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 mea sured at four different temperatures, 5 degrees, 15 degrees, 25 degree s and 35 degrees C, in three populations of Espeletia schultzii at dif ferent altitudes, 3100, 3550 and 4200 ma.s.l. The fixation rate increa sed with temperature increase in the populations studied. The populati on at 4200 m showed the higher rate at any temperature, followed by th ose at 3550 and 3100 m. The Km(CO2) increased with temperature increas e, but the values were similar among populations. The V-max values inc reased with temperature and were higher for the 4200-m population. The se results suggest that the RBPC enzyme is more activated in the highl and population and that the enzyme kinetics are not similar among popu lations.