Net Photosynthesis, Diffusive Resistance, and Chlorophyll Content of Shade- and Sun-tolerant Plants Grown under Different Light Regimes1

Abstract

Abstract Diffusive resistance decreased and chlorophyll content increased in leaves of Impatiens hybrida (shade tolerant) subjected to 14 days of low quantum flux density (QFD) compared with high QFD. There was no difference in diffusive resistance or chlorophyll content in Pelargonium X hortorum Bailey (sun tolerant) regardless of QFD treatment. Light saturation of net photosynthesis (Pn) occurred at higher light levels in impatiens treated with low QFD compared with those treated with high QFD. Light saturation in geraniums treated with high QFD was the same as in those treated with low QFD. Stomatal density in impatiens was greater, and stomatal area was smaller than in geranium. Physiological processes of impatiens appear to be more sensitive to changes in QFD than those of geraniums.