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Durak R, Bednarski W, Formela-Luboińska M, Woźniak A, Borowiak-Sobkowiak B, Durak T, Dembczyński R, Morkunas I. Defense responses of Thuja orientalis to infestation of anholocyclic species aphid Cinara tujafilina. J Plant Physiol 2019; 232:160-170. [PMID: 30537603 DOI: 10.1016/j.jplph.2018.11.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2018] [Revised: 11/18/2018] [Accepted: 11/19/2018] [Indexed: 05/20/2023]
Abstract
The aim of this study was to determine an interdependence between generation of semiquinone radicals, superoxide anion (O2-), manganese ions (Mn2+) and phenolic content in leaves of Thuja orientalis in response to infestation by varying populations of Cinara tujafilina, i.e. 40 or 80 aphids per plant. Also, superoxide dismutase (SOD) and β-d-glucosidase activities in leaves of T. orientalis in a defense response to C. tujafilina was recorded. Analyses of electron paramagnetic resonance (EPR) showed generally a higher concentration of semiquinone radicals with g-values of 2.0051 ± 0.0005 and 20032 ± 0.0005 after C. tujafilina infestation in leaves in comparison to the control. Up to 48 h post-infestation in leaves infested by 80 aphids the level of semiquinone radicals was significantly higher than in the control, while in leaves infested by 40 aphids the highest concentrations of these radicals were recorded at later time points (i.e. at 72 and 96 hpi). In parallel, the highest total generation of O2- and low activity of SOD were recorded in 24-h leaves infested by 80 aphids. Additionally, analysis of confocal images showed that the strongest yellow fluorescence indicating O2- generation was detected in epidermal cells of leaves up to 48 hpi. Significant reduction of Mn2+ ions detected by EPR spectroscopy in relation to the control was observed in 4-w leaves infested by 80 and 40 aphids and in 48-h leaves infested by 40 aphids. Phenolic contents in leaves infested by 80 and 40 aphids at all time points were higher than in the control. The greatest β-d-glucosidase activity and phenolic contents were recorded at 96 h of feeding. These results indicate that the perception of C. tujafilina infestation by T. orientalis leaves induces a specified sequence of defense mechanisms in the course of time.
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Affiliation(s)
- Roma Durak
- Department of Experimental Zoology, University of Rzeszów, Pigonia 1, 35-310, Rzeszów, Poland
| | - Waldemar Bednarski
- Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań, Poland
| | - Magda Formela-Luboińska
- Department of Plant Physiology, Poznań University of Life Sciences, Wołyńska 35, 60-637 Poznań, Poland
| | - Agnieszka Woźniak
- Department of Plant Physiology, Poznań University of Life Sciences, Wołyńska 35, 60-637 Poznań, Poland
| | - Beata Borowiak-Sobkowiak
- Department of Entomology and Environmental Protection, Poznań University of Life Sciences, Dąbrowskiego 159, 60-594 Poznań, Poland
| | - Tomasz Durak
- Department of Plant Physiology and Ecology, University of Rzeszów, Rejtana 16c, 35-959, Rzeszów, Poland
| | - Radosław Dembczyński
- Department of Biotechnology and Food Microbiology, Poznań University of Life Sciences, Wojska Polskiego 48, 60-627 Poznan, Poland
| | - Iwona Morkunas
- Department of Plant Physiology, Poznań University of Life Sciences, Wołyńska 35, 60-637 Poznań, Poland.
