| Sumario: | Cavitation is a physiological dysfunction that takes place in the xylem of water stressed
plants. It leads to a loss of hydraulic conductance (kL) as the vessels are filled with air. This
impacts water supply, water potential (ΨL) and canopy hydration. Stomatal clossure