Effects of light conditions during nursery period on the characters ofrice nurseling seedlings, their taking root and early growth aftertransplanting

Abstract

Rice nurseling seedlings were raised under temperature-controlledcondition (32°C) in darkness or with illumination of 500 lux (Exp. 1) and170 lux (Exp.2) by fluorescent lamp for 1,2 and 4 days before the end ofexperiment to clarify the effects of light conditions during the nurseryperiod (4 days) on the seedling characters, taking root and early growthafter transplanting. Exp.2 included an additional plot in which the seedlingswere raised under 32°C with natural indoor light (Maximum: 70~80lux duringdaytime) through plastic panel of the incubator. 1) Rice nurseling seedlingswith 2.1~2.3 plant age in leaf number, 7~8cm in plant length and remainedca. 40% endosperm could be raised under 32°C, irrespective of lightconditions tested in this study. Plant age in leaf number of the seedlingswas a little promoted by illumination during raising period. 2) Although thechlorophyll content of the seedlings increased with increasing lightintensity, the effect of the illumination period (1~4 days) on that wasscarcely detected. 3) The day of first tiller apperance, as an indicator oftaking root, was faster in the seedlings raised under illumination,irrespective of the illumination intensity or period, than those under darkcondition, and this result led to better early growth in those seedlings,especially in the case of removal of endosperm. 4) The results mentionedabove showed that weak illumination, ranging from 100 to 500 lux, during thenursery period hardly inhibited elongation growth of the seedlings, and thesuitable rice nurseling seedlings with a length of 7~8cm for trasnsplanterand ca. 40% of the endosperm remaining could be raised under 32°C with weakillumination for 4 days. Moreover, weak illumination promoted taking root andearly growth of the seedlings due to the production of chlorophyll.