Nectary structure and nectar presentation in Aloe castanea and A. greatheadii var. davyana (Asphodelaceae) |
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Authors: | M Nepi H Human S W Nicolson L Cresti E Pacini |
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Institution: | (1) Department of Environmental Sciences ``G. Sarfatti', University of Siena, Via Mattioli 4, 53100 Siena, Italy;(2) Department of Zoology and Entomology, University of Pretoria, Pretoria, 0002, South Africa |
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Abstract: | This paper deals with the nectary structure and nectar presentation of two species belonging to different sections of the
genus Aloe: A. castanea (Anguialoe) and A. greatheadii var. davyana (Pictae). The development of the nectary was studied by means of bright field and fluorescence light microscopy and scanning electron
microscopy (SEM) in three flower stages (young, intermediate, old). Both species have septal nectaries. In A. castanea, a subsidiary tissue, not present in A. greatheadii var. davyana, was found beneath the nectary epithelium. This tissue accumulated starch that was hydrolyzed during secretion. Starch was
slightly accumulated around the nectary in A. greatheadii var. davyana. The distribution of chlorophyll in the ovary was also different in the two species. These anatomical differences are not,
however, correlated with greater nectar production in A. castanea. In this species, the nectary seems to degenerate after secretion, while in A. greatheadii var. davyana no sign of degeneration was observed. Differences in nectar presentation among the two species may account for different
pollinators visiting their flowers. |
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Keywords: | Aloe castanea Aloe greatheadii var davyana septal nectary nectary structure nectar presentation nectar ducts |
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