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Dinteria 27/2002

Dinteria 27/2002

Contributions to the Flora and Vegetation of Namibia
Namibia Scientific Society (ed.)
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Authors: Please check list below
Series: Dinteria; Number 27, February 2002
Publisher: Namibia Scientific Society
Windhoek, 2002
ISSN: 0012-3013
Soft cover, 15x21 cm, 112 pages, bw-illustrated


Our note:

Are you interested in writing a contribute for DINTERIA? Please check on the chapter “Author's Guidelines” further down.


Content:

- Hermann Heilmeier, Rainer Wolf, Robin Wacker, Markus Woitke and
Wolfram Hartung:
Observations on the anatomy of hydrated and dehydrated roots of Chamaegigas intrepidus Dinter

- T. Bornefeld and O.H. Volk:
Annotations to a collection of liverworts (Hepaticae, Marchantiales) from Omaruru District, Namibia, during summer 1995

- F. P. Graz:
Description and Ecology of Schinziophyton rautanenii (Schinz) Radcl.-Sm. in Namibia

- D.F. Joubert and P.L. Cunningham:
The distribution and invasive potential of Fountain Grass Pennisetum setaceum in Namibia

- Ibo Zimmermann and Fidelis Nyambe Mwazi:
The effect of a prescribed burn, followed up with browsing pressure, on rangeland condition in the Mountain savanna and Karstveld of Namibia

- Guide for Authors


Extract:

Observations on the anatomy of hydrated and dehydrated roots of Chamaegigas intrepidus Dinter

By Hermann Heilmeier*, Rainer Wolf**, Robin Wacker, Markus Woitke and Wolfram Hartung***

* Interdisziplinares Okologisches Zentmm, TU Bergakademie Freiberg, Leipziger Str. 29, D-09599 Freiberg, Germany
** Biozentrum der Universitat Wurzburg, Am Hubland, D-97070 Würzburg, Germany
***Julius-von-Sachs-Institut fur Biowissenschaften der Universitat Würzburg, Lehrstuhl Botanik I, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany

Abstract:

During dehydration, the length of roots of the aquatic resurrection plant Chamaegigas intrepidus is reduced by only 15%, whereas the diameter of fully differentiated roots is reduced by 30 to 35%. Lateral shrinking of roots is exclusively caused by collapsing cells in the rhizodermis and exodermis, which cover the cortex like a velamen radicum. Apart from the endodermis the root cortex is composed of a single layer of extremely large and thin-walled cells which show a high stability even when desiccated. Within the central stele there is a simple diarchic xylem. The rhizodermis is absolutely free of root hairs. The short cells within the dimorphic exodermis have exterior walls with characteristic thickenings, which act as valves closing the short cells and thus slowing down water loss during dehydration.

Zusammenfassung:

Während des Eintrocknens schrumpfen die haarlosen Wurzein der aquatischen Auferstehungspflanze Chamaegigas intrepidus um nur 15%, während der Durchmesser der voll ausdifferenzierten Wurzein um 30 bis 35% abnimmt. Letzteres rührt ausschließlich vom Kollabieren der Rhizodermis und Exodermis her, welche sich dann wie ein Velamen radicum der Rinde aniegen. Die Rinde besteht neben der Endodermis meistens aus einer einzigen extrem großlumigen und zartwandigen Zellschicht, welche auch im desikkierten Zustand eine erstaunliche Stabilitat aufweist. Der Zentralzylinder besitzt ein einfaches diarches Xylem. Bei der Hypodermis handelt es sich um eine Kurzzellenexodermis mit charakteristischen äußeren Zellwandverdickungen, welche die Durchlass (= Kurz-) zeilen wie ein Ventil verschließen und somit den Wasserverlust wahrend des Eintrocknens verlangsamen können.


Keywords:

aquatic resurrection plant, poikilohydric cormophyte, dimorphic exodermis, hypodermis, rhizodermis, root cortex, velamen radicum Dedicated to two pioneers of Namibian Botany, Willy Giess (1910-2000) and Prof. O.H. Volk (1903-2000)


Introduction:

Poikilohydric angiosperms or resurrection plants are characterised by most remarkable adaptations to their arid habitats. They can survive tissue water potentials of -200 MPa, even equilibration with 0% relative air humidity without damage over extended periods (Gaff & Giess 1986). Apart from a number of biochemical and physiological adaptations (Heilmeier & Hartung 2001), a unique trait of resurrection plants is their capability of an extreme shrinkage of their leaves during dehydration. The most extreme example is Chamaegigas intrepidus Dinter (formerly Lindernia intrepidus Dinter Oberm.) which only grows endemically in temporarily water-filled rock pools on granite outcrops in Central Namibia.

The distribution of this species was described by Giess (1969), the morphology and resumption of growth after rewatering ("resurrection") by Smook (1969). When the shallow pools dry out, the size of submerged leaves is reduced by 90%. Thus the plants withdraw into the sediment at the bottom of the pools. Through this behaviour leaves are protected from manifold environmental stress, among others the high ultraviolet radiation. This remarkable trait was already mentioned by Heil (1924), whilst Hickel (1967) and Schiller et al. (1999) provide more details. Figure 1 shows a hand-made drawing by Prof. O.H. Volk, which he prepared during one of his many expeditions in the former Southwest Africa to the natural sites of C. intrepidus using a plain pocket microscope. The drawing emphasises the unique anatomical traits which enable the drastic shrinkage, contractive tracheides and their endplates with very narrow holes. They can contract and expand like an accordion, making the extreme contraction of the desiccated leaf possible. Until now the roots of Chamaegigas intrepidus have only been rarely studied.

