Studies on the forcing of Aster Savatieri MAKINO var. hortorum MAKING. X.

Abstract

1. This study was carried out to examine the growth and flowering of Aster Savatieri var. hortorum as affected by night temperature, day-length, various light intensities and light qualities during the forcing.The experiments of night temperature and day-length comprised 4 treatments; two different night temperatures from p.m. 4.30 to a.m.8.30, namely, 10°C and 15°C, two different day-length, namely, the plants received natural light 8 hours in short Eday plots, or artificial light of 16 hours in addition to the 8 hours in long day plots.The light source used was fluorescent lamps with about 1, 000Lux. Various light intensities of 51. 3, 32.5 and 12.5per cent of full sun were obtained by shading with cheese cloth, marsh-reed screen and straw mat, respectively. Various light qualities were obtained by covering with red, blue, yellow and transparent cellophane.2. Growth and flowering of the plants were accerelated, when they were grown under higher night temperature (15°C) and long day (24hr.) during the forcing.At a controlled night temperature of 15°C plants vwith a 24 hour photoperiod were more accerelated in growth and flowering than plants with a 8 hour photoperiod.Ten degrees C of night temperature given during long day was more effective in promoting flowering than 15°C of night temperature given during short day (8hr.).The interactions of night tomperature and day-length were observed in flowering date, stem length, leaf number and flower head diameter. Therefore, with respect to accerelation of growth and flowering to a certain degree a reciprocal compensation may exist between the effects of night temperature and daylength.3. Higher intensity of lights during forcing period to the plants caused an accerelation in flowering and a decrease in growth, while, lower intensity of lights retarded in flowering, increased in growth, up to 32.5% of full sun.The plants grown under the light intensity of 12.5% of full sun induced 60% blind.4. Growth and flowering of the plants were accerelated when they were grown under red light with red cellophane, but those grown under blue, yellow and white light were not sufficiently accerelated.