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Nature Conservation in Southern Africa

Morality and Marginality : Towards Sentient Conservation?

Series:

Nature conservation in southern Africa has always been characterised by an interplay between Capital, specific understandings of Morality, and forms of Militarism, that are all dependent upon the shared subservience and marginalization of animals and certain groups of people in society. Although the subjectivity of people has been rendered visible in earlier publications on histories of conservation in southern Africa, the subjectivity of animals is hardly ever seriously considered or explicitly dealt with. In this edited volume the subjectivity and sentience of animals is explicitly included. The contributors argue that the shared human and animal marginalisation and agency in nature conservation in southern Africa (and beyond) could and should be further explored under the label of ‘sentient conservation’.

Contributors are Malcolm Draper, Vupenyu Dzingirai, Jan-Bart Gewald, Michael Glover, Paul Hebinck, Tarito Kamuti, Lindiwe Mangwanya, Albert Manhamo, Dhoya Snijders, Marja Spierenburg, Sandra Swart, Harry Wels.
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ATLAS OF VESSEL ELEMENTS

Identification of Asian Timbers

Stephanie Helmling, Andrea Olbrich, Immo Heinz and Gerald Koch

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Veronica De Micco, Enrica Zalloni, Giovanna Battipaglia, Arturo Erbaggio, Pasquale Scognamiglio, Rosanna Caputo and Chiara Cirillo

ABSTRACT

Projected changes in drought occurrence in the Mediterranean region are raising concerns about the adaptive capability of rainfed crops, such as grapevine, to increasing aridity. Cultivation management, especially the techniques influencing the hydraulic pathway, can play a role in plant adaptation to drought for the consequent changes in wood anatomical functional traits. The aim of this study was to assess the effect of grafting on wood anatomy in tree-ring series of Vitis vini-fera L. ‘Piedirosso’ grapevine cultivated in a volcanic area in Southern Italy. Tree-ring anatomy was analysed in vines grown on their own roots or grafted onto 420A rootstock. Results showed that grafted vines had a higher occurrence of wood traits linked with safety of water transport if compared with non-grafted vines. Grafting induced the formation of tree rings with higher incidence of latewood also characterised by narrower and more frequent vessels if compared with non-grafted vines. This study suggested a different regulation of water flow in the grafted and non-grafted vines. Such findings support the analysis of wood anatomy as a tool to drive decisions linked with plant cultivation management. In this specific case, our results encourage to further explore the change from a traditional cultivation with own-rooted grapevines towards grafted models inducing better xylem adaptation to increasing drought.

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Rena T. Schott and Anita Roth-Nebelsick

Abstract

In this study, the ice nucleation activity (INA) and ice nucleation temperature (INT) as well as extracellular ice formation within the bark were determined for three woody species with different degrees of frost resistance, Betula nana, Betula albosinensis and Castanea sativa. Current-year stems and at least 2-year old stems of B. nana and C. sativa as well as current-year stems of B. albosinensis were compared, during summer (non-acclimated state) and winter (acclimated state), to evaluate possible ontogenetic and seasonal differences. Acclimated plant parts of the selected species revealed nearly similar results, with an INT from -7.52 to -8.43°C. The current-year stems of B. nana had a somewhat higher INT than the older stems. Microscopic analysis showed that extra-cellular ice formation occurred in the intercellular spaces within the bark of stems of B. nana, B. albosinensis and C. sativa. Size of the intercellular spaces of the bark were species-specific, and B. nana showed the largest intercellular space volume. While freezing behavior and extracellular ice formation thus followed principally the same pattern in all considered species, B. nana is obviously capable of dealing with large masses of extracellular ice which accumulate over extended periods of frost, making B. nana capable of protecting living tissue in colder regions from freezing damage.

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Ekaterina L. Kotina, Patricia M. Tilney, Abraham E. van Wyk, Alexei A. Oskolski and Ben-Erik van Wyk

ABSTRACT

A remarkable, almost fur-like “indumentum” of velvety “hairs” (sometimes referred to as “fungi”) occurs on the roots (and to a lesser extent also on the trunk) of Lannea schweinfurthii var. stuhlmannii and is known as vhulivhadza in the Venda language (Tshivenḓa). The hairs are traditionally used by the Venda people (Vhavenḓa) of the Limpopo Province of South Africa, for various biocultural purposes. A detailed anatomical study of the origin, structure and development of these unusual “hairs” showed that they are of peridermal origin and develop from dense clusters of phelloid cells which are scattered within the stratified phellem. These cells are capable of considerable radial elongation thus forming hair-like radial files of elongated phelloid cells. The “hairy” patches on the bark may also develop from lenticels which become hypertrophied. These clusters of phelloid cells resemble the hyperhydric tissue which is reportedly formed in periderm of stems exposed to a water-saturated environment in some plant species. The formation of hyperhydric-like tissue in roots and stems of L. schweinfurthii var. stuhlmannii occurs, however, under relatively arid conditions. Since this tissue contains large intercellular spaces, it may also be regarded as a specialized type of aerenchymatous phellem. The adaptive significance, if any, of the phelloid “hairs” remains unknown.

