TY - JOUR T1 - Gas Exchange and Water Relations in Field-Grown Sauvignon blanc Grapevines JF - American Journal of Enology and Viticulture JO - Am J Enol Vitic. SP - 423 LP - 428 DO - 10.5344/ajev.1994.45.4.423 VL - 45 IS - 4 AU - A. Naor AU - B. Bravdo AU - J. Gelobter Y1 - 1994/01/01 UR - http://www.ajevonline.org/content/45/4/423.abstract N2 - Two post-veraison irrigation levels, 1.0 and 3.5 mm/day [low (L) and control (C) treatments, respectively] were applied in an eight-year-old Sauvignon blanc vineyard. Simultaneous measurements of gas exchange parameters and leaf water potential (LWP) were made on the same leaves four weeks after veraison. Midday LWP at veraison was -1.2 MPa. A significant difference between treatments developed from veraison to mid-August. Midday LWPs in mid-August were -2 MPa and -1.4 MPa for the L and the C treatments, respectively. Photosynthesis rate (A) was found to decline with LWP with no differences between treatments. The similar ratio of stomatal conductance (gs) to A in both treatments suggests that water stress did not affect the photosynthetic apparatus. However a temporary decrease in non-stomatal conductance was detected below LWPs of -1.5 MPa. Similar gs-LWP relationships in both treatments indicates that osmotic adjustment was not responsible for the differences measured between the two irrigation treatments. A direct effect of vapor pressure gradient on gs was indicated. ER -