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- Author or Editor: C. M. Sean Carrington x
Activity of ß-galactosidase II (EC 3.2.1.23), which can hydrolyze ß-galactan from tomato cell walls, increased markedly during ripening of `Roma' and `Rutgers' tomatoes (Lycopersicon esculentum Mill.). Activity of two other ß-galactosidase isozymes, incapable of galactan hydrolysis, was present in green fruit and remained unchanged throughout ripening. ß-Galactosidase II activity was not detectable in green fruit of either cultivar, appearing first at the breaker stage of `Roma' fruit and not until the pink stage of `Rutgers' fruit. Consistent with this, galactose loss from Na2CO3-soluble pectin (NSP) was detectable at an earlier stage in `Roma' vs. `Rutgers' fruit. A greater decline in NSP galactose was evident in `Roma' fruit compared to `Rutgers' fruit, in keeping with the higher levels and longer period of ß-galactosidase II expression in the former. Significant galactose loss from trans -1,2-diaminocyclohexane-N,N,N',N' -tetraacetic acid-soluble pectin, in contrast, was not seen until the last stage of ripening. These results indicate that the long-reported, net galactosyl loss from the cell walls of ripening tomatoes correlates with ß-galactosidase II activity. Nonetheless, the observation that softening commenced before ß-galactosidase II activity or galactose loss was detectable suggests some other basis for the earliest stages of ripening-related fruit softening in tomato.
Growth and development were characterised in two compound tropical fruit, soursop, Annona muricata L., and breadfruit, Artocarpus altilis (Park.) Fosb. The growth curves of both fruit were typically sigmoidal as determined by length, diameter, fresh weight and dry weight measurements. Soursop showed biphasic development with the flower/fruit remaining in an apparent resting state for some 12 weeks post anthesis before entering the second or true phase of growth leading to maturity. For both fruit, size increase extended over a 3 month period. Maturity indices were derived for each fruit and simple post harvest changes in texture, respiration and ethylene evolution investigated. storing either fruit under refrigeration down to 14°C significantly extended storage life though at temperatures below this chilling injury was evident.