Browsing by Subject "Craterostigma"

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    Anomalous pressure volume curves of resurrection plants do not suggest negative turgor.
    (Oxford University Press, 2001) Willigen, Clare Vander; Farrant, Jill; Pammenter, N W
    Pressure-volume (PV) curves of the desiccation-tolerant angiosperms, Eragrostis nindensis, Craterostigma wilmsii and Xerophyta humilis, and the desiccation-sensitive species, E. curvula, were compared. The shape of curves for E. nindensis and C. wilmsii differed from the usual curvilinear form. Over the relative water content (RWC) range of approx. 70 to 25%, PV curves indicated water potentials higher than directly measured water activity on frozen-thawed tissue. Anatomical studies showed considerable cell wall folding and a consequent reduction in cell volume in these two species; this was not seen in X. humilis or E. curvula which showed normal PV curves. It is suggested that this wall folding may have prevented the development of negative turgor and physical stress in the cells, and contributed to desiccation tolerance. Copyright 2001 Annals of Botany Company.
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    An overview of mechanisms of desiccation tolerance in selected angiosperm resurrection plants
    (Global Science Books, 2007) Farrant, Jill M; Brandt, Wolf B; Lindsey, George G
    The vegetative tissues of resurrection plants, like seeds, can tolerate desiccation to 5% relative water content (RWC) for extended periods and yet resume full metabolic activity on re-watering. In this review we will illustrate how this is achieved in a variety of angiosperm resurrection plants, our studies ranging from the ecophysiological to the biochemical level. At the whole plant level, leaf folding and other anatomical changes serve to minimise light and mechanical stress associated with drying and rehydration. The mechanisms of cell wall folding are described for Craterostigma wilmsii and Myrothanmus flabellifolia. Free radicals, radical oxygen species (ROS) usually generated under water-deficit stress by photosynthesis, are minimised by either homoiochlorophylly (e.g. C. wilmsii and M. flabellifolia) or poikilochlorophylly (e.g. Xerophyta sp.). The antioxidant systems of these plants effectively deal with ROS generated by other metabolic processes. In addition to antioxidants common to most plants, resurrection plants also accumulate polyphenols such as 3, 4, 5 tri-O-galloylquinic acid in M. flabellifolia, and seed-associated antioxidants (e.g. 1-cys-peroxiredoxin and metallothionines) as effective ROS scavengers. Sucrose accumulates at low RWC, presumably protecting the sub-cellular milieu against desiccation-induced macromolecular denaturation.