1
|
Kafuti C, Lehnebach R, Bourland N, Beeckman H, Van Acker J, Luambua NK, Van den Bulcke J. Earlier onset and slower heartwood investment in faster-growing trees of African tropical species. ANNALS OF BOTANY 2024; 133:905-916. [PMID: 37409979 PMCID: PMC11082515 DOI: 10.1093/aob/mcad079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 07/04/2023] [Indexed: 07/07/2023]
Abstract
BACKGROUND AND AIMS Heartwood plays an important role in maintaining the structural integrity of trees. Although its formation has long been thought to be driven solely by internal ageing processes, more recent hypotheses suggest that heartwood formation acts as a regulator of the tree water balance by modulating the quantity of sapwood. Testing both hypotheses would shed light on the potential ecophysiological nature of heartwood formation, a very common process in trees. METHODS We measured quantities of heartwood and sapwood, xylem conduits and the width and number of growth rings on 406 stems of Pericopsis elata with ages ranging from 2 to 237 years. A subset of 17 trees with similar ages but varying growth rate were sampled in a shaded (slower-growth) site and a sun-exposed (faster-growth) site. We used regression analysis and structural equation modelling to investigate the dynamics and drivers of heartwood formation. KEY RESULTS We found a positive effect of growth rate on the probability of heartwood occurrence, suggesting an earlier heartwood onset in faster-growing stems. After this onset age, heartwood area increased with stem diameter and age. Despite the similar heartwood production per unit stem diameter increment, shaded trees produced heartwood faster than sun-exposed trees. Tree age and hydraulics showed similar direct effects on heartwood and sapwood area of sun-exposed trees, suggesting their mutual role in driving the heartwood dynamics of sun-exposed trees. However, for shaded trees, only tree hydraulics showed a direct effect, suggesting its prominent role over age in driving the heartwood dynamics in limited growing conditions. The positive relationship between growth rate and maximum stomatal conductance supported this conclusion. CONCLUSIONS Heartwood area increases as the tree ages, but at a slower rate in trees where water demand is balanced by a sufficient water supply. Our findings suggest that heartwood formation is not only a structural process but also functional.
Collapse
Affiliation(s)
- Chadrack Kafuti
- UGent-Woodlab, Laboratory of Wood Technology, Department of Environment, Ghent University, Coupure Links 653, 9000 Gent, Belgium
- Service of Wood Biology, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium
- Faculty of Agricultural Sciences, Department of Natural Resources Management, University of Kinshasa, 117 Kinshasa XI, Democratic Republic of the Congo
| | - Romain Lehnebach
- UGent-Woodlab, Laboratory of Wood Technology, Department of Environment, Ghent University, Coupure Links 653, 9000 Gent, Belgium
- CIRAD, UMR Ecologie des Forêts de Guyane (EcoFoG), AgroParisTech, CNRS, INRA, Université Des Antilles, Université de Guyane, 97310 Kourou, France
| | - Nils Bourland
- Service of Wood Biology, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium
- Center for International Forestry Research, Situ Gede, Sindang Barang, Bogor (Barat) 16115, Indonesia
| | - Hans Beeckman
- Service of Wood Biology, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium
| | - Joris Van Acker
- UGent-Woodlab, Laboratory of Wood Technology, Department of Environment, Ghent University, Coupure Links 653, 9000 Gent, Belgium
| | - Nestor K Luambua
- Service of Wood Biology, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium
- Faculté des sciences Agronomiques, Université Officielle de Mbujimayi, Mbujimayi, Democratic Republic of Congo
| | - Jan Van den Bulcke
- UGent-Woodlab, Laboratory of Wood Technology, Department of Environment, Ghent University, Coupure Links 653, 9000 Gent, Belgium
| |
Collapse
|
2
|
Xu GQ, Chen TQ, Liu SS, Ma J, Li Y. Within-crown plasticity of hydraulic properties influence branch dieback patterns of two woody plants under experimental drought conditions. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 854:158802. [PMID: 36115397 DOI: 10.1016/j.scitotenv.2022.158802] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 09/11/2022] [Accepted: 09/12/2022] [Indexed: 06/15/2023]
Abstract
