ISHS Acta Horticulturae 390: Internat. Symposium on Medicinal and Aromatic Plants
PUNGENT COMPONENT CONCENTRATION OF BLANCHED JAPANESE RADISH SEEDLINGS AS AFFECTED BY LIGHTING PERIOD |
| Authors: | M. Kimura, K. Tsushima, I. Kouno, M. Ichimura, Y. Tomitaka, H. Ito, T. Anan |
| Keywords: | Japanese radish, Seedling, Cotyledon, Hypocotyl, Pungent component, Isothiocyanate, Lighting period |
| Abstract:
The principal pungent component in fresh juice of Japanese radish (Raphanus sativus L. cv. Osaka-Shijyunichi) seedlings, as called kaiware-daikon in Japan was determined by gas chromatography and gas chromatography-mass spectrometry, and the relationship between pungent component concentration and lighting period was investigated. Japanese radish seedlings were grown in growth chambers under darkness and/or lighting (fluorescent lamp: FL20SEX-N, 7000 luxes) at 25 °C for 8 days after sowing. Treatments were five as follows : 0, 2, 4, 6 and 8 days of darkness combined with 8, 6, 4, 2 and 0 days of lighting, respectively. The pungent component of Japanese radish seedlings was identified to be mostly (more than 90 %) 4-methylthio-3-butenyl isothiocyanate (MTB-ITC). The MTB-ITC concentration in the top of seedlings tended to be higher in continuous lighting (dark 0 day + light 8 days) than continuous darkness (dark 8 days + light 0 day), at most of seedling stages except 2 days after sowing. A marked decrease of MTB-ITC concentration in the top of seedlings was observed from 2 days to 6 days after sowing in the above both treatments, in contrast to increasing of the top fresh weight. In cotyledons, MTB-ITC concentration decreased with 6 ≈ 8 days of lighting, but their fresh weight increased. On the contrary, MTB-ITC concentration of hypocotyls decreased with the decrease of lighting period, but their fresh weight increased. The inverse relation between MTB-ITC concentration and fresh weight in hypocotyls and cotyledons suggests that the decrease of MTB-ITC concentration may be caused by a dilution effect accompanied with fresh weight increase of the respective organ as affected by lighting period. | |
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