A long-term record of the physiological plasticity of stomatal condactance in Proteaceae

Simple item page
dc.contributor.advisorWest, Adamen_ZA
dc.contributor.authorCronin, Kateen_ZA
dc.date.accessioned2015-09-30T13:24:45Z
dc.date.available2015-09-30T13:24:45Z
dc.date.issued2013en_ZA
dc.description.abstractBioclimatic models suggest that Protea species are likely to be severely affected by predicted increases in temperature and reductions in rainfall in the Western Cape. However, throughout their 400 million year history, land plants have been exposed to considerable climatic variations that have driven physiological adaptations promoting long-term resilience. A principal response of plants to increases in atmospheric CO2 concentration and changing rainfall regimes is to minimise water loss by reducing stomatal conductance (gs) and simultaneously increasing intrinsic water-use efficiency (iWUE). Plasticity in these two physiological traits may enhance the ability of plants to survive future climate change. There is considerable evidence in the literature for major changes in gs and iWUE in response to both short-term and long-term changes in environmental conditions. However, to date, the effects of decadal climate change on plant physiology are still largely uncertain. In this study, the responses of gs and iWUE to perturbations in rainfall and atmospheric CO2 are reconstructed from a chronological sequence of herbarium and modern Protea specimens. The results indicate that in the two high-altitude study species, P.cryophila (t= -2.44, df=7, p= 0.045) and P.venusta (t=3.08, df=5, p=0.027), stomatal conductance has significantly declined in response to increasing atmospheric CO2 concentrations over the past century. The low altitude species appears to maintain fixed stomatal conductance trajectories as a response to more xeric conditions. It is difficult to draw inferences about stomatal physiological plasticity from iWUE data as it is not possible to distinguish between the effects of physiological reductions in stomatal conductance and biochemical enhancement of photosynthesis. Microhabitat sensitivity in iWUE is a further factor confounding interpretation. This highlights the importance of using multiple parameters as analytical tools for assessing long-term physiological change. A key contribution of this study is that it has confirmed the value of using archival material and highlights methodologies that may aid future herbarium-based interpretations. In addition, despite some methodological limitations, the study has identified interesting trends at climate change-relevant timescales that point the way for further research to understand relative vulnerabilities and inform conservation strategies. Specifically, it suggests that future research and conservation efforts may need to be focused on species occurring at low altitudes because of their apparently more limited physiological plasticity.en_ZA
dc.identifier.apacitationCronin, K. (2013). <i>A long-term record of the physiological plasticity of stomatal condactance in Proteaceae</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/14120en_ZA
dc.identifier.chicagocitationCronin, Kate. <i>"A long-term record of the physiological plasticity of stomatal condactance in Proteaceae."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2013. http://hdl.handle.net/11427/14120en_ZA
dc.identifier.citationCronin, K. 2013. A long-term record of the physiological plasticity of stomatal condactance in Proteaceae. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Cronin, Kate AB - Bioclimatic models suggest that Protea species are likely to be severely affected by predicted increases in temperature and reductions in rainfall in the Western Cape. However, throughout their 400 million year history, land plants have been exposed to considerable climatic variations that have driven physiological adaptations promoting long-term resilience. A principal response of plants to increases in atmospheric CO2 concentration and changing rainfall regimes is to minimise water loss by reducing stomatal conductance (gs) and simultaneously increasing intrinsic water-use efficiency (iWUE). Plasticity in these two physiological traits may enhance the ability of plants to survive future climate change. There is considerable evidence in the literature for major changes in gs and iWUE in response to both short-term and long-term changes in environmental conditions. However, to date, the effects of decadal climate change on plant physiology are still largely uncertain. In this study, the responses of gs and iWUE to perturbations in rainfall and atmospheric CO2 are reconstructed from a chronological sequence of herbarium and modern Protea specimens. The results indicate that in the two high-altitude study species, P.cryophila (t= -2.44, df=7, p= 0.045) and P.venusta (t=3.08, df=5, p=0.027), stomatal conductance has significantly declined in response to increasing atmospheric CO2 concentrations over the past century. The low altitude species appears to maintain fixed stomatal conductance trajectories as a response to more xeric conditions. It is difficult to draw inferences about stomatal physiological plasticity from iWUE data as it is not possible to distinguish between the effects of physiological reductions in stomatal conductance and biochemical enhancement of photosynthesis. Microhabitat sensitivity in iWUE is a further factor confounding interpretation. This highlights the importance of using multiple parameters as analytical tools for assessing long-term physiological change. A key contribution of this study is that it has confirmed the value of using archival material and highlights methodologies that may aid future herbarium-based interpretations. In addition, despite some methodological limitations, the study has identified interesting trends at climate change-relevant timescales that point the way for further research to understand relative vulnerabilities and inform conservation strategies. Specifically, it suggests that future research and conservation efforts may need to be focused on species occurring at low altitudes because of their apparently more limited physiological plasticity. DA - 2013 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2013 T1 - A long-term record of the physiological plasticity of stomatal condactance in Proteaceae TI - A long-term record of the physiological plasticity of stomatal condactance in Proteaceae UR - http://hdl.handle.net/11427/14120 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/14120
dc.identifier.vancouvercitationCronin K. A long-term record of the physiological plasticity of stomatal condactance in Proteaceae. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2013 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/14120en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Biological Sciencesen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherBotanyen_ZA
dc.titleA long-term record of the physiological plasticity of stomatal condactance in Proteaceaeen_ZA
dc.typeBachelor Thesis
dc.type.qualificationlevelHonours
dc.type.qualificationnameBSc (Hons)en_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
thesis_sci_2013_cronin_kate.pdf
Size:
4.04 MB
Format:
Adobe Portable Document Format
Description:
Download
Collections
Other Theses