THE INFLUENCE OF THIDIAZURON ON IN VITRO SHOOT PROLIFERATION OF OAKLEAF HYDRANGEA (HYDRANGEA QUERCIFOLIA BARTR.)

Abstract

The objectives of this study were to promote adventitious shoots from leaf explants and axillary shoots from nodes in vitro. Leaf explants were excised from 12-15 month old shoot cultures and the nodal explants were taken from greenhouse-grown stock plants. The leaf explants were obtained by cutting leaves that formed in vitro in half and placing them on MS medium with 1 μM indolebutyric acid (IBA) plus thidiazuron (TDZ) at 5x10 -8 , 1x10 -7 , 5x10 -7 , 1x10 -6 , or 5x10 -6 M. The explants were transferred to fresh media every 28 days and the shoot number and shoot length data were taken at the end of 16 weeks. The concentration of TDZ in the medium significantly affected adventitious shoot number with the most shoots forming on leaf explants on medium with 5x10 M TDZ. Although a mean of 68.7 shoots formed with this concentration of TDZ, the majority were < 0.5 cm long. As the concentration of TDZ decreased, the number of adventitious shoots that formed were significantly fewer, but longer. Nodal and terminal bud explants from greenhouse-grown plants were placed horizontally on MS media with 1 μM IBA plus 10 -10 , 10 -9 , 10 -8 , 10 -7 , or 10 -6 M TDZ. The nodal explants were transferred to fresh media every 28 days and data were taken at 9 weeks. Total shoot production was greatest at 10 -6 M TDZ, with a mean of 5.2 shoots. At this concentration, there was a combination of axillary and adventitious shoots but as the concentration of TDZ decreased there were predominately axillary shoots.