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Mechanism of Structural Freezing Injury in Citrus Fruit Segments

Ilan Shomer
Botanical Gazette
Vol. 147, No. 1 (Mar., 1986), pp. 55-64
Stable URL: http://www.jstor.org/stable/2474808
Page Count: 10
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Mechanism of Structural Freezing Injury in Citrus Fruit Segments
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Abstract

Peeled segments of grapefruit, Citrus paradisi Mcf. `Marsh seedless,' were sensitive to either macrostructural or ultrastructural freezing injury. Large crystals injured the ultrastructure of the juice sac tissue but preserved the integrity of the segment. In contrast, rapid cryogenic cooling prevented destruction of tissue, but the juice sac expanded, and the segments tended to fragment into separate juice sacs. Ice crystals split thick cell walls or were incorporated during their growth within protoplasmic structures and thin cell walls. After thawing, the destroyed protoplasmic matrix concentrated adjacent to the undamaged thick wall or were seen as dispersed fragments beside the thin ground walls. Protoplasmic membranes were completely destroyed, and organelles with various degrees of damage were identifiable after rapid cryogenic cooling and thawing. Tissue structures were not injured by rapid cryogenic cooling alone, and each type of membrane, organelle, oil droplet, and wall was characterized by typical surface topography.

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