Micropropagation of Theobroma cacao, a recalcitrant species, with high CO2
Cacao (Theobroma cacao) has long been considered a recalcitrant species in regard to micropropagation. Although axillary shoots from cotyledonary nodes will proliferate and grow in vitro provided either cotyledons or roots are attached, excised shoots fail to grow in spite of conventional medium and hormonal modifications. Charcoal supplemented medium and rapid medium change are only marginally effective in inducing shoot elongation. The recalcitrance of cacao appears to be due to the presence of gums which are produced from stem tissues in response to wounding. However, growth of axillary cotyledonary shoots as well as mature shoots was obtained under conditions of high CO2 (20.000 ppm) and high light (quantum flux of 200 ¿mol m exponent -2s exponent -1) with or without sugar. Under these conditions leaves develop and shoots elongate which can be subdivided and subcultured. Shoots root under these conditions in vitro. We hypothesize that growth of cacao shoots in response to high CO2 is due to translocation of metabolites from photosynthesizing leaves and stems.
| Main Authors: | , , , |
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| Format: | biblioteca |
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| Subjects: | THEOBROMA CACAO, MICROPROPAGACION, CULTIVO IN VITRO, CULTIVO DE TEJIDOS, MERISTEMAS APICALES, |
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| Summary: | Cacao (Theobroma cacao) has long been considered a recalcitrant species in regard to micropropagation. Although axillary shoots from cotyledonary nodes will proliferate and grow in vitro provided either cotyledons or roots are attached, excised shoots fail to grow in spite of conventional medium and hormonal modifications. Charcoal supplemented medium and rapid medium change are only marginally effective in inducing shoot elongation. The recalcitrance of cacao appears to be due to the presence of gums which are produced from stem tissues in response to wounding. However, growth of axillary cotyledonary shoots as well as mature shoots was obtained under conditions of high CO2 (20.000 ppm) and high light (quantum flux of 200 ¿mol m exponent -2s exponent -1) with or without sugar. Under these conditions leaves develop and shoots elongate which can be subdivided and subcultured. Shoots root under these conditions in vitro. We hypothesize that growth of cacao shoots in response to high CO2 is due to translocation of metabolites from photosynthesizing leaves and stems. |
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