In recent year, widespread declines of Populus bolleana Lauche trees (P. bolleana, which dieback from the top down) and Haloxylon ammodendron shrubs (H. ammodendron, which dieback starting from their outer canopy) have occurred. To investigate how both intra-canopy hydraulic changes and plasticity in hydraulic properties create differences in vulnerability between these two species, we conducted a drought simulation field experiment. We analyzed branch hydraulic vulnerability, leaf water potential (Ψ), photosynthesis (A), stomatal conductance (gs), non-structural carbohydrate (NSCs) contents and morphological traits of the plants as the plants underwent a partial canopy dieback. Our results showed that: (1) the hydraulic architecture was very different between the two life forms; (2) H. ammodendron exhibited a drought tolerance response with weak stomatal control, and thus a sharp decline in Ψ while P. bolleana showed a drought avoidance response with tighter stomatal control that maintained a relatively stable Ψ; (3) the Ψ of H. ammodendron showed relative consistent symptoms of drought stress with increasing plant stature, but the Ψ of P. bolleana showed greater drought stress in higher portions of the crown; (4) prolonged drought caused P. bolleana to consume and H. ammodendron to accumulate NSCs in the branches of their upper canopy. Thus, the prolonged drought caused the shoots of the upper canopy of P. bolleana to experience greater vulnerability leading to dieback of the upper branches first, while all the twigs of the outer canopy of H. ammodendron experienced nearly identical degrees of vulnerability, and thus dieback occurred uniformly. Our results indicate that intra-canopy hydraulic change and their plasticity under drought was the main cause of the observed canopy dieback patterns in both species. However, more work is needed to further establish that hydraulic limitation as a function of plant stature was the sole mechanism for causing the divergent canopy dieback patterns.
Collapse
Affiliation(s)
- Gui-Qing Xu
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China; Fukang Station of Desert Ecology, Chinese Academy of Sciences, Fukang 831505, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Tu-Qiang Chen
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China; Fukang Station of Desert Ecology, Chinese Academy of Sciences, Fukang 831505, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shen-Si Liu
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China; Fukang Station of Desert Ecology, Chinese Academy of Sciences, Fukang 831505, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jie Ma
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China; Fukang Station of Desert Ecology, Chinese Academy of Sciences, Fukang 831505, China
| | - Yan Li
- State Key Lab of Subtropical Siviculture, Zhejiang A&F University, 666Wusu Street, Lin-An, Hangzhou 311300, China
| |
Collapse
|
3
|
Lachenbruch B, St Clair JB, Harrington CA. Differences in branch hydraulic architecture related to the aridity of growing sites and seed sources of coastal Douglas-fir saplings. TREE PHYSIOLOGY 2022; 42:351-364. [PMID: 34553758 DOI: 10.1093/treephys/tpab106] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Accepted: 08/05/2021] [Indexed: 06/13/2023]
Abstract
To better understand hydraulic adaptations of coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) to local climate, we examined genetic (G) and environmental (E) responses of branch hydraulic architecture of 7-year-old saplings from dry and wet climates of origin grown at a relatively dry and a relatively wet common garden site in western Oregon. We sampled 2 years of branch growth from three dry-source and three wet-source families grown at both sites (72 branches, total). Overall, only 4 of the 11 traits had significant genetic (G) effects, whereas 9 traits had significant environmental (E) effects (P < 0.05). Both dry and wet sources had higher leaf-specific conductance (kl) at the dry than the wet site, but the values were achieved by different mechanisms and driven by G × E effects for leaf area/sapwood area (Al/As), shoot length (L), specific conductivity (Ks) and leaf-specific conductivity (Kl). Dry sources achieved higher kl in the dry site through higher Kl (via a lower Al/As and no change in Ks) with no difference in L. Wet sources achieved higher kl at the dry site through no difference in Kl (via no effect on Al/As, despite decreases in Al and As, and lower Ks) with lower L. Vulnerability to embolism (measured as percentage loss of conductivity at 4 MPa) had no G effect but an E effect, with slightly lower values at the dry site. Specific leaf area had G and E effects, with lower values for the dry sources and site. There were no G or E effects on wood density. The different responses of dry and wet sources to site aridity suggest that populations are differentially adapted to the aridity of growing sites. Population variation in response to aridity should be considered when selecting seed sources for establishing forests for future climates.
