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Tree Physiology

Elena Dobbelstein, Daniel Fink, Soner Öner-Sieben, Laura Czempik, Gertrud Lohaus
In temperate woody species, carbon transport from source to sink tissues is a striking physiological process, particularly considering seasonal changes. The functions of different tissues can also alternate across the seasons. In this regard, phloem loading and sugar distribution are important aspects of carbon partitioning, and sucrose uptake transporters (SUTs) play a key role in these processes. Therefore, the influence of seasons and different light-dark conditions on the expression of SUTs from 3-year-old Fagus sylvatica L...
November 2, 2018: Tree Physiology
Benjamin D Hesse, Michael Goisser, Henrik Hartmann, Thorsten E E Grams
Phloem sustains maintenance and growth processes through transport of sugars from source to sink organs. Under low water availability, tree functioning is impaired, i.e., growth/photosynthesis decline and phloem transport may be hindered. In a 3-year throughfall exclusion (TE) experiment on mature European beech (Fagus sylvatica L.) we conducted 13CO2 branch labeling to investigate translocation of recently fixed photoassimilates under experimental drought over 2 years (2015 and 2016). We hypothesized (H1) that mean residence time of photoassimilates in leaves (MRT) increases, whereas (H2) phloem transport velocity (Vphloem) decreases under drought...
November 2, 2018: Tree Physiology
Agne Gvozdevaite, Imma Oliveras, Tomas Ferreira Domingues, Theresa Peprah, Mickey Boakye, Lydia Afriyie, Karine Peixoto da Silva, Josenilton de Farias, Edmar Almeida de Oliveira, Cassia Cristina Almeida Farias, Nayane Cristina Candida Dos Santos Prestes, Margot Neyret, Sam Moore, Beatriz Schwantes Marimon, Ben Hur Marimon Junior, Stephen Adu-Bredu, Yadvinder Malhi
Forest-savanna boundaries extend across large parts of the tropics but the variability of photosynthetic capacity in relation to soil and foliar nutrients across these transition zones is poorly understood. For this reason, we compared photosynthetic capacity (maximum rate of carboxylation of Rubisco at 25 C° (Vcmax25), leaf mass, nitrogen (N), phosphorus (P) and potassium (K) per unit leaf area (LMA, Narea, Parea and Karea, respectively), in relation to respective soil nutrients from 89 species at seven sites along forest-savanna ecotones in Ghana and Brazil...
November 2, 2018: Tree Physiology
Choimaa Dulamsuren, Sholpan B Abilova, Madina Bektayeva, Mahammad Eldarov, Bernhard Schuldt, Christoph Leuschner, Markus Hauck
The branch xylem of six important Inner Asian southern boreal forest trees was studied for wood-anatomical and hydraulic traits in order to infer the species' drought tolerance from embolism resistance, potential hydraulic conductivity, mean conduit diameters and conduit density. The only studied angiosperm tree, Betula pendula Roth, was much more sensitive to cavitation than all five conifers (evergreen or summer-green), even when using 88% loss of conductivity (P88) in birch, but 50% (P50) in the conifers as critical thresholds...
November 1, 2018: Tree Physiology
Simon M Landhäusser, Pak S Chow, L Turin Dickman, Morgan E Furze, Iris Kuhlman, Sandra Schmid, Julia Wiesenbauer, Birgit Wild, Gerd Gleixner, Henrik Hartmann, Günter Hoch, Nate G McDowell, Andrew D Richardson, Andreas Richter, Henry D Adams
Non-structural carbohydrates (NSCs), the stored products of photosynthesis, building blocks for growth and fuel for respiration, are central to plant metabolism, but their measurement is challenging. Differences in methods and procedures among laboratories can cause results to vary widely, limiting our ability to integrate and generalize patterns in plant carbon balance among studies. A recent assessment found that NSC concentrations measured for a common set of samples can vary by an order of magnitude, but sources for this variability were unclear...
October 30, 2018: Tree Physiology
Ai-Ying Wang, Shi-Jie Han, Jun-Hui Zhang, Miao Wang, Xiao-Han Yin, Li-Dong Fang, Da Yang, Guang-You Hao
Nonstructural carbohydrates (NSC) have been proposed to play an important role in maintaining the hydraulic integrity of trees, particularly in environments with high risks of embolism formation, but knowledge about the interaction between NSC reserves and xylem hydraulics is still very limited. We studied the variation of NSC reserves and hydraulic traits in Pinus koraiensis Sieb. et Zucc. (Korean pine) in March and June across a relatively large altitudinal gradient in Changbai Mountain of Northeast China...
