The node position from which axillary buds were isolated from shoots of rose (Rosa hybrida L.) markedly affected their growth and development in culture. Those buds nearest to and furthest from the apex either failed to develop or took the longest time to develop in culture compared to those buds in the middle portion of the stem. Benzylamino purine (BA) at low concentrations (0.03 to 0.3 mg/liter) stimulated the development of the axillary buds of ‘Gold Glow’ but not of ‘Improved Blaze’. A photon flux density (400-700 nm) of 17μE m−2 s−1 for 12 to 24 hours daily was optimum for the stimulation of shoot multiplication, while 66 μE mm−2s−1 for 12 to 24 hr was optimum for root initiation and for subsequent successful transplantation to soil of tissue culture-derived plants. A constant temperature of 21°C resulted in the highest rate of shoot multiplication and root initiation. Plants which initiated roots at 16, 21, or 26° had the highest level of transplant survival. An alteration in the temperature of the 8-hr dark period from 21° did not increase shoot multiplication, although root initiation was enhanced by lowering the night temperature to 11 or 16°. Histological analysis indicated that shoot multiplication of rose shoots occurs through the growth and development of axillary buds. The development of axillary buds is apparently under the repressive influence of the shoot apex, because physical excision of the apex or application to the shoot apex of 2,3,5-triiodobenzoic acid (TIBA) facilitated axillary bud development. Root initiation was affected markedly by the length of time that cultures had been maintained on shoot multiplication medium prior to transfer to rooting medium. This effect may be attributable to the BA in the shoot multiplication medium which may have accumulated in the tissue. If the endogenous cytokinin level is too high, root initiation may be inhibited and if it is too low the shoot undergoes senescence before it becomes cytokinin-autonomous, which occurs after root initiation.
Received for publication Nov. 30, 1981. Journal paper 8788 of the Purdue University Agricultural Experiment Station.
This research was supported by grants from Michigan Bulb Company, Grand Rapids, MI 49501 and Nor’ East Miniature Roses, Rowley, MA 01969.
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Department of Horticulture, Jeju National University, Seowipo, Jejudo, Republic of Korea.