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Anna B. Wilczek, Muhammad Iqbal, Wieslaw Wloch and Marcin Klisz

ABSTRACT

All cell types of the secondary xylem arise from the meristematic cells (initials) of the vascular cambium and grow under mechanical constraints emerging from the circular-symmetrical geometry that characterises many tree trunks. The course of intrusive growth of cambial initials has been elucidated, but is yet to be described in the case of xylem fibres. This study explains the geometry of intrusive growth of the secondary xylem fibres in the trunk of Robinia pseudoacacia. Long series of serial semi-thin sections of the vascular cambium and the differentiating secondary xylem were analysed. Since fibres grow in close vicinity to expanding cells of the derivatives of the vascular cambium, we assumed that they have similar growth conditions. Dealing with the cylindrical tissue of the vascular cambium in a previous study, we used a circularly symmetrical equation for describing the growth mechanism of cambial initials. Like the cambial initials, some of the cambial derivatives differentiating into the various cell types composing the secondary xylem also exhibit intrusive growth between the tangential walls of adjacent cells. As seen in cross sections of the cambium, intrusively growing initials form slanted walls by a gradual transformation of tangential (periclinal) walls into radial (anticlinal) walls. Similarly, the intrusive growth of xylem fibres manifests initially as slants, which are formed due to axial growth of the growing cell tips along the tangential walls of adjacent cells. During this process, the tangential walls of adjacent cells are partly separated and dislocated from the tangential plane. The final shape of xylem fibres, or that of vessel elements and axial parenchyma cells, depends upon the ratio of their intrusive versus symplastic growths in the axial, circumferential and radial directions.

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Vladimír Račko, Ol’ga Mišíková, Jaroslava Štefková and Igor Čunderlík

ABSTRACT

Biologically degraded wood in advanced stages of decay has a very soft and brittle structure that causes many problems during sectioning. Embedding wood specimens in different kinds of media ensures preparation of good quality microsections, but the preparation time is very long. The proposed method does not only have a reduced preparation time but also minimizes costs and consumption of chemicals while improving stabilization of the specimen and enhancing the quality of sections. The crux of the method is application of a reinforcing layer of transparent nail polish gel on a dry specimen that has been only stabilized (not embedded) with PEG 1500 medium. The gel is applied on a specimen in two layers just before sectioning. The first layer infiltrates the specimen sufficiently deep to fill the lumens and cell walls and allows preparation of thin sections from decayed wood. The second layer reinforces the section and allows better handling. Subsequently, the reinforcing and embedding layers are removed using pure acetone. This innovative method has so far been successfully tested on specimens that were degraded by the fungus Pleurotus ostreatus (mass loss 55% and 83%) and the fungus Phaeolus schweinitzii (mass loss 45%), taken from Fagus sylvatica and Pinus sylvestris species, a hardwood and softwood respectively with contrasting wide vessels and narrow tracheids.

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Tatiana V. Tarelkina, Ludmila L. Novitskaya and Nadezhda N. Nikolaeva

Associate-editor Veronica De Micco

ABSTRACT

This study is a continuation of research on the role of sucrose in figured wood formation in temperate trees. Different concentrations of sucrose solutions were administered for 7 weeks to trunk tissues of Betula pendula Roth, Alnus incana (L.) Moench and Populus tremula L. Then xylem anatomy was examined with particular emphasis to the number of vessels and the spatial orientation of xylem elements. In B. pendula and A. incana a high level of exogenous sucrose caused a reduction in the number and size of xylem vessels, even to the point of absence of vessels. Sucrose concentrations of 100 and 200 g l-1 induced the formation of curly grain and anomalous club-shaped rays in xylem of B. pendula. Populus tremula xylem was not significantly altered by the experiment; the xylem anatomy was more seriously affected by wounding than by sucrose. In B. pendula and A. incana the wood formed during the experiment was similar to figured wood of these species. The decrease in the number and size of vessels in the xylem formed during the experiment possibly suggests that high concentrations of sucrose lead to a decline in the level of physiologically active auxin. Changes in the orientation of xylem elements points to a disruption of basipetal auxin transport. Further biochemical and physiological studies are needed to provide more comprehensive understanding of the relationship between sucrose and auxin during the development of figure in wood.