TEMPERATURE RESPONSE OF PHOTOSYNTHESIS AN D ACTIVITIES OF PHOSPHOENOLPYRUVATE CARBOXYLASE AND RIBULOSE 1,5-BISPHOSPHATE CARBOXYLASE IN GREENED CALLI INDUCED FROM ICEPLANT, MESEMBRYANTHEMUM-CRYSTALLINUM L., LEAVES

Iceplant is a halophyte with two different photosynthetic modes of C-3 and crassulacean acid metabolism (CAM). Environmental stress, such as a high salinity condition, is known as a trigger for shifting the pho tosynthetic mode from C-3 to CAM in a plant. The application of 6-benz ylaminopurine to cell culture medium was effective to induce green cal li from leaves of C-3 and CAM plants. The photosynthesis of greened ca lli obtained from C-3 and CAM plant leaves showed low temperature abap tation and wide temperature adaptation, respectively. In the calli der ived from the C-3 plant, the activity of ribulose 1,5-bisphosphate car boxylase (RuBPCase) was higher than that of phosphoenolpyruvate carbox ylase (PEPCase), while in the calli from the CAM plant, the activity o f PEPCase was higher than that of RuBPCase. Thus, the greened calli sh owed the original levels of enzymatic activity in their donor plants. The activity of PEPCase in the greened calli obtained from the C-3 pla nt increased with the application of NaCl to the cell culture medium, but this effect was not detected on nongreened calli.