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Cui YM, Sun B, Wang HF, Ferguson DK, Wang YF, Li CS, Yang J, Ma QW. Exploring the Formation of a Disjunctive Pattern between Eastern Asia and North America Based on Fossil Evidence from Thuja (Cupressaceae). PLoS One 2015; 10:e0138544. [PMID: 26393513 PMCID: PMC4579098 DOI: 10.1371/journal.pone.0138544] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 09/01/2015] [Indexed: 11/19/2022] Open
Abstract
Thuja, a genus of Cupressaceae comprising five extant species, presently occurs in both East Asia (3 species) and North America (2 species) and has a long fossil record from Paleocene to Pleistocene in the Northern Hemisphere. Two distinct hypotheses have been proposed to account for the origin and present distribution of this genus. Here we recognize and describe T. sutchuenensis Franch., a new fossil Thuja from the late Pliocene sediments of Zhangcun, Shanxi, North China, based on detailed comparisons with all living species and other fossil ones, integrate the global fossil records of this genus plotted in a set of paleomaps from different time intervals, which show that Thuja probably first appeared at high latitudes of North America in or before the Paleocene. This genus reached Greenland in the Paleocene, then arrived in eastern Asia in the Miocene via the land connection between East Asia and western North America. In the late Pliocene, it migrated into the interior of China. With the Quaternary cooling and drying, Thuja gradually retreated southwards to form today's disjunctive distribution between East Asia and North America.
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Affiliation(s)
- Yi-Ming Cui
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, No. 20 Nan Xin Cun, Xiangshan, Beijing, 100093, China
- University of the Chinese Academy of Sciences, Beijing, 100039, China
| | - Bin Sun
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, No. 20 Nan Xin Cun, Xiangshan, Beijing, 100093, China
- University of the Chinese Academy of Sciences, Beijing, 100039, China
| | - Hai-Feng Wang
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, No. 20 Nan Xin Cun, Xiangshan, Beijing, 100093, China
| | - David Kay Ferguson
- Department of Paleontology, University of Vienna, Althanstrasse 14, A-1090, Vienna, Austria
| | - Yu-Fei Wang
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, No. 20 Nan Xin Cun, Xiangshan, Beijing, 100093, China
- * E-mail: (Y-FW); (JY)
| | - Cheng-Sen Li
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, No. 20 Nan Xin Cun, Xiangshan, Beijing, 100093, China
| | - Jian Yang
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, No. 20 Nan Xin Cun, Xiangshan, Beijing, 100093, China
- * E-mail: (Y-FW); (JY)
| | - Qing-Wen Ma
- Beijing Museum of Natural History, Beijing, 100050, China
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Zhao J, Hartmann H, Trumbore S, Ziegler W, Zhang Y. High temperature causes negative whole-plant carbon balance under mild drought. New Phytol 2013; 200:330-339. [PMID: 23822669 DOI: 10.1111/nph.12400] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 06/06/2013] [Indexed: 05/29/2023]
Abstract
Theoretically, progressive drought can force trees into negative carbon (C) balance by reducing stomatal conductance to prevent water loss, which also decreases C assimilation. At higher temperatures, negative C balance should be initiated at higher soil moisture because of increased respiratory demand and earlier stomatal closure. Few data are available on how these theoretical relationships integrate over the whole plant. We exposed Thuja occidentalis to progressive drought under three temperature conditions (15, 25, and 35°C), and measured C and water fluxes using a whole-tree chamber design. High transpiration rates at higher temperatures led to a rapid decline in soil moisture. During the progressive drought, soil moisture-driven changes in photosynthesis had a greater impact on the whole-plant C balance than respiration. The soil moisture content at which whole-plant C balance became negative increased with temperature, mainly as a result of higher respiration rates and an earlier onset of stomatal closure under a warmer condition. Our results suggest that the effect of drought on whole-plant C balance is highly temperature-dependent. High temperature causes a negative C balance even under mild drought and may increase the risk of C starvation.
