Browsing by Author "Wiswedel, Stefan"

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    Desiccation tolerance in the vegetative tissues of the fern Mohria caffrorum is seasonally regulated
    (Blackwell Publishing, 2009) Farrant, Jill M; Lehner, Arnaud; Cooper, Keren; Wiswedel, Stefan
    As there is limited information on the mechanisms of vegetative desiccation tolerance in pteridophytes, we undertook a comprehensive anatomical, ultrastructural, physiological and biochemical study on the fern Mohria caffrorum. Our data show that this species is desiccation-tolerant during the dry season, and desiccation-sensitive in the rainy season. This system allows the verification of protection mechanisms by comparison of tolerant and sensitive tissues of the same species at the same developmental age. Tolerant fronds acquire protection mechanisms during drying that are mostly similar to those reported for angiosperms. These include: (i) chlorophyll masking by abaxial scales and frond curling; (ii) increased antioxidant capacity that is maintained in dry tissues; (iii) mechanical stabilization of vacuoles in the dry state; (iv) de novo production of heat stable proteins (at least one identified as a putative chaperonin); (v) accummulation of protective carbohydrates (sucrose, raffinose family oligosaccharides and cyclitols). This study has implications for the biotechnological production of drought-tolerant crops, and allows speculation on the evolution of vegetative desiccation tolerance.
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    Isolepis R.Br. (Cyperaceae) revisited : a phylogeny based on plastid and nuclear ribosomal DNA data
    (2006) Wiswedel, Stefan; Muasya, Mutham
    The approximately 75 species of Isolepis R Br. are currently described as annual or short lived perennials with predominantly terete spikelet's
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    Mohria caffrorum (L.) Desv. : a new, unique model organism for the study of desiccation tolerance
    (2006) Wiswedel, Stefan; Farrant, Jill M
    Vegetative desiccation tolerance is the ability of a plant to dry to equilibrium with its surrounding atmosphere and remain in this dry state for prolonged periods of time. Upon rehydration, these plants are able to regain full physiological functionality. Vegetative desiccation tolerance is common and partially understood in the less complex clades including the algae, bryophytes and lichens but is uncommon in the vascular land plants. Vegetative desiccation tolerance is partially understood in the angiosperms but there has been little work on desiccation tolerance in pteridophytes Mohria caffrorum (L.) Desv is one such desiccation tolerant pteridophyte This fern has the unique characteristic of having both desiccation tolerant and desiccation sensitive forms, which alternate seasonally, which this study is the first to show. We show here that; 1) M caffrorum is indeed a desiccation tolerant fern. 2) M. caffrorum has desiccation tolerant and desiccation sensitive frond types. which are morphologically distinct. 3) These morphological differences are directly related to the ability to survive desiccation as well as playing a role in tine ecologies of the two growth forms. 4) The spores of M. caffrorum are also desiccation tolerant. A hypothesis is proposed detailing why M. caffrorum is able to change between being desiccation tolerant and desiccation sensitive.