REGULATION OF CAM AND RESPIRATORY RECYCLING BY WATER-SUPPLY IN HIGHERPOIKILOHYDRIC PLANTS - HABERLEA-RHODOPENSIS FRIV AND RAMONDA-SERBICA PANC AT TRANSITION FROM BIOSIS TO ANABIOSIS AND VICE-VERSA

In this paper the expression of C-3 and CAM in the resurrection plants Haberlea rhodopensis Friv. and Ramonda serbica Panc. during the trans ition from biosis to anabiosis and vice verse is reported for the firs t time. The transition from predominantly C-3 metabolism to net dark f ixation of CO2 occurred in leaves of R. serbica during desiccation. De siccated plants of H. rhodopensis react by reducing light assimilation of CO2, When watering was resumed night time fixation of CO2 by R. se rbica was observed within 24 hours, The recovery of CO2 fixation by H. rhodopensis was not seen until the 8th 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 recy cling of CO2 following drought could be an important mechanism for pot entially saving water.