Stomata in southern African Icacinaceae

F. Cuticle preparation (abaxial) of A. dim/dia/a: scale bar = 10 )..lm .

 

Leaf anatomy of the southern African Icacinaceae and its taxonomic significance

by Potgieter M. J., van Wijk A. E. (1999)

M. J. Potgieter* and A. E. van Wijk1

University of Limpopo, Polokwane, South Africa

Department of Botany, University of the North, Private Bag X1106, Sovenga, 0727 Republic of South Africa 1H.G.W J. Schweickerdt Herbarium, Department of Botany, University of Pretoria, 0002 Republic of South Africa

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in S. Afr. J. Bot. 65(2): 53-62 –

https://ac.els-cdn.com/S0254629915309558/1-s2.0-S0254629915309558-main.pdf?_tid=f60e6b27-297f-4d31-9dee-0402cdc93c4a&acdnat=1525425559_8e6a06e676863296e8144758a39015ae

Figure 2 SEM micrographs of abaxial leaf surfaces. A. Stomata ofApodyles dimidiata. note cuticular striations. B. Stoma ofA. abbOllii. C. Stoma of A. geldenhuysii. Scale bars = 10 ~lIn . D, Trichome of A. dimidiara: scale bar = I 00 ~1l1 . E. Stoma of CasfllI/opsis iliciJofia. F. Stoma of C. tfni/olia, note peri stomal rim formed by cuticular striations. E & F scale bars = 10 Mm.

Leaf structure of the three southern African genera of Jcacinaceae was examined by light and scanmng electron microscopy. Diagnostic characters include the stoma and trichome type, and lamina characters, such as mucilage cells, pectic warts and ‘unidentified cell inclusions’,

In southern Africa both Cassinopsis Sand. and Pyrenacantha Hook. have cyclocytic stomata, as opposed to the anomocytic type of Apodytes E. Mey. Ex Arn. The presence of a stomatal ridge in A. dimidiata is a useful character in separating this species from the other two southern African members of this genus. A peristomal rim in Cassinopsis tinifolia Harv. and its absence in C. ilicifolia (Hochst.) Kuntze allow the separation of these two species.

Figure 4 SEM micrographs of abaxial kafsurfaces ofPyrenacantha. A, Stoma of P. grandijlora: scale bar = 1 () pm. S, Simple trichome in P grondijlora. note cuticular markings and bulging basal rim: scale bar = 100 /.un . C, Stoma of P kaurabassana. D. Trichome of P. kourabassana. E, Stoma of P. scandens. F. ‘Globular’ trichome of P scandens, Scale bars = 10 ).1111 .

The indumentum of Pyrenacantha consists of simple (unmodified), ‘globular’ and ‘uncinate’ trichomes, whereas that of Apodytes and Cassinopsis consists of simple hairs.

Mucilage cells were found only in members of Apodytes. ln terce!lular, predominantly wart-like pectic protuberances are present in the mesophyll of mature leaf samples of A. ge/denhuysiiVan Wyk & Potgieter and Cassinopsis. Small,

Irregularly shaped , yellowish cell inclusions were found subepidermally to the abaxial epidermis in C. Ificifolia. Their chemical composition and function (if any) is still unknown.

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In southern Africa both Cassinopsis and Pyrenacantha have cyclocytic stomata, as opposed to the anomocytic type of Apodytes. According to Van Staveren and Baas (1973) anomocytic stomata are restricted to genera with a low level of specialization, thus representing a primitive condition. Cyclocytic stomata, according to the same authors, occur in genera with a wide range of specialization. Although this type of stomata can be found in genera with a low level of specialization, it is most frequent in highly specialized genera, indicating that this may represent an advanced condition.

Van Staveren and Baas (1 973) found the stomatal index for A. dimidiala to vary between 7 and 21. Research on Celastraceae and Winteraceae also indicates that the stomatal index may be extremely variable within a single species. This invalidates claims by authors in the past that the stomatal index is a diagnostic character at the species level. For this reason we have not considered the stomatal index in this study. In their survey of 26 genera of Maletian lcacinaceae, Van Staveren and Baas (1973) found peristomal rims only in the three genera Codiocarpus Howard, Platea Blume and Stemonurus Blume, indicating that this is a taxonomically useful character state in the Icacinaceae. The presence of a peristomal rim in C. i1iciiolia and its absence in C. tinifolia allows the separation of these two species.

 

Structure and taxonomic value of stomata in Eugenia (Myrtaceae)

Photo credit: Google

Eugenia uniflora, with common names Pitanga, Suriname cherry, Brazilian cherry, Cayenne cherry

The genus Eugenia (Myrtaceae) in southern Africa: the structure and taxonomic value of stomata

by Van Wijck A. E., Robbertse P. J., Kok P.D.F. (1982)

A. E. Van Wijk, P. J. Robbertse, P. D. F. Kok,

H. G. W. J. Schweirkerdt Herbarium, Department of Botany, University of Pretoria, South A frira

in Bot. J. Linn. Soc. London 84: 411-456 –DOI: 10.1111/j.1095-8339.1982.tb00359.x – 

http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8339.1982.tb00359.x/abstract

Abstract

The mature stomatal morphology of 11 southern African species of Eugenia, and also of E. uniflora L. (naturalized) and E. incerta Diimmer (a garden plant of unknown origin) has been studied by light and scanning electron microscopy.

Leaves of all the species are hypostomatic and water-stomata are occasionally present. Two different stomatal types, X and Y, differing mainly in their cuticular ornamentation, were found in the southern African species. The grouping of species based on stomatal characters supports a previous grouping of species on the basis of periderm and seed characters.

Conspicuous lipid bodies, usually present in the subsidiary cells, are limited to the southern African species. Although the subsidiary cells do not differ in shape and size from adjacent epidermal cells, their contents often have a higher tannin content than ordinary epidermal cells. The variable patterns of arrangement of the three to five subsidiary cells makes it difficult to identify the stomata with existing classifications based on mature topography. Thus, a new term ‘anomostaurocytic’ is proposed for the stomatal type found in the southern African species.

Stomata of E. uniflora and E. incerta are paracytic and anomocytic respectively, and the cuticular ornamentation of their stomata differs from those of the southern African species.

The view that E. incerta is not closely related to the southern African species is supported by differences in its cuticular ornamentation, lack of lipid bodies in the subsidiary cells, anomocytic stomata and prominent T-pieces at the guard cell poles.

Figures 18-21. Light micrographs to show the morphology of stomatal type X. Fig. 18. Eugenia capenis (Van Wyk, 422@, abaxial epidermis stained with Sudan Black B, showing stained lipid bodies in subsidiary cells. Fig. 19. E. capensis (Van Wyk, 4226), unstained epidermis showing stomata with front cavities plugged with a resinous mass. Fig. 20. E. capensis (Van Wvk, 4226), transverse section of stoma stained with Sudan Black B and showing position of cuticular membrane. Fig. 21. E. cf. mossambicensis (Van der Schiff, 3751), safranin-stained cuticular preparation showing a single water-stoma.