a1 Embrapa/Cenargen, CP 02372, 70849-970 Brasília, Brazil
a2 Universidade de Brasília, Departamento de Botânica, Brasília, Brazil
Introduction. Many shoots or bud-like structures are lost in the final stage of plant micropropagation because of being too short for handling. Yellow and red lights induce in vitro plant growth of some species, and blue light reduces it instead. Yellow cellophane film passes through from the yellow to red light spectrum but cuts off the blue one. Growth of banana in vitro shoots was thus compared with or without yellow-cellophane-film shading. Materials and methods. Field-grown banana normal and dwarf variant plants of Nanicão cv. (Musa sp., AAA group, Cavendish subgroup) derived from micropropagation were re-established in vitro. They were then transferred to MS medium without growth regulator in test tubes covered by yellow cellophane film under cool white fluorescent lamps at a light intensity of 46 μmol·m–2·s–1. Shoot growth was measured as height was evaluated after (20 and 30) days of culture. Results and discussion. The yellow-cellophane-film shading stimulated the growth of banana in vitro shoots. When cultured under the yellow-cellophane-film shading for 20 days, the normal true-to-type plants showed an increase of about 25% in shoot height compared with the plants cultured without cellophane film. Similar growth response was also observed on the in vitro shoots of the dwarf plants but the increment was only about 12%. This shading technique can aid shoot elongation and consequently reduction of plantlet loss at the final stage of plant micropropagation. The differing sensibility of the normal true-to-type plants and dwarf variants to the yellow-cellophane-film shading may be used for reduction of the dwarf variant population in banana micropropagation. Conclusion. Yellow-cellophane-film shading stimulates growth of banana in vitro shoots.
(Online publication June 1 2007)