Research ArticlePLANT SCIENCES

Drought will not leave your glass empty: Low risk of hydraulic failure revealed by long-term drought observations in world’s top wine regions

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Science Advances  31 Jan 2018:
Vol. 4, no. 1, eaao6969
DOI: 10.1126/sciadv.aao6969
  • Fig. 1 Ψmdl depending on Ψpd in different V. vinifera varieties.

    Syrah (A) and Grenache (B) were measured in the field [domain “Pech Rouge” (PR); dark colors] and during a drydown experiment in greenhouse (GH; light colors). The slope σ of the linear regressions was not statistically different across varieties in the field (P = 0.074) nor in the greenhouse (P = 0.225). Top left insets represent the slope σx (sensitivity to declining water availability) depending on the range of Ψpd (from 0 to x; x representing the lower limit of the range of Ψpd) combining field and greenhouse data. Bottom right insets represent the correlation between Ψpd and minimum Ψmdl (that is, average value of three lowest Ψmdl per 0.1-MPa wide class of Ψpd) combining field and greenhouse data. This linear regression is used to define the lower range of the hydroscape (colored by a blue-to-red gradient representing increasing water stress on the main figure).

  • Fig. 2 Response of stomatal conductance depending on decreasing Ψ in different V. vinifera varieties.

    (A) Midmorning (9:00 a.m. to 12:00 p.m.) stomatal conductance measured on individual leaves (gs), depending on Ψmdl in four grapevine varieties [V. vinifera cv. Grenache (n = 58; blue), V. vinifera cv. Syrah (n = 61; red), 110 Richter (n = 48; green), and V. riparia (n = 51; pink)] during a drydown experiment in greenhouse. (B) Midmorning (9:00 a.m. to 12:00 p.m.) stomatal conductance calculated at the whole-plant scale (Gs; obtained from 150 individuals over 2 months) depending on Ψleaf. Symbol and bars represent the mean and SEs of 0.1-MPa classes. Lines represent the best fit using sigmoid functions for each variety. (C) Sensitivity to vapor pressure deficit [that is, dGs/Ln(D)] depending on Gsref in four grapevine varieties (V. vinifera cv. Grenache and Syrah, 110 Richter, and V. riparia), along a water deficit gradient [Ψmdl, from −0.8 (blue) to −2.3 MPa (red)]. Gsref and sensitivity were calculated as the intercept and slope of the logarithmic correlation between Gs and D (as presented in fig. S3) from a sliding frame of 500 consecutive values sorted by increasing drought stress. The line (slope = 0.6) represents the theoretical slope between stomatal conductance at D = 1 kPa and stomatal sensitivity to D, which is consistent with the role of stomata in regulating minimum Ψleaf in isohydric species according to the hydraulic limitation theory (29). The inset represents the estimates (±SE) of Gsref and sensitivity at four different level of drought stress: well hydrated (>−0.5 MPa) in blue, mild stress (−0.5; −1.0 MPa) in green, moderate stress (−1.0; −1.5 MPa) in yellow, and severe stress (<−1.5 MPa) in red in four different varieties of grapevine. Syr, Syrah; Gre, Grenache; 110R, 110 Richter.

  • Fig. 3 Hydraulic vulnerability to drought of different grapevine varieties, seasons, and techniques.

    (A to C) Percent stem loss of hydraulic conductivity depending on applied pressure (A and B) or minimum Ψstem experienced by the plant (C). Vulnerability curves were obtained either during the growing season [n = 6 to 8; July (A)] or after growth cessation [n = 6 to 8; September (B)], using a dedicated 1-m-diameter Cavitron device. FC, flow centrifuge. Loss of hydraulic conductivity was also measured using the bench dehydration (BD) technique combined with the gravimetric method after relaxation of the tension in the xylem sap [n = 15 to 20 (C)]. Lines and colored areas represent modeled vulnerability curves and the confidence interval at 95% for each model.

  • Fig. 4 Leaf mortality (percent of whole leaves per plant) and recovery time (that is, inverse of the time to recover half of control gs) versus minimum Ψpd experienced by different grapevine varieties.

    The intersection between linear regression and x axis gives the minimum Ψrecov for each variety. Lines and colored areas represent modeled leaf mortality curves and the confidence interval at 95% level for each model (n = 21 to 24). The inset represents the recovery time measured via Gs (that is, whole-plant stomatal conductance).

  • Fig. 5 Physiological thresholds for drought-induced mortality in stems and leaves versus long-term drought survey in Napa Valley and Saint-Emilion.

