Anomalous pressure volume curves of resurrection plants do not suggest negative turgor

Pressure-volume (PV) curves of the desiccation-tolerant angiosperms, Eragro stis nindensis, Craterostigma wilmsii and Xerophyta humilis, and the desicc ation-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 ind icated water potentials higher than directly measured water activity on fro zen-thawed tissue. Anatomical studies showed considerable cell wall folding and a consequent reduction in cell volume in these two species; this was n ot seen in X. humilis or E. curvula which showed normal PV curves. It is su ggested that this wall folding may have prevented the development of negati ve turgor and physical stress in the cells, and contributed to desiccation tolerance. (C) 2001 Annals of Botany Company.