Estudo do metabolismo fotoquímico nas folhas e perfil da atividade da celulase e b-galactosidase nos frutos de Carica papaya L., cultivares Golden e Gran Golden
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2006-02-08
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Gallon, Camilla Zanotti
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Universidade Federal do Espírito Santo
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This study focused the photochemical metabolism of leaves and the pattern of activity of the cellulase and ß-galactosidase enzymes in the Carica papaya L. fruit, Golden and Gran Golden cultivars. The content of chlorophyll was taken with a portable chlorophyll measuring device (SPAD 502) and the kinetics of the emission of fluorescence from chlorophyll awith a portable fluorometer, Handy PEA (Hansatech Instruments Ltd., King’s Lynn, Norfolk, UK). The leaves, after previously going through a thirty minute adjustment to the dark, underwent a flow of photons at 680 µmol m-2 s-1. The amount of rain and the temperature of the area cultivated were taken into account when analyzing the data. The polyphasic curve of the fluorescence of chlorophylla for both cultivars of papaya during the time frame of the study demonstrates that there was not a significant difference among phases O, J, I and P. Differences in the parameters of the energy flow by cross-section of the photosystem II were observed. The Golden cultivar showed a higher rate of absorption of excited energy (ABS/CS), capture of excited energy (TRo/CS) and transport of that energy (ETo/CS). These results suggest that the Golden cultivar showed more efficiency than the Gran Golden cultivar when utilizing luminous energy in the period with the highest level of precipitation. However, Golden cultivar also showed a higher rate of dissipation of energy (DIo/CS) reflected in an increase of initial fluorescence (Fo), considered an indication of stress in plants, and the lessening of the quantum efficiency of the photosystem II. The Gran Golden cultivar showed an increase in the capture of energy by cross-section (TRo/CS) and the transport of that energy (ETo/CS). This increase may have contributed to this cultivar presenting greater quantum efficiency of the photosystem II in the period of lowest precipitation levels. The analysis of the cultivated fruit was conducted in the Laboratory of Protein Chemistry of the Federal University of Espirito Santo (in the XIIPortuguese acronym, UFES). The action of the enzymes cellulase and ß-galactosidase during ripening was observed in the 8 days following harvest and analysis of pulp firmness and loss of water were also conducted. The percentage of water lost in the fruit was calculated according to the loss of fresh mass and the percentage of the loss of firmness was obtained with the aid of a penetrometer. The activities of the enzymes cellulase and ß-galactosidase were previously standardized for the papaya tree and then measured for the obtainment of the relation with the loss of water and the changes in the firmness of the pulp. The results showed that the greatest loss in firmness in the fruit of the Golden and Gran Golden cultivars occurred between the 3rd and the 4th days after the harvest and that the fruit of the Gran Golden cultivar lose pulp firmness faster than those of the Golden cultivar. These results confirm a visual observation reported by papaya growers, and that is that the fruit of the Gran Golden cultivar have a shorter post harvest period. Observation showed that cellulase activity was greatest on the 5th day after harvest in the fruit of the Gran Golden cultivar and on the 6th day after harvest in the fruit of the Golden cultivar. The activity of ß-galactosidase increased in both cultivars until the 5th day after harvest, but in the Gran Golden cultivar the activity of this enzyme was higher in the post harvest period. These results illustrate the role these enzymes play in the decrease of firmness, evidencing the need for further study of the factors that interfere in the activation of these enzymes in order to allow the understanding of the physiology of the papaya
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GALON, Camilla Zanotti. Estudo do metabolismo fotoquímico nas folhas e perfil da atividade da celulase e b-galactosidase nos frutos de Carica papaya L., cultivares Golden e Gran Golden. 2006. 102 f. Dissertação (Mestrado em Biologia Vegetal) - Universidade Federal do Espírito Santo, Centro de Ciências Humanas e Naturais, Vitória, 2006.