Agricultural Water Management 137 (2014) 59–67 Contents lists available at ScienceDirect Agricultural Water Management jou rn al hom ep age: www.elsevier.com/locate/agwat Tree water relations: Flow and fruit P.F. Measham a,∗ , S.J. Wilson a , A.J. Gracie a , S.A. Bound b a Tasmanian Institute of Agriculture, University of Tasmania, Hobart, TAS 7001, Australia b Tasmanian Institute of Agriculture, 13 St Johns Ave, New Town, TAS 7008, Australia a r t i c l e i n f o Article history: Received 23 June 2013 Accepted 7 February 2014 Available online 6 March 2014 Keywords: Sap flow Fruit growth rate Water potential Water movement a b s t r a c t 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 ( F ) was greater than leaf water potential ( L ) 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. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Perennial tree fruit horticulture is a high risk and high input production system in which water management, usually as irri- gation, is a critical component. Many studies relate water use to yield or productivity (Kang et al., 2003, 2002; Livellara et al., 2011; Acevedo-Opazo et al., 2010) and some to fruit size (Boland et al., 2000; Morandi et al., 2007). Tree water use has been extensively studied in a number of fruit crops; apple (O’Connell and Goodwin, 2007), pear (Kang et al., 2002), peach (Cohen et al., 2001), kiwifruit (Morandi et al., 2010), grape (Acevedo-Opazo et al., 2010), apricot (Ruiz-Sanchez et al., 2007) and cherry (Li et al., 2010; Oyarzún et al., 2008). Water supply is essential for normal fruit growth (Gibert et al., 2005) and water deficits can reduce fruit quality (Green et al., 1997). It is widely accepted that tension caused by potential gradients between the soil, through the plant, and to the ambient aerial envi- ronment is the major driving force for water movement through plants (Zimmerman et al., 2002; Tyree et al., 2003). This soil plant atmosphere continuum (SPAC) has been widely studied. For fruit production, research has focussed on improved scheduling and ∗ Corresponding author. Tel.: +61 3 62261870. E-mail address: Penelope.Measham@utas.edu.au (P.F. Measham). water use through understanding whole tree evapotranspiration (Liu et al., 2012; Livellara et al., 2011; Li et al., 2010) given the increasing need to manage water resources (Rijsberman, 2006; Intrigliolo and Castel, 2010; Collins et al., 2010). In spite of these and earlier studies, the detail of water pathways and potential gradients remains poorly understood in bearing fruit trees. Diurnal patterns of water potential recorded in fruits, including peach (McFayden et al., 1996), apricot (Alarcon et al., 2003) and grape (Greenspan et al., 1994), have been shown to affect diurnal changes in volume and diameter of growing fruit with shrinkage during daylight hours followed by expansion at night. Severe damage (cracking) occurred in bell pepper fruits that had experienced high diurnal amplitudes of expansion and shrinkage (Yao et al., 2000). It has been suggested that cherry trees do not have a signif- icant water storage capacity (Oyarzún et al., 2008) and studies on other species have shown that phloem-supplied water flow to fruit may supplement reduced xylem flow under high evaporative demand (Choat et al., 2009; Lang, 1990). Thus, water flow to the fruit may be influenced by multiple factors such as changing diur- nal water potentials between the fruit and the leaf (Morandi et al., 2007), changing diurnal light intensity (Yamasaki, 2003) and by source–sink interactions (Zhang et al., 2006). In order to maintain fruit integrity, firmness and size, diurnal patterns of fruit influx and/or efflux should be considered in orchard practices, such as irrigation, and warrant investigation. http://dx.doi.org/10.1016/j.agwat.2014.02.005 0378-3774/© 2014 Elsevier B.V. All rights reserved.