PLANT PHYSIOLOGY , Vol 106, Issue 1 165-171, Copyright © 1994 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Ripening of Nectarine Fruit (Changes in the Cell Wall, Vacuole, and Membranes Detected Using Electrical Impedance Measurements)
F. R. Harker and J. H. Maindonald
The Horticulture and Food Research Institute of New Zealand, Mt. Albert Research Centre, Private Bag 92 169, Auckland, New Zealand
Electrical impedance measurements were used to characterize changes in
intracellular and extracellular resistance as well as changes in the
condition of membranes during ripening of nectarines (Prunus persica [L.]
Batsch cv Fantasia). These measurements were related to changes in fruit
texture assessed by flesh firmness and apparent juice content. An
electrical model indicated that, during ripening (d 1-5) of freshly
harvested fruit, the resistance of the cell wall and vacuole declined by 60
and 26%, respectively, and the capacitance of the membranes decreased by
9%. Accurate modeling of the impedance data required an additional
resistance component. This resistance, which declined by 63% during
ripening, was thought to be associated with either the cytoplasmic or
membrane resistance. Changes in tissue resistance measured using low
frequencies of alternating current were closely related to flesh firmness.
After storage at 0[deg]C for 8 weeks, the nectarines developed a woolly
(dry) texture during ripening at 20[deg]C. The main difference between
these chilling-injured nectarines and fruit ripened immediately after
harvest was the resistance of the cell wall, which was higher in woolly
tissue (4435 [omega] after 5 d at 20[deg]C) than in nonwoolly tissue (2911
[omega] after 5 d at 20[deg]C). The results are discussed in relation to
physiological changes that occur during the ripening and development of
chilling injury in nectarine fruit.