Stimulation of emergence of root apical meristems in horseradish hairy root by auxin supplementation and its kinetic model

1-Naphthaleneacetic acid (NAA) in the medium strongly inhibited horseradish hairy root elongation. In hatch culture, NAA in the medium was absorbed by the root at the beginning of the culture (0-4 d). After the depletion of NAA, root apical meristems emerged, and then the growth rate of the root increased dramatically. The batch culture with 1 × 10^-3 kg/m³ of NAA reached the highest biomass, 10.9 kg-dry weight/m³ at 21 d. Modification of a kinetic model previously developed resulted in a favorable fit with the growth curve of horseradish hairy root treated with NAA. Furthermore, in repeated batch culture, the NAA-treated root culture exhibited a 1.7-fold increase in dry weight, 57 kg/m³ at 40 d, compared with that of no NAA-treated root. The modified kinetic model also correlated well with the experimental results in repeated batch culture.