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Affiliation(s)
- R. B. Pratt
- Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830
| | - J. D. Sease
- Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830
| | - W. H. Pechin
- Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830
| | - A. L. Lotts
- Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830
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Pratt RB, MacKinnon ED, Venturas MD, Crous CJ, Jacobsen AL. Root resistance to cavitation is accurately measured using a centrifuge technique. Tree Physiol 2015; 35:185-196. [PMID: 25716876 DOI: 10.1093/treephys/tpv003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [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: 06/04/2023]
Abstract
Plants transport water under negative pressure and this makes their xylem vulnerable to cavitation. Among plant organs, root xylem is often highly vulnerable to cavitation due to water stress. The use of centrifuge methods to study organs, such as roots, that have long vessels are hypothesized to produce erroneous estimates of cavitation resistance due to the presence of open vessels through measured samples. The assumption that roots have long vessels may be premature since data for root vessel length are sparse; moreover, recent studies have not supported the existence of a long-vessel artifact for stems when a standard centrifuge technique was used. We examined resistance to cavitation estimated using a standard centrifuge technique and compared these values with native embolism measurements for roots of seven woody species grown in a common garden. For one species we also measured vulnerability using single-vessel air injection. We found excellent agreement between root native embolism and the levels of embolism measured using a centrifuge technique, and with air-seeding estimates from single-vessel injection. Estimates of cavitation resistance measured from centrifuge curves were biologically meaningful and were correlated with field minimum water potentials, vessel diameter (VD), maximum xylem-specific conductivity (Ksmax) and vessel length. Roots did not have unusually long vessels compared with stems; moreover, root vessel length was not correlated to VD or to the vessel length of stems. These results suggest that root cavitation resistance can be accurately and efficiently measured using a standard centrifuge method and that roots are highly vulnerable to cavitation. The role of root cavitation resistance in determining drought tolerance of woody species deserves further study, particularly in the context of climate change.
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Affiliation(s)
- R B Pratt
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA
| | - E D MacKinnon
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA
| | - M D Venturas
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA
| | - C J Crous
- Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria 0002, South Africa
| | - A L Jacobsen
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA
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Tobin MF, Pratt RB, Jacobsen AL, De Guzman ME. Xylem vulnerability to cavitation can be accurately characterised in species with long vessels using a centrifuge method. Plant Biol (Stuttg) 2013; 15:496-504. [PMID: 23127246 DOI: 10.1111/j.1438-8677.2012.00678.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2012] [Accepted: 08/23/2012] [Indexed: 06/01/2023]
Abstract
Vulnerability to cavitation curves describe the decrease in xylem hydraulic conductivity as xylem pressure declines. Several techniques for constructing vulnerability curves use centrifugal force to induce negative xylem pressure in stem or root segments. Centrifuge vulnerability curves constructed for long-vesselled species have been hypothesised to overestimate xylem vulnerability to cavitation due to increased vulnerability of vessels cut open at stem ends that extend to the middle or entirely through segments. We tested two key predictions of this hypothesis: (i) centrifugation induces greater embolism than dehydration in long-vesselled species, and (ii) the proportion of open vessels changes centrifuge vulnerability curves. Centrifuge and dehydration vulnerability curves were compared for a long- and short-vesselled species. The effect of open vessels was tested in four species by comparing centrifuge vulnerability curves for stems of two lengths. Centrifuge and dehydration vulnerability curves agreed well for the long- and short-vesselled species. Centrifuge vulnerability curves constructed using two stem lengths were similar. Also, the distribution of embolism along the length of centrifuged stems matched the theoretical pressure profile induced by centrifugation. We conclude that vulnerability to cavitation can be accurately characterised with vulnerability curves constructed using a centrifuge technique, even in long-vesselled species.
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Affiliation(s)
- M F Tobin
- Department of Biology, California State University, Bakersfield, Bakersfield, CA 93311, USA.
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Abstract
Xylem traits were examined among 22 arid-land shrub species, including measures of vessel dimensions and pit area. These structural measures were compared with the xylem functional traits of transport efficiency and safety from cavitation. The influence of evolution on trait relationships was examined using phylogenetic independent contrasts (PICs). A trade-off between xylem safety and efficiency was supported by a negative correlation between vessel dimensions and cavitation resistance. Pit area was correlated with cavitation resistance when cross species data were examined, but PICs suggest that these traits have evolved independently of one another. Differences in cavitation resistance that are not explained by pit area may be related to differences in pit membrane properties or the prevalence of tracheids, the latter of which may alter pit area through the addition of vessel-to-tracheid pits or through changes in xylem conduit connectivity. Some trait relationships were robust regardless of species ecology or evolutionary history. These trait relationships are likely to be the most valuable in predictive models that seek to examine anatomical and functional trait relationships among extant and fossil woods and include the relationship among hydraulic conductivity and vessel diameter, between vessel diameter and vessel length, and between hydraulic conductivity and wood density.
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Affiliation(s)
- U G Hacke
- Department of Renewable Resources, 442 ESB, University of Alberta, Edmonton, AB, Canada.
