Effects of IAA, Zeatin, Ammonium Nitrate and Sucrose on the Initiation and Development of Floral Buds inToreniaStem Segments Cultured In Vitro

摘要

InToreniastem segments cultured on a defined medium from which ammonium nitrate and growth regulators were omitted, adventitious buds were readily formed from epidermal tissue, with subsequent differentiation of floral buds. Using this plant material, the correlation between the time of application of various chemicals and the time-course of floral bud differentiation was investigated. Histological examination showed that adventitious buds were vegetative during the first two weeks of the culture, and floral primordia appeared after about three to four weeks of culture. We divided the flowering process inToreniastem segments into the following 3 phases: the first phase (first 2 weeks) during which adventitious buds are formed, the second phase (3rd and 4th weeks) during which floral buds are initiated and the third phase (5th to 12th weeks) during which floral buds develop. Then we added IAA, zeatin, ammonium nitrate or a high concentration of sucrose to the medium during one, two or three of these phases. Ammonium nitrate added during the third phase suppressed floral bud development, but the high concentration of sucrose given during this phase stimulated it. These two chemicals influenced only the development of floral buds previously initiated. The application of IAA during the first phase promoted both the initiation and development of floral buds. However, its application after 2 weeks of culture failed to promote floral bud formation. Zeatin inhibited floral bud formation in a manner similar to ammonium nitrate, but if it was added to the medium only during the first phase, it slightly promoted the initiation and development of floral buds.