Heil (1924) and Hickel (1967) describe the dimorphic exodermis with short cells of Chamaegigas roots. However, there are no further investigations on tissues interior to the hypodermis, either in the hydrated or in the desiccated state. Heil (1924) assumes that the root cortex of Chamaegigas represents an aerenchyma with small, radially orientated cells; however, this hypothesis is not supported by any figures or detailed information on root anatomy. Therefore we will present results from studies, using scanning electron (SEM) and light microscopy, showing most remarkable features of the roots of Chamaegigas intrepidus. [...]


Author's Guidelines:

Editorial policy:

The Dinteria publishes articles in the field of botany related to Namibia. All contributions must be based on original research, must not be under consideration for publication elsewhere, and should constitute a definite advance in knowledge in that field. Authors bear sole responsibility for the factual accuracy of their papers. Referees will review submitted papers and on their advice the Editor will accept or reject contributions. All refereeing is strictly confidential. Articles that contain less than 2000 words may be considered for publication as a Short Note, in which case no separate Introduction, Methods, Results and Discussion are necessary. Short Notes must contain References however, and Acknowledgements may be made if necessary.

Presentation:

Contributions must be written in English. Authors can (optionally) publish a second abstract in a language of their choice. Submit two clear copies of the manuscript, including all drawings, graphs and photographs. For articles that are processed on a computer, please supply also an electronic copy in New Roman font of the manuscript on diskette (or CD), using WORD (6.0 or later) or Rich Text Format (*.rtf). Photographs, figures, drawings and graphs can optionally be submitted in a general graphical form such as Windows Metafiles (*.wmf), GIF (for graphs), JPG or TIF. Please do not embed illustrations into the text. Colour plates may be printed, but the author(s) will have to bear the costs.

The layout should conform to the following sequence: Title page with title, author's name(s), address(es) (including, if relevant, an e-mail address), both abstracts, keywords (maximum 8), and then, beginning on a new page.

Introduction, Materials and Methods, Results, Discussion, Acknowledgements and References. Tables (each on a separate page). Captions for Figures (grouped together) and the figures should then follow. All pages must be numbered consecutively, including the title page and those containing references, tables and captions for figures.

Manuscripts should be submitted to:
The Editor: Dinteria, c/o Namibia Scientific Society, P.O. Box 67, Windhoek, Namibia.

E-mail:
nwg@iafrica.com.na, clearly stating that the paper is submitted for publication in Dinteria.

References:
References in the text should be cited as follows: 'Mendelsohn and Roberts (1974) stated ..." or '... (Mendelsohn & Roberts 1997)', when giving a reference simply as authority for a statement. Use the name of the first author followed by et al. when the complete citation involves more than two authors, e.g. 'Schulze et al. (1991)'. A list of publications to which reference has been made in the text must be presented alphabetically according to authors' names and
chronologically under each author, with a, b, c, etc. when more than one reference per year from the same author(s) is involved. A personal communication must be confined to the text and not be included in the list of references. In the list, authors' names should be typed in capitals as indicated below.
JANKOWITZ, W.J. 1983. Die plantekologie van die Waterberg Platopark. Ph.D. thesis. University of the Orange Free State, Bloemfontein. MENDELSOHN, J. & ROBERTS, C. 1997. An Environmental Profile and Atlas of Caprivi. Directorate of Environmental Affairs, Namibia. SCHULZE, E.D., LANGE, O.L. & GEBAUER, G. 1991. Carbon and nitrogen isotope ratios of mistletoes growing on nitrogen and non-nitrogen fixing hosts and on CAM plants in the Namib desert confirm partial heterotrophy.

Oecologia 88:457-462. STOCKING, M.A. 1994. Assessing vegetative cover and management effects. In: Lal, R. (ed.), >S'o;7 Erosion Research Methods, 2nd edition, pp. 211-232. Soil and Water Conservation Society and St. Lucie Press, Akeny / Delray Beach.

Tables:
Keep tables to a minimum. The same data should not be duplicated in tables and graphs. Each table must be typed on a separate sheet and be numbered consecutively in order of appearance, using Arabic numerals. Pay attention to the limitations imposed by the size of the printed page (A5).

Illustrations:
Please do not embed illustrations in the text, but submit these separately. The rules for numbering are the same as for tables. Photographs must be of a good quality on glossy paper, with clear details and adequate contrast. Please contact the editor if slides are to be reproduced. Drawings, diagrams and graphs should be done in black India ink on good-quality paper or tracing film. An illustration may not exceed twice the linear dimensions desired in the final reproduction. Allow space for the caption when presenting a figure that will occupy a whole page. It is important that lines and symbols be drawn sufficiently boldly to withstand reduction. The size of the lettering on the original must be such that the letters will be about 1.8 mm high after reduction. If the author(s) require a figure to be reproduced without reduction, this is to be clearly indicated. It is, however, recommended that use be made of a scale bar on figures. Write in soft pencil, the name of the author(s) and the figure number, as well as an arrow indicating the top of the figure on the reverse side. Place captions of figures collectively on a separate sheet of paper.

Reprints:
Dinteria supplies, free of charge to the author(s), 10 reprints of each full-length paper.