Changes in stem diameter of blueberries from dormant period to bud opening

Shortening the dormant period of plants is an effective method for shortening the life cycle for year-round production. Measurement using strain-gauge-type displacement gauges can detect slight changes in stem diameter. It is known that changes in stem diameter occur with changes in water balance in plants. During the dormant period, changes in stem diameter due to changes in water content do not occur. The purpose of this study was to reveal the relationship between the phenological stages of a blueberry bush and changes in stem diameter. We investigated whether and how diameter changes occur in tree stems from winter to spring. Two potted blueberry bushes were cultivated in a thermostatic chamber. Blueberries were first cultivated at 5°C (low-temperature period) then cultivated at 20°C (bud-opening period). Strain-gauge-type displacement gauges were attached to the stems and output voltages were recorded into a data logger every minute. The number of opened buds and leaves were then counted. During the low-temperature period, no stem diameter fluctuations were measured, and during the bud-opening period, daily stem diameter shrinkage increased with the number of opened buds.