Growth promotion and secondary metabolite accumulation of Phyllanthus amarus cultured photoautotrophically under carbon dioxide enriched condition
Keywords:Phyllanthus amarus, carbon dioxide, net photosynthetic rate, photoautotrophy, secondary metabolites.
Studying the effect of carbon dioxide on growth and secondary metabolite accumulation of Phyllanthus amarus has brought benefits not only to in vitro plant production, but also to secondary metabolite production from in vitro plants. Leafy nodal cuttings of P. amarus plants were cultured photoautotrophically with a density of 4 explants/vessel. The 370 ml Magenta GA-7 vessel had 2 holes (Φ = 1 cm) on the cap attached by 2 Millipore filters with a pore size of 0.45 µm. The culture medium, without sugar and vitamin, was composed of macro-elements 1/2 MS and micro-elements MS. Explants were cultured for 45 days in the Percival growth chamber under CO2 concentration of 400 or 1200 μmol mol-1, PPF of 160 µmol m-2 s-1, photoperiod of 16 h d-1, day/night temperature of 27/22oC and relative humidity of 50%. On day 45, the in vitro plants were transferred to the ex vitro stage for 32 days. The growth of P. amarus plants under high CO2 concentration was greater in both in vitro and ex vitro stages compared with those under low CO2 concentration. Increased fresh and dry weights, shoot diameter and root length of plants treated with 1200 μmol mol-1 CO2 were larger. Lignan compounds accumulated inside in vitro plants including phyllanthin, hypophyllanthin and niranthin (1.27, 0.51 and 2.01 mg g-1 dry weight, respectively) were all higher in high CO2 treatment comparing with those of low CO2 treatment (0.57, 0.45 and 1.05 mg g-1 dry weight, respectively) on day 45.