Adapting agriculture to climate change is driving the need for the selection and breeding of drought-tolerant crops. The aim of this study was to identify key drought tolerance traits and determine ...the sequence of their water potential thresholds across three grapevine cultivars with contrasting water use behaviors, Grenache, Syrah, and Semillon. We quantified differences in water use between cultivars and combined this with the determination of other leaf-level traits (e.g. leaf turgor loss point, π TLP), leaf vulnerability to embolism (P50), and the hydraulic safety margin (HSM P50). Semillon exhibited the highest maximum transpiration (Emax), and lowest sensitivity of canopy stomatal conductance (Gc) to vapor pressure deficit (VPD), followed by Syrah and Grenache. Increasing Emax was correlated with more negative water potential at which stomata close (Pgs90), π TLP, and P50, suggesting that increasing water use is associated with hydraulic traits allowing gas exchange under more negative water potentials. Nevertheless, all the cultivars closed their stomata prior to leaf embolism formation. Modeling simulations demonstrated that despite a narrower HSM, Grenache takes longer to reach thresholds of hydraulic failure due to its conservative water use. This study demonstrates that the relationships between leaf hydraulic traits are complex and interactive, stressing the importance of integrating multiple traits in characterizing drought tolerance.
Hydraulics of plants that have different strategies of stomatal regulation under water stress are relatively poorly understood. We explore how root and shoot hydraulics, stomatal conductance (
g
s
), ...leaf and root aquaporin (AQP) expression, and abscisic acid (ABA) concentration in leaf xylem sap (ABA
xylemsap
) may be coordinated under mild water stress and exogenous ABA applications in two
Vitis vinifera
L. cultivars traditionally classified as near-isohydric (Grenache) and near-anisohydric (Syrah). Under water stress, Grenache exhibited stronger adjustments of plant and root hydraulic conductances and greater stomatal sensitivity to ABA
xylemsap
than Syrah resulting in greater conservation of soil moisture but not necessarily more isohydric behavior. Correlations between leaf (Ψ
leaf
) and predawn (Ψ
PD
) water potentials between cultivars suggested a “hydrodynamic” behavior rather than a particular iso-anisohydric classification. A significant decrease of Ψ
leaf
in well-watered ABA-fed vines supported a role of ABA in the soil-leaf hydraulic pathway to regulate
g
s
. Correlations between leaf and root AQPs expression levels under water deficit could explain the response of leaf (
K
leaf
) and root (
Lp
r
) hydraulic conductances in both cultivars. Additional studies under a wider range of soil water deficits are required to explore the possible differential regulation of
g
s
and plant hydraulics in different cultivars and experimental conditions.
Climate change will likely increase the risk of drought because of increased temperatures and changing rainfall patterns, and growers are already struggling to adapt. This is apparent in the ...increased use of irrigation in traditionally rain-fed regions, which threatens environmental sustainability (Costa et al., 2016). In a water scarce future where irrigation cannot be universally implemented, the use of more drought tolerant varieties and vineyard designs can provide a more cost effective and sustainable solution (van Leeuwen et al., 2019).
Water availability is arguably the most important environmental factor limiting crop growth and productivity. Erratic precipitation patterns and increased temperatures resulting from climate change ...will likely make drought events more frequent in many regions, increasing the demand on freshwater resources and creating major challenges for agriculture. Addressing these challenges through increased irrigation is not always a sustainable solution so there is a growing need to identify and/or breed drought-tolerant crop varieties in order to maintain sustainability in the context of climate change. Grapevine (Vitis vinifera), a major fruit crop of economic importance, has emerged as a model perennial fruit crop for the study of drought tolerance. This review synthesizes the most recent results on grapevine drought responses, the impact of water deficit on fruit yield and composition, and the identification of drought-tolerant varieties. Given the existing gaps in our knowledge of the mechanisms underlying grapevine drought responses, we aim to answer the following question: how can we move towards a more integrative definition of grapevine drought tolerance?
