The Effect of Root Formation on Photosynthesis of Detached Leaves

Abstract

The CO₂ exchange of fully expanded detached primary leaves of dwarf bean (Phaseolus vulgaris) with roots on the petioles has been measured. Rates of apparent photosynthesis and respiration increased as roots grew, decreased when roots were removed, and increased again as root regenerated. Rates of photosynthesis of different leaves were highly correlated with the dry weight of root on their petioles. Photosynthesis and respiration were decreased when root growth was restricted by kinetin, and were increased when root growth was stimulated by IAA. Photosynthesis of an attached leaf declined with time while that of a comparable detached leaf increased. The results suggest that photosynthesis is correlated with the size of the roots that are a sink for photosynthates.