Indicator Of Vine Water Status Research Articles

Carbon Isotope Discrimination as an Indicator of Vine Water Status is Comparable in Grape Must, Wine, and Distilled Wine Spirits

Measurement of carbon isotope discrimination (δ13C) in berry juice sugars provides an integrative indicator of grapevine water status during berry ripening. Characterizing vine water status during this critical period is useful because it has an important effect on the quality of grapes and the resulting wine. The δ13C of the sugar in grapes is also strongly correlated to the δ13C of the ethanol that results when they are fermented into wine. This then provides a means of estimating from a sample of wine the vine water status that existed during the corresponding berry ripening period, and can be used to establish relations between vine water status and specific sensory attributes of wine quality. The same would be possible for evaluating the sensory attributes of wine spirit (eau de vie) if it was understood how the δ13C signal was affected by the distillation process. In this study, the δ13C in eau de vie, produced by a double distillation process similar to that used in the Cognac region of France, was measured and compared to its source wine and parent grape must. A strong relationship was found between the δ13C of grape must and subsequent wine and eau de vie, suggesting the latter can indeed be used to estimate the vine water status that existed during the corresponding berry ripening period. In this way, future studies of sensory attributes of eau de vie can be linked to vine water status during berry ripening, such as has been done previously for wine.

Application of a Daily Crop Water Stress Index to Deficit Irrigate Malbec Grapevine under Semi-Arid Conditions

Precision irrigation of wine grape is hindered by the lack of an automated method for monitoring vine water status. The objectives of this study were to: Validate an automated model for remote calculation of a daily crop water stress index (CWSI) for the wine grape (Vitis vinifera L.) cultivar Malbec and evaluate its suitability for use in irrigation scheduling. Vines were supplied weekly with different percentages of evapotranspiration-based estimated water demand (ETc) over four growing seasons. In the fifth growing season, different daily CWSI threshold values were used to trigger an irrigation event that supplied 28 mm of water. All three indicators of vine water status (CWSI, midday leaf water potential (Ψlmd), and juice carbon isotope ratio (δ13C)) detected an increase in stress severity as the irrigation amount decreased. When the irrigation amount decreased from 100% to 50% ETc, 70% to 35% ETc, or the daily CWSI threshold value increased from 0.4 to 0.6, berry fresh weight and juice titratable acidity decreased, juice δ13C increased, the weekly CWSI increased, and Ψlmd decreased. Under the semi-arid conditions of this study, utilizing a daily CWSI threshold for irrigation scheduling reduced the irrigation amount without compromising the yield or changes in berry composition and remotely provided automated decision support for managing water stress severity in grapevine.

Evaluating Remotely-Sensed Grapevine (Vitis vinifera L.) Water Stress Responses Across a Viticultural Region

The evolving spatial and temporal knowledge about vineyard performance through the use of remote sensing offers new perspectives for vine water status studies. This paper describes the application of aerial thermal imaging to evaluate vine water status to improve irrigation scheduling decisions, water use efficiency, and overall winegrape quality in the Coonawarra viticultural region of South Australia. Airborne infrared images were acquired during the 2016 and 2017 growing seasons in the region of Coonawarra, South Australia. Several thermal indices of crop water status (CWSI, Ig, (Tc-Ta)) were calculated that correlated with conventional soil and vine water status measures (Ψpd, Ψs, gs). CWSI and Ig could discriminate between the two cultivars used in this study, Cabernet Sauvignon (CAS) and Shiraz (SHI), as did the conventional water stress measures. The relationship between conventional vine water status measures appeared stronger with CWSI in the warmer and drier season (2016) compared to the cooler and wetter season (2017), where Ig and (Tc-Ta) showed stronger correlations. The study identified CWSI, Ig and (Tc-Ta) to be reliable indicators of vine water status under a variety of environmental conditions. This is the first study to report on high resolution vine water status at a regional scale in Australia using a combination of remote and direct sensing methods. This methodology is promising for aerial surveillance of vine water status across multiple blocks and cultivars to inform irrigation scheduling.

Physiological indicators to assess water status in potted grapevine (Vitis vinifera L.)