Collapse
Affiliation(s)
- Barbara Lachenbruch
- Department of Forest Ecosystems and Society, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331, USA
| | - J Bradley St Clair
- USDA-Forest Service, Pacific Northwest Research Station, 3200 SW Jefferson Way, Corvallis, OR 97331, USA
| | - Constance A Harrington
- USDA-Forest Service, Pacific Northwest Research Station, 3625 93rd Avenue SW, Olympia, WA 98512, USA
| |
Collapse
|
4
|
McMann N, Peichel A, Savage JA. Early spring flowers rely on xylem hydration but are not limited by stem xylem conductivity. THE NEW PHYTOLOGIST 2022; 233:838-850. [PMID: 34618926 DOI: 10.1111/nph.17782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 09/13/2021] [Indexed: 06/13/2023]
Abstract
Many woody plants produce large floral displays early in the spring when xylem transport can be variable and often reduced. To determine whether stem hydraulics impact floral water use, we quantified floral transpiration and tested whether it was correlated with stem xylem conductivity in five temperate woody species that flower before producing leaves. We measured inflorescence gas exchange, examined the relationship between diffusive conductance and inflorescence morphology, and estimated the amount of water supplied to an inflorescence by the phloem. We also tested for correlation between transpiration and native stem xylem conductivity for branches with leaves and branches with flowers. The flowers of our study species obtain most of their water from the xylem. Diffusive conductance was higher in small inflorescences, but water content and daily transpiration rates were greater for larger inflorescences. We found no correlation between floral transpiration per branch and stem xylem conductivity within species. The data suggest that inflorescence water loss during anthesis is not limited by the xylem in our study species. We highlight the impact of floral morphology on hydraulic traits and encourage exploration into temporal shifts in floral hydration.
Collapse
Affiliation(s)
- Natalie McMann
- Department of Biology, University of Minnesota Duluth, 207 Swenson Science Building, 1035 Kirby Drive, Duluth, MN, 55812, USA
| | - Alexander Peichel
- Department of Biology, University of Minnesota Duluth, 207 Swenson Science Building, 1035 Kirby Drive, Duluth, MN, 55812, USA
| | - Jessica A Savage
- Department of Biology, University of Minnesota Duluth, 207 Swenson Science Building, 1035 Kirby Drive, Duluth, MN, 55812, USA
| |
Collapse
|
5
|
Rodríguez-Gamir J, Xue J, Meason DF, Clearwater M, Clinton PW, Domec JC. Interclonal variation, coordination, and trade-offs between hydraulic conductance and gas exchange in Pinus radiata: consequences on plant growth and wood density. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:2419-2433. [PMID: 33337485 DOI: 10.1093/jxb/eraa587] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 12/17/2020] [Indexed: 05/24/2023]
Abstract
Stem growth reflects genetic and phenotypic differences within a tree species. The plant hydraulic system regulates the carbon economy, and therefore variations in growth and wood density. A whole-organism perspective, by partitioning the hydraulic system, is crucial for understanding the physical and physiological processes that coordinately mediate plant growth. The aim of this study was to determine whether the relationships and trade-offs between (i) hydraulic traits and their relative contribution to the whole-plant hydraulic system, (ii) plant water transport, (iii) CO2 assimilation, (iv) plant growth, and (v) wood density are revealed at the interclonal level within a variable population of 10 Pinus radiata (D. Don) clones for these characters. We demonstrated a strong coordination between several plant organs regarding their hydraulic efficiency. Hydraulic efficiency, gas exchange, and plant growth were intimately linked. Small reductions in stem wood density were related to a large increase in sapwood hydraulic efficiency, and thus to plant growth. However, stem growth rate was negatively related to wood density. We discuss insights explaining the relationships and trade-offs of the plant traits examined in this study. These insights provide a better understanding of the existing coordination, likely to be dependent on genetics, between the biophysical structure of wood, plant growth, hydraulic partitioning, and physiological plant functions in P. radiata.
