AN ESTIMATE OF THE PHOTOSYNTHATE POOL SIZE FROM THE EQUILIBRATION OF (CO2)-C-14

When the plants were enclosed in a chamber under irradiation, the conc entration of CO2 rapidly decreased for a certain period and then remai ned constant. In contrast, the concentration of (CO2)-C-14 released up on the enclosure continued to decrease even after the CO2 reduction ha d ceased. To understand different characteristics of CO2 and (CO2)-C-1 4 observed, a carbon pool, in which substrates were readily available for maintaining dark respiration, was introduced The carbon pool size was estimated to be about 2 and 5.5 mmol(C) per plant in actively grow ing rice and maize, respectively. This amount is large enough to suppo rt growth for at least a whole night (11 to 15 h).