Cell wall hydrolytic enzyme activity during development of nonclimacteric sweet cherry (Prunus aviumL.) fruit

SummarySummaryThe cell wall hydrolytic enzyme activities of polygalacturonase (PG, EC 3.2.1.15), pectinmethylesterase (PME, EC 3.1.1.11) and carboxymethylcellulase (Cx-cellulase, EC 3.2.1.4) were detected during development of nonclimacteric sweet cherry (Prunus avium L. 'Bing') fruit in 1992. Peak specific activity of all three hydrolytic enzymes occurred when fruit was red, 65 d after anthesis. Total protein content of fruit decreased from the earliest green coloured stage, 34 d after anthesis, until the later red-coloured stage, then increased to a maximum in mature, dark-red fruit, 74 d after anthesis. Thus, the highest enzyme activities on a tissue fresh weight basis occurred in dark-red fruit. Fruit firmness declined significantly after endocarp lignification ('pit hardening'), 45 d after anthesis, and, therefore, was inversely related with increases in PG, PME and Cx-cellulase activities. Two in situ applications of 20 mg 1−1 gibberellic acid (GA3) decreased the activities of PG and PME and increased fruit firmness relative to water-treated control fruit. Thus, these cell wall hydrolytic enzymes may affect fruit softening in non-climacteric sweet cherry fruit and GA3 may maintain fruit firmness by regulating their activities.