial ecology ; Biological Evolution ; Magnoliopsida - physiology ; Magnoliopsida - anatomy & histology ; Climate ; Plant Stems - anatomy & histology ; Ecosystem ; Linear Models ; Magnoliopsida - classification ; Plant Stems - physiology ; Analysis ; Index Medicus ; Life Sciences ; Ecosystems ; Botanics ; Ecology, environment ; Vegetal Biology ; Biodiversity ; Systematics, Phylogenetics and taxonomy ; Biodiversity and Ecology ; Environmental Sciences
    ISSN: 1461-023X
    E-ISSN: 1461-0248
    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, 2020-12, Vol.43 (12), p.3068-3080
    Description: While plant height is the main driver of variation in mean vessel diameter at the stem base (VD) across angiosperms, climate, specifically temperature, does play an explanatory role, with vessels being wider with warmer temperature for plants of the same height. Using a comparative approach sampling 537 species of angiosperms across 19 communities, we rejected selection favouring freezing‐induced embolism resistance as being able to account for wider vessels for a given height in warmer climates. Instead, we give reason to suspect that higher vapour pressure deficit (VPD) accounts for the positive scaling of height‐standardized VD (and potential xylem conductance) with temperature. Selection likely favours conductive systems that are able to meet the higher transpirational demand of warmer climates, which have higher VPD, resulting in wider vessels for a given height. At the same time, wider vessels are likely more vulnerable to dysfunction. With future climates likely to experience ever greater extremes of VPD, future forests could be increasingly vulnerable. In angiosperms, individuals from warmer climates have wider vessels than similar‐sized plants in colder climates. This trend is consistent with scaling of vessel diameter with vapour pressure deficit (VPD). Because VPD will be higher in future climates, and because wider vessels are potentially more vulnerable to embolism, future forests could be increasingly vulnerable.
    Subject(s): allometry ; xylem embolism ; ecological wood anatomy ; xylem vessels ; drought induced embolism ; adaptation ; climate change ; freezing‐induced embolism ; Climate ; Climatic changes ; Plants ; Droughts ; Index Medicus
    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: Journal of experimental botany, 2012-01-01, Vol.63 (2), p.837-845
    Description: The diameter of vascular conduits increases towards the stem base. It has been suggested that this profile is an efficient anatomical feature for reducing the hydraulic resistance when trees grow taller. However, the mechanism that controls the cell diameter along the plant is not fully understood. The timing of cell differentiation along the stem was investigated. Cambial activity and cell differentiation were investigated in a tree (11.5 m in height) collecting microsamples at nine different heights (from 1 to 9 m) along the stem with a 4 d time interval. Wood sections (8–12 μm thick) were stained and observed under a light microscope with polarized light to differentiate the developing xylem cells. Cell wall lignification was detected using cresyl violet acetate. The first enlarging cells appeared almost simultaneously along the tree axis indicating that cambium activation is not heightdependent. A significant increase in the duration of the cell expansion phase was observed towards the tree base: at 9 m from the ground, xylem cells expanded for 7 d, at 6 m for 14 d, and at 3 m for 19 d. The duration of the expansion phase is positively correlated with the lumen area of the tracheids ( ² =0.68, 〈 0.01) at the same height. By contrast, thickness of the cell wall of the earlywood did not show any trend with height. The lumen area of the conduits down the stem appeared linearly dependent on time during which differentiating cells remained in the expansion phase. However, the inductive signal of such long-distance patterned differentiation remains to be identified.
    Subject(s): Trees ; Xylem ; Lignification ; Tracheids ; Cell walls ; Hydraulics ; Stem cells ; Auxins ; Plants ; Cellular differentiation ; RESEARCH PAPER ; Fundamental and applied biological sciences. Psychology ; Biological and medical sciences ; Plant physiology and development ; Forestry ; Temperature ; Indoleacetic Acids - metabolism ; Xylem - anatomy & histology ; Trees - growth & development ; Trees - anatomy & histology ; Cambium - growth & development ; Lignin - metabolism ; Plant Stems - anatomy & histology ; Wood - anatomy & histology ; Time Factors ; Cambium - anatomy & histology ; Picea - anatomy & histology ; Picea - growth & development ; Cell Wall - metabolism ; Xylem - growth & development ; Italy ; Cell Differentiation ; Wood - growth & development ; Plant Stems - growth & development ; Index Medicus ; Picea abies polar pattern growth ; Research Papers ; cell differentiation ; Auxin ; cambium ; conduit tapering
    ISSN: 0022-0957
    E-ISSN: 1460-2431
    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: Current Forestry Reports, 2017-03, Vol.3 (1), p.46-59
    Description: This review shows that a more or less constant rate of tip-to-base vessel widening across species, together with the assumption that wider vessels are more vulnerable to embolism, suggests how climate should limit maximum vegetation height; together, these two factors predict a maximum mean vessel diameter permitted by temperature and water availability at a site and thus maximum plant height.Empirical work makes it increasingly clear that the main driver of variation in mean vessel diameter is plant size, specifically the length of the conductive stream. Anatomical evidence, together with hydraulic optimality models, suggests that this vessel diameter-stem length relationship is the result of natural selection favoring the maintenance of constant hydraulic resistance over size increases. From their very narrow termini, vessels widen predictably from the stem tip to the base, following approximately a power law, i.e., with very rapid widening toward the tips and nearly constant diameter toward the base. This size dependence must be taken into account when studying the hydraulics-climate relationship.This review discusses outstanding predictions that require testing, including the following: variation in the vessel diameter-stem length relationship should involve factors such as vessel length distributions, pit characteristics, leaf area, and wood density; leaves higher in trees should have higher terminal leaf vein-petiole base vessel widening rates; species without “disposable” units (e.g., columnar cacti) might have different widening rates; and within-plant widening rate should vary as plants approach their height limits. Finally, we emphasize the need to standardize for size in making comparisons of vessel diameter variation.
