Effects of Blue Light and Red Light on Kidney Bean Plants Grown under Combined Radiation from Narrow-Band Light Sources.

Abstract

Kidney bean (Phaseolus vulgaris L.) plants were grown at different levels of blue and red light under broad-spectrum radiation over 12 d. Using four kinds of narrow-band fluorescent lamps, blue or red light was increased at the same levels of photosynthetic photon flux density (100μmol m-2 s-1) and red to far-red photon flux ratio (R: FR; 1.1) . Increases in both blue and red light caused increases in total dry matter, but also quite different dry matter distribution. Increasing blue light did not have a significant influence on leaf area but caused a large decrease in stem length. On the other hand, increasing red light caused both increases in leaf area and a small, but consistent, increase in stem length. The data suggest that increases in total dry matter are due to increases in dry matter production per unit leaf area in the case of increasing blue light, and on the other hand, due to increases in leaf area in the case of increasing red light. Besides the growth response caused by R : FR, the results indicate that increases in blue light cause great inhibition of stem extension and thickening of leaf, while increases in red light at constant R : FR accelerates both stem extension and leaf expansion without modifying leaf thickness.