Two Dracaena plant species, D. sanderiana (ribbon plant) and D. fragrans (corn plant), were used in this study. Plants that had stems with an approximate length of 40 cm and 10–15 leaves were purchased from a plant nursery at Jatujak market in Bangkok, Thailand. The stems were washed by tap water to remove dirt, rinsed with distilled water and the brown leaves were removed. The washed stems were cultivated in a hydroponic system using a 400 ml half-strength Hoagland's nutrient solution [12] in a 2-l glass jar. The plant was placed 30 cm under natural luminescence using four cool-white fluorescent lamps (25 μmol m−2 s−1 PAR). The plant cultivation was a daily 12 h/12 h light–dark cycle at room temperature (ca. 31 °C) for 4 weeks until the roots grew. The nutrient solution was removed and replaced with a new one once a week. The plant was allowed to grow to 2 months in age and then the roots were washed with distilled water several times. The initial fresh weights were determined before the experiment was set up. At 2 months old, each stem of D. sanderiana and D. fragrans generally had stem diameters of approximately 0.5 and 3 cm, respectively and initial fresh weights of approximately 20 and 200 g, respectively.