Growth of in vitro banana (Musa spp.) shoots under photomixotrophic and photoautotrophic conditions

Abstract

In vitro banana (Musa spp.) shoots were cultured under photomixotrophic (30 g l21 sucrose and 0.2 h21 number of air exchanges of culture vessels) and photoautotrophic (0 g l21 sucrose and 3.9 h21 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 22.2mM N6 -benzyladenine (BA). The effects of varying CO2 concentration (475 or 1340 mmol mol21 ) and light intensity (photosynthetic photon flux (PPF) of 100 or 200mmol m22 s 21 ) were investigated. Fresh and dry weights of banana shoots grown photomixotrophically were significantly greater on day 28 than those grown photoautotrophically. Photoautotrophic 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 mmol m22 s 21 than at 100 mmol m22 s 21 . 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 100mmol m22 s 21 PPF and 475 mmol mol21 CO2