Beitrag in Konferenzband

Water absorption into stems affects the measurement of vulnerability curves as a function of plant water status


Details zur Publikation

AutorenlisteZinkernagel J., Mayer N.

Jahr der Veröffentlichung2018

QuelleActa Horticulturae

Bandnummer1222

Erste Seite21

Letzte Seite26

VerlagInternational Society for Horticultural Science (ISHS)

ISSN0567-7572

eISSN2406-6168

DOI10.17660/ActaHortic.2018.1222.4

SprachenEnglisch

Peer reviewed


Abstract

Xylem hydraulic properties are of great significance for plant growth
and performance under drought.
The ability of plants to avoid drought-induced cavitation and loss of
hydraulic conductivity (K) can be characterized with vulnerability
curves (VC). A VC describes the sigmoidal relationship between
percentage loss of K (PLC) and xylem water potential (ψxyl). The ψ at 50% loss of conductance indicates a commonly used threshold for detrimental embolism (P50).
The slope (b) represents cavitation resistance.
The standard hydraulic method to determine VC's requires the measurement
of water flow rate (WFR) per pressure gradient through stem segments,
either by measuring outflow from the stem gravimetrically or inflow
using a flow meter.
In a comparative study using both measurements of inflow and outflow in
asparagus stems, we found considerable disparities in the resulting
shapes of VCs (P50 and b). We hypothesized that water uptake
of stem tissue occurs during the pressure-driven water transit,
particularly at low water potential and that differences in the initial K
might result from measurements of inflow or outflow.
To determine whether water uptake of stem tissue occurs during K
measurements of asparagus plants, we tested for effects of ψxyl
on the initial inflow and outflow K at different pressure gradients and
investigated if passive water uptake can be estimated by extrapolation
from the linear regression between WFR and pressure gradient based on K
at two pressures.
Initial K differed significantly between inlet and outlet measurements
at low ψxyl, whereas maximum K did not, providing evidence of water uptake during transit through droughted stems.
The resulting parameters P50 and b, and thus the shape of
VCs, differed as well.
The extrapolation resulted in the first estimate of passive water
uptake, leading to a convergence of the VC at inlet and at outlet.
We conclude that differences between in- and outflow may play a major
role in K measurements.