Leaf tensile properties of resurrection plants differ among species in their response to drying

Previous studies report that leaf tensile strength (TS) of the desiccation tolerant (resurrection) grass Eragrostis nindensis does not change on drying, but increases in dried desiccation sensitive Eragrostis species. In this paper we tested whether unchanging TS on dehydration is a common feature among 4 resurrection species, Craterostigma wilmsii, Sporobolus stapfianus, Xerophyta humilis and Xerophyta schlecteri, and how this might relate to leaf structure and mechanisms of protection against mechanical stress of drying. Desiccation sensitive controls were Zea mays and Arabidopsis thaliana. Light and transmission electron microscopy of leaves was performed to determine lignification and the nature of subcellular mechanical stabilization. There was a positive correlation between % lignin/unit cross-sectional area and TS of hydrated leaves. Only the grass, S. stapfianus, did not change TS when naturally dried. All others increased in TS when naturally dried, but there was variation among them when flash dried. In S. stapfianus, mechanical stabilization was by both wall folding (mesophyll) and vacuole packaging (bundle sheath) as reported for E. nindensis. This combination may account, in part, for unchanging TS during drying and may be a feature of resurrection grasses. We conclude that leaf tensile properties differ among resurrection plants and are not necessarily affected by protection mechanisms associated with mechanical stress.