Physiological Thresholds for Efficient Regulated Deficit-Irrigation Management in Winegrapes Grown under Semiarid Conditions

Pascual Romero; Jose Ignacio Fernández-Fernández; Adrián Martinez-Cutillas

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Figure 1
Relationship between midday stem water potential (Ψ_s) and (A) whole plant hydraulic conductance (K_plant) during pre- and postveraison (K_plant = 0.88 + 0.55 Ψ_s) and (B) root to stem hydraulic conductance (K_root-stem) (K_root-stem = 0.23 + 0.14 Ψ_s) in 2006.
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Figure 2
Seasonal patterns during 2006 and 2007 of (A, B) midday stem water potential (Ψ_s) and leaf relative water content (RWC); (C, D) leaf photosynthesis rate (A); (E, F) stomatal conductance to water vapor (g_s); and (G, H) transpiration rate (E). Vertical bars indicate the standard error of the mean. Each point is the average of eight measurements for Ψ_s and RWC and 12 measurements for gas exchange parameters.
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Figure 3
(A) Stomatal conductance (g_s) and intrinsic water use efficiency (A/g_s) measured midmorning (9:00–10:30): A/g_s = 74.3 + 277.9g_s − 1327.7g_s². (B, inset) g_s and A/g_s measured midday (12:30–14:00) during postveraison (most water-stressed period): A/g_s = 102.9e^{(−0.5ln(gs/0.0634)/1.1535)2}. (C) Midday stem water potential (Ψ_s) and midmorning A/g_s: −122.3 − 308.6 Ψ_s − 111.3 . (D) g_s and instantaneous water use efficiency (A/E) measured midmorning: A/E = 2.6 + 19.2g_s − 66.9g_s². (E) Midday Ψ_s and A/E measured midmorning: A/E = −0.79 − 7.5 Ψ_s − 2.96 . (F) Relationship between midday Ψ_s and midmorning g_s (g_s = 0.43 + 0.22 Ψ_s) and (G) midmorning leaf photosynthesis rate (A) during postveraison period (A = 16.3/1 + e^{(−(Ψs − (−1.5))/0.25)}). Horizontal and vertical dashed lines indicate different threshold values. Maximum values ranges of different indicators were calculated using the equations. Measurements were taken pre- and postveraison, June–Sept 2007.
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Figure 4
Relationship between photosynthesis (A) and stomatal conductance (g_s) (linear, A = 4.23 + 48.5^gs, r = 0.94, p < 0.001; exponential, A = 19.4(1 − e^(−6.29gs)), r = 0.95, p < 0.001). Each value is the mean per plot calculated before and after veraison (early June–end Sept) for each treatment in the two years.
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Figure 5
Development of total leaf area (A), main leaf area (B), and lateral leaf area (C) per vine at four representative times in 2007. Vertical bars represent the standard error of the mean. Each point is the average of 16 measurements.
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Figure 6
(A) Mean total leaf area and mean berry temperature in non-sun-exposed bunches, July–Sept 2007. Each point is a single measurement per vine. (B) Mean total leaf area and photosynthetically active radiation (PAR) in fruiting positions, July–Sept 2007. Each point is a single measurement per vine. (C) Evolution (morning) of PAR in fruiting positions for each treatment, postveraison Aug 2006–2007. Each point is the average of 12 measurements/treatment. (D) Evolution (morning) of berry temperature in non-sun-exposed bunches (inside canopy) for each treatment, preveraison July 2006–2007. Each point is the average of 20 measurements/treatment. In C and D, vertical bars represent standard error of the mean.
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Figure 7
(A) Midmorning leaf photosynthesis rate (A) at postveraison and total soluble solids (TSS) at harvest: TSS = 23.9(1 − e^(−0.28A). (B) Midday stem water potential (Ψ_s) and TSS at pre- and postveraison: postveraison TSS = 20.5 + 2.7/(1 + e^{(−(Ψs−(−1.4))/0.0535)}). (C) Midday Ψ_s and extractable polyphenols: poly_ext = −103.9 − 224.2 Ψ_s − 81.9 . (D) Ψ_s and total anthocyanins: anth_tot = −555.4 − 1968.6 Ψ_s − 684.5 . (E) Preveraison midday Ψ_s and extractable polyphenols just after veraison: poly_ext = −68.9 − 126.9 Ψ_s. (F) Postveraison (Aug–early Sept) midday Ψ_s and % reduction of extractable polyphenols: %reducpoly_ext = −27.9 − 46.1 Ψ_s. In A–E, each point is the average of one plot for 2006 and 2007. Thresholds and maximum values calculated using the equations. Vertical and horizontal dashed lines represent different threshold values proposed.

Tables

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Table 1
Climate measures during different phenological stages, 2006 to 2007.
Table 2
Mean volumetric soil water content (𝛉_v) (%) in the highest fine root density zone (0–30 cm) for each treatment at four representative periods, 2006 and 2007.
Table 3
Mean values of whole plant hydraulic conductance (K_plant: g MPa⁻¹ s⁻¹) and hydraulic conductance from root to stem(K_root-stem: g MPa⁻¹ m⁻² s⁻¹) for each treatment in different phenological stages, 2006.
Table 4
Mean leaf chlorophyll and photosynthetic nitrogen use efficiency (NUE_ph) for different treatments, pre- and postveraison, 2006 to 2007.
Table 5
Yield response for each treatment, 2006 and 2007.
Table 6
Berry composition parameters at harvest, 2006 and 2007.
Table 7
Threshold ranges for optimum and dangerous water stress proposed for pre- and postveraison in RDI Monastrell grapevines to avoid severe damage in root and leaf function and to improve berry quality under these edaphoclimatic conditions. Mean values of different physiological indicators maintained pre- (early June–end July) and postveraison (Aug–mid-Sept) in 2007.