Effect of sucrose on the photosynthetic capacity of coconut vitroplants
1998
Santamaria, J.M. | Fuentes, G. | Quiroz, A. | Talavera, C. | Espadas, F. | Nato, Aimé | Rival, Alain | Oropeza, Carlos
Safe germoplasm exchange systems and mass-production protocols are becoming increasingly important in breeding programs of coconut palms particularly due to a lethal disease called lethal yellowing. Coconut plants cultured #in vitro# often show low survival and poor performance when transferred to the field. Many factors can be responsible for this poor performance of vitroplants in the field. Added sugars, however, can potentially be a factor involved as they might be detrimental to the development of autotrophy in vitroplants. In the present work, experiments were performed to evaluate the effect of 3 different sucrose concentrations (0,22.5 and 45 g/l) in the medium, on the photosynthetic capacity of coconut vitroplants derived from the culture #in vitro# of zygotic embryos. Our results showed that the reduction in sucrose, resulted in decreased chloroplast numbers and chlorophyll content. On the other hand, the reduction of sucrose from 45 to 0 g/l resulted in increased photosynthetic rates and RubisCO activity while in a decreased PEPc activity. The resulting lower PEPC/RubisCO ratio suggests that the reduction of sucrose from the medium resulted in coconut vitroplants with higher levels of autotrophy. It might be suggested that while sucrose in early stages of embryo cultures might favor chloroplast development and chlorophyll contents, the continuous growth under sucrose-rich medium will decrease RubisCO activities while favoring PEPc activities slowering the development of autotrophy of vitroplants that might result in poor performance when transferred to the field. (Résumé d'auteur)
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