(A) Effect of water stress (WS) on leaf transpiration rate (E) of M4 (open circles) and 101.14 (filled circles) grapevine rootstocks. Average ±SE values of E are expressed as a proportion of the control (i.e. E values of 2.7±0.3 and 2.4±0.2 mmol H2O m–2 s–1 for M4 and 101.14 genotypes, respectively, at T0). Well-watered (WW) plants were maintained at 80% of soil field capacity. WS was induced by progressively reducing the soil water content down to 30% of field capacity. A field capacity of 30% by weight was obtained gravimetrically by the difference in weight between the wet and the dry soil. T1–T4 represent sampling times throughout the experimental period after control (T0). Significant differences amongst genotypes within a given time point are indicated as **(P< 0.01) and *(P<0.05) according to the Student’s t-test. (B) Leaf ABA content in 101.14 and M4 plants in both WW (empty bars) and WS conditions (solid bars). Measurements were carried out at T1, T2, and T4, corresponding to 2, 4, and 10 days after stress imposition (DASI), respectively. Letters indicate statistical differences in (two-tailed unpaired) Student’s t–test at P<0.01.
