Foliar secretory structures in Ekebergia capensis (Meliaceae)

Show simple item record Tilney, Patricia M. Nel, Magda Van Wyk, Abraham Erasmus (Braam) 2018-08-30T07:15:58Z 2018-08-30T07:15:58Z 2018-02
dc.description.abstract Ekebergia capensis is a medium-sized to large evergreen to deciduous tree ranging from southern Africa to Ethiopia. Two morphologically-distinct variants of E. capensis, southern and northern, may be recognized in southern Africa. Despite its wide distribution range there appear to be no published reports on the secretory structures occurring on the leaves. In very young leaves, colleters on the petiolules, adjacent portions of the rachis and the midrib of the adaxial leaflet surfaces, secrete fluid which at least partly covers these developing areas. This is the first record of colleters in Meliaceae. In addition, several extrafloral nectaries (EFNs) are found in variable positions on the abaxial side of the leaflets. No stomata are associated with the EFNs. The glandular tissue of active EFNs is surrounded by druse crystals of calcium oxalate and consists of secretory cells some of whose walls are separated by “strands” of amorphous lipophilic material, especially in a radial orientation. EFNs on developing leaves are inconspicuous but with time, frequently become more easily visible due to the accumulation of pinkish/reddish anthocyanins. Even on senescent leaves, shed in autumn, large droplets of nectar are frequently visible on the EFNs. The secretory tissue originates from protoderm and ground tissues. Slight differences in abundance, size, shape, position and structure exist between the EFNs of the southern and northern forms. Varying proportions of glucose, fructose and sucrose were detected in the rather viscous nectar with the most abundant sugar usually being fructose. Ants were only rarely observed feeding on the nectar. This finding is in conflict with the generally accepted idea that EFNs provide food for ants which in turn protect the plant from herbivores. More detailed studies of the chemistry of the nectar, which is relatively copious, may provide clues as to the function. en_ZA
dc.description.department Plant Production and Soil Science en_ZA
dc.description.librarian am2018 en_ZA
dc.description.uri en_ZA
dc.identifier.citation Patricia M. Tilney, Magda Nel, Abraham E. van Wyk. Foliar secretory structures in Ekebergia capensis (Meliaceae). Heliyon 4 (2018) e00541. DOI: 10.1016/j.heliyon.2018.e00541 en_ZA
dc.identifier.issn 2405-8440 (online)
dc.identifier.other 10.1016/j.heliyon.2018.e00541
dc.language.iso en en_ZA
dc.publisher Elsevier en_ZA
dc.rights © 2018 The Authors. This is an open access article under the CC BY-NC-ND license. en_ZA
dc.subject Plant biology en_ZA
dc.subject Ekebergia capensis en_ZA
dc.subject Secretory structures en_ZA
dc.subject Colleters en_ZA
dc.subject Meliaceae en_ZA
dc.subject Extrafloral nectaries (EFNs) en_ZA
dc.subject Leaflets en_ZA
dc.title Foliar secretory structures in Ekebergia capensis (Meliaceae) en_ZA
dc.type Article en_ZA

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