Growth and Nitrogen Fixation of Phaseolus vulgaris L. at Two Irradiances 1. Growth

Abstract

Plants of Phaseolus vulgaris grown at 7 and 28 W m⁻² showed no differences in rate of development of leaves or flowers. At 7 W m-Z plants had longer internodes, more succulent stems and leaves, higher ratios of shoot:root and greater leaf areas that those at 28 W m⁻². These differences were established prior to detectable differences in photosynthesis and could partly be attributed to an increased proportion of far-red light. Although the final d. wt, carbon content, and fruit yield were higher at 28 W m⁻², plants at 7 W m⁻² apparently had similar relative growth rates and greater photosynthetic efficiency. Dry weight differences are most easily interpreted as resulting from the establishment of an earlier net carbon gain at 28 W m⁻² than at 7 W m⁻².