October 30, 2018: Tree Physiology
Anna Korhonen, Tarja Lehto, Jaakko Heinonen, Tapani Repo
Ectomycorrhizal trees are common in the cold regions of the world, yet the role of the mycorrhizal symbiosis in plant cold tolerance is poorly known. Moreover, the standard methods for testing plant frost hardiness may not be adequate for roots and mycorrhizas. The aims of this study were to compare the frost hardiness of mycorrhizal and non-mycorrhizal Scots pine (Pinus sylvestris L.) seedlings and to test the use of reverse-flow root hydraulic conductance (Kr) measurement for root frost hardiness determination...
October 29, 2018: Tree Physiology
Martina Lazzarin, Roman Zweifel, Niels Anten, Frank J Sterck
Diel stem diameter changes measured at the stem base of temperate tree species can be mostly explained by a hydraulic system of flow and storage compartments passively driven by transpiration. Active, osmotic processes are considered to play a minor role only. Here we explore whether such osmotic processes have a stronger impact on diel changes in twig diameter than in stem diameter because twigs are closer to the leaves, the main source of newly acquired carbon. We investigated stem and twig diameter changes of wood and bark of pine trees in parallel to fluctuations of the osmolality in needles and in the bark at the stem base...
October 29, 2018: Tree Physiology
Ying Jin, Chuankuan Wang, Zhenghu Zhou
Vulnerability segmentation (VS), an important mechanism for protecting plants from drought, hypothesizes that the distal organs of a plant should be more susceptible to embolism than the basal organs. However, experimental studies testing the VS hypothesis for trees are limited and have reached inconsistent conclusions. Here, we tested the VS hypothesis with three angiosperms and four conifers co-existing in a temperate forest in northeastern China. The results showed that the difference in vulnerability to cavitation between leaves and branches (P50leaf-branch) was positive for the conifers but negative for the angiosperms, implying that the conifers rather than the angiosperms exhibited VS...
October 15, 2018: Tree Physiology
José A Ramírez-Valiente, Julie R Etterson, Nicholas J Deacon, Jeannine Cavender-Bares
Heritable variation in polygenic (quantitative) traits is critical for adaptive evolution and is especially important in this era of rapid climate change. In this study, we examined the levels of quantitative genetic variation of populations of the tropical tree Quercus oleoides Cham. and Schlect. for a suite of traits related to resource use and drought resistance. We tested whether quantitative genetic variation differed across traits, populations and watering treatments. We also tested potential evolutionary factors that might have shaped such a pattern: selection by climate and genetic drift...
October 15, 2018: Tree Physiology
Houjun Zhou, Xueqin Song, Kaili Wei, Yanqiu Zhao, Cheng Jiang, Jinnan Wang, Fang Tang, Mengzhu Lu
Growth-regulating factors (GRFs) are involved in various developmental events, particularly leaf development. However, the functions of GRFs in woody plants remain elusive. In this study, functional characterization of GRF15 in Populus was performed. Most GRFs are preferentially expressed in young leaves. As GRF15 was expressed at the highest level and with highest ratio in Populus species with large leaves, this gene was investigated through transgenic analyses. Promotor-β-glucuronidase analysis revealed expression of GRF15 at the leaf expansion zone...
October 11, 2018: Tree Physiology
Tadeja Savi, Johannes Tintner, Luca Da Sois, Michael Grabner, Giai Petit, Sabine Rosner
Xylem resistance to embolism formation determines the species-specific drought tolerance and the survival prospects of plants under extreme climatic conditions. Fourier Transform-Infrared (FTIR) spectroscopy is a cost-effective and rapid analytical tool with potential beyond its current use in plant physiology. We tested the use of FTIR spectroscopy as a method for estimating wood density (WD) and xylem resistance to embolism formation (P50) in 24 angiosperm species. Higher WD was associated with more negative P50 (r2 = 0...
October 11, 2018: Tree Physiology
Andrew R Benson, Andrew K Koeser, Justin Morgenroth
Accurately estimating sapwood area is essential for modelling whole-tree or stand-scale transpiration from point-flow sap-flux observations. In this study, we tested the validity of electrical resistance tomography (ERT) to locate the sapwood-heartwood (SW/HW) interface for two ring porous (Quercus nigra L. and Quercus virginiana Mill.) and one diffuse porous (Acer rubrum L.) species. Estimates derived from the ERT analyses were compared with the SW/HW interface measured following dye perfusion testing. The ERT results revealed spatial variation in electrical resistance, with higher resistivity in the inner part of the cross sections...
