ISHS Acta Horticulturae 138: Postharvest Physiology and Storage, XXI IHC
UTILIZATION OF ISOLATED APPLE FRUIT CUTICLES TO STUDY THE BEHAVIOUR OF CALCIUM SUPPLIED DIRECTLY TO THE FRUIT |
| Author: | A. Chamel |
| Abstract:
The possibilities of retention of exogenous calcium at cuticular level were determined in vitro, using chemically isolated apple fruit cuticles (cultivar Golden Delicious). Cuticular discs were immersed for 24 hours, in 45 CaC12 (20 meq/1) then submitted to a series of washings with deionized water. Ca may easily be retained by the apple fruit cuticle; more than 80 % of this retention occurred within the first five minutes of immersion. It was possible to distinguish a sorbed fraction lost during the washing with deionized water, and an exchangeable fraction which could easily be determined due to the high selectivity of cuticular constituents for Ca. The cuticular retention increased with the concentration, but it rapidly approached the saturation limit from 1 meqCa/1, the global effect was limited to a ratio equal to 2.2 between the values corresponding to the two extreme concentrations (0.1 and 1000 meqCa/1). It increased greatly with buffers whose pH varied from 3 to 8, 38.6 to 154.2 ueqCag-1 for the exchangeable fraction. It was greater with dewaxed cuticles but only on the dry weight basis. Great variations between cultivars appeared; the retention decreased in the following order : Golden Delicious > Melrose > Reine des Reinettes >Akane or Prima. These results might partly explained the important superficial localization of calcium observed when it is supplied directly to the entire fruit. | |
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