Intraspecific Measurements of Photorespiration 1
AUTOR(ES)
Martin, F. A.
RESUMO
The relative magnitudes of (a) CO2 compensation concentration, (b) zero CO2 intercept of the CO2 response curve, (c) O2 suppression of net photosynthesis, (d) differential 12CO2 and 14CO2 uptake, and (e) 14CO2 efflux into CO2-free air were determined in the dry bean (Phaseolus vulgaris L.) varieties Michelite-62 (M-62) and Red Kidney (RK). In comparing the two varieties for each of the above processes, there were three categories of response, M-62 > RK, M-62 = RK, and M-62 < RK. Since these processes did not give the same relative difference for the two varieties being studied, it was concluded that these phenomena cannot validly be used to estimate the magnitude of photorespiration, although they do identify its presence. The results suggest that photorespiration is but one component of O2 inhibition of net photosynthesis and that photorespiration itself has two or more component metabolic pathways.
