Abstract
Light quality and quantity of the environment, where lettuce seedlings were grown, affected the mesophyll tissue and the shoot formation in cotyledons excised and cultured in vitro. When cultured on MS medium for 5 days, the cotyledonary tissues of the seedlings were poorly developed under an illumination level of 150 lx with fluorescent light but well-developed both under 5, 000 and 10, 000 lx, The mesophyll cells of cotyledons were rich in cytoplasm when excised from the seedling grown under BOC lamp or 150 lx of fluorescent light but vacuolated under 5, 000 and 10, 000 lx. Frequecy of adventitious buds on the cotyledons grown under high-level light intensity was less than low-level intensity. In addition, the adventitious bud formation decreased as the age of the cotyledons advanced. This trend was clear under the high light intensity.
