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The leaf of a deciduous species completes its life cycle in a few months. During leaf maturation, osmolyte accumulation leads to a significant reduction of the turgor loss point (Ψ TLP ), a known marker for stomatal closure. Here we exposed two grapevine cultivars to drought at three different times during the growing season to explore if the seasonal decrease in leaf Ψ TLP influences the stomatal response to drought. The results showed a significant seasonal shift in the response of stomatal conductance to stem water potential (g s ~Ψ stem ), demonstrating that grapevines become increasingly tolerant to low Ψ stem as the season progresses in coordination with the decrease in Ψ TLP . We also used the SurEau hydraulic model to demonstrate a direct link between osmotic adjustment and the plasticity of g s ~Ψ stem . To understand the possible advantages of g s ~Ψ stem plasticity, we incorporated a seasonally dynamic leaf osmotic potential into the model that simulated stomatal conductance under several water availabilities and climatic scenarios. The model demonstrated that a seasonally dynamic stomatal closure threshold results in trade-offs: it reduces the time to turgor loss under sustained long-term drought, but increases overall gas exchange particularly under seasonal shifts in temperature and stochastic water availability. A projected hotter future is expected to lower the increase in gas exchange that plants gain from the seasonal shift in g s ~Ψ stem . These findings show that accounting for dynamic stomatal regulation is critical for understanding drought tolerance., (© 2021 The Authors. The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.)

Plant stress experiments are commonly performed with plants grown in containers to better control environmental conditions. Nevertheless, the container can constrain plant growth and development, and this confounding effect is generally ignored, particularly in studies on woody species. Here, we evaluate the effect of the container volume in drought experiments using grapevine as a model plant. Grapevines grown in small (7 L, S) or large (20 L, L) containers were subjected to drought stress and rewatering treatments. We monitored plant stomatal conductance (g s ), midday stem water potential (Ψ s ), and photosynthetic rate (A N ) throughout the experiment. The effect of the container volume on the stem and petiole xylem anatomy, as well as on the total leaf area (LA), was assessed before drought imposition. The results showed that LA did not differ between plants in L or S containers, but S vines exhibited a higher theoretical hydraulic conductance at the petiole level. Under drought L and S similarly reduced g s and A N , but plants in S containers reached lower Ψ s than those in L. Nevertheless, upon rewatering droughted plants in S containers exhibited a faster stomata re-opening than those in L, probably as a consequence of the differences in the stress degree experienced and the biochemical adjustment at the leaf level. Therefore, a suitable experimental design should consider the container volume used in relation to the desired traits to be studied for unbiased results., (© 2021 The Authors. Physiologia Plantarum published by John Wiley & Sons Ltd on behalf of Scandinavian Plant Physiology Society.)

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?, (© The Author(s) 2020. Published by Oxford University Press on behalf of the Society for Experimental Biology.)

Background: Intensity of drought stress and pest attacks is forecasted to increase in the near future posing a serious threat to natural and agricultural ecosystems. Knowledge on potential effects of a combined abiotic-biotic stress on whole-plant physiology is lacking. We monitored the water status and carbon metabolism of a vine rootstock with or without scion subjected to water shortening and/or infestation with the sucking insect phylloxera (Daktulosphaira vitifoliae Fitch). We measured non-structural carbohydrates and biomass of different plant organs to assess the stress-induced responses at the root, stem, and leaf level. Effects of watering on root infestation were also addressed., Results: Higher root infestation was observed in drought-stressed plants compared to well-watered. The drought had a significant impact on most of the measured functional traits. Phylloxera further influenced vines water and carbon metabolism and enforced the sink strength of the roots by stimulating photosynthates translocation. The insect induced carbon depletion, reprogramed vine development, while preventing biomass compensation. A synergic effect of biotic-abiotic stress could be detected in several physiological and morphological traits., Conclusions: Our results indicate that events of water shortage favour insects' feeding damage and increase the abundance of root nodosities. Root phylloxera infestation imposes a considerable stress to the plants which might exacerbate the negative effects of drought.

The article discusses the role of water availability in plant productivity and yield. It focuses on the measurement of leaf solute potential, which is an indicator of a plant's ability to adapt to heat and drought. The study specifically examines the seasonal changes in solute potential in grapevine cultivars and finds that the seasonal decrease in solute potential is more significant than the differences between cultivars or the response to drought. The findings suggest that solute accumulation is not solely a response to drought, but is also influenced by other factors such as leaf age and atmospheric conditions. The study highlights the importance of considering seasonal osmotic adjustment in improving water use efficiency and soil water conservation strategies. [Extracted from the article]

Grapevine interspecific hybrids (PIWIs) represent an interesting alternative to classic cultivars in several wine regions, especially under sustainable and organic production systems. While such gentopyes are well characterised for some agronomic aspects and mainly because their response to biotic stressors such as powdery and downey mildews, little is known about their response to abiotic stressors such as drought. Here we studied the response of three different commercial PIWI genotypes (Donauriesling, Muscaris, and Souvignier gris, all grafted on rootstock Kober 5BB) to drought by monitoring their leaf gas exchange and water potential during dehydration in two seasons (2020 and 2021). We quantified the leaf area development and some leaf hydraulic traits to understand how they relate to the drought response in a pot experiment under controlled conditions. The results showed slight differences between genotypes only during the first days of dehydration, where Souvignier gris exhibited a less tight stomatal control as compared with the other PIWIs and in coordination with a lower (more negative) osmotic potential and turgor loss point. However, after five days under drought, all genotypes exhibited similar stomatal behaviour (gs<0.05 mol m-2 s-1). Our study shows that PIWIs behave and operate within similar ranges of stomatal conductance and water potentials as compared with other V. vinifera cultivars used in this study (Grüner Veltliner and Riesling). Acclimation to long-term water deficit and impacts on fruit composition is needed to better understand PIWIs ability to grow under limited water scenarios. [ABSTRACT FROM AUTHOR]

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