Ripening characteristics of a tomato mutant, dark green
1989
Tong, C.B.S. | Gross, K.C.
Respiration, ethylene production, firmness, polygalacturonase activity, cell wall composition, and soluble uronide content were measured during ripening of two tomato (Lycopersicon esculentum Mill.) genotypes, 'Manapal' and dark green (dg). Respiration rates and cell wall uronide contents of the two genotypes were similar. Climacteric ethylene production rates of dg fruit were about half that of 'Manapal' fruit. Firmness and polygalacturonase activity of dg tomateos were similar to that of 'Manapal' fruit until 55 days postpollination, when dg fruit were twice as firm as 'Manapal' fruit and exhibited greater polygalacturonase activity. Soluble uronide content did not differ between the two genotypes, except at 50 days postpollination, when that of dg fruit was 60% that of 'Manapal' fruit. Cell wall uronide content of dg fruit was 1.5 times greater than 'Manapal' fruit at 55 days postpollination. Although dg fruit contained larger, absolute amounts of cell wall noncellulosic neutral sugars than 'Manapal' fruit, net changes in sugar composition were similar throughout ripening. Also, ratios of cell wall arabinosyl or galactosyl residues to cell wall galacturonic acid were similar in both genotypes. These data suggest that firmness differences between dg and 'Manapal' fruit are not due to differing activities of polygalacturonase or changes in cell wall composition during ripening, but to other factors that may affect solubilization of cell wall uronides.
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