Many physiological parameters were compared to identify the most sensitive and reliable indicator of grapevine water status. One-year-old potted grapevines (Vitis vinifera L., cvs. ‘Sangiovese’ and ‘Cabernet Sauvignon’) were studied under two irrigation treatments: 100% and 0% of daily water consumption. Measurements of pre-dawn (PD) and midday (MD) leaf water potential (Ψw), MD stem water potential (ΨS), leaf temperature (T°L) and stomatal conductance (gS) were taken throughout twenty days and analyzed in conjunction with climatic data, relative cumulative sap flow (RCSF) and the maximum daily shrinkage (MDS) of the vine stock. Physiological indicators showed substantial differences in sensitivity. The first indication of changes in vine water status was the increase of MDS and the decrease of gS. MDS and RCSF revealed significant differences between the two irrigation treatments even when PDΨw, up to now widely accepted as the benchmark of water status indicators, did not show any significant variation. Measurements of water potential showed ΨS to be a better indicator of vine water status than Ψw and T°L. In conclusion, we classified the tested indicators according to a descending order of their early detection capability: gS = MDS > RCSF > PDΨw = MDΨS > T°L > MDΨw.

Carbon isotope compositions of whole wine, wine solid residue, and wine ethanol, determined by EA/IRMS and GC/C/IRMS, can record the vine water status-a comparative reappraisal.

Recently, we reported that the carbon isotope composition of the solid residues obtained by freeze-drying white and red wines (δ13CWSR) could be used for tracing the water status of the vines whose grapes were used to produce them. Here, we compare different methods using δ13C values of other wine components, particularly those of whole wine (δ13CWW) obtained by elemental analysis and isotope ratio mass spectrometry (EA/IRMS) and of wine ethanol (δ13CWEtOH) obtained by gas chromatography/combustion/IRMS (GC/C/IRMS), for their suitability to assess the vine water status. The studied wines were obtained from field-grown cultivars (Vitis vinifera L. cv. Chasselas, Petite Arvine, and Pinot noir) under different water treatments during the 2009-2014 seasons and were the same wines in which the δ13CWSR was measured previously. The EA/IRMS method for whole wine used two successive EA analytical cycles in each acquisition period to reduce the residence time of the sample capsules in the autosampler. The sample aliquots for the EA/IRMS and GC/C/IRMS analyses were optimized for peak-size differences less than 10% between the sample and reference gas. For all wine varieties, the δ13CWW and δ13CWEtOH values were linearly correlated with the predawn leaf water potential (Ψpd) and therefore serve as reliable indicators of vine water status, as do the δ13C values for must sugars and wine solid residues. The strongest negative correlations with Ψpd were for δ13Csugars (r = -0.94, n = 54) and δ13CWEtOH (r = -0.91) and were lower but still highly significant (p < 0.00001) for δ13CWW (r = -0.71) and δ13CWSR (r = -0.70). An evaluation of the advantages and drawbacks of the different methods is presented, showing that the δ13C analysis of wine ethanol by GC/C/IRMS is the most appropriate.

Carbon-13 composition of bulk dry wines by irm-EA/MS and irm-13C NMR: An indicator of vine water status

Measurements performed on a set of 32 authentic wines (not submitted to any oenological treatment) and their ethanol, recovered by distillation, show high correlation between δ13 C of bulk wine and its ethanol. These measurements were performed by isotope ratio monitoring by mass spectrometry coupled to an elemental analyzer (irm-EA/MS). Then a series of wines produced by vines of which water status was assessed during the growing season with predawn leaf water potential measurements, was studied by irm-EA/MS. As expected δ13 C is correlated to vine water status conditions, as a result of stomatal closure. The ethanol of these specific wines was also analyzed by isotope ratio monitoring and by nuclear magnetic resonance (irm-13 C NMR) to determine carbon-13 composition on the two specific sites of the ethanol skeleton. If these measurements confirm the correlation between 13 C composition and vine growth conditions, the 13 C stereospecific information does not make vine water status assessment more precise.

