THE EFFECT OF CALCIUM AND ZINC SPRAYS ON THE TEXTURE OF "COX¿S ORANGE PIPPIN" APPLES IN CONTROLLED ATMOSPHERE STORAGE

D.S. Johnson, C.J. Dover
In 1996 and 1998 sprays containing 1 ml L-1 of ‘Zintrac’ (70% w/v Zn) or 10 ml L-1 of ‘Stopit’ (16% w/v Ca) were applied at 500 L ha-1 to apple tree of cv Cox Orange Pippin trees during the cell division or cell expansion phase of fruit development. In 1996, early and late Zn sprays increased Zn concentration in the cortical tissue by 61 and 50 µg 100 g-1 fresh weight respectively. Late Ca sprays increased tissue Ca by 0.75 mg 100 g-1 fresh weight but early Ca sprays had no affect on tissue Ca. Early sprays of Zn and Ca had beneficial effects on the firmness (penetrometer) and mechanical properties of apple tissue at harvest that included a higher stiffness and work of fracture. There was less effect of spray treatments on mechanical properties of tissue from fruit stored in controlled atmosphere (CA) conditions (1.2 kPa O2, <1kPa CO2 at 3.5 °C) for 7 months. However, after a further 7 days at 20 °C firmness was higher in fruit sprayed early with Zn and Ca. Early sprays of Zn and Ca reduced fruit yield at harvest and increased cell wall content of the tissue. Effects of spray treatments on tissue mechanical properties were attributable to crop reduction and this was confirmed where firmness data was analysed using yield as a covariate. In 1998 early sprays of ‘Zintrac’ or ‘Stopit’ again increased the firmness of fruit at harvest and also in fruit stored in CA for 4 or 6 months. There were consistent improvements in tissue mechanical properties of stored apples as a result of early sprays. Early Zn application increased tissue Zn by 16 µg 100 g-1 fresh weight and, as in 1996, reduced fruit numbers and yield and increased total and alcohol insoluble dry matter. However, contrary to previous results, there was no significant yield reduction from early Ca sprays. Although improvements in firmness appeared to be related directly to supplementing Ca nutrition early in fruit development, there was no increase in tissue Ca at harvest. Electron energy loss spectroscopy (EELS) of cell walls also confirmed no changes in the Ca concentration of the middle lamella region or in the primary cell wall due to early Ca application although early Zn sprays appeared to increase Ca in these domains. Zn was not detected in any domain of the cell walls analysed using EELS. Late Ca application had no positive effect on tissue texture despite increasing tissue Ca from 2.9 to 3.8 mg 100 g-1 fresh weight.
Johnson, D.S. and Dover, C.J. (2002). THE EFFECT OF CALCIUM AND ZINC SPRAYS ON THE TEXTURE OF "COX¿S ORANGE PIPPIN" APPLES IN CONTROLLED ATMOSPHERE STORAGE. Acta Hortic. 594, 427-433
DOI: 10.17660/ActaHortic.2002.594.55
https://doi.org/10.17660/ActaHortic.2002.594.55
Malus domestica, Zn, Ca, sprays, mechanical properties, storage
English

Acta Horticulturae