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Affiliation(s)
- Junbin Zhao
- Max Planck Institute for Biogeochemistry, Jena, 07745, Germany
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, 666303, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Henrik Hartmann
- Max Planck Institute for Biogeochemistry, Jena, 07745, Germany
| | - Susan Trumbore
- Max Planck Institute for Biogeochemistry, Jena, 07745, Germany
| | | | - Yiping Zhang
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, 666303, China
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Yu X, Zha T, Pang Z, Wu B, Wang X, Chen G, Li C, Cao J, Jia G, Li X, Wu H. Response of soil respiration to soil temperature and moisture in a 50-year-old oriental arborvitae plantation in China. PLoS One 2011; 6:e28397. [PMID: 22163012 PMCID: PMC3232204 DOI: 10.1371/journal.pone.0028397] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Accepted: 11/07/2011] [Indexed: 11/29/2022] Open
Abstract
China possesses large areas of plantation forests which take up great quantities of carbon. However, studies on soil respiration in these plantation forests are rather scarce and their soil carbon flux remains an uncertainty. In this study, we used an automatic chamber system to measure soil surface flux of a 50-year-old mature plantation of Platycladus orientalis at Jiufeng Mountain, Beijing, China. Mean daily soil respiration rates (Rs) ranged from 0.09 to 4.87 µmol CO2 m−2s−1, with the highest values observed in August and the lowest in the winter months. A logistic model gave the best fit to the relationship between hourly Rs and soil temperature (Ts), explaining 82% of the variation in Rs over the annual cycle. The annual total of soil respiration estimated from the logistic model was 645±5 g C m−2 year−1. The performance of the logistic model was poorest during periods of high soil temperature or low soil volumetric water content (VWC), which limits the model's ability to predict the seasonal dynamics of Rs. The logistic model will potentially overestimate Rs at high Ts and low VWC. Seasonally, Rs increased significantly and linearly with increasing VWC in May and July, in which VWC was low. In the months from August to November, inclusive, in which VWC was not limiting, Rs showed a positively exponential relationship with Ts. The seasonal sensitivity of soil respiration to Ts (Q10) ranged from 0.76 in May to 4.38 in October. It was suggested that soil temperature was the main determinant of soil respiration when soil water was not limiting.
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Affiliation(s)
- Xinxiao Yu
- Chinese Institute of Green Carbon, The School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Tianshan Zha
- Chinese Institute of Green Carbon, The School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
- * E-mail:
| | - Zhuo Pang
- Chinese Institute of Green Carbon, The School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Bin Wu
- Chinese Institute of Green Carbon, The School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Xiaoping Wang
- Chinese Institute of Green Carbon, The School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Guopeng Chen
- The Faculty of Forestry, Sichuan Agricultural University, Yaan, China
| | - Chunping Li
- Chinese Institute of Green Carbon, The School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Jixin Cao
- Research Institute of Forest Ecology, Chinese Academy of Forestry, Beijing, China
| | - Guodong Jia
- Chinese Institute of Green Carbon, The School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Xizhi Li
- Chinese Institute of Green Carbon, The School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Hailong Wu
- Chinese Institute of Green Carbon, The School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
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Abstract
Conductance to CO(2) inside leaves, known as mesophyll conductance (g(m)), imposes large limitations on photosynthesis. Because g(m) is difficult to quantify, it is often neglected in calculations of (13)C photosynthetic discrimination. The 'soluble sugar method' estimates g(m) via differences between observed photosynthetic discrimination, calculated from the δ(13)C of soluble sugars, and discrimination when g(m) is infinite. We expand upon this approach and calculate a photosynthesis-weighted average for canopy mesophyll conductance ((c) g(m)) using δ(13)C of stem phloem contents. We measured gas exchange at three canopy positions and collected stem phloem contents in mature trees of three conifer species (Pseudotsuga menziesii, Thuja plicata and Larix occidentalis). We generated species-specific and seasonally variable estimates of (c)g(m) . We found that (c)g(m) was significantly different among species (0.41, 0.22 and 0.09 mol m(-2) s(-1) for Larix, Pseudotsuga and Thuja, respectively), but was similar throughout the season. Ignoring respiratory and photorespiratory fractionations ((c)Δ(ef)) resulted in ≈30% underestimation of (c)g(m) in Larix and Pseudotsuga, but was innocuous in Thuja. Substantial errors (~1-4‰) in photosynthetic discrimination calculations were introduced by neglecting (c)g(m) and (c)Δ(ef) . Our method is easy to apply and cost-effective, captures species variation and would have captured seasonal variation had it existed. The method provides an average canopy value, which makes it suitable for parameterization of canopy-scale models of photosynthesis, even in tall trees.
