RIBULOSE-1,5-BIS-PHOSPHATE CARBOXYLASE ACTIVITY IN ALTITUDINAL POPULATIONS OF ESPELETIA-SCHULTZII WEDD

The ribulose-1,5-bis-phosphate (RBPC) (CO2)-C-14 fixation rate was measured at four different temperatures, 5 degrees, 15 degrees, 25 degrees and 35 degrees C, in three populations of Espeletia schultzii at different altitudes, 3100, 3550 and 4200 ma.s.l. The fixation rate increased with temperature increase in the populations studied. The population at 4200 m showed the higher rate at any temperature, followed by those at 3550 and 3100 m. The Km(CO2) increased with temperature increase, but the values were similar among populations. The V-max values increased with temperature and were higher for the 4200-m population. These results suggest that the RBPC enzyme is more activated in the highland population and that the enzyme kinetics are not similar among populations.