Regulation of CAM and Respiratory Recycling by Water Supply in Higher Poikilohydric Plants — Haberlea rhodopensis Friv. and Ramonda serbica Panč, at Transition from Biosis to Anabiosis and Vice Versa

In this paper the expression of C₃ and CAM in the resurrection plants Haberlea rhodopensis Friv. and Ramonda serbica Pan?, during the transition from biosis to anabiosis and Wee versa is reported for the first time. The transition from predominantly C₃ metabolism to net dark fixation of CO₂ occurred in leaves of R.serbica during desiccation. Desiccated plants of H. rhodopensis react by reducing light assimilation of CO₂. When watering was resumed night time fixation of CO₂ by R. serbica was observed within 24 hours. The recovery of CO₂ fixation by H. rhodopensis was not seen until the 8 th day. Desiccated and rehydrated plants of H. rhodopensis recapture a higher proportion of respiratory CO₂ than well-watered plants. Since both species have little capacity for water conservation in their tissues, the early onset of high recycling of CO₂ following drought could be an important mechanism for potentially saving water.