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Affiliation(s)
- Nerea Ubierna
- Department of Forest Resources, University of Idaho, Moscow, ID 83844-1133, USA.
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Dutilleul P, Han L, Smith DL. Plant light interception can be explained via computed tomography scanning: demonstration with pyramidal cedar (Thuja occidentalis, Fastigiata). Ann Bot 2008; 101:19-23. [PMID: 17981879 PMCID: PMC2701837 DOI: 10.1093/aob/mcm273] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
BACKGROUND AND AIMS Light interception by the leaf canopy is a key aspect of plant photosynthesis, which helps mitigate the greenhouse effect via atmospheric CO(2) recycling. The relationship between plant light interception and leaf area was traditionally modelled with the Beer-Lambert law, until the spatial distribution of leaves was incorporated through the fractal dimension of leafless plant structure photographed from the side allowing maximum appearance of branches and petioles. However, photographs of leafless plants are two-dimensional projections of three-dimensional structures, and sampled plants were cut at the stem base before leaf blades were detached manually, so canopy development could not be followed for individual plants. Therefore, a new measurement and modelling approach were developed to explain plant light interception more completely and precisely, based on appropriate processing of computed tomography (CT) scanning data collected for developing canopies. METHODS Three-dimensional images of canopies were constructed from CT scanning data. Leaf volumes (LV) were evaluated from complete canopy images, and fractal dimensions (FD) were estimated from skeletonized leafless images. The experimental plant species is pyramidal cedar (Thuja occidentalis, Fastigiata). KEY RESULTS The three-dimensional version of the Beer-Lambert law based on FD alone provided a much better explanation of plant light interception (R(2) = 0.858) than those using the product LV*FD (0.589) or LV alone (0.548). While values of all three regressors were found to increase over time, FD in the Beer-Lambert law followed the increase in light interception the most closely. The delayed increase of LV reflected the appearance of new leaves only after branches had lengthened and ramified. CONCLUSIONS The very strong correlation obtained with FD demonstrates that CT scanning data contain fundamental information about the canopy architecture geometry. The model can be used to identify crops and plantation trees with improved light interception and productivity.
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Affiliation(s)
- Pierre Dutilleul
- Department of Plant Science, McGill University, Macdonald Campus, 21,111 Lakeshore Road, Ste-Anne-de-Bellevue, Québec, Canada H9X 3V9.
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Terskikh VV, Zeng Y, Feurtado JA, Giblin M, Abrams SR, Kermode AR. Deterioration of western redcedar (Thuja plicata Donn ex D. Don) seeds: protein oxidation and in vivo NMR monitoring of storage oils. J Exp Bot 2008; 59:765-777. [PMID: 18349051 DOI: 10.1093/jxb/erm357] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Deterioration of conifer seeds during prolonged storage has a negative impact on reforestation and gene conservation efforts. Western redcedar (Thuja plicata Donn ex D. Don) is a species of tremendous value to the forest industry. The seeds of this species are particularly prone to viability losses during long-term storage. Reliable tools to assess losses in seed viability during storage and their underlying causes, as well as the development of methods to prevent storage-related deterioration of seeds are needed by the forest industry. In this work, various imaging methods and biochemical analyses were applied to study deterioration of western redcedar seeds. Seedlots that exhibited poor germination performance, i.e. those that had experienced the greatest losses of viability during prolonged storage, exhibited greater abundance of oxidized proteins, detected by protein oxidation assays, and more pronounced changes in their in vivo (13)C NMR spectra, most likely due to storage oil oxidation. The proportion of oxidized proteins also increased when seeds were subjected to accelerated ageing treatments. Detection of oxidized oils and proteins may constitute a reliable and useful tool for the forest industry.
