Responses of plastid pigments to desiccation and rehydration in the desertlichen Ramalina maciformis

Plastid pigments were analysed in thalli of the desert lichen Ramalina maci formis (Delile) Bory during a desiccation period of 30 d, and during rehydr ation following short-term (6 d) and long-term (30 d) desiccation. Desiccat ion and rehydration were performed in either constant light or constant dar k. While further desiccation of freshly collected, air dried thalli did not affect the contents of violaxanthin and zeaxanthin, conversion from zeaxan thin to violaxanthin occurred during rehydration, regardless of whether lic hens have been exposed to constant light or dark. In addition, de novo synt hesis of violaxanthin took place during rehydration of short-term desiccate d thalli exposed to constant light. Neither desiccation nor rehydration aff ected the contents of lutein, neoxanthin, antheraxanthin and beta -carotene . Chlorophyll a and b, and alpha -carotene were slightly increased or decre ased, respectively, during rehydration.