Effects of light conditions during nursery period on the characters of rice [Oryza sativa] nurseling seedlings, their taking root and early growth after transplanting

Rice nursling seedling were raised under temperature-controlled condition (32 degrees C) in darkness or with illumination of 5f00 lux (Exp.1) and 170 lux (Exp.2) by fluorescent lamp for 1, 2 and 4 days before the end of experiment to clarify the effects of light conditions luring the nursery period (4 days) on the seedling characters, taking root and early growth after transplanting. Exp.2 included an additional plot in which the seedlings were raised under 32 degrees C with natural indoor light (Maximum: 70-80f lux during daytime) through plastic panel of the incubator. (1) Rice nursling seedlings with 2.1-2.3 plant age in leaf number, 7-8cm in plant length and remained ca. 40% endosperm could be raised under 32 degrees C, irrespective of light conditions tested in this study. Plant age in leaf number of the seedlings was a little promoted by illumination during raising period. (2) Although the chlorophyll content of the seedlings increased with increasing light intensity, the effect of the illumination period (1-4 days) on that was scarcely detected. (3) the day of first tiller appearance, as an indicator of taking root, was faster in the seedlings raised under illumination, irrespective of the illumination intensity or period, than those under dark condition, and this result led to better early growth in those seedlings, especially in the case of removal of endosperm. (4) the results mentioned above showed that weak illumination, raging from 100 to 500 lux, during the nursery period hardly inhibited elongation growth of the seedlings, and the suitable rice nursling seedlings with a length of 7-8cm for transplanter and ca. 40% of the endosperm remaining could be raised under 32 degrees C with weak illumination for 4 days. Moreover, weak illumination promoted taking root and early growth of the seedlings due to the production of chlorophyll