Abstract
The authors reported that marketable cut flowers of dahlia were obtained in winter season when plants were grown under a favorable day-length of 13 to 14 hours, using young plants propagated by cutting, in the previous paper.
In the present experiments, the effects of mature leaves left at basal positions of the main stem and of the position of the bud from which lateral shoot elongated after pinching, on the growth rate of the lateral shoot and flowering were examined. Lateral shoots at the first or third node were allowed to elongate after decapitation, with 0, 2, 4 or 6 leaves left on the main shoot.
The elongation of lateral shoots from the stem with no leaf was very slow, and their flowering was retarded over 20 days in comparison with flowering of those with leaves. Although there were slight differences, stem elongation and flowering were delayed most in the plants with two leaves among the plants with two or more leaves.
Flowering of the shoots from the first node was earlier than flowering of those from the third node, without reference to the number of leaves on the main stem. Length, weight and number of leaves of the lateral shoot from the stem with two leaves were a little less than those of the lateral shoot from the stem with four or six leaves. On the contrary, length, weight and number of leaves of the lateral shoot from the first node of the main stem without leaves were remarkably great. Length and weight of the lateral shoot from the third node of the main stem were less than those of other lots, except that number of nodes of shoots from third node without leaf was slightly larger.
Judging from the quality of the cut flower, the lateral shoot from the first node was better than that from the third node. There were two flowering periods 75 days apart in the lateral shoots from the third node. The lateral shoots that reached the first flowering period had shorter and lighter stems and a smaller number of leaves than those of shoots that reached the second flowering period. The number of nodes of shoots that flowered in the earlier period was similar to that of shoots from the third node of the main stem with two leaves.
The fact mentioned above suggests that flower primordia are formed in an early stage of development of the lateral bud. And, the lateral shoots from the third node may be just in the inductional stage for flower formation.