Climate change is driving the search for grapevine cultivars and/or rootstocks that use water more efficiently. Recently, there has been increasing attention on nighttime transpiration. The reasoning ...is simple. While daytime transpiration results from the necessity to have stomata open so the plant can take up carbon dioxide for photosynthesis, nighttime transpiration could be considered a “waste” of water since no photosynthesis occurs at night. So how significant is nighttime water use in grape, and does it serve some other purpose that benefits the vine?
Climate change is driving the search for grapevine cultivars and/or rootstocks that use water more efficiently. Recently, there has been increasing attention on nighttime transpiration. The reasoning ...is simple. While daytime transpiration results from the necessity to have stomata open so the plant can take up carbon dioxide for photosynthesis, nighttime transpiration could be considered a “waste” of water since no photosynthesis occurs at night. So how significant is nighttime water use in grape, and does it serve some other purpose that benefits the vine?
Nighttime transpiration has been previously reported as a significant source of water loss in many species; however, there is a need to determine if this trait plays a key role in the response to ...drought. This study aimed to determine the magnitude, regulation and relative contribution to whole plant water‐use, of nighttime stomatal conductance (gnight) and transpiration (Enight) in grapevine (Vitis vinifera L.). Our results showed that nighttime water loss was relatively low compared to daytime transpiration, and that decreases in soil and plant water potentials were mainly explained by daytime stomatal conductance (gday) and transpiration (Eday). Contrary to Eday, Enight did not respond to VPD and possible effects of an innate circadian regulation were observed. Plants with higher gnight also exhibited higher daytime transpiration and carbon assimilation at midday, and total leaf area, suggesting that increased gnight may be linked with daytime behaviors that promote productivity. Modeling simulations indicated that gnight was not a significant factor in reaching critical hydraulic thresholds under scenarios of either extreme drought, or time to 20% of soil relative water content. Overall, this study suggests that gnight is not significant in exacerbating the risk of water stress and hydraulic failure in grapevine.
Our study demonstrates that in grapevine (Vitis vinifera L.), nighttime water loss is not significant in exacerbating the risk of water stress, and in addition, we offer evidence that it may be positively linked to daytime productivity.
Abstract
Climate change is challenging the resilience of grapevine (Vitis), one of the most important crops worldwide. Adapting viticulture to a hotter and drier future will require a multifaceted ...approach including the breeding of more drought-tolerant genotypes. In this study, we focused on plant hydraulics as a multi-trait system that allows the plant to maintain hydraulic integrity and gas exchange rates longer under drought. We quantified a broad range of drought-related traits within and across Vitis species, created in silico libraries of trait combinations, and then identified drought tolerant trait syndromes. By modeling the maintenance of hydraulic integrity of current cultivars and the drought tolerant trait syndromes, we identified elite ideotypes that increased the amount of time they could experience drought without leaf hydraulic failure. Generally, elites exhibited a trait syndrome with lower stomatal conductance, earlier stomatal closure, and a larger hydraulic safety margin. We demonstrated that, when compared with current cultivars, elite ideotypes have the potential to decrease the risk of hydraulic failure across wine regions under future climate scenarios. This study reveals the syndrome of traits that can be leveraged to protect grapevine from experiencing hydraulic failure under drought and increase drought tolerance.
In the context of climate change, plant mortality is increasing worldwide in both natural and agroecosystems. However, our understanding of the underlying causes is limited by the complex ...interactions between abiotic and biotic factors and the technical challenges that limit investigations of these interactions. Here, we studied the interaction between two main drivers of mortality, drought and vascular disease (esca), in one of the world's most economically valuable fruit crops, grapevine. We found that drought totally inhibited esca leaf symptom expression. We disentangled the plant physiological response to the two stresses by quantifying whole-plant water relations (i.e., water potential and stomatal conductance) and carbon balance (i.e., CO
assimilation, chlorophyll, and nonstructural carbohydrates). Our results highlight the distinct physiology behind these two stress responses, indicating that esca (and subsequent stomatal conductance decline) does not result from decreases in water potential and generates different gas exchange and nonstructural carbohydrate seasonal dynamics compared to drought.
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