Collapse
Affiliation(s)
- Juan Rodríguez-Gamir
- Producción Vegetal en zonas tropicales y subtropicales, Instituto Canario de Investigaciones Agrarias (ICIA), Ctra de El boquerón s/n, 38270 San Cristóbal de La Laguna, Tenerife, Canary Islands, Spain
- Forest Systems, Scion, Christchurch, New Zealand
| | - Jianming Xue
- Forest Systems, Scion, Christchurch, New Zealand
| | - Dean F Meason
- Forest Systems, Scion, Private Bag 3020, Rotorua, New Zealand
| | - Michael Clearwater
- Environmental Research Institute, University of Waikato, Private Bag 3105, Hamilton, New Zealand
| | | | - Jean-Christophe Domec
- Bordeaux Sciences Agro, UMR INRA ISPA 1391, Gradignan, France
- Nicholas School of the Environment, Duke University, Durham, NC, USA
| |
Collapse
|
6
|
Harayama H, Kitao M, Agathokleous E, Ishida A. Effects of major vein blockage and aquaporin inhibition on leaf hydraulics and stomatal conductance. Proc Biol Sci 2019; 286:20190799. [PMID: 31161902 PMCID: PMC6571453 DOI: 10.1098/rspb.2019.0799] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 05/08/2019] [Indexed: 01/25/2023] Open
Abstract
The density and architecture of leaf veins determine the network and efficiency of water transport within laminae and resultant leaf gas exchange and vary widely among plant species. Leaf hydraulic conductance ( Kleaf) can be regulated by vein architecture in conjunction with the water channel protein aquaporin. However, our understanding of how leaf veins and aquaporins affect leaf hydraulics and stomatal conductance ( gs) remains poor. By inducing blockage of the major veins and inhibition of aquaporin activity using HgCl2, we examined the effects of major veins and aquaporins on Kleaf and gs in species with different venation types. A vine species, with thick first-order veins and low vein density, displayed a rapidly declined gs with high leaf water potential in response to vein blockage and a greatly reduced Kleaf and gs in response to aquaporin inhibition, suggesting that leaf aquaporins are involved in isohydric/anisohydric stomatal behaviour. Across species, the decline in Kleaf and gs due to aquaporin inhibition increased linearly with decreasing major vein density, possibly indicating that a trade-off function between vein architecture (apoplastic pathway) and aquaporin activity (cell-to-cell pathway) affects leaf hydraulics.
Collapse
Affiliation(s)
- Hisanori Harayama
- Hokkaido Research Center, Forestry and Forest Products Research Institute, 7 Hitsujigaoka, Toyohira-Ku, Sapporo, Hokkaido 062-8516, Japan
| | - Mitsutoshi Kitao
- Hokkaido Research Center, Forestry and Forest Products Research Institute, 7 Hitsujigaoka, Toyohira-Ku, Sapporo, Hokkaido 062-8516, Japan
| | - Evgenios Agathokleous
- Hokkaido Research Center, Forestry and Forest Products Research Institute, 7 Hitsujigaoka, Toyohira-Ku, Sapporo, Hokkaido 062-8516, Japan
- Institute of Ecology, Key Laboratory of Agrometeorology of Jiangsu Province, School of Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, People's Republic of China
| | - Atsushi Ishida
- Center for Ecological Research, Kyoto University, Otsu, Shiga 520-2113, Japan
| |
Collapse
|
7
|
Wang N, Palmroth S, Maier CA, Domec JC, Oren R. Anatomical changes with needle length are correlated with leaf structural and physiological traits across five Pinus species. PLANT, CELL & ENVIRONMENT 2019; 42:1690-1704. [PMID: 30684950 DOI: 10.1111/pce.13516] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 12/22/2018] [Accepted: 12/27/2018] [Indexed: 06/09/2023]
Abstract
The genus Pinus has wide geographical range and includes species that are the most economically valued among forest trees worldwide. Pine needle length varies greatly among species, but the effects of needle length on anatomy, function, and coordination and trade-offs among traits are poorly understood. We examined variation in leaf morphological, anatomical, mechanical, chemical, and physiological characteristics among five southern pine species: Pinus echinata, Pinus elliottii, Pinus palustris, Pinus taeda, and Pinus virginiana. We found that increasing needle length contributed to a trade-off between the relative fractions of support versus photosynthetic tissue (mesophyll) across species. From the shortest (7 cm) to the longest (36 cm) needles, mechanical tissue fraction increased by 50%, whereas needle dry density decreased by 21%, revealing multiple adjustments to a greater need for mechanical support in longer needles. We also found a fourfold increase in leaf hydraulic conductance over the range of needle length across species, associated with weaker upward trends in stomatal conductance and photosynthetic capacity. Our results suggest that the leaf size strongly influences their anatomical traits, which, in turn, are reflected in leaf mechanical support and physiological capacity.
