Induction of Crassulacean Acid like Metabolism in the C4 plant Portulaca oleracea L. under drought conditions. Changes in PEPCarboxylase

LARA, MARIA V.; DISANTE, KAREN B.; PODESTÁ, FLORENCIO E.; ANDREO, CARLOS S.; DRINCOVICH, MARÍA F.; LARA, MARÍA VALERIA

Brisbane

Congreso; 12th International Congress of Photosynthesis; 2001

Metabolism) according to the photosynthetic pathway (Ehleringer and Monson 1993), a wide variety of species share characteristics of the different photosynthetic groups. For example, C3-C4 intermediate species are thought to represent a stage in the evolutionary transition from C3 to C4 photosynthesis (Rawsthorne 1992), while other species shift from one type of photosynthesis to other depending on the age or environment as the shift from C3 photosynthesis to CAM (Osmond 1978, Winter and Smith 1989). The transition from C4 photosynthesis to CAM has been previously suggested in P. oleracea, P. grandiflora and P. mundula when subject to drought-stress conditions or short photoperiods by acid malic fluctuations and CO2 exchange measurements (Koch and Kennedy 1980, 1982; Ku et al. 1981; Kraybill and Martin 1996; Mazen 1996). Nevertheless, characteristics of this transition at molecular level have not been studied. Portulaca is an excellent system to study photosynthetic metabolism transitions because not only may involve expression/regulation of photosynthetic enzymes but also may increased our understanding of C4 plant responses to environmental stress. The aim of this study was to find out the conditions for the induction of a CAM-like metabolism in P. oleracea L. and to compare physiological and biochemical parameters in both conditions. Because PEPC is regulated in a different manner in C4 and CAM plants, this enzyme was studied in detail.