Studies on the blindness in gladiolus. V

Abstract

Many studies on the physiology of flowering clari-fied that the flowering in short-day plants may be controlled by the application of plant growth regulating substances, the so-called “auxin” or “antiauxin”. It is recognized in the gladiolus culture that the .short day promotes the flowering slightly, but ex-treme short day causes the blindness. It is supposed that the application of growth regulating substance is effective to decrease the number of blindness in gladiolus, For the first step of the study from the point of view mentioned above, the experiments were conducted to know the auxin level in the flower buds of gladiolus which had been held under long photoperiods (24 hours) and short photoperiods (8 hours). The variety used was “Spotlight”. The average-weight of corms which had been grown at Ueno in Mie prefecture was 26. 5g. The corms were plant-ed in the experimental farm of Kyoto University on August 27, 1958. Shading and lighting were made from October 10 to November 6, 1958. Sampl-ings were made at one-week intervals during the .course of the experiments and the avena tests were mad eon each sample. Avena sativa, variety Victory grown at Hokkaido University was used for the .curvature test. And the diffusion method, in which 3 hours diffusion was made at 25°C, was employed for the test. Beside avena test, anatomical obser-vations were made. The results obtained were summarized as follows: 1. Two weeks after the start of treatment, it -was observed that the length of flower spikes in short-day plot was getting shorter than that in long-day plot, nevertheless no difference was observ-ed between long-day and short-day plots on height of plants, number of leaves, and length of stems. And the difference in length of spike increased gradually as the time progressed. Finally, the blindness occurred in short-day plot, four weeks after the start of treatment. 2. The value of avena test with the plants under short-day condition was smaller than that under long-day condition two weeks after the start of treatment. And as the time progressed, the difference in the measurement values between long-day and short-day plots became greater. Finally, few avenas were curved with the plants under short-day. 3. Anatomical observations showed that the death of cells appeared at the top of the flower spike in three week treatments of short-day. Then the death of cells advanced downwards with the succeed-ing of treatment. The perfect death of flower spike was observed in the samples taken from the plants treated with four week short photoperiods. The archesporium formation was observed in the flower buds that died at their most developed stage. 4. From the results mentioned above, it seems that the gladiolus under short-day condition results in the decrease in auxin content in the flower buds, and consequently shows the blindness. 5. Anatomical studies showed that the flower buds, which had reached to the tetrard stage at the end of four week short-day treatments, were not damaged.