Collapse
Affiliation(s)
- Na Wang
- School of Forestry, Northeast Forestry University, Harbin, 150040, China
- Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA
| | - Sari Palmroth
- Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA
| | | | - Jean-Christophe Domec
- Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA
- Bordeaux Sciences Agro, UMR 1391 INRA-ISPA, 33175 Gradignan Cedex, France
| | - Ram Oren
- Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA
- Department of Forest Sciences, University of Helsinki, Helsinki, Finland
| |
Collapse
|
8
|
Lechthaler S, Turnbull TL, Gelmini Y, Pirotti F, Anfodillo T, Adams MA, Petit G. A standardization method to disentangle environmental information from axial trends of xylem anatomical traits. TREE PHYSIOLOGY 2019; 39:495-502. [PMID: 30299505 DOI: 10.1093/treephys/tpy110] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 09/05/2018] [Accepted: 09/13/2018] [Indexed: 06/08/2023]
Abstract
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. For example, we do not know if they allow water to bypass embolized vessels, or increase the risk of spread of embolisms, or how their arrangement varies within a tree. Here we demonstrate the benefit of removing the independent effect of stem length on assessment of effects of external (e.g., climatic) factors on such xylem traits. We measured the hydraulic diameter (Dh) and vessel conductivity index (VCI) along the stem of 21 shrubs/trees of similar height (1.19 < H < 5.45 m) belonging to seven Acacia species, across a wide aridity gradient in Australia. All trees showed similar scaling exponents of Dh (b = 0.33) and VCI (b = 0.53) vs axial distance from the apex (L), thus conforming with general patterns in woody plants. After de-trending for L, neither Dh (P = 0.21) nor VCI (P = 0.109) differed across the aridity gradient. We found that across a wide gradient of aridity, climate had no effect on xylem anatomy of Acacia spp, which was instead dictated by axial distances from stem apices. We argue that the use of standardization procedures to filter out intrinsic patterns of vascular traits is an essential step in assessing climate-driven modifications of xylem architecture.
Collapse
Affiliation(s)
- Silvia Lechthaler
- Università degli Studi di Padova, Dept Territorio e Sistemi Agro-Forestali, Forest Ecology Research Unit, Viale dell'Università 16, Legnaro (PD), Italy
| | - Tarryn L Turnbull
- Centre for Carbon Water and Food, Faculty of Science, University of Sydney, 380 Werombi Road, Brownlow Hill, NSW, Australia
| | - Ylenia Gelmini
- Università degli Studi di Padova, Dept Territorio e Sistemi Agro-Forestali, Forest Ecology Research Unit, Viale dell'Università 16, Legnaro (PD), Italy
| | - Francesco Pirotti
- Università degli Studi di Padova, Dept Territorio e Sistemi Agro-Forestali, Forest Ecology Research Unit, Viale dell'Università 16, Legnaro (PD), Italy
| | - Tommaso Anfodillo
- Università degli Studi di Padova, Dept Territorio e Sistemi Agro-Forestali, Forest Ecology Research Unit, Viale dell'Università 16, Legnaro (PD), Italy
| | - Mark A Adams
- Centre for Carbon Water and Food, Faculty of Science, University of Sydney, 380 Werombi Road, Brownlow Hill, NSW, Australia
| | - Giai Petit
- Università degli Studi di Padova, Dept Territorio e Sistemi Agro-Forestali, Forest Ecology Research Unit, Viale dell'Università 16, Legnaro (PD), Italy
| |
Collapse
|
9
|
Skelton RP, Brodribb TJ, Choat B. Casting light on xylem vulnerability in an herbaceous species reveals a lack of segmentation. THE NEW PHYTOLOGIST 2017; 214:561-569. [PMID: 28124474 DOI: 10.1111/nph.14450] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 12/22/2016] [Indexed: 05/13/2023]
Abstract