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Affiliation(s)
- Victor V Terskikh
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
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Kavanagh KL, Pangle R, Schotzko AD. Nocturnal transpiration causing disequilibrium between soil and stem predawn water potential in mixed conifer forests of Idaho. Tree Physiol 2007; 27:621-9. [PMID: 17242003 DOI: 10.1093/treephys/27.4.621] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Soil water potential (Psi(s)) is often estimated by measuring leaf water potential before dawn (Psi(pd)), based on the assumption that the plant water status has come into equilibrium with that of the soil. However, it has been documented for a number of plant species that stomata do not close completely at night, allowing for nocturnal transpiration and thus preventing nocturnal soil-plant water potential equilibration. The potential for nighttime transpiration necessitates testing the assumption of nocturnal equilibration before accepting Psi(pd) as a valid estimate of Psi(s). We determined the magnitude of disequilibrium between Psi(pd) and Psi(s) in four temperate conifer species across three height classes through a replicated study in northern Idaho. Based on both stomatal conductance and sap flux measurements, we confirmed that the combination of open stomata and high nocturnal atmospheric vapor pressure deficit (D) resulted in nocturnal transpiration in all four species. Nocturnal stomatal conductance (g(s-noc)) averaged about 33% of mid-morning conductance values. We used species-specific estimates of g(s-noc) and leaf specific conductance to correct Psi(pd) values for nocturnal transpiration at the time the samples were collected. Compared with the unadjusted values, corrected values reflected a significantly higher Psi(pd) (when D > 0.12 kPa). These results demonstrate that comparisons of Psi(pd) among species, canopy height classes and sites, and across growing seasons can be influenced by differential amounts of nocturnal transpiration, leading to flawed results. Consequently, it is important to account for the presence of nocturnal transpiration, either through a properly parameterized model or by making Psi(pd) measurements when D is sufficiently low that it cannot drive nocturnal transpiration. Violating these conditions will likely result in underestimation of Psi(s).
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Affiliation(s)
- Kathleen L Kavanagh
- Department of Forest Resources, University of Idaho, P.O. Box 441133, Moscow, ID 83844-1133, USA.
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9
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Abstract
Among annual plants, daily transpiration rates, expressed as a fraction of volumetric soil water content available for transpiration, show a common pattern in response to soil drying. Initially, as soil dries, there is little decrease in transpiration rate until water availability has fallen to about one third that at field capacity. With further soil drying, relative transpiration rate decreases in a more-or-less linear fashion until all available water has been used. Data previously obtained for perennial woody species have often been confounded by different methods for determining available soil water. In this study, we investigated the daily transpiration response to soil drying in five woody perennial species: Thuja plicata Donn ex D. Don, Acer rubrum L., Robinia pseudoacacia L., Hibiscus sp. and Ibex aquifolium L. Transpiration was unaffected by soil drying until the initial estimated transpirable soil water fraction had decreased to between 0.23 and 0.32 of that at field capacity. Beyond this point, transpiration rate declined linearly with available soil water fraction until reaching one fifth the rate observed in well-watered plants. With further soil drying, the relative transpiration rates remained between 10 and 20% of that observed in well-watered plants. Maintenance of transpiration at these rates with further soil drying was hypothesized to result from contributions to transpiration of water stored in plant tissues. After taking tissue water storage into account, it was estimated that transpiration was curtailed as the available soil water fraction fell to between 0.26 and 0.37 of that at field capacity, which is comparable to values reported for annual crop plants.
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Affiliation(s)
- Thomas R Sinclair
- Agronomy Physiology Laboratory, University of Florida, Gainesville, 32611-0965, USA.
