Chilling temperature storage changes the inorganic phosphate pool distribution in cherimoya (Annona cherimola) fruit

Phophorous nuclear magnetic resonance (P-31-NMR) spectroscopy was used to s tudy the vacuolar and cytoplasmic pH and the inorganic phosphate (Pi) pool distribution in 'Fino de Jete' cherimoya (Annona cherimola Mill.) fruit sto red at a chilling temperature (6 degreesC), Fruit stored at the ripening te mperature (20 degreesC) for 3 days were used as a control. P-31-NMR results confirmed that 6 degreesC storage caused cytoplasmic acidosis (a decrease of 0.72 +/- 0.08 pH units) and a notable increase in the amount of Pi in th e cytoplasm, Spectra of perchloric acid extracts also revealed that storage at 6 degreesC was associated with an increase in the total amount of Pi an d phosphorylated metabolites, Moreover, perfusion experiments with a phosph ate medium confirmed the preferential accumulation of Pi in the cytoplasm i n chilled tissues. Specific activation of phosphoenolpyruvate carboxylase ( PEPC) (32.1 +/- 1.7 mu mol.min(-1).mg(-1)) was observed in those fruit, In chilled fruit the amount of ADP was held at steady-state levels and ATP lev els increased, contrary to observations for ripe fruit, where the pool of t otal nucleotides decreased beyond the point of NMR detection, Fruit stored at 6 degreesC exhibited a low respiration rate, but metabolism was not arre sted and an increase in total soluble solid contents was also observed.