Studies on the flower bud formation in Platycodon grandiflorum. A. DC. (II)

Abstract

Experiments were carried out to determine the factors affecting the time of flower bud initiation and flowering in Platycodon grandiflorum (var. Samidare), by means of the following procedure: (A) Temperature test: in which the night temperatures were maintained at about 20°, 15° and 0_??_5°C from January 18 to April 13, 1956. (B) Day length test: in which artificial lighten-ing during the night and shading with black vinyl film from 5p.m. to 9a.m. were carried out from April 25 to July 2, 1956. The results are summarized as follows: (A) Temperature test (1) Flower bud initiation was first observed among the plants exposed to 20°C, on February 27, 40 days after planting. The plants exposed to 15°C began initiating their flower bud on May 19, 60 days after planting, and the plants exposed to 0_??_5°C began initiating their flower buds on April 24, 95 days after planting. (2) Flowering of plants at 20°C began on March 27, 68 days from planting. The plants at 15°C began flowering on April 16, 88 days from planting. and the plants at 0_??_5°C began flowering on June 1, 134 days from planting. (3) The plants grown at 0_??_5°C were the largest and those at 20°C were the smallest in height of plant, number of leaves, and number of flowers. on a plant. (4) From these results the author concluded that the time of flower bud initiation and flowering in Platycodon grandiflorum A. DC. can be controlled by temperature treatment. (B) Day length test No difference was observed among the plants. exposed to long days, short days and those of control, in time of flower bud initiation and flowering, height of plant, number of leaves, and number of flowers on a plant.