    Subject(s): Sustainable Development ; Ecology ; Vessel diameter ; Xylem embolism ; Allometry ; Ecological wood anatomy ; Xylem anatomy ; Nature Conservation ; Forestry ; Forestry Management ; Environment ; Plant height ; Environmental Management ; Leaves ; Computational fluid dynamics ; Hydraulics ; Vessels ; Cacti ; Dependence ; Fluid flow ; Blood vessels ; Maintenance ; Widening
    ISSN: 2198-6436
    E-ISSN: 2198-6436
    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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  • 8
    Language: English
    In: Trees (Berlin, West), 2019-12, Vol.33 (6), p.1657-1665
    Description: The axial structure of the hydraulic system in trees is relatively invariant and insensitive to temperature, while trees plastically adjust the number of cells within the tree ring.At higher elevations and latitudes in the treeline ecotone, reduction in the heat accrued during the growing season is reflected in gradually decreasing tree size. Due to low temperatures, treeline trees might produce smaller xylem cells and, as a consequence, tree growth could be limited. However, some xylem traits (i.e., cell lumen area) are considered relatively insensitive to climatic factors but highly dependent on tree size because of the natural widening of xylem conduits towards the stem base. We tested the hypothesis that earlywood cell lumen area is essentially invariant and depends largely on tree size. Tracheid traits in four conifer species from the lower (“timberline”) and upper (“treeline”) parts of the treeline ecotone (Picea engelmannii, Picea abies, Pinus cembra and Larix decidua) were measured in the Colorado Front Range (U.S.A.), Krkonoše Mts. (Czech Republic) and Dolomites (Italy). On transversal sections sampled at 1 m of stem height, we measured cell lumen areas, transversal cell size, cell wall thickness, tree-ring width and number of cells per radial file. Cell lumen areas were always greater at the timberline than treeline. When tree height is accounted for, the earlywood cell area did not differ between the two sites, thus showing that difference in temperature did not affect earlywood cell area in any of the four measured species. The number of cells within tree rings exhibited high inter-annual variability according to environmental factors. The fundamental hydraulic structure in trees is relatively rigid and insensitive to temperature, while trees plastically adjust the number of cells within the tree ring as a result of inter-annual climate variability and leaf production.
    Subject(s): Plant Anatomy/Development ; Cell widening ; Larix decidua ; Wood anatomy ; Plant Physiology ; Picea engelmannii ; Stem allometry ; Life Sciences ; Plant Pathology ; Pinus cembra ; Forestry ; Conduit diameter ; Agriculture ; Alpine treeline ; Plant Sciences ; Picea abies
    ISSN: 0931-1890
    E-ISSN: 1432-2285
    Source: Alma/SFX Local Collection
    Source: ProQuest Central
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  • 9
    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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  • 10
    Language: English
    In: Global ecology and biogeography, 2008-11-01, Vol.17 (6), p.696-707
    Description: Aim: To identify temperatures at which cell division and differentiation are active in order to verify the existence of a common critical temperature determining growth in conifers of cold climates. Location: Ten European and Canadian sites at different latitudes and altitudes. Methods: The periods of cambial activity and cell differentiation were assessed on a weekly time-scale on histological sections of cambium and wood tissue collected over 2 to 5 years per site from 1998 to 2005 from the stems of seven conifer species. All data were compared with daily air temperatures recorded from weather stations located close to the sites. Logistic regressions were used to calculate the probability of xylogenesis and of cambium being active at a given temperature. Results: Xylogenesis lasted from May to October, with a growing period varying from 3 to 5 months depending on location and elevation. Despite the wide geographical range of the monitored sites, temperatures for onset and ending of xylogenesis converged towards narrow ranges with average values around 4-5, 8-9 and 13-14 °C for daily minimum, mean and maximum temperature, respectively. On the contrary, cell division in the cambium stopped in July-August, when temperatures were still high. Main conclusions: Wood formation in conifers occurred when specific critical temperatures were reached. Although the timing and duration of xylogenesis varied among species, sites and years, the estimated temperatures were stable for all trees studied. These results provide biologically based evidence that temperature is a critical factor limiting production and differentiation of xylem cells in cold climates. Although daily temperatures below 4-5 °C are still favourable for photosynthesis, thermal conditions below these values could inhibit the allocation of assimilated carbon to structural investment, i.e. xylem growth.
    Subject(s): Trees ; Xylem ; Tracheids ; Plant ecology ; Conifers ; Biogeography ; Timberlines ; Critical temperature ; Cambium ; Stems ; xylem ; Boreal forest ; microcoring ; pinning ; cambium ; wood formation ; growing period ; tree line ; Fundamental and applied biological sciences. Psychology ; General forest ecology ; General aspects ; Synecology ; Animal, plant and microbial ecology ; Forestry ; Biological and medical sciences ; Animal and plant ecology ; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology ; Climate ; Life Sciences
    ISSN: 1466-822X
    E-ISSN: 1466-8238
    Source: Alma/SFX Local Collection
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