The photoconvertible chlorophyll-protein complex CP668-*CP743 could be observed in situ after a freeze-thaw treatment in Chenopodium and Amaranthus. The concentration of the complex was highest in sections of the upper part of the stem. Capacity for photoconversion developed gradually after thawing. With Chenopodium the yield of CP668->CP743 depended to a large extent on growing conditions of the plant, with Amaranthus much less variability was found. In preparations from Amaranthus efficient energy transfer between pigments attached to a common protein carrier could be demonstrated. The initial quantum efficiency of Cp668 -»Cp743 photoconversion was similar to that of protochlorophyll-chlorophyll photoconversion. A possible relation between various photoprocesses in the measured plants is discussed.