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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
    ISSN: 0029-8549
    E-ISSN: 1432-1939
    Source: JSTOR Life Sciences
    Source: JSTOR Ecology & Botany II
    Source: Alma/SFX Local Collection
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  • 2
    Language: English
    In: The New phytologist, 2008-01-01, Vol.177 (1), p.199-208
    Description: • Neither anatomical change nor physiological abnormalities have been observed in the cambia of older trees. However, different sensitivity and period of significant responses to climate suggest the existence of some age-related change in the patterns of cambial activity and/or wood cell formation. • Here, weekly cambial activity and timing and duration of xylem cell enlargement and wall thickening were compared in adult (50-80 yr) and old (200-350 yr) trees of Larix decidua, Pinus cembra and Picea abies at the Alpine timberline during 2004 and 2005. • Timings and durations of xylogenesis differed between adult and old trees, with 2-3 wk shorter cambial activity found in the latter. The delayed onset of cambium division and lower cell production in old trees, with respect to adult trees, led to reductions of 15-20% in the overall duration of xylem differentiation. • These results demonstrate that cambial dynamics change during the tree lifespan and that the time window of tree-ring production shortens with age. Variations in the period of xylem growth may be the cause of age-dependent responses to climate. The observed shorter xylogenesis in older plants at the Alpine timberline could be related to a size effect and not just to age per se.
    Subject(s): Trees ; Dendroclimatology ; Xylem ; Tracheids ; Cell walls ; Timberlines ; Pine trees ; Cambium ; Tree age ; Growth rings ; Alps ; cell differentiation ; cambial activity ; wood formation ; timberline ; uniformitarian principle ; tree age ; tree ring ; Xylem - cytology ; Aging - physiology ; Time Factors ; Xylem - metabolism ; Ecosystem ; Italy ; Pinaceae - metabolism ; Altitude
    ISSN: 0028-646X
    E-ISSN: 1469-8137
    Source: JSTOR Life Sciences
    Source: Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals
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  • 3
    Language: English
    In: Sensors (Basel, Switzerland), 2019-05-02, 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): Engineering ; Physical Sciences ; Chemistry ; Technology ; Instruments & Instrumentation ; Engineering, Electrical & Electronic ; Chemistry, Analytical ; Science & Technology ; trees ; hazelnut ; water management
    ISSN: 1424-8220
    E-ISSN: 1424-8220
    Source: Academic Search Ultimate
    Source: Web of Science - Science Citation Index Expanded - 2019〈img src="http://exlibris-pub.s3.amazonaws.com/fromwos-v2.jpg" /〉
    Source: PubMed Central
    Source: Alma/SFX Local Collection
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  • 4
    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
    ISSN: 0721-7714
    E-ISSN: 1432-203X
    Source: Springer Online Journal Archives (DFG Nationallizenzen)
    Source: Alma/SFX Local Collection
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  • 5
    Language: English
    In: The New phytologist, 2016-01-01, Vol.209 (1), p.216-227
    Description: Leaves of vascular plants use specific tissues to irrigate the lamina (veins) and to regulate water loss (stomata), to approach homeostasis in leaf hydration during photosynthesis. As both tissues come with attendant costs, it would be expected that the synthesis and spacing of leaf veins and stomata should be coordinated in a way that maximizes benefit to the plant. We propose an innovative geoprocessing method based on image editing and a geographic information system to study the quantitative relationships between vein and stomatal spatial patterns on leaves collected from 31 angiosperm species from different biomes. The number of stomata within each areole was linearly related to the length of the looping vein contour. As a consequence of the presence of free-ending veinlets, the minimum mean distance of stomata from the nearest veins was invariant with areole size in most of the species, and species with smaller distances carried a higher density of stomata. Uniformity of spatial patterning was consistent within leaves and species. Our results demonstrate the existence of an optimal spatial organization of veins and stomata, and suggest their interplay as a key feature for achieving a constant mesophyll hydraulic resistance throughout the leaf.
    Subject(s): Full papers ; vein network ; geographic information system (GIS) ; stomata ; leaf hydraulics ; free‐ending veinlets ; angiosperms ; Magnoliopsida - physiology ; Magnoliopsida - anatomy & histology ; Plant Stomata - anatomy & histology ; Plant Transpiration - physiology ; Biological Transport ; Photosynthesis - physiology ; Water - metabolism ; Plant Leaves - anatomy & histology ; Plant Stomata - physiology ; Plant Leaves - physiology ; Photosynthesis ; Phytochemistry
    ISSN: 0028-646X
    E-ISSN: 1469-8137
    Source: JSTOR Life Sciences
    Source: Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals
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  • 6
    Language: English
    In: The New phytologist, 2021-02, Vol.229 (4), p.1877-1893
    Description: Summary In the stems of terrestrial vascular plants studied to date, the diameter of xylem water‐conducting conduits D widens predictably with distance from the stem tip L approximating D ∝ Lb, with b ≈ 0.2. Because conduit diameter is central for conductance, it is essential to understand the cause of this remarkably pervasive pattern. We give reason to suspect that tip‐to‐base conduit widening is an adaptation, favored by natural selection because widening helps minimize the increase in hydraulic resistance that would otherwise occur as an individual stem grows longer and conductive path length increases. Evidence consistent with adaptation includes optimality models that predict the 0.2 exponent. The fact that this prediction can be made with a simple model of a single capillary, omitting much biological detail, itself makes numerous important predictions, e.g. that pit resistance must scale isometrically with conduit resistance. The idea that tip‐to‐base conduit widening has a nonadaptive cause, with temperature, drought, or turgor limiting the conduit diameters that plants are able to produce, is less consistent with the data than an adaptive explanation. We identify empirical priorities for testing the cause of tip‐to‐base conduit widening and underscore the need to study plant hydraulic systems leaf to root as integrated wholes.
    Subject(s): allometry ; plant hydraulics ; tracheids ; developmental constraint ; adaptation ; conduit taper ; hydraulic architecture ; vessels ; Adaptation, Physiological ; Water ; Xylem ; Droughts ; Plant Leaves ; Acclimatization ; Plant Stems ; Analysis ; Natural selection
    ISSN: 0028-646X
    E-ISSN: 1469-8137
    Source: Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals
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  • 7
    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 ; 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
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  • 8
    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
    ISSN: 0140-7791
    E-ISSN: 1365-3040
    Source: Alma/SFX Local Collection
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  • 9
    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 ; Picea abies polar pattern growth ; Research Papers ; cell differentiation ; Auxin ; cambium ; conduit tapering
    ISSN: 0022-0957
    E-ISSN: 1460-2431
    Source: JSTOR Ecology & Botany II
    Source: Alma/SFX Local Collection
    Source: Oxford Journals 2016 Current and Archive A-Z Collection
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  • 10
    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
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