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LD2668 .T4 1941 B51 / Master of Science

2 v. : ill., photos, maps, tables, graphs ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 1980

Most plants produce leaves with stomata on either both surfaces (amphistomatous) or on the lower surface only (hypostomatous). The importance of stomata to plant survival suggests that these two stomatal distribution patterns may be adaptive, and this problem is explored. It is concluded that amphistomaty is an adaptation to produce a high conductance to CO₂ diffusion into the leaf. As such it is advantageous to plants with high photosynthetic capacity leaves in high light environments, experiencing rapidly fluctuating or continuously available soil water. Plants meeting these criteria are found to be almost exclusively amphistomatous; those not meeting the criteria are mostly hypostomatous. Also investigated is the adaptive significance of differences in stomatal conductances and conductance responses to environmental factors between the two surfaces of amphistomatous leaves. Although differences in stomatal conductance are found between the two surfaces in sunflower, differences in conductance response to light intensity and water vapor pressure difference across the stomatal pore were neglible. Water stress relieved one day prior to experiments caused upper stomatal conductance to be reduced more than lower, but responses to light and water vapor pressure difference remained essentially parallel for the two surfaces. For these differences in conductance to be adaptive differences in photosynthetic characteristics between the two surfaces. In addition, estimation of the resistance to diffusion of CO₂ across the mesophyll yields values low enough to preclude steep gradients in CO₂ partial pressure in the mesophyll. In the absence of CO₂ gradients within the leaf, differences in photosynthetic characteristics between the two surfaces cannot exist. It is concluded that differences in stomatal conductance between the two surfaces of amphistomatous leaves are not adaptations to differences in CO₂ uptake characteristics.

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Typescript (photocopy). / Digitized by Kansas Correctional Industries

Abstract not available

M.Sc. / Pteronia L. is a genus of 70 species of woody shrublets occurring mainly in southern Africa (Leistner, 2000). Published and unpublished ethnobotanical information exists for nine of the species. The uses of these species in traditional medicine are poorly recorded or have remained scientifically unknown. In addition, some unpublished vernacular names have been recorded during this study. Hutchinson and Phillips revised the genus Pteronia in 1917 and grouped the species into four sections. The nine ethnobotanically important species were placed in four sections: Incanae (P. incana and P. cinerea), Papillatae (P. lucilliodes and P. divaricata), Ciliatae (P. camphorata, P. stricta, P. onobromoides and P. adenocarpa) and Glabratae (P. succulenta). Pteronia onobromoides is the original source of Nama buchu that was first recorded by Van der Stel in 1685 (De Wet & Pheiffer, 1979), but which has remained poorly known. Surprisingly, this study has revealed the existence of an important Cape herbal medicine (P. divaricata) for which no record could be found in the scientific literature. Pteronia incana is not widely known for its traditional medicinal uses (although a few have indeed been recorded) but rather as a source of valuable essential oil that has been commercially exploited to some extent. Other species with at least one published anecdote of traditional use include P. adenocarpa, P. camphorata, P cinerea, P. lucilioides, P. stricta and P. succulenta. This means that a total of nine species are now known to have traditional medicinal and/or cosmetic uses. Most of the species are used for intestinal disorders (including stomach pain) and respiratory ailments (coughs, colds and influenza). The topical application of P. onobromoides and P. adenocarpa is clearly aimed at more than just a cosmetic effect and includes the alleviation of pain and the treatment of wounds and skin ailments. These uses all suggest that Pteronia species may have antimicrobial activity and also possible anti-inflammatory and analgesic properties. Pteronia adenocarpa is only known from a single literature record.

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