Effect of leaf age on light and dark14CO2fixation in a CAM plant,Bryophyllum calycinum

摘要

Leaves of different ages fromB. calycinumwere exposed to14CO2in light during day and night. The labelling pattern on the chromatogram differed with leaf age. Young leaves had similar patterns to those of C3 plants during both day and night. Mature leaves showed high incorporation of14C into C4 acids, especially at night. In contrast, no significant difference with leaf age was observed in the pattern of dark14CO2fixation products. Study of the enzyme activity and the content of titratable acid at each leaf age suggested that high incorporation of14C in C4 acids during the night was due to the simultaneous absorption of CO2by both enzymes RuDPcarboxylase and PEPcarboxylase.