The physiological importance of small leaf sizes in the mediterranean type ecosystem vegetation of the Cape floristic region

 

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dc.contributor.advisor Cramer, Michael D en_ZA
dc.contributor.author Yates, Megan en_ZA
dc.date.accessioned 2017-11-16T07:12:58Z
dc.date.available 2017-11-16T07:12:58Z
dc.date.issued 2007 en_ZA
dc.identifier.citation Yates, M. 2007. The physiological importance of small leaf sizes in the mediterranean type ecosystem vegetation of the Cape floristic region. University of Cape Town. en_ZA
dc.identifier.uri http://hdl.handle.net/11427/26302
dc.description.abstract Numerous "Fynbos" species of the Cape Floristic Region (CFR) have particularly fine, narrow leaves. The rates of transpiration and heat loss are partially dependent on boundary layer conductance, which is determined by leaf shape and size, surface modifications and wind speed. We expected fine-leaved species with higher boundary layer conductance to transpire faster than broad-leaved species at low temperatures whereas at higher temperatures we expected transpiration to be limited by stomata! conductance. In contrast, the rate of heat loss may be constrained by thick boundary layers in larger leaves at high temperatures. Leaf gas exchange characteristics at various temperatures were correlated with boundary layer thickness, leaf area and specific leaf area for 14 Proteaceae species using phylogenetically independent contrast species. When the temperatures of individual leaves were altered, while ambient temperature was kept at l 8°C, water loss decreased significantly at both 12°C and 30°C with increased leaf size and thus boundary layer thickness. At 30°C, small leaves with thin boundary layers resulted in leaf temperatures below ambient, while larger leaves with thicker boundary layers had leaf temperatures closer to ambient. However, at 30°C the variation in leaf temperature between the smallest and largest leaves was only 3.4°C. Such a small variation in leaf temperature is unlikely to alter temperature-dependent physiological processes. We conclude that the small boundary layer associated with small leaves enables fine-leaved species to transpire at faster rates when water is plentiful. This may be a particularly important strategy for plants that take up most of their nutrients in the wet winter months from nutrient-poor highly leached soils of the CFR region. We suggest that fine leaves are an adaptation for nutrient uptake during winter, although they may also have the benefit of improved coupling of leaf to ambient temperature during the summer drought period. en_ZA
dc.language.iso eng en_ZA
dc.subject.other Botany en_ZA
dc.subject.other Ecosystems en_ZA
dc.title The physiological importance of small leaf sizes in the mediterranean type ecosystem vegetation of the Cape floristic region en_ZA
dc.type Bachelor Thesis
dc.date.updated 2017-02-02T13:42:51Z
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Science en_ZA
dc.publisher.department Department of Biological Sciences en_ZA
dc.type.qualificationlevel Honours
dc.type.qualificationname BSc (Hons) en_ZA
uct.type.filetype
uct.type.filetype Text
uct.type.filetype Image
dc.identifier.apacitation Yates, M. (2007). <i>The physiological importance of small leaf sizes in the mediterranean type ecosystem vegetation of the Cape floristic region</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/26302 en_ZA
dc.identifier.chicagocitation Yates, Megan. <i>"The physiological importance of small leaf sizes in the mediterranean type ecosystem vegetation of the Cape floristic region."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2007. http://hdl.handle.net/11427/26302 en_ZA
dc.identifier.vancouvercitation Yates M. The physiological importance of small leaf sizes in the mediterranean type ecosystem vegetation of the Cape floristic region. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2007 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/26302 en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Yates, Megan AB - Numerous "Fynbos" species of the Cape Floristic Region (CFR) have particularly fine, narrow leaves. The rates of transpiration and heat loss are partially dependent on boundary layer conductance, which is determined by leaf shape and size, surface modifications and wind speed. We expected fine-leaved species with higher boundary layer conductance to transpire faster than broad-leaved species at low temperatures whereas at higher temperatures we expected transpiration to be limited by stomata! conductance. In contrast, the rate of heat loss may be constrained by thick boundary layers in larger leaves at high temperatures. Leaf gas exchange characteristics at various temperatures were correlated with boundary layer thickness, leaf area and specific leaf area for 14 Proteaceae species using phylogenetically independent contrast species. When the temperatures of individual leaves were altered, while ambient temperature was kept at l 8°C, water loss decreased significantly at both 12°C and 30°C with increased leaf size and thus boundary layer thickness. At 30°C, small leaves with thin boundary layers resulted in leaf temperatures below ambient, while larger leaves with thicker boundary layers had leaf temperatures closer to ambient. However, at 30°C the variation in leaf temperature between the smallest and largest leaves was only 3.4°C. Such a small variation in leaf temperature is unlikely to alter temperature-dependent physiological processes. We conclude that the small boundary layer associated with small leaves enables fine-leaved species to transpire at faster rates when water is plentiful. This may be a particularly important strategy for plants that take up most of their nutrients in the wet winter months from nutrient-poor highly leached soils of the CFR region. We suggest that fine leaves are an adaptation for nutrient uptake during winter, although they may also have the benefit of improved coupling of leaf to ambient temperature during the summer drought period. DA - 2007 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2007 T1 - The physiological importance of small leaf sizes in the mediterranean type ecosystem vegetation of the Cape floristic region TI - The physiological importance of small leaf sizes in the mediterranean type ecosystem vegetation of the Cape floristic region UR - http://hdl.handle.net/11427/26302 ER - en_ZA


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