Articles
PUNGENT COMPONENT CONCENTRATION OF BLANCHED JAPANESE RADISH SEEDLINGS AS AFFECTED BY LIGHTING PERIOD
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.