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10
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Abstract
Leaf longevity determines the annual cost of replacing foliage biomass and influences water and nutrient budgets. Longevity is readily estimated in most evergreen species by annual bud scars along the shoot. However, some species with indeterminate growth do not show these annual markers, making estimation of longevity difficult. One of these species is the widespread and economically valuable western red cedar (Thuja plicata J. Donn ex D. Don), for which no dependable estimates of leaf longevity exist. In this study, we estimated leaf longevity for western red cedar by counting growth rings in shoots at the point of leaf abscission. Estimates were obtained on 26 dominant or codominant trees growing in natural stands in a montane forest in northern Idaho, USA. Leaf longevity averaged 8.9 (SE = 0.2) years, but it strongly increased with depth in the canopy (0.3 year m(-1); mean crown depth was 15 m), increasing from a mean of 6.8 years in the upper third of the canopy to 10.6 years in the lower third. The increase in longevity with depth in the crown is consistent with many reports showing that longevity increases in resource-limiting environments. Longevity did not vary significantly with altitude or solar insolation in these montane forests. Among stand-level variables, longevity was correlated only with leaf area index: it increased slightly in stands with high leaf area indices. This approach to longevity estimation may be useful for any species that produces annual rings but no obvious bud scars, including many Cupressaceae species.
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Affiliation(s)
- Benjamin A Harlow
- Department of Forest Resources, University of Idaho, Moscow, ID 83844-1133, USA.
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11
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Bennett JN, Prescott CE. Organic and inorganic nitrogen nutrition of western red cedar, western hemlock and salal in mineral N-limited cedar-hemlock forests. Oecologia 2004; 141:468-76. [PMID: 15322895 DOI: 10.1007/s00442-004-1622-3] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2004] [Accepted: 05/14/2004] [Indexed: 11/30/2022]
Abstract
Western red cedar (Thuja plicata Donn.), western hemlock (Tsuga heterophylla Raf. Sarge) and salal (Gaultheria shallon Pursh) are the main species growing in cedar-hemlock forests on Vancouver Island, Canada. Based on the dominance of organic N in these systems, we tested the hypotheses that: (1) organic N can be utilized by the three plant species; and (2) salal, which is ericoid mycorrhizal and has high tannin concentration in its tissues, would absorb more N from the complex organic N compounds than the other two species. The abilities of cedar, hemlock and salal to take up 15N,13C-labelled glutamic acid were measured and the capacities of the three species to use nitrate (NO3-), ammonium (NH4+), glutamic acid, protein and protein-tannin N were compared over a 20-day period. Based on 13C enrichment, all three species absorbed at least a portion of glutamic acid intact. Cedar, hemlock and salal also showed similar patterns of N uptake from the NO3-, NH4+, glutamic acid, protein and protein-tannin treatments. The largest proportions of applied N were taken up from the NO3- and NH4+ treatments while smaller amounts of N were absorbed from the organic N compounds. Thus organic N was accessed to a modest degree by all three species, and salal did not have a greater capacity to utilize protein and protein-tannin-N.
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Affiliation(s)
- Jennifer N Bennett
- Forestry Department, North Carolina State University, 3106 Jordan Hall, Raleigh, NC 27601-8008, USA.
