Anomalous Pressure Volume Curves of Resurrection Plants Do Not Suggest Negative Turgor

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.