USE OF POLARIZED FLUORESCENCE SPECTROSCOPY TO MEASURE FLUIDITY OF MITOCHONDRIAL MEMBRANES FROM COLD-TREATED TULIP BULBS

Cold treatment of tulip bulbs is common practice. For the production of good quality flowers a cooling period is necessary: for the cv. Apeldoorn a 12-week period at 5°C is optimal. The adaptation of the cell membranes to this cold treatment was studied with membrane preparations from isolated mitochondria. A rapid increase of the membrane fluidity was observed after transfer of the bulbs from 17 to 5°C, although clear phase transitions were not observed during measurement of the fluidity at temperatures between 4 and 30°C. When after cooling bulbs were transferred back to 17°C the membrane fluidity remained at the 5°C level for at least one week. The changes in membrane fluidity were not reflected in a changed fatty-acid composition of the mitochondrial membrane. Apparently, polarized-fluorescence spectroscopy is a rapid method to detect overall changes in membrane fluidity. These changes in fluidity relate to the storage temperature but not to the length of this storage period.

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