Taxonomic significance of the abaxial lemma surface in southern African members of Helictotrichon (Poaceae)
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Abstract
Background: Helictotrichon (excluding Amphibromus, Avenula, Helictochloa and Tricholemma), a genus of temperate C3 grasses, is represented by 14 species in southern Africa. Members of the genus are difficult to identify at species level on the basis of macromorphology alone.
Objectives: The primary objective of this study was to investigate the usefulness of the micromorphology of the lemma surface for differentiating amongst the southern African members of Helictotrichon.
Method: Lemma surfaces were studied with scanning electron microscopy (SEM). Lemmas were obtained from herbarium specimens housed in the National Herbarium, Pretoria (PRE). These were mounted on aluminium stubs using double-sided adhesive tape, sputter-coated with gold, and photographs were taken using a J840 scanning electron microscope.
Results: Based on whether the lemma surface is smooth, papillate, scaberulous, scabrid or a combination of these, five groups of species are distinguished. All species, except Helictotrichon barbatum which has a smooth lemma surface, have small prickles (scaberulous). Helictotrichon leoninum, Helictotrichon quinquesetum and Helictotrichon rogerellisii have only small prickles, whilst Helictotrichon dodii, Helictotrichon hirtulum, Helictotrichon namaquense and Helictotrichon roggeveldense have, in addition, medium to large prickles (scabrid). Helictotrichon capense, Helictotrichon longifolium, Helictotrichon longum and Helictotrichon turgidulum have a combination of small prickles and papillae whilst Helictotrichon galpinii and Helictotrichon natalense have a
combination of all three. A key to the groups and photos of the different types of surfaces are provided.
Conclusion: The micromorphology of the lemma surface was shown to be of considerable taxonomic significance and to be extremely useful for differentiating amongst species.
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References
Chippindall, L.K.A., 1955, ‘A guide to the identification of grasses in South Africa’, in D. Meredith (ed.), The grasses and pastures of South Africa, n.p., Central News Agency, Cape Town.
Ellis, R.P., 1979, ‘A procedure for standardizing comparative leaf anatomy in the Poaceae, II, The epidermis as seen in surface view’, Bothalia 12, 641–671.
Gibbs Russell, G.E., Watson, L., Koekemoer, M., Smook, L., Barker, N.P., Anderson, H.M. et al., 1990, ‘Grasses of southern Africa’, Memoirs of the Botanical Survey of South Africa 58, 175–177.
Mabberley, D.J., 2008, Mabberley’s plant-book, 3rd edn., Cambridge University Press, Cambridge.
Mashau, A.C., Fish, L. & Van Wyk, A.E., 2010a, ‘Two new species of Helictotrichon (Pooidae: Aveneae) from South Africa’, Bothalia 40, 179–183.
Mashau, A.C., Fish, L. & Van Wyk, A.E., 2010b, ‘The correct author citation of Helictotrichon (Pooideae: Aveneae)’, Bothalia 40, 184–185.
Romero-Zarco, C., 2011, ‘Helictochloa Romero Zarco (Poaceae), a new genus of oat grass’, Candollea 66, 87–103. http://dx.doi.org/10.15553/ c2011v661a6
Röser, M., Döring, E., Winterfeld, G. & Schneider, J., 2009, ‘Generic realignments in the grass tribe Aveneae (Poaceae)’, Schlechtendalia 19, 27–38.
Schweickerdt, H.G.W.J., 1937, ‘A revision of the South African species of Helictotrichon Bess. ex Schultes’, Bothalia 3, 185–203.
Soreng, R.J., Davis, J.I. & Voionmaa, M.A., 2007, ‘A phylogenetic analysis of Poaceae tribe Poeae sensu lato based on morphological characters and sequence data from three plastid-encoded genes: Evidence for reticulation, and a new classification for the tribe’, Kew Bulletin 62, 425–454.
Stapf, O., 1899, ‘Gramineae’, Flora capensis 7, 472–477.
Van Wyk, A.E. & Smith, G.F., 2001, Regions of floristic endemism in southern Africa: A review with emphasis on succulents, Umdaus Press, Pretoria.