生長素撒布によるキクの開花抑制に関する研究(第3報)

In the previous papers the auther reported that growth substances may be successfully used for delaying flowering of chrysanthemum. The present study deals with the effects of combined applica-tion of electric light and auxin on delaying flowering and on flower characters.<br> In the light culture of chrysanthemum, the light effect for delaying flowering decreases with an increase in distance from the light source due to the reduction in light intensity.<br> If the auxin supply complements the deficiency of light intensity, then its application would be an advantageous method to save the cost of electric equipment.<br> The variety “December King”, which is popularly cultivated by delaying its flowering for winter sale in Japan was used in this study. “Yellow Boyce”, which is a mid-season autumn variety and is not suitable for delaying was added for compari-son with “December King”. The materials were propagated by cuttings on July 11, planted in 6 inch pots on Aug. 4, and pinched on Aug. 14. Three shoots were selected for every plant.<br> Total materials were divided into three lots each containing 13 pots. In each lot, pots were arranged in a row which extended from under the lamp to 3.2 meters away, and were labelled with no. 1, 2, 3, ……13. These pots were placed in the green-house which was heated with an electric cable after early January.<br> The intensity of illumination from the 80 W Mazda lamp decreased from 60 lux nearest for the lamp to 2 lux at a distance 3.2 meters away. The first lot was applied with 50ppm of NAA, the second lot with 100ppm of NAA, and third lot was control. The auxin was supplied at every three day intervals. The long day (17 hrs.) and auxin treatments were started on Aug. 25 and ended on Oct. 10.<br> At the termination of both treatments slight inhibition of growth of plants of “December King” was seen in the lot with 50ppm of NAA and heavy inhibition in the lot with 100ppm of NAA. However, with “Yellow Boyce” heavy inhibition seen in both of the treated lots. In this variety was the treated plants did not differentiate flower buds and showed the rosette habit after the termina-tion of treatments. Budding date, flowering date, . height of plant, number of leaves and flower size, , etc. were recorded.<br> The experimental results on “December King” are summarized as follows:<br> (1) The budding dates of control plants were delayed according to the position in relation to the light source. In the control, the budding date in the 10th pot was Oct. 12, while in the first pot which was placed nearest for the lamp, it was Nov. 16.<br> With 50ppm of NAA the date of budding was delayed 17 days in the 13th pot, and 5 days in the first pot in comparison with the 13 th and the first pot of control respectively. However, they were delayed at the same rate in all plants applied with 100ppm of NAA.<br> (2) The date of flowering in the treated plants were delayed according to the delay in bud-ding compared with control, however, those of the first pot treated with 50ppm of NAA and control were the same.<br> (3) In the control and 50ppm of NAA lots, it was observed that the earlier the flowering date the shorter is the stem length. After the termina-tion of auxin spray all inhibited plants recovered their growing power and elongated.<br> (4) There is no difference in number of florets among the flowers which opened before the last of December, but the flowers opened after late January had slightly fewer florets.<br> (5) The differences in stem length, flower size, number of florets and number of leaves be-tween the treated lots and control were not' re-markable. From these results, it may be conclud-ed that, the application of auxin for delaying chry-santhemum flowering is practical. However, it is important to select a variaty which grows vigorously.