MODULATION OF ROOT-GROWTH AND ORGANOGENESIS IN THIDIAZURON-TREATED GINSENG (PANAX-QUINQUEFOLIUM L)

The morphoregulatory effect of thidiazuron (TDZ) applications to ginse ng (Panax quinquefolium L.) seedlings and 3-year-old plants was determ ined. Applications of TDZ (0.22 and 2.20 ppm), either as foliar sprays or soil drench to greenhouse-grown seedlings over 18 weeks (2 weeks a fter sowing to 20 weeks when plants were harvested) induced similar re sponses, in particular, increased stem length and diameter, and shoot and root weight (economic yield). Single foliar applications of TDZ at 62.5 and 125 ppm to 3-year-old field-grown ginseng plants 3 months pr ior to harvest increased root biomass (economic yield) by 19 to 23%. R oots of TDZ-treated seedlings and 3-year-old field-grown plants develo ped thickened secondary roots on the upper part of the taproot. The ro ot-like structure of these secondary roots was confirmed by histology. In addition, TDZ treatments induced adventitious buds on the shoulder of 3-year-old roots. These buds developed into shoots to give multi-s tem plants following a period of dormancy, which was overcome with GA( 3) (gibberellic acid) treatment prior to planting.