Vol. 70 No: 4

Title:
Cell Wall Hydrolytic Enzyme Activity During Development of Nonclimacteric Sweet Cherry (Prunus Avium L.) Fruit

Authors:
P.K. ANDREWS and SHULIN LI

pp: 561-568

Abstract:
The cell wall hydrolytic enzyme activities of polygalacturonase (PG, EC 3.2.1.15), pectinmethylesterase (PME, EC 3.1.1.11) and carboxymethylcellulase (C_x-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 C_x-cellulase activities. Two in situ applications of 20 mg l^-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.

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