Grapevine species from varied native habitats exhibit differences in embolism formation/repair associated with leaf gas exchange and root pressure

Abstract

Drought induces xylem embolism formation, but grapevines can refill non-functional vessels to restore transport capacity. It is unknown whether vulnerability to embolism formation and ability to repair differ among grapevine species. We analysed in vivo embolism formation and repair using x-ray computed microtomography in three wild grapevine species from varied native habitats (Vitis riparia, V. arizonica, V. champinii) and related responses to measurements of leaf gas exchange and root pressure. Vulnerability to embolism formation was greatest in V. riparia, intermediate in V. arizonica and lowest in V. champinii. After re-watering, embolism repair was rapid and pronounced in V. riparia and V. arizonica, but limited or negligible in V. champinii even after numerous days. Similarly, root pressure measured after re-watering was positively correlated with drought stress severity for V. riparia and V. arizonica (species exhibiting embolism repair) but not for V. champinii. Drought-induced reductions in transpiration were greatest for V. riparia and least in V. champinii. Recovery of transpiration after re-watering was delayed for all species, but was greatest for V. champinii and most rapid in V. arizonica. These species exhibit varied responses to drought stress that involve maintenance/recovery of xylem transport capacity coordinated with root pressure and gas exchange responses.

Stomatal Closure, Basal Leaf Embolism, and Shedding Protect the Hydraulic Integrity of Grape Stems

“…For example, when Schultz (2003) stopped irrigation in a cv Chardonnay vineyard (with less than 50 mm seasonal precipitation), it took 3 months to reach a C l of 21.8 MPa, and at the end of that period, the vines had less than half of the leaf area of the irrigated controls. If all lines of defense are breached and the stem is significantly cavitated, assuming rehydration will take place when the plant is still alive, root pressure combined with the absence of leaves should lead to positive pressures for a sufficient time to refill the xylem in the stem, such that it may again sustain negative pressures and allow the emergence of new buds (Knipfer et al, 2015;Charrier et al, 2016).…”

Hydraulic Anatomy and Function of Trees—Basics and Critical Developments

“…MicroCT can attain much higher spatial resolutions and has been particularly effective when derived from synchrotron radiation [109,110]. High-resolution imaging has helped to confirm that air seeding through pit membranes is the primary mechanism by which cavitation occurs in both angiosperms and gymnosperms [13,102,111]. In-situ high-resolution imaging of plant hydraulic functions can assist in resolving questions about the evolution and reversal of vascular cavitation.…”

Mechanical Failure of Fine Root Cortical Cells Initiates Plant Hydraulic Decline during Drought

“…For coarse root set-up, each plant analyzed (n = 12, range in C stem of 0.3 to 23.7 MPa), the plastic cylinder and sand medium surrounding coarse roots was carefully removed, and the plastic pot was placed in an aluminum cage and fixed on an air-bearing stage (Supplemental Fig. S5A; Brodersen et al, 2010;McElrone et al, 2013;Knipfer et al, 2015). For fine root set-up, in each plant analyzed (n = 12, range in C stem of 20.3 to 21.7 MPa), the lower portion of the plastic cylinder with sand medium surrounding fine roots was carefully removed, the excavated fine roots were inserted into a plastic tube (length 15 cm) that was fixed to the remaining upper portion of the remaining plastic cylinder, and the plastic tube was inserted into the drill chuck and then placed on the stage (Supplemental Fig.…”

“…Vessel diameter (d) was derived by A ¼ pðd=2Þ 2 . Percentage theoretical loss of xylem hydraulic conductivity was determined using a modified Hagen-Poiseuille equation (Tyree and Ewers, 1991;Brodersen et al, 2013;Knipfer et al, 2015). The xylem hydraulic conductivity (k h ) of the population of embolized and water-filled vessels of the roots was calculated according to:…”