Phloem girdling
We compared the growth rate of fruit with intact xylem and phloem to that of fruit with only intact xylem to determine the relative importance of xylem and phloem water delivery for fruit expansion during water stress. Phloem tissue was selectively killed by heat girdling the pedicel, according to Guichard, Gary, Leonardi, and Bertin (2005) and Van De Wal, Windt, Leroux, and Steppe (2017). In brief, a length of insulated nichrome wire (length, 0.5 m; diameter, 0.25 mm) was coiled around the pedicel between the peduncle joint and the abscission zone, covering half of the total 8mm length and an electrical current was applied via a transformer to raise the temperature to 75oC for 1 min. Temperature was measured using a thermocouple in contact with the plant tissue under the heating coil (Van De Wal et al., 2017). Measurements were performed on three plants, using paired fruit supported by the same peduncle, with one fruit per pair heat girdled and the other maintained as an ungirdled control. Following girdling images were captured to monitor the projected area of both fruits as the plant dried. Plants were kept under laboratory light conditions with additional white light LED illumination, and water potential was recorded using an ICT psychrometer. Tomato fruit undergo a phase of cell division for 1-2 weeks post fertilisation, and then a period of cell expansion (2~6 weeks), driven by the filling of cells with osmolytes and water (Bertin, 2003; Gillaspy, Ben-David, & Gruissem, 1993; L. Ho, Sjut, & Hoad, 1982; Renaudin, Deluche, Cheniclet, Chevalier, & Frangne, 2017; Shameer et al., 2020), so larger fruits (2+cm diameter) were selected here to ensure fruit filling was responsible for growth rather than cell division.