ISHS Acta Horticulturae 907: VI International Symposium on Light in Horticulture
CHERRY RADISH GROWTH UNDER DIM LED LIGHTING TO THE ROOT ZONE |
| Authors: | J.S. Park, J.E. Son, K. Kurata, K. Fujiwara |
| Keywords: | artificial light, light-emitting diodes, PPFD, root-zone lighting, root development |
| DOI: | 10.17660/ActaHortic.2011.907.18 |
| Abstract:
Effects of dim lighting to root zone on the growth of cherry radish (Raphanus sativus L. ‘Komedo’) were investigated in a preliminary experiment using blue, green, red, far-red, and white light-emitting diodes (LEDs). Radish plants in the control group were cultivated without dim lighting to the root zone. On a black polystyrene plate floating in a transparent container on a nutrient solution, 24 seedlings with two true leaves each were planted. Six containers were used, each covered with black drawing paper on its four lateral surfaces to prevent light transmission. Radish plants in the containers were cultivated under a photosynthetic photon flux density (PPFD) of 180±25 μmol m-2 s-1 (at the canopy level) at 21±1/18±1°C (day/night) during the 3-week experimental period. For root-zone dim-lighting treatments, blue, green, red, far-red, or white LEDs were installed under the bottom of each container to expose the root zone to dim light at a PPFD of 15±2 µmol m-2 s-1. Shoot fresh and dry weights of radish plants under blue and red LEDs were significantly greater than those of plants grown in the dark. Root dry weights were significantly greater under white and red LED irradiation although root fresh weight under the far-red LED was lower than for those grown in the dark. Dim lighting to the root zone with different wavelengths of LEDs appeared to influence the growth of radish leaves and roots even though the PPFDs for dim lighting were less than one-tenth of the level that is normally required for cultivation. | |
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