Abstract
Measuring seasonal plant water status is critical in choosing appropriate management strategies to ensure yields and quality of agricultural products, particularly in a context of climate change. Water status of grapevines is known to be a key factor for yield, grape composition, and wine quality. Predawn leaf water potential (PLWP) and stem water potential (SWP) proved to be simple and precise indicators for assessing grapevine water status and subsequent same-day spatial comparisons. A drawback of SWP is that it does not allow for temporal comparisons, because the measured value is impacted both by soil water availability and climatic conditions on the day of measurement. The objectives of this study are i) to provide a model that separates the effect of soil water content from the effect of climatic conditions on the SWP value and ii) to standardize the SWP value to a value under predefined reference climatic conditions in order to compare SWP values collected under different climatic conditions. SWP and PLWP were temporally assessed on three soil types in Saint-Émilion (Bordeaux, France) in 2015 and on five soil types in Margaux (Bordeaux, France) in 2018 using a pressure chamber. SWP measurements on two consecutive days with contrasting climatic conditions allowed to assess the impact of these conditions on SWP values. A large portion of the variability in SWP values was explained by PLWP. Model selection further showed that the addition of maximum air temperature and seasonality explained a significant amount of the remaining variability in SWP values. SWP values could be successfully standardized to a theoretical value under reference climatic conditions, which allows for temporal comparisons of SWP values. A plant-based measurement, such as the water potential, can be considered as the most straightforward indicator of plant water status as it integrates the effects of soil, plant, and atmospheric conditions. More precise interpretation of SWP values provides winegrowers with a tool to more adequately implement short- and long-term management strategies to adapt to drought in order to ensure yield and grape quality.
Highlights
Climate change will result in an increase in temperature and an intensification of drought in many regions across the globe (IPCC, 2014)
predawn leaf water potential (PLWP) values ranged from −0.06 to −0.86 MPa in 2015 and from −0.01 to −0.90 MPa in 2018 (Figure 1)
Severe water deficit with stem water potential (SWP) values below −1.4 MPa and PLWP values below −0.8 MPa were recorded in both SaintÉmilion in 2015 and in Margaux in 2018
Summary
Climate change will result in an increase in temperature and an intensification of drought in many regions across the globe (IPCC, 2014). PLWP tends to overestimate soil water availability in conditions of heterogeneous soil humidity Under these conditions, PLWP will equilibrate with the most humid soil layer and is not related to the mean water status of the soil in the root zone (Améglio et al, 1999). PLWP will equilibrate with the most humid soil layer and is not related to the mean water status of the soil in the root zone (Améglio et al, 1999) Another drawback of PLWP measurements is that they must be measured before dawn, which does not make it practical to implement. SWP measured in the early afternoon is more implemented as there is more time available to take readings under stable conditions than at early morning when environmental conditions change more quickly (Intrigliolo and Castel, 2010). SWP is known to decrease with increasing vapor maximum deficit (VPD), but this relationship has been demonstrated to change over the growing season (Olivo et al, 2009) and to be different among and within species (McCutchan and Shackel, 1992; De Swaef et al, 2009; Rogiers et al, 2009; Marchin et al, 2016), and irrigation treatments (Williams and Baeza, 2007; Gálvez et al, 2014)
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