PT - JOURNAL ARTICLE AU - C. Ginestar AU - J. Eastham AU - S. Gray AU - P. Iland TI - Use of Sap-Flow Sensors to Schedule Vineyard Irrigation. II. Effects of Post-Veraison Water Deficits on Composition of Shiraz Grapes AID - 10.5344/ajev.1998.49.4.421 DP - 1998 Jan 01 TA - American Journal of Enology and Viticulture PG - 421--428 VI - 49 IP - 4 4099 - http://www.ajevonline.org/content/49/4/421.short 4100 - http://www.ajevonline.org/content/49/4/421.full SO - Am J Enol Vitic.1998 Jan 01; 49 AB - Transpiration rates of Shiraz vines grown on a two wire vertical trellis were measured using sap-fow sensors and used as a basis for applying different levels of post-véraison irrigation. The effect of this differential irrigation on plant water status and grape composition were investigated with responses of vines on the upper and lower wires of the trellis studied separately. The concentration of juice total soluble solids and pH was unaffected by irrigation treatment but the concentration of berry anthocyanins and phenolics, expressed as mg/g berry mass and absorbance units/g berry mass respectively, decreased with increase in water application, mainly due to an increase in berry weight. Predawn leaf water potential was measured from veraison to harvest and the water stress integral (Sψ) was calculated as an indication of the intensity and duration of water stress in the three irrigation treatments. Sψ was found to be closely correlated with post-veraison water use and with grape composition.