Physiological characterisation of tissue differentiation in response to desiccation in the homoiochlorophyllous dicot resurrection plant Craterostigma pumilum Hochst

Resurrection plants are a polyphyletic group of angiosperms which display true desiccation tolerance (DT) - the ability to survive near complete loss of cellular water for extended periods while recovering metabolic competence upon watering. This is achieved by employing tailored protection behaviours depending on the relative state of (de)hydration. Recent work has raised interest in desiccation-associated changes related to tissue destiny in desiccation tolerant vegetative tissues. Homoiochlorophyllous species, such as those in the Craterostigma genus, maintain their photosynthetic apparatus during the dehydration process, employing considerable protection thereof. In the current study, detailed phenotypic characterisation and pulse-amplitude modulated chlorophyll fluorometry were used to identify the critical water contents at which key physiological changes occur in leaves of Craterostigma pumilum and how this relates to desiccation-associated differentiation between Tip and Base tissues of leaf blades. This differentiation appeared to be realised only during early rehydration and after initial water movement through the leaf tissues. This work provides strong evidence for the existence of desiccation-associated tissue differentiation in C.pumilum and, potentially, other homoiochlorophyllous resurrection plants.