Diurnal root growth dynamics in mature grapevines

Six-year-old 'Shiraz' vines were grown under field-like conditions in 780-L soil filled plastic bins. One year after transplanting, root growth was monitored non-destructively using minirhizotron tubes. Images of the roots were collected at sunrise, midday, sunset and midnight over six consecutive days during flowering. It was found that the vines displayed a diurnal dynamic in root growth with a maximum in the afternoon and evening, and a minimum in the morning. While it was not possible to separate the effects of time of day and soil temperature a positive relationship between soil temperature and root elongation was observed. The diurnal dynamics of root growth was consistent with earlier observations in young potted vines and is the first indication that mature vines also exhibit a pronounced diurnal dynamic of fine root growth. The possible influence of carbon supply and the role of the circadian clock in these diurnal growth dynamics are discussed.