Improvement of culture and acclimation conditions in a bio-nursery system for <i>Paeonia lactiflora</i>

<i>Paeonia lactiflora</i>, the roots of which are used as a crude drug, is one of the most widely used and important medicinal plants. The long cultivation period and low proliferation rate of <i>P. lactiflora</i> makes it difficult to propagate large numbers of plants within a short period. We developed a bio-nursery system using plant tissue culture techniques to contribute to the supply of <i>P. lactiflora</i> seeds and seedlings in Japan. Here, we report on the improved tissue culture and acclimation conditions for a more stable and efficient bio-nursery system. We investigated the effect of culture conditions on shoot proliferation and the effect of calcium concentration during root induction and acclimation of cultured plantlets. The results demonstrated that the number of shoots increased under the 15/5°C diurnal temperature changing treatment [15°C, 12 h light (fluorescent light, 80-130 µmol m^-2 s^-1)/5°C, 12 h dark] compared to a constant temperature of 15°C. A higher calcium concentration (6 mM Ca²⁺) during root induction resulted in more vigorous growth after transplantation to the soil. In addition, it was found that planting in a closed greenhouse at a constant temperature of 20°C after cold treatment was suitable for acclimation of cultured plantlets. These findings are expected to contribute to the future seedling supply of <i>P. lactiflora.</i>