Developmental changes in carboxylase activities in in vitro cultured coconut zygotic embryos: comparison with corresponding activities in seedlings
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Date
1997
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Abstract
Phosphoenolpyruvate Carboxylase (PEPC; EC: 4.1.1.31) and Ribulose 1,5-bisphosphate Carboxylase / Oxygenase (RubisCO; EC: 4.1.1.39) enzyme specific activities were measured during the in vitro development of coconut (Cocos nucifera L.) zygotic mature embryos into plantlets and compared with those of palms produced by conventional seed germination. At the time of initiation of germination, high PEPC and low RubisCO activities were measured in both cultured and conventionally germinated embryos, thus indicating an anaplerotic CO2 fixation. During both in vitro and in planta development, RubisCO progressively took over and became the main route for inorganic carbon fixation. The in vitro-grown coconut plantlets showed a faster decrease in their PEPC:RubisCO ratio than the seedlings, suggesting that an earlier transition from a heterotrophic to an autotrophic mode of carbon fixation takes place in the in vitro-derived material. Just before acclimatization, the RubisCO activity in in vitro-derived plantlets (2.83 mol CO2h-1mg-1 TSP) was lower than that in seedlings (6.98 mol CO2h-1mg-1 TSP) of the same age. Nevertheless, after acclimatization, RubisCO activities were comparable in both in vitro and in planta germinated material
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Keywords
carbon metabolism, CO2 fixation, embryo culture, PEPC, photosynthesis, RubisCO
Citation
Plant Cell, Tissue and Organ Culture 49: 227–231, 1997.