    (A) The upper panel depicts stomatal conductance (gs; green), leaf mortality (brown), and stem loss of hydraulic conductivity (red) depending on organ Ψ. The three curves describe an average V. vinifera variety because no significant differences were observed across varieties in the responses of these physiological parameters to Ψ during the greenhouse experiment [namely, Ψ inducing 50% reduction in stomatal conductance (dotted line), leaf vitality (short-dashed line), and stem hydraulic conductivity (long-dashed line)]. The lower panel shows the standardized hydroscape for V. vinifera (see Fig.1; colored by a blue-to-red gradient representing increasing water stress), and the box plots depict the distribution of Ψstem in September observed during a decade in two regions of grapevine production (Saint-Emilion and Napa Valley). PLC, percentage loss of conductance. (B and C) The observed range of stem xylem pressure (that is, limited by the average of the three minimum Ψstem observed under field conditions) in Saint-Emilion (B; over the 2003–2016 period in Cabernet Franc and Merlot) and in Napa Valley (C; over the 2010–2016 period in Cabernet Sauvignon, Cabernet Franc, Syrah, and Merlot) per month. In parallel, the dynamic patterns of Ψ12 (green squares; mean ± SE) and Ψ50 (blue circles; mean ± SE) along the growing season, based on results obtained using HRCT in May (18) and Cavi-1000 (July, September, and October on different Vitis varieties—V. vinifera cv. Cabernet Sauvignon, Grenache, Merlot, Regent, and Syrah).

  • Fig. 6 Distribution of Ψpd (blue) and Ψmds (red) water potential observed during June and July in Napa Valley in V. vinifera cv. Syrah.

    The insets represent transverse HRCT images of intact plants from the same variety at Ψ under this normal operating range: from predawn (Ψpd = −0.15 MPa) to midday (Ψmds = −1.3 MPa). Theoretical loss of hydraulic conductivity for each image is calculated from functional (gray) and air-filled (black) xylem vessels and indicated as PLC (%). White bars, 1 mm.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/1/eaao6969/DC1

    fig. S1. Ψmdl depending on Ψpd in different V. vinifera varieties and under environmental conditions.

    fig. S2. Correlations between Ψpd and minimum Ψleafmin; that is, average value of three lowest Ψmdl per 0.1 MPa wide class of Ψpd) in different V. vinifera varieties (Grenache and Syrah) and under environmental conditions (field and greenhouse).

    fig. S3. Midmorning stomatal conductance measured on individual leaves, depending on predawn leaf water potential Ψpdl in four grapevine varieties (V. vinifera cv. Grenache, blue; V. vinifera cv. Syrah, red; 110 Richter, green; V. riparia, pink) during a drydown experiment in greenhouse.

    fig. S4. Whole-plant stomatal conductance under saturating light, depending on vapor pressure deficit, in four grapevine varieties.

    fig. S5. Percent stem loss of hydraulic conductivity depending on applied pressure in V. vinifera cv. Syrah and Grenache grafted on different rootstocks (V. riparia, SO4, and 110 Richter) after growth cessation (September), using a dedicated 1-m-diameter Cavitron device (Cavi-1000).

    fig. S6. Whole-plant stomatal conductance Gs depending on leaf-scale stomatal conductance gs, measured at the same moment (±1 hour).

    fig. S7. Ψpd depending on RWC in four grapevine varieties (V. vinifera cv. Grenache and Syrah, 110 Richter, and V. riparia) during a drydown experiment in a greenhouse.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Ψmdl depending on Ψpd in different V. vinifera varieties and under environmental conditions.
    • fig. S2. Correlations between Ψpd and minimum Ψleafmin; that is, average value of three lowest Ψmdl per 0.1 MPa wide class of Ψpd) in different V. vinifera varieties (Grenache and Syrah) and under environmental conditions (field and greenhouse).
    • fig. S3. Midmorning stomatal conductance measured on individual leaves, depending on predawn leaf water potential Ψpdl in four grapevine varieties (V. vinifera cv.Grenache, blue; V. vinifera cv. Syrah, red; 110 Richter, green; V. riparia, pink) during a drydown experiment in greenhouse.
    • fig. S4. Whole-plant stomatal conductance under saturating light, depending on vapor pressure deficit, in four grapevine varieties.
    • fig. S5. Percent stem loss of hydraulic conductivity depending on applied pressure in V. vinifera cv. Syrah and Grenache grafted on different rootstocks (V. riparia, SO4, and 110 Richter) after growth cessation (September), using a dedicated 1-m-diameter Cavitron device (Cavi-1000).
    • fig. S6. Whole-plant stomatal conductance Gs depending on leaf-scale stomatal conductance gs, measured at the same moment (±1 hour).
    • fig. S7. Ψpd depending on RWC in four grapevine varieties (V. vinifera cv. Grenache and Syrah, 110 Richter, and V. riparia) during a drydown experiment in a greenhouse.

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