COS 213-2 - Effects of foliar spraying 6-benzylaminopurine on the growth and flowering of Sedirea japonica seedling

Abstract: Sedirea japonica is one of the critically endangered species in South Korea mostly due to artificial harms such as illegal collection and habitat destruction. Therefore, artificial propagation through improving germination rate, increasing growth, and controlling flowering is meaningful for the conservation and reintroduction of S. japonica. It is suggested that cytokinins are one of the multi-factors that contribute to plant growth and floral responses. Especially, exogenous cytokinins have been known to induce shoot growth or earlier flowering in orchids. Therefore, it was investigated how the application of 6-benzylaminopurine (BA) influenced the growth and flowering of S. japonica orchid clones. 50 clones of S. japonica seedlings were grown in a growth chamber from 14^th April to 30^th June 2021, and each treatment by different BA concentrations including the control consisted of 10 clones. A foliar-spray containing BA at 100, 200, 300, and 400 ppm was applied from 1^st July to 30^th December 2021, weekly from the first 5 weeks, and biweekly from the next 12 weeks. Each seedling was sprayed with 10 ml of freshly prepared BA at the concentrations mentioned above, and the controls were sprayed with 10 ml of distilled water. After that, all the seedlings were transferred to the growth chamber, with a temperature of 15 ℃ for 12 weeks. The percentage of inflorescence production (%), the number of inflorescences, flowers per inflorescence, and leaves, the length of inflorescence (cm), and the mean length and width of the longest leaf (cm) were monitored. Inflorescence production increased by spraying 100 and 200 ppm of BA, while 300 and 400 ppm BA showed lower inflorescence production than the control. The number of inflorescences per seedling was no more than two for all the treatments. The number of flowers per inflorescence varied from 4 to 14, but there was no significant difference among the treatments. The length of the inflorescence ranged from 4 to 15 cm, and treatment differences did not exist. The number of leaves slightly increased with the increasing BA concentration and then decreased at 400 ppm. The mean length and width of the longest leaf of each seedling were both higher under the 200 ppm of BA treatment. An iterative experiment with more seedlings would be helpful to figure out the effects of exogenous BA treatment on S. japonica, and it can be applied for mass propagation.

This study was supported by the National Institute of Ecology, NIE-B-2023-47.