Isolation and characterisation of chloroplasts from Myrothamnus flabellifolius Welw.

Chloroplasts isolated from the resurrection plant Myrothamnus flabellifoliu s using trehalose gradients had a higher buoyant density than chloroplasts isolated from another resurrection plant Craterostigma wilmsii. The latter had the same buoyant density as those isolated from the desiccation-sensiti ve (DS) plant Pisum sativum. The increased buoyant density in M. flabellifo lius was ascribed to the unusual ultrastructure of the thylakoid membranes. Standard chloroplast isolation protocols resulted in membrane damage in bo th resurrection planes. Trehalose rather than sucrose gradients were requir ed for isolation of intact chloroplasts. Immunological studies shaved that epitopes related to the desiccation stress protein dsp 21 from Craterostigm a plantagineum were present in M. flabellifolius. Several small (10-15 kDa) unique stromal proteins were also present. Polyphenolics, including anthoc yanins, accumulated in leaves and chloroplasts of M. flabellifolius during drying. Envisaged functions for these are maintenance of membrane integrity , chlorophyll masking and antioxidant protection. Metal (Ca2+, Cu2+, Fe2+, Mg2+ and Mn2+) concentrations declined and thylakoid membranes separated up on drying. We propose that this might be a mechanism to put a stasis on pho tosynthesis and minimise photo-oxidation damage under water stress conditio ns.