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Pratt RB, Jacobsen AL, Golgotiu KA, Sperry JS, Ewers FW, Davis SD. LIFE HISTORY TYPE AND WATER STRESS TOLERANCE IN NINE CALIFORNIA CHAPARRAL SPECIES (RHAMNACEAE). ECOL MONOGR 2007. [DOI: 10.1890/06-0780] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Pratt RB, Jacobsen AL, Ewers FW, Davis SD. Relationships among xylem transport, biomechanics and storage in stems and roots of nine Rhamnaceae species of the California chaparral. New Phytol 2007; 174:787-798. [PMID: 17504462 DOI: 10.1111/j.1469-8137.2007.02061.x] [Citation(s) in RCA: 183] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Here, hypotheses about stem and root xylem structure and function were assessed by analyzing xylem in nine chaparral Rhamnaceae species. Traits characterizing xylem transport efficiency and safety, mechanical strength and storage were analyzed using linear regression, principal components analysis and phylogenetic independent contrasts (PICs). Stems showed a strong, positive correlation between xylem mechanical strength (xylem density and modulus of rupture) and xylem transport safety (resistance to cavitation and estimated vessel implosion resistance), and this was supported by PICs. Like stems, greater root cavitation resistance was correlated with greater vessel implosion resistance; however, unlike stems, root cavitation resistance was not correlated with xylem density and modulus of rupture. Also different from stems, roots displayed a trade-off between xylem transport safety from cavitation and xylem transport efficiency. Both stems and roots showed a trade-off between xylem transport safety and xylem storage of water and nutrients, respectively. Stems and roots differ in xylem structural and functional relationships, associated with differences in their local environment (air vs soil) and their primary functions.
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Affiliation(s)
- R B Pratt
- Department of Biology, California State University, Bakersfield, Bakersfield, CA 93311, USA
| | - A L Jacobsen
- Michigan State University, Department of Plant Biology, East Lansing, MI 48824, USA
| | - F W Ewers
- Biological Sciences Department, California State Polytechnic University, Pomona, CA 91768, USA
| | - S D Davis
- Natural Science Division, Pepperdine University, Malibu, CA 90263, USA
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Pratt RB, Jacobsen AL, Ewers FW, Davis SD. Relationships among xylem transport, biomechanics and storage in stems and roots of nine Rhamnaceae species of the California chaparral. New Phytol 2007. [PMID: 17504462 DOI: 10.1111/j.1469-8137.2007.02061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Here, hypotheses about stem and root xylem structure and function were assessed by analyzing xylem in nine chaparral Rhamnaceae species. Traits characterizing xylem transport efficiency and safety, mechanical strength and storage were analyzed using linear regression, principal components analysis and phylogenetic independent contrasts (PICs). Stems showed a strong, positive correlation between xylem mechanical strength (xylem density and modulus of rupture) and xylem transport safety (resistance to cavitation and estimated vessel implosion resistance), and this was supported by PICs. Like stems, greater root cavitation resistance was correlated with greater vessel implosion resistance; however, unlike stems, root cavitation resistance was not correlated with xylem density and modulus of rupture. Also different from stems, roots displayed a trade-off between xylem transport safety from cavitation and xylem transport efficiency. Both stems and roots showed a trade-off between xylem transport safety and xylem storage of water and nutrients, respectively. Stems and roots differ in xylem structural and functional relationships, associated with differences in their local environment (air vs soil) and their primary functions.
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Affiliation(s)
- R B Pratt
- Department of Biology, California State University, Bakersfield, Bakersfield, CA 93311, USA
| | - A L Jacobsen
- Michigan State University, Department of Plant Biology, East Lansing, MI 48824, USA
| | - F W Ewers
- Biological Sciences Department, California State Polytechnic University, Pomona, CA 91768, USA
| | - S D Davis
- Natural Science Division, Pepperdine University, Malibu, CA 90263, USA
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Pratt RB, Ewers FW, Lawson MC, Jacobsen AL, Brediger MM, Davis SD. Mechanisms for tolerating freeze-thaw stress of two evergreen chaparral species: Rhus ovata and Malosma laurina (Anacardiaceae). Am J Bot 2005; 92:1102-1113. [PMID: 21646132 DOI: 10.3732/ajb.92.7.1102] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The response to freeze-thaw stress was examined for two co-occurring evergreen species, Malosma laurina and Rhus ovata. Laboratory and field experiments on adults and seedlings were made in the spring and winter in 1996 and again on adults in 2003 and 2004. Laboratory and field results indicated that the stem xylem for adults of M. laurina and R. ovata were similarly susceptible to freezing-induced cavitation (percentage loss of conductivity = 92 ± 2.6% for R. ovata and 90 ± 4.2% for M. laurina at ≤ -6°C). In contrast, leaves of M. laurina were more susceptible to freezing injury than leaves of R. ovata. Among seedlings in the field, leaves of M. laurina exhibited freezing injury at -4°C and total shoot mortality at -7.2°C, whereas co-occurring seedlings of R. ovata were uninjured. Surprisingly, R. ovata tolerates high levels of freezing-induced xylem embolism in the field, an apparently rare condition among evergreen plants. Rhus ovata avoids desiccation when xylem embolism is high by exhibiting low minimum leaf conductance compared to M. laurina. These results suggest a link between minimum leaf conductance and stem hydraulics as a mechanism permitting the persistence of an evergreen leaf habit in freezing environments.
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Affiliation(s)
- R B Pratt
- Natural Science Division, Pepperdine University, Malibu, California 90263 USA
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Jackson FE, Pratt RB, Back JB, Fleming PM, Juteau L. Multiple intracranial arterial aneurysms: current thoughts about diagnosis and treatment. Mil Med 1974; 139:37-40. [PMID: 4204921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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Jackson FE, Back JB, Pratt RB, Whiteley R. Advances in the treatment of missile wounds of the brain. Nurs Times 1971; 67:819-21. [PMID: 5092283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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