Abstract
The author reported in a previous paper that an application of 50ppm of NAA at three-day intervals inhibits the flower bud differentiation of December King chrysanthemums placed under an incandescent lamp of low light intensity. This report is a continuation of that study. NAA was employed as the auxin, and combined with gibberellin, ascorbic acid, thiamine or tryptophane. In addition, urea was applied with the NAA. These chemicals were sprayed on chrysanthemums receiving different light intensities.
The inhibitory effects of NAA, GA or tryptophane in single or mixed solutions for flower bud formation were examined using Shintoa chrysanthemums grown under an artificial short day conditon. The limiting light intensity for flower bud inhibition was 8 to 12lux without auxin spray and only 2 lux with auxin spray. Inhibition of flower buds caused by 100ppm of NAA spray was the same as those illuminated with light of about 40lux. However, the formative effect of 100ppm was quite strong. The concentration of 50ppm showed weak formative damage, but caused little inhibitory effect on flower bud formation. This dosage was equivalent to the effect of light intensity of 40lux, if supplemented with light of 2 to 3lux.
Application of ascorbic acid slightly inhibited flower bud differentiation of December King chrysanthemums. Therefore, the spray solution of 25 ppm of NAA and 50ppm of ascorbic acid resulted in an inhibitory effect as did 50ppm of NAA. This was also true when 25ppm of NAA were mixed with 1% urea. Thiamine showed a similar response but its effect was weaker than that of ascorbic acid. Tryptophane inhibited flower bud differentiation at dosages of 100ppm and 200ppm, but showed no appreciable influence on Shintoa or December King varieties when sprayed with a mixed solution of ascorbic acid.
The response to gibberellin was far greater. It slightly inhibited flower bud formation at 50ppm. When mixed at this concentration with 50ppm of NAA, gibberellin inhibited flower bud formation to a greater degree than the application of 50ppm of NAA alone. This response suggests that there is a synergistic relationship with gibberllin and auxin in inhibiting flower bud formation.
From these results it is concluded that equal quantities of 50ppm of NAA and 50ppm of GA inhibit flower bud differentiation of chrysanthemums when applied at three day intervals under a low light intensity of 2 lux.