Evaluation of neural network modeling to predict non-water-stressed leaf temperature in wine grape for calculation of crop water stress index

Precision irrigation management of wine grape requires a reliable method to easily quantify and monitor vine water status to allow effective manipulation of plant water stress in response to water demand, cultivar management and producer objective. Mild to moderate water stress is desirable in wine grape in determined phenological periods for controlling vine vigor and optimizing fruit yield and quality according to producer preferences and objectives. The traditional leaf temperature based crop water stress index (CWSI) for monitoring plant water status has not been widely used for irrigated crops in general partly because of the need to know well-watered and non-transpiring leaf temperatures under identical environmental conditions. In this study, leaf temperature of vines irrigated at rates of 35, 70 or 100% of estimated evapotranspiration demand (ETc) under warm, semiarid field conditions in southwestern Idaho USA was monitored from berry development through fruit harvest in 2013 and 2014. Neural network (NN) models were developed based on meteorological measurements to predict well-watered leaf temperature of wine grape cultivars ‘Syrah’ and ‘Malbec’ (Vitis vinifera L.). Input variables for the cultivar specific NN models with lowest mean squared error were 15-min average values for air temperature, relative humidity, solar radiation and wind speed collected within ±90min of solar noon (13:00 and 15:00 MDT). Correlation coefficients between NN predicted and measured well-watered leaf temperature were 0.93 and 0.89 for ‘Syrah’ and ‘Malbec’, respectively. Mean squared error and mean average error for the NN models were 1.07 and 0.82°C for ‘Syrah’ and 1.30, and 0.98°C for ‘Malbec’, respectively. The NN models predicted well-watered leaf temperature with significantly less variability than traditional multiple linear regression using the same input variables. Non-transpiring leaf temperature was estimated as air temperature plus 15°C based on maximum temperatures measured for vines irrigated at 35% (ETc). Daily mean CWSI calculated using NN estimated well-watered leaf temperatures between 13:00 and 15:00 MDT and air temperature plus 15°C for non-transpiring leaf temperature consistently differentiated between deficit irrigation amounts, irrigation events, and rainfall. The methodology used to calculate a daily CWSI for wine grape in this study provided a daily indicator of vine water status that could be automated for use as a decision-support tool in a precision irrigation system.

Carbon isotope discrimination (δ13C) as an indicator of vine water status and water use efficiency (WUE): Looking for the most representative sample and sampling time

Dry mass Carbon isotope composition (δ13C) is a representative parameter of water use efficiency (WUE) in plants, as previously demonstrated by different authors for different species under different environmental conditions. Nevertheless, the relationship between δ13C and WUE in grapevines shows important variations among different experiments thus limiting its interest as indicator of water status or WUE. Our hypothesis was that such representativeness could be improved choosing an adequate sample and sampling time. Thus, the main objective of the present work was to identify the most representative sample and sampling time for a better assessment of grapevine water status and WUE by measuring: (i) the variability of WUE and δ13C in leaves and berries along growing season; (ii) the effect of water availability on WUE parameters and on δ13C; (iii) the relationships between leaf and plant WUE and the δ13C. Experiments were performed in the field at the Univertsity of Balearic Islands (Mallorca, Spain). The first experiment was carried out during the 2012 and 2013 seasons using cv. Tempranillo plants growing in 30-l pots under three levels of soil water content: (i) Control (100% of Field Capacity); (ii) Moderate water deficit (50% of Field Capacity) and (iii) Severe water deficit (25% of Field Capacity). The second experiment was performed under field-grown grapevines in the 2013 season, in cvs. Tempranillo and Grenache under two treatments: (i) Control (irrigation, 50% ETo) and (ii) No irrigation. In both experiments the correlation between the measured δ13C, in both young leaves (located in the middle zone of stem) and mature leaves (located in the basal zone of the stem) and berries in different growth stages and water use efficiency measured at the leaf level defined as intrinsic WUE (AN/gs) were studied, as well as at the whole plant level, defined as WUEplant (biomass increment/water consumed) and at the crop level, WUEc (yield/water applied). The best correlations were attained between δ13C and soil water status or intrinsic WUE (AN/gs). Berries at ripening showed to be the most appropriate organ to estimate both, the plant water status and the leaf and plant water use efficiency in grapevines.

