The lateral root formation in soybean sprout culture declines its quality. This study was done to measure the effect of fluorescent light treatment during 24 hour imbibition and 6-day culture on seed germination and growth of soybean sprout. After 6 day culture, the sprouts were sorted as normal (＞4cm), abnormal (＜4cm) and non-germination by their hypocotyl lengths, and lateral roots, fresh and dry weights were measured. Lateral roots were less formed in the fluorescent light treatment lasted during the whole period of the imbibition than in the treatment for 50 minutes a day during the culture. The fluorescent light treatment during the imbibition mainly affected the germination and growth compared to the treatment done during the culture. Compared to the dark imbibition, the light treatment during the imbibition resulted in more normal sprouts, thicker diameters of hypocotyl and hook, and more fresh weights in cotyledon, hypocotyl, whole sprout, and economic yield. However, these results were reverse in lengths of hypocotyl and root, and fresh and dry weights of roots. It is concluded that the fluorescent lamp mainly irradiating red and blue lights can be used for the sprout production as an alternative light replacing blue and red lights treated during the imbibition because it blocked the lateral root appearance and stimulated growth of the sprout.

Soybean seeds were treated with blue, red and far-red lights for 0, 6, 12, and 24 hours during 24-hour imbibition before culture for 6 days. The soybean sprouts raised were classified by their hypocotyl lengths; normal (＞4cm), abnormal (＜4cm) and non-germination, and their lateral roots, hypocotyl diameters and component dry weights were measured. Red light treatment and dark imbibition reduced the abnormal soybean sprouts more than far-red and blue light treatments, meaning that the former treatments produced more commercial sprouts. The lateral roots were more formed in blue light and dark imbibition than the other light treatments, but were completely blocked by any light treatment lasted during the whole imbibition. Although any light quality treatment did not influence their primary root lengths, blue light one lengthened the hypocotyl more than the others treated during the imbibition, and far-red light enlarged its diameter. Despite this morphological change, component, total or economic yield was not significantly different among the light quality treatments during the imbibition.