Finding thresholds at which loss of plant functionality occurs during drought is critical for predicting future crop productivity and survival. Xylem resistance to embolism has been suggested as a key trait associated with water-stress tolerance. Although a substantial literature exists describing the vulnerability of woody stems to embolism, leaves and roots of herbaceous species remain under-represented. Also, little is known about vulnerability to embolism at a whole-plant scale or propagation of embolism within plants. New techniques to view the process of embolism formation provide opportunities to resolve long-standing questions. Here, we used multiple visual techniques, including X-ray micro-computed tomography and the optical vulnerability method, to investigate the spread of embolism within intact stems, leaves and roots of Solanum lycopersicum (common tomato). We found that roots, stems and leaves of tomato plants all exhibited similar vulnerability to embolism, suggesting that embolism rapidly propagates among tissues. Although we found scarce evidence for differentiation of xylem vulnerability among tissues at the scale of the whole plant, within a leaf the midrib embolized at higher water potentials than lower order veins. Substantial overlap between the onset of cavitation and incipient leaf damage suggests that cavitation represents a substantial damage to plants, but the point of lethal cavitation in this herbaceous species remains uncertain.
Collapse
Affiliation(s)
- Robert P Skelton
- School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, TAS, 7001, Australia
| | - Timothy J Brodribb
- School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, TAS, 7001, Australia
| | - Brendan Choat
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, 2753, Australia
| |
Collapse
|
10
|
Apgaua DMG, Tng DYP, Cernusak LA, Cheesman AW, Santos RM, Edwards WJ, Laurance SGW. Plant functional groups within a tropical forest exhibit different wood functional anatomy. Funct Ecol 2016. [DOI: 10.1111/1365-2435.12787] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- Deborah M. G. Apgaua
- Centre for Tropical, Environmental and Sustainability Sciences College of Science and Engineering James Cook University 14‐88 McGregor Rd Smithfield Qld 4878 Australia
- Programa de Pós‐Graduação em Engenharia Florestal Universidade Federal de Lavras Caixa Postal 3037, CEP 37200‐000 Lavras MG Brazil
| | - David Y. P. Tng
- Centre for Tropical, Environmental and Sustainability Sciences College of Science and Engineering James Cook University 14‐88 McGregor Rd Smithfield Qld 4878 Australia
| | - Lucas A. Cernusak
- Centre for Tropical, Environmental and Sustainability Sciences College of Science and Engineering James Cook University 14‐88 McGregor Rd Smithfield Qld 4878 Australia
| | - Alexander W. Cheesman
- Centre for Tropical, Environmental and Sustainability Sciences College of Science and Engineering James Cook University 14‐88 McGregor Rd Smithfield Qld 4878 Australia
| | - Rubens M. Santos
- Programa de Pós‐Graduação em Engenharia Florestal Universidade Federal de Lavras Caixa Postal 3037, CEP 37200‐000 Lavras MG Brazil
| | - Will J. Edwards
- Centre for Tropical, Environmental and Sustainability Sciences College of Science and Engineering James Cook University 14‐88 McGregor Rd Smithfield Qld 4878 Australia
| | - Susan G. W. Laurance
- Centre for Tropical, Environmental and Sustainability Sciences College of Science and Engineering James Cook University 14‐88 McGregor Rd Smithfield Qld 4878 Australia
| |
Collapse
|
11
|
Johnson DM, Wortemann R, McCulloh KA, Jordan-Meille L, Ward E, Warren JM, Palmroth S, Domec JC. A test of the hydraulic vulnerability segmentation hypothesis in angiosperm and conifer tree species. TREE PHYSIOLOGY 2016; 36:983-93. [PMID: 27146334 DOI: 10.1093/treephys/tpw031] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 03/15/2016] [Indexed: 05/05/2023]
Abstract
Water transport from soils to the atmosphere is critical for plant growth and survival. However, we have a limited understanding about many portions of the whole-tree hydraulic pathway, because the vast majority of published information is on terminal branches. Our understanding of mature tree trunk hydraulic physiology, in particular, is limited. The hydraulic vulnerability segmentation hypothesis (HVSH) stipulates that distal portions of the plant (leaves, branches and roots) should be more vulnerable to embolism than trunks, which are nonredundant organs that require a massive carbon investment. In the current study, we compared vulnerability to loss of hydraulic function, leaf and xylem water potentials and the resulting hydraulic safety margins (in relation to the water potential causing 50% loss of hydraulic conductivity) in leaves, branches, trunks and roots