Tree water relations: Flow and fruit

• Provides evidence of diurnal and weekly growth rates in sweet cherry.
• Highlights variable diurnal flow rates for fruit.
• Investigates climatic drivers for flow to or from fruit.
• Exposes the need to include fruit in decisions regarding irrigation.

This study explores vascular influx of water in sweet cherry (Prunus avium L.) fruit because water is a key component of fruit quality and has been implicated in cherry fruit cracking. Flow to fruit is influenced by changing water potential of the fruit, and of potential gradients between the fruit and the spur. Water potential was influenced by vapour pressure deficit. In all seasons of this study, the most negative fruit water potential occurred in mid-afternoon when the magnitude of fruit water potential (ΨF) was greater than leaf water potential (ΨL) and analysis showed that there was a significant difference in this potential gradient between days with and without rainfall. Frequency analysis of days monitored over seasons further showed a significant association between the incidence of natural or simulated rainfall and the direction of sap flow to the fruit. This implies that manipulation of the driving forces within sweet cherry trees could be a viable management strategy for the prevention of cracking in cherry fruit. Furthermore, it suggests a role for orchard irrigation, in avoiding development of water potential gradients of fruit that favour rapid vascular influx of water following rainfall.