Studies were conducted to determine the effects of daylength and GA₃ treatments on the conversion of cleistogamous flowers to chasmogamous flowers in Viola mandshurica W. Becker. The results were as follows:
1. Short-day (10 hr) treatment was effective to convert cleistogamous flowers to chasmogamous flowers, and it took 40 days from the treatment to the blooming of chasmogamous flowers.
2. Short-day treatment reduced the length of leaf blade, leaf petiole, and leaf width compared to natural or long-day (15 hr) treatments.
3. GA₃ did not affect the conversion of flower form and plant growth, however, high concentration teatment of GA₃ (500 ppm) seemed to delay the flowering by 10days, compared to low concentration treatment of GA₃ (0, 20, and 100 ppm).
4. Calyx and ovary size were similar in both flower types; however flower, anther, and peduncle size were bigger in chasmogamous flowers than in cleistogamous flowers.
5. Selfing occurred in cleistogamous flower, whereas outcrossing in chasmogamous flower, and the number of seeds in cleistogamous flowers was approximately 3 times as much as that of chasmogamous flowers.
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