of four angiosperms and four conifer tree species. Across all species, our results supported strongly the HVSH as leaves and roots were less resistant to embolism than branches or trunks. However, branches were consistently more resistant to embolism than any other portion of the plant, including trunks. Also, calculated whole-tree vulnerability to hydraulic dysfunction was much greater than vulnerability in branches. This was due to hydraulic dysfunction in roots and leaves at less negative water potentials than those causing branch or trunk dysfunction. Leaves and roots had narrow or negative hydraulic safety margins, but trunks and branches maintained positive safety margins. By using branch-based hydraulic information as a proxy for entire plants, much research has potentially overestimated embolism resistance, and possibly drought tolerance, for many species. This study highlights the necessity to reconsider past conclusions made about plant resistance to drought based on branch xylem only. This study also highlights the necessity for more research of whole-plant hydraulic physiology to better understand strategies of plant drought tolerance and the critical control points within the hydraulic pathway.
Collapse
Affiliation(s)
- Daniel M Johnson
- Department of Forest, Rangeland and Fire Sciences, University of Idaho, 875 Perimeter Drive MS1133, Moscow, ID 83844, USA
| | - Remi Wortemann
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | | | | | - Eric Ward
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27607, USA
| | - Jeffrey M Warren
- Environmental Sciences Division and Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Sari Palmroth
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Jean-Christophe Domec
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA Bordeaux Sciences Agro, UMR INRA-ISPA 1391, 33195 Gradignan, France
| |
Collapse
|
12
|
Götmark F, Götmark E, Jensen AM. Why Be a Shrub? A Basic Model and Hypotheses for the Adaptive Values of a Common Growth Form. FRONTIERS IN PLANT SCIENCE 2016; 7:1095. [PMID: 27507981 PMCID: PMC4961008 DOI: 10.3389/fpls.2016.01095] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 07/11/2016] [Indexed: 05/08/2023]
Abstract
Shrubs are multi-stemmed short woody plants, more widespread than trees, important in many ecosystems, neglected in ecology compared to herbs and trees, but currently in focus due to their global expansion. We present a novel model based on scaling relationships and four hypotheses to explain the adaptive significance of shrubs, including a review of the literature with a test of one hypothesis. Our model describes advantages for a small shrub compared to a small tree with the same above-ground woody volume, based on larger cross-sectional stem area, larger area of photosynthetic tissue in bark and stem, larger vascular cambium area, larger epidermis (bark) area, and larger area for sprouting, and faster production of twigs and canopy. These components form our Hypothesis 1 that predicts higher growth rate for a small shrub than a small tree. This prediction was supported by available relevant empirical studies (14 publications). Further, a shrub will produce seeds faster than a tree (Hypothesis 2), multiple stems in shrubs insure future survival and growth if one or more stems die (Hypothesis 3), and three structural traits of short shrub stems improve survival compared to tall tree stems (Hypothesis 4)-all hypotheses have some empirical support. Multi-stemmed trees may be distinguished from shrubs by more upright stems, reducing bending moment. Improved understanding of shrubs can clarify their recent expansion on savannas, grasslands, and alpine heaths. More experiments and other empirical studies, followed by more elaborate models, are needed to understand why the shrub growth form is successful in many habitats.
Collapse
Affiliation(s)
- Frank Götmark
- Department of Biological and Environmental Sciences, University of GothenburgGöteborg, Sweden
- *Correspondence: Frank Götmark
| | - Elin Götmark
- Mathematical Sciences, Chalmers University of Technology and University of GothenburgGöteborg, Sweden
| | - Anna M. Jensen
- Department of Forestry and Wood Technology, Linnaeus UniversityVäxjö, Sweden
| |
Collapse
|