Leaf water potentials of sunlit and/or shaded grapevine leaves are sensitive alternatives to stem water potential

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aims&lt;/strong&gt;: Leaf (Ψ&lt;sub&gt;l&lt;/sub&gt;) and stem (Ψ&lt;sub&gt;stem&lt;/sub&gt;) water potentials were measured on grapevines to determine the effects of shoot location on both methods to assess vine water status.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: Cabernet-Sauvignon and Merlot used in this study were grown at two locations in California. Measurements were taken at midday in July (Merlot) and at two times of the day (morning and afternoon), on two dates in August (Cabernet- Sauvignon). Measurements of Ψ&lt;sub&gt;l&lt;/sub&gt; and Ψ&lt;sub&gt;stem&lt;/sub&gt;, stomatal conductance and transpiration were taken on shoots entirely exposed to direct solar radiation or on shoots totally in the shade at the times of measurement. There were significant differences (&lt;em&gt;P&lt;/em&gt; &amp;lt; 0.05) between Ψ&lt;sub&gt;l&lt;/sub&gt; and/or Ψ&lt;sub&gt;stem&lt;/sub&gt; measured on shoots exposed to direct solar radiation and those in the shade. Both Ψ&lt;sub&gt;l&lt;/sub&gt; and Ψ&lt;sub&gt;stem&lt;/sub&gt; were significantly greater on the shoots exposed to direct sunlight compared to those in the shade. There was no significant difference between Ψ&lt;sub&gt;l&lt;/sub&gt; measured on shaded leaves and Ψ&lt;sub&gt;stem&lt;/sub&gt; determined on the fully exposed shoots.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusions&lt;/strong&gt;: Regardless of method used, water potentials were highly correlated with stomatal conductance measured on leaves in direct sunlight at the same time. All means of measuring grapevine water potential used in this study were highly correlated with one another.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Significance and impact of the study&lt;/strong&gt;: The data indicate that any of the techniques used in this study would be a sensitive indicator of vine water status and that the Ψ of shaded leaves would be an alternative to the measurement of Ψ&lt;sub&gt;stem&lt;/sub&gt;.&lt;/p&gt;

Assessment of grape yield and composition using the reflectance based Water Index in Mediterranean rainfed vineyards

In rainfed vineyards water deficits play a major role in determining berry yield and composition. Therefore, reliable indicators of vine water status might be of great value for the optimization of grape yield and quality. In the present study the feasibility of using hyperspectral reflectance indices related to plant biophysical properties at predicting berry yield and quality attributes in rainfed vineyards is assessed. The study was conducted on Vitis vinifera cv. Chardonnay in commercial vineyards in the D.O. Penedès region (Catalonia, Spain) over two consecutive years (2007–2008). Field measurements of fractional intercepted Photosynthetic Active Radiation (fIPAR), canopy reflectance, predawn water potential (Ψp) and the canopy to air temperature difference at midday (ΔTmidday) were conducted at the stage of veraison. Yield, Total Soluble Solids (TSS), Titratable Acidity (TA) and the ratio TSS/TA (maturation index, IMAD) were determined at harvest. Contrasted water availability among vineyards prompted considerable variation in berry yield and quality attributes. Across years, higher yield was accompanied by higher TA (r=0.59, p<0.01) and lower IMAD (r=−0.63, p<0.01) while no significant relationship was observed between yield and TSS. Yield was related to canopy vigor (fIPAR) in a variable extend: in 2007, yield was positively related to fIPAR (r=0.71, p<0.05) while yield was found to decrease along with increasing fIPAR in 2008 (r=−0.62, p<0.05). Contrastingly, NDVI provided consistent estimates of yield across years (r=0.57, p<0.05). These results suggest that NDVI might be more appropriate to characterize the effects of varying water availability on yield than fIPAR. In addition, yield was found to be related to ΔTmidday (r=−0.63 and r=−0.66, in 2007 and 2008, respectively). Accordingly, the Water Index (WI), an indicator of vine water status, provided robust estimates of yield across years (r=0.61, p<0.01). The strength of the correlation between NDVI and WI vs. yield suggests that yield was influenced by changes in both leaf area (intercepted light) and photosynthesis (stomatal aperture) in a variable extent according to the timing and severity of water deficits in the years of study. Berry quality attributes did not show significant relationships against fIPAR but were related to ΔTmidday. Accordingly, NDVI did not show significant correlation with berry quality attributes, while WI was found to be consistently related to TA (r=0.70, p<0.01) and IMAD (r=−0.71, p<0.01) across years. The results obtained suggest that the WI might provide reliable estimates of berry quality attributes in vineyards experiencing moderate to severe water deficits with potential application in precision viticulture activities such as selective harvesting according to grape quality attributes as well as for ripening assessment.

