Circadian rhythms of dark respiration, flowering, net photosynthesis, chlorophyll content, and dry weight changes in Chenopodium rubrum

Abstract

There are circadian rhythmic changes in dark respiration, net photosynthesis, chlorophyll content, and dry weight in Chenopodium rubrum, ecotype 60°47′ N, 137°32′ W. The rhythm in dark respiration has a period of about 27 h and its phasing is quite closely correlated with the rhythm in flowering response, which has a period of about 30 h. A close similarity in the periodicity (21 h) and phasing of the rhythms in net photosynthesis and chlorophyll content suggests that the photosynthetic rhythm may be partly attributed to rhythmic changes in chlorophyll content. The rhythmic changes in dry weight, with a period of 18 h, could be due to a rhythm in dark fixation of carbon dioxide. The possible relationship of rhythmicity in these processes to other circadian rhythms that occur in C. rubrum is discussed. The concurrent existence of various rhythms in biochemical and physiological processes that differ in period and phase within a single ecotype of C. rubrum clearly reflects the possible involvement of metabolic activity in circadian rhythms.