Spindly growth of watercress observed under the monochromatic light of a red light-emitting diode improved with slight changes in light quality using white light-emitting diode

Abstract: The suppression effect of white light-emitting diode (LED) on spindly growth observed under monochromatic light of the red LED in watercress (Nasturtium officinale R. Br.) was investigated for production in plant factory. Watercress was cultured in a growth chamber under total photosynthetic photon flux density (PPFD) of 100 ?mol?m^?2?s^?1 using three differential treatments; the ratio of red LED to white LED based on PPFD was 100:0 (R100W0), 90:10 (R90W10), and 75:25 (R75W25). Watercress was harvested 33 days after sowing. The longest internode length was observed with R100W0. Watercress in R100W0 was observed lowest value for node number, maximum leaf length, shoot fresh weight, shoot dry weight, dry matter rate, and SPAD. R90W10 recorded higher values for maximum leaf length, shoot fresh weight, shoot dry weight, dry matter rate, and SPAD than R100W0. Therefore, in watercress cultivation, replacing the red LED with a white LED by 10% was effective for morphological changes and dry matter production.