An increase in xylem embolism resistance of grapevine leaves during the growing season is coordinated with stomatal regulation, turgor loss point and intervessel pit membranes

Abstract

Although xylem embolism resistance is traditionally considered as static, we hypothesized that in grapevine (Vitis vinifera) leaf xylem becomes more embolism-resistant over the growing season. We evaluated xylem architecture, turgor loss point (Ψ TLP) and water potentials leading to 25% of maximal stomatal conductance (g s25) or 50% embolism in the leaf xylem (P 50) in three irrigation treatments and at three time points during the growing season, while separating the effects of leaf age and time of season. Hydraulic traits acclimated over the growing season in a coordinated manner. Without irrigation, Ψ TLP , g s25 , and P 50 decreased between late May and late August by 0.95, 0.77 and 0.71 MPa, respectively. A seasonal shift in P 50 occurred even in mature leaves, while irrigation had only a mild effect (< 0.2 MPa) on P 50. Vessel size and pit membrane thickness were also seasonally dynamic, providing a plausible explanation for the shift in P 50. Our findings provide clear evidence that grapevines can modify their hydraulic traits along a growing season to allow lower xylem water potential, without compromising gas exchange, leaf turgor or xylem integrity. Seasonal changes should be considered when modeling ecosystem vulnerability to drought or comparing datasets acquired at different phenological stages.

Pore constrictions in intervessel pit membranes provide a mechanistic explanation for xylem embolism resistance in angiosperms

“…It is possible that variation in T PM within a vessel or within the vessel network provides additional chances of leakiness, and small differences in T PM across organs (Kotowska et al ., 2020) could influence embolism resistance. Capturing this variation, however, is difficult because measuring T PM may not be straightforward, for instance due to TEM preparation artefacts, aggregation of cellulose fibrils into larger aggregates, and seasonal shrinkage of pit membranes (Schmid & Machado, 1968; Sorek et al ., 2021).…”

“…embolism) (Choat et al ., 2008; Kaack et al ., 2019). Since water transport efficiency is tightly related to transpiration and photosynthesis, drought‐induced embolism formation can have major implications for plant performance, especially under drought (Li et al ., 2016a,b; Sorek et al ., 2021). Yet many details about the mechanistic relationship between embolism formation and the anatomical determinants of pits remain unclear.…”

Primary tissues may affect estimates of cavitation resistance in ferns

“…Seasonality is known to affect the hydraulic performance and embolism resistance in woody species (Kolb & Sperry, 1999; Jacobsen et al ., 2014) and, in this study, seasonality may also have affected the degree to which the laboratory‐generated curves agree with the field data. Recent work has shown that seasonal changes in xylem lumen to cell wall ratios, the progressive addition of xylem tissue and ion‐mediated shifts in conductivity have led to some combination of increased cavitation resistance or higher transport efficiency toward the end of the growing season (Jupa et al ., 2019; Sorek et al ., 2020). Similar phenomena may affect fern hydraulics.…”

Response of Merlot Grapevine to Drought Is Associated to Adjustments of Growth and Nonstructural Carbohydrates Allocation in above and Underground Organs

“…It has been ascertained that future global warming scenarios will increase the drought risk in most cultivated regions in the next several decades [1][2][3]. Drought can seriously affect crop yield and quality, and, in exceptional cases, crop survival [4][5][6]. Where applicable, irrigation practices are largely adopted to compensate seasonal water deficit, even though such practices may also generate negative environmental aftermaths [7].…”