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12
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Abstract
Survival after freezing was measured for seeds and germinants of four seedlots each of interior spruce (Picea glauca x engelmannii complex), lodgepole pine (Pinus contorta Dougl. ex Loud.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western red cedar (Thuja plicata Donn ex D. Donn). Effects of eight seed treatments on post-freezing survival of seeds and germinants were tested: dry, imbibed and stratified seed, and seed placed in a growth chamber for 2, 5, 10, 15, 20 or 30 days in a 16-h photoperiod and a 22/17 degrees C thermoperiod. Survival was related to the water content of seeds and germinants, germination rate and seedlot origin. After freezing for 3 h at -196 degrees C, dry seed of most seedlots of interior spruce, Douglas-fir and western red cedar had 84-96% germination, whereas lodgepole pine seedlots had 53-82% germination. Freezing tolerance declined significantly after imbibition in lodgepole pine, Douglas-fir and interior spruce seed (western red cedar was not tested), and mean LT50 of imbibed seed of these species was -30, -24.5 and -20 degrees C, respectively. Freezing tolerance continued to decline to a minimum LT50 of -4 to -7 degrees C after 10 days in a growth chamber for interior spruce, Douglas-fir and lodgepole pine, or after 15 days for western red cedar. Minimum freezing tolerance was reached at the stage of rapid hypocotyl elongation. In all species, a slight increase in freezing tolerance of germinants was observed once cotyledons emerged from the seed coat. The decrease in freezing tolerance during the transition from dry to germinating seed correlated with increases in seed water content. Changes in freezing tolerance between 10 and 30 days in the growth chamber were not correlated with seedling water content. Within a species, seedlots differed significantly in freezing tolerance after 2 or 5 days in the growth chamber. Because all seedlots of interior spruce and lodgepole pine germinated quickly, there was no correlation between seedlot hardiness and rate of germination. Germination rate and freezing tolerance of Douglas-fir and western red cedar seedlots was negatively correlated. There was a significant correlation between LT50 after 10 days in the growth chamber and minimum spring temperature at the location of seedlot origin for interior spruce and three seedlots of western red cedar, but no relationship was apparent for lodgepole pine and Douglas-fir.
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Affiliation(s)
- B J Hawkins
- Centre for Forest Biology, University of Victoria, P.O. Box 3020, STN CSC, Victoria, B.C., V8W 3N5, Canada.
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13
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Pepin S, Livingston NJ, Whitehead D. Responses of transpiration and photosynthesis to reversible changes in photosynthetic foliage area in western red cedar (Thuja plicata) seedlings. Tree Physiol 2002; 22:363-371. [PMID: 11960761 DOI: 10.1093/treephys/22.6.363] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Experiments were conducted on 1-year-old western red cedar (Thuja plicata Donn.) seedlings to determine the response of illuminated foliage to reversible changes in total photosynthetic foliage area (L(A)). Reductions in L(A) were brought about by either shading the lower foliage or by reducing the ambient CO2 concentration (c(a)) of the air surrounding the lower part of the seedling. In the latter case, the vapor pressure was also changed so that transpiration rates (E) could be manipulated independently of photosynthetic rates (A). We hypothesized that following such treatments, short-term compensatory changes would occur in stomatal conductance (g(s)) and A of the remaining foliage. These changes would occur in response to hydraulic signals generated by changes in the water potential gradient rather than changes in the distribution of sources and sinks of carbon within the seedling. When a portion of the foliage was shaded, there was an immediate reduction in whole-seedling E and a concomitant increase in g(s), A and E in the remaining illuminated foliage. However, the intercellular CO2 concentration did not change. These compensatory effects were fully reversed after the shade was removed. When the lower foliage A was reduced to < 0 micromol m-2 s-1, by shading or lowering c(a), and E was either unchanged or increased (by adjusting the vapor pressure deficit), there was no significant increase in g(s) and A in the remaining foliage. We conclude that compensatory responses in illuminated foliage occur only when reductions in L(A) are accompanied by a reduction in whole-plant E. The relationship between the reduction in whole-seedling E and the increase in A is highly linear (r2 = 0.68) and confirms our hypothesis of the strong regulation of g(s) by hydraulic signals generated within the seedling. We suggest that the mechanism of the compensatory effects is a combination of both increased CO2 supply, resulting from increased g(s), and a response of the rate of carboxylation, possibly related to the activity of Rubisco.
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Affiliation(s)
- S Pepin
- Institute of Botany, University of Basel, Schönbeinstrasse 6, Ch-4056, Switzerland.
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