Comparing Hydraulics Between Two Grapevine Cultivars Reveals Differences in Stomatal Regulation Under Water Stress and Exogenous ABA Applications.

Silvina Dayer,Franziska C Doerflinger,Johannes D Scharwies,Vinay Pagay,Wendy Sullivan,Stephen D Tyerman,Sunita A Ramesh

doi:10.3389/fpls.2020.00705

Silvina Dayer, Franziska C Doerflinger + Show 5 more

Open Access

https://doi.org/10.3389/fpls.2020.00705

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Abstract

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 (gs), 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 (Ψleaf) and predawn (ΨPD) water potentials between cultivars suggested a “hydrodynamic” behavior rather than a particular iso-anisohydric classification. A significant decrease of Ψleaf in well-watered ABA-fed vines supported a role of ABA in the soil-leaf hydraulic pathway to regulate gs. Correlations between leaf and root AQPs expression levels under water deficit could explain the response of leaf (Kleaf) and root (Lpr) hydraulic conductances in both cultivars. Additional studies under a wider range of soil water deficits are required to explore the possible differential regulation of gs and plant hydraulics in different cultivars and experimental conditions.

Highlights

To withstand abiotic stresses such as drought, plants have evolved complex adaptive mechanisms that are regulated dynamically
A soil moisture deficit imposed on the two cultivars in this study, Syrah and Grenache, resulted in similar values of PD on Day 5 for the water deficit (WD) vines (Figure 1D) and a range of PD values from −0.2 to −0.5 MPa were measured in WD vines for Days 5 and 7 (Figures 1D,E)
We investigated specific mechanisms that may explain the differences in iso/anisohydry, in particular, root hydraulics, leaf gas exchange, leaf and root AQP expression, and xylem abscisic acid (ABA)

Summary

Introduction

To withstand abiotic stresses such as drought, plants have evolved complex adaptive mechanisms that are regulated dynamically. There is an interplay between stomatal regulation of transpiration (Chaves et al, 2010) and changes in the hydraulic conductivity of roots [Lpr; (Maurel et al, 2010)], and leaves [Kleaf; Sack and Holbrook (2006)]. Grapevine Hydraulics Under Water Stress stomata, is regulated by stomatal conductance (gs) and strongly influenced by vapor pressure deficit [VPD; Aphalo and Jarvis (1991); McAdam et al (2016)] as well as changes in Kleaf (Pou et al, 2013), through changes of stomatal guard cell turgor. Changes in guard cell turgor involve complex and still debated mechanisms that are mediated by chemical and/or hydraulic signals (Comstock, 2002). A root peptide signal was discovered in Arabidopsis during soil moisture deficit, that could induce ABA synthesis in the leaves (Takahashi et al, 2018)

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