Application of a temporary immersion system in mass propagation of Phalaenopsis

Abstract

A temporary immersion system consisting of a series of five-litre twin glass vessels was successfully used for in vitro adventitious shoot multiplication and rooting of Phalaenopsis. Highest shoot multiplication rate of 25.4 was achieved after twelve weeks when eight immersions per day, of ten minutes each, were used. Fresh medium containing 0.5 mg l⁻¹ TDZ was supplemented every two weeks. The different periods of TDZ exposure affect the multiplication rate, fresh weight rate and shoot size. Seven-week culture on TDZ-containing medium, followed by five weeks on TDZ-free medium, resulted in 18 % of shoots smaller than 1 cm, 56 % were of 1–3 cm and 26 % exceeded 3 cm in length, respectively. Small shoots are suitable as inoculum for the next multiplication cycle, whereas shoots larger than 1 cm can be rooted on cytokinin-free medium. Highest percentage of rooted shoots (93.8 %) and highest root number (3.7 roots per shoot) were achieved in 1.0 mg l⁻¹ IAA — containing medium after exposure to six immersions per day, ten minutes each. The mean survival rate of plants rooted in TIS was 94 % under standard greenhouse conditions.