October 9, 2018: Tree Physiology
Mohitul Hossain, Erik J Veneklaas, Giles E St J Hardy, Pieter Poot
There is increasing concern about tree mortality around the world due to climatic extremes and associated shifts in pest and pathogen dynamics. Yet, empirical studies addressing the interactive effect of biotic and abiotic stress on plants are very rare. Therefore, in this study, we examined the interaction between drought stress and a canker pathogen, Quambalaria coyrecup, on the eucalypt - Corymbia calophylla (marri), which is experiencing increasing drought stress. We hypothesized that drought stress would increase marri's susceptibility to canker disease, and cankers would have the largest negative effect on plants that are already drought stressed before pathogen inoculation...
October 9, 2018: Tree Physiology
Silvia Lechthaler, Tarryn L Turnbull, Ylenia Gelmini, Francesco Pirotti, Tommaso Anfodillo, Mark A Adams, Giai Petit
Anatomical traits such as xylem conduit diameter and vessel connectivity are fundamental characteristics of the hydraulic architecture of vascular plants. Stem xylem conduits are narrow at the stem apex, and this confers resistance to embolisms that might otherwise be induced by large, negative water potentials at the top of tall trees. Below the apex, conduits progressively widen and this characteristic minimizes effects of path length on total hydraulic resistance. While interconnections among xylem vessels have been noted for decades, their role(s) are not fully clarified...
October 9, 2018: Tree Physiology
Wilfried Konrad, Gabriel Katul, Anita Roth-Nebelsick, Kaare H Jensen
Xylem and phloem are the two main conveyance systems in plants allowing exchanges of water and carbohydrates between roots and leaves. While each system has been studied in isolation for well over a century, the coupling and coordination between them remains the subject of inquiry and active research and frames the scope of the review here. Using a set of balance equations, hazards of bubble formation and their role in shaping xylem pressure and its corollary impact on phloem pressure and sugar transport are featured...
October 9, 2018: Tree Physiology
Chunhao Chang, Zhiwen Liu, Yanyan Wang, Zhonghua Tang, Fang Yu
Camptothecin (CPT) has powerful biological activities and its analogs, irinothecan and topothecan, are effective anti-cancer drugs for clinical therapy. Camptothecin was first isolated from Camptotheca acuminata and its low accumulation in planta limits drug supply in the market. Previous works have confirmed that many environmental factors and plant hormones/elicitors could regulate CPT biosynthesis, but only light irradiance has a negative effect on CPT production in C. acuminata. Although light irradiance has been identified as a negative CPT biosynthesis regulator in C...
October 4, 2018: Tree Physiology
Natalie A McBranch, Charlotte Grossiord, Henry Adams, Isaac Borrego, Adam D Collins, Turin Dickman, Max Ryan, Sanna Sevanto, Nate G McDowell
The leaf area to sapwood area ratios of trees (Al:AS) can shift to maintain homeostatic gas exchange per unit leaf area in response to climate variability. We tested the hypothesis that trees alter their Al:AS ratios in response to long-term warming and reduced precipitation in order to maintain leaf-specific gas exchange rates under more stressful conditions. Whole-tree Al:AS was measured on mature piñon pine (Pinus edulis Engelm.) and one-seed juniper (Juniperus monosperma (Engelm.) Sarg.) trees after 5 years (2012-16) of chronic exposure to increased temperature (+4...
September 29, 2018: Tree Physiology
Frank M Thomas, Andreas Rzepecki, Andreas Lücke, Inge Wiekenkamp, Inken Rabbel, Thomas Pütz, Burkhard Neuwirth
Among the environmental factors that have an effect on the isotopic signature of tree rings, the specific impact of soil moisture on the Δ13C and, in particular, the δ18O ratios has scarcely been investigated. We studied the effects of soil type and soil moisture (from moderately moist [Cambisol] to wet [Gleysol]) on the growth and isotopic signature of tree rings of Norway spruce (Picea abies [L.] H. Karst.), a widely distributed forest tree species in Central Europe, at a small spatial scale in a typical mature forest plantation in the low mountain ranges of Western Germany...
September 28, 2018: Tree Physiology
Xiaoli Fu, Frederick C Meinzer
Plants operate along a continuum of stringency of regulation of plant water potential from isohydry to anisohydry. However, most metrics and proxies of plant iso/anisohydric behavior have been developed from limited sets of site-specific experiments. Understanding the underlying mechanisms that determine species' operating ranges along this continuum, independent of site and growing conditions, remains challenging. We compiled a global database to assess the global patterns of metrics and proxies of plant iso/anisohydry and then explored some of the underlying functional traits and trade-offs associated with stringency of regulation that determines where species operate along the continuum...
September 26, 2018: Tree Physiology
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