Effects of C0₂ enrichment on the rates of photosynthesis and translocation of tomato leaves

SUMMARY Effects of C0 2 enrichment on the rates of net photosynthesis (carbon fixation) and translocation (carbon transport) of tomato leaves were examined on a single mature leaf (seventh basal leaf) of plants grown initially under a light flux density of 40 W m ‐2 with 350 (control) or 1000 vpm (enriched) CO 2 , and then exposed for 6 h to various light flux densities (7, 20, 40 and 130 W m ‐2 ) or CO 2 concentrations (350, 500, 700 and 1000 vpm). When measurements were made in the conditions in which plants were grown, the rates of carbon fixation and carbon transport were 20 and 40% respectively higher in enriched plants than in the control ones. Under conditions different from the growing conditions, the rates of carbon transport in the enriched plants were generally higher than those of the controls with a similar rate of carbon fixation. Leaves grown under a C0 2 enriched environment have a greater constant supply of mobile leaf assimilate than those under atmospheric C0 2 . The higher efficiency of carbon transport in enriched plants was apparently retained even when the leaf was temporarily exposed to lower levels of light or CO 2 .