Growth of In vitro banana (Musa SPP.) shoots under photomixotrophic and photoautotrophic conditions

Summary In vitro banana (Musa spp.) shoots were cultured under photomixotrophic (30 gl⁻¹ sucrose and 0.2 h⁻¹ number of air exchanges of culture vessels) and photoautotrophic (0 gl⁻¹ sucrose and 3.9 h⁻¹ number of air exchanges) conditions for 28 d in 370 cm³ Magenta boxes (GA7-type) containing 70 ml of half-strength Murashige and Skoog (MS) medium with 22.2 μM N⁶-benzyladenine (BA). The effects of varying CO₂ concentration (475 or 1340 μmol mol⁻¹) and light intensity (photosynthetic photon flux (PPF) of 100 or 200 μmol m⁻² s⁻¹) were investigated. Fresh and dry weights of banana shoots grown photomixotrophically were significantly greater on day 28 than those grown photoautotrophically. Photoautorophic shoots had a larger number of unfolded leaves and greater leaf area than photomixotrophic plants by days 14 and 28, regardless of CO₂ concentration. The shoot fresh and dry weights on day 14 in photoautotrophic conditions were significantly greater at PPF of 200 μmol m⁻² s⁻¹ than at 100 μmol m⁻² s⁻¹. The increase in net photosynthetic rate of photoautotrophic banana shoots was significant compared with photomixotrophic shoots. The multiplication ratio of in vitro banana shoots grown photoautotrophically in a 28-d culture period was the greatest at 100 μmol m⁻² s⁻¹ PPF and 475 μmol mol⁻¹ CO₂.