The effect of Ca++ on various parameters of apple fruit senescence was investigated. Distinct and specific changes in polypeptide and phosphoprotein patterns were observed in Ca++ treated as compared to control fruits. A 70 kDa salt-extracted polypeptide became apparent in control fruits after 8 months of cold storage which was not apparent in Ca++-treated fruits until 12 months. The soluble protein profile of Ca++-treated fruits showed an accumulation of a 30 kDa polypeptide while the control fruits accumulated a 60 kDa polypeptide. Autoradiographs of phosphorylated polypeptides revealed a 60 kDa membrane polypeptide becoming phosphorylated in the Ca++-treated and not in the control fruit protein fractions. Transmission electron micrographs of the cell showed Ca++ to be effective in maintaining the cell wall structure, particularly the middle lamella. Furthermore, increase in fruit Ca++ reduced CO2 and C2H2 evolution and altered chlorophyll content, ascorbic acid level and hydraulic permeability.
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Glenn et al. (1988) studied this question.