Identification and significance of sources of spatial variation in grapevine water status

Background and Aims: Water stress in grapevines is directly linked to grape quality. Differential vine water management should therefore be strongly linked to the water stress in the vine. To do this, an understanding of the dominant drivers and indicators of vine water status are needed from a sub-block to whole vineyard level. This understanding will help generate effective vine water status models for variable rate irrigation systems. Methods and Results: A vineyard in the south of France was sampled for pre-dawn leaf water potential (ΨPD) at several dates during the growing season for two consecutive years. Sampling was stratified by soil types and relative within-block vegetative expression. A recursive partitioning analysis identified that cultivar had a dominant effect at low water stress, while vegetative expression and then soil unit effects became dominant as water restriction increased. Variance in ΨPD was calculated at difference scales (plant, site, block and vineyard) and Smith's heterogeneity law was used to evaluate the scalar nature of ΨPD variance. Spatial heterogeneity increased as the season and water restriction increased. Conclusion: Variance in ΨPD changed temporally through a season and the dominant drivers/indicators also changed. The opportunity to spatially manage water stress (irrigation) increased as water restriction increased. Significance of the Study: Managing vine water stress helps optimise production and a ΨPD model would be a useful addition to a viticulture decision support system. This study identified how the variance in ΨPD evolved during a season and the best ancillary indicators of ΨPD for spatial and temporal modelling.

A model-based diagnosis tool to evaluate the water stress experienced by grapevine in field sites

Soil water deficit is a major factor influencing yield and grape berry composition, with an optimal situation corresponding to a moderate water deficit. A computer-based diagnosis tool requiring a limited number of measurements was developed and used to characterise the typology of soil water deficit experienced by grapevine in field sites over the cropping season with the aim of producing acceptable yields and achieving good quality red wine. The tool combined a simple soil water balance model parameterised for vine, to simulate the fraction of transpirable soil water (FTSW) at a daily time step, and an indicator of vine water status in terms of source/sink relationships and canopy microclimate. This indicator was developed from quantitative relationships between FTSW and maximal net assimilation (Anmax), under optimal conditions of light and temperature, the leaf emergence rate on first-order lateral branches (LER I), the leaf emergence rate on second-order lateral branches (LER II) and the final length of first-order lateral branches (BL I). These relationships were parameterised in a greenhouse on Syrah (syn. Shiraz) grafted onto Fercal rootstock. The computer-based diagnosis tool was used on 24 fields within 4 vineyards of Mediterranean southern France covering contrasting pedoclimatic conditions, cultivar/rootstock pairs and receiving different water regimes. The key soil parameter of the water balance model, the total vine's transpirable soil water (TTSW), was estimated in each field from measurements of predawn leaf water potential (Ψl) at different vine growth stages in conjunction with an optimisation algorithm of the simulated FTSW as a function of predawn Ψl obtained with an independent data set. The tool enabled classification of the fields on the basis of the changes of the indicator of vine water status across four phases of the plant cycle, from budburst to harvest, relative to an optimum change of this indicator defined for production of a good quality wine. Such a tool will be useful to farm advisers and researchers for the evaluation of management practices as for comparative analysis between vineyards.

The assessment of vine water and nitrogen uptake by means of physiological indicators influence on vine development and berry potential (&lt;em&gt;Vitis vinifera&lt;/em&gt; L. cv Merlot, 2000, Bordeaux)

&lt;p style="text-align: justify;"&gt;Vine water and nitrogen uptake can be assessed by means of physiological indicators in field conditions. In this study, pre-dawn leaf water potential (ψB) and stem water potential (ψT) were used to indicate vine water status of &lt;em&gt;Vitis vinifera&lt;/em&gt; L cv. Merlot. Carbon isotope composition of grape sugar (ΔC13) was used as an integrative indicator of vine water deficit during the ripening period. Must assimilable nitrogen and leaf blade colour intensity, were used to assess vine nitrogen status. All of the three indicators of vine water status allowed a clear differentiation of vine water uptake conditions in the ten experimental plots. The indicators of vine nitrogen status showed more ambiguous results. Must assimilable nitrogen content did not only vary with vine nitrogen uptake, but also with yield. Leaf colour was more easy to interpret. Vine development and berry composition were more influenced by water uptake conditions than by vine nitrogen status. In 2000, which was a dry vintage in Bordeaux, water stress induced early growth slackening and a small berry size. Grapes contained more sugar, anthocyanin and total phenolics and less malic acid when water availability was low. On plots where water uptake conditions were similar, low vine nitrogen status increased berry potential.&lt;/p&gt;