Seasonal changes in fluorescence intensity of kiwifruit nuclei stained with propidium iodide and measured by flow cytometry

Abstract Nuclei were extracted from kiwifruit (Actinidia deliciosa) axillary buds and shoot apices at intervals during two growing seasons. Nuclei from fruit tissues were also examined. Extracted nuclei were stained with propidium iodide, which intercalates into double stranded nucleic acids, and the intensity of the staining reaction (fluorescence channel number) was measured by flow cytometry. Fluorescence intensity (mean channel number) of 2C nuclei varied during seasonal growth in both 1991 and 1992. In 1991, channel numbers of nuclei from shoot apices of pistillate and staminate vines were highest at the time of bud break and then declined. A similar change was observed in nuclei from pistillate shoots grown in a glasshouse. In 1992, however, nuclei extracted during bud break from axillary buds and shoot apices had low channel numbers. In this year, highest channel number values occurred during mid summer and the values for nuclei from fruit tissues were also high at this time. Lower channel number v...