Comparison of Violet, Red, and Green Light on Early-Stage Common Bean (Phaseolus vulgaris L.) Development

Abstract

The energy efficiency of light-emitting diodes (LEDs) makes them attractive for indoor plant lighting. LEDs, however, do not produce broad-spectrum light efficiently. The effects of LED lighting on common bean (Phaseolus vulgaris L.) growth are not well known. This study sought to find the colors of light that most effectively grow common bean plants under indoor conditions. The hypothesis was that red light would promote early common bean growth better, both qualitatively and quantitatively, than violet or green light. After planting the seeds in soil, 20 common bean plants were each grown under red, or green, or violet LED lights (PHILIPS®) (8 watt), or natural sunlight, for 16 days: a total of 80 plants. Bonferroni adjusted t-tests showed that the plants under the violet light grew significantly taller than the plants under red or green light with p-values 0.000 respectively; the plants under red or green light had significantly larger leaves than those under the violet light with p-values 0.000. Qualitative observations (based upon visual inspections of leaf health, maturity, and root development) revealed the plants under red light were the healthiest, most mature, and exhibited the most developed roots—followed by those under green light. The findings of this study suggested early common bean growth performed better under red light than under violet or green light.