Carbon Dioxide Exchange in Compact and Semi‐Open Sorghum Inflorescences1

Abstract

Carbon dioxide exchange rates were monitored in light and dark in compact and semi‐open heads of sorghum (Sorghum bicolor (L.) Moench). Developmental stages ranged frmn bloom to hard dough in the grain. Highest CO2 uptake in both head types occurred at the bloom stage when net uptake rates for semi‐open and compact type heads were 3.9 and 1.2 mg CO2 g dry wt‐1 hr‐1, respectively. Beginning at the ,milk stage, a net CO2 evolution on the order of 1 to 1.4 mg g dry wt‐1 hr‐1 occurred in compact heads in the light. The semi‐open head type continued a small net CO2 uptake in the light through the milk and soft dough stages. Both head types evolved CO2 at hard dough stage. Dark respiration was similar in both head types and decreased from about 4 to 1 mg CO2 g dry wt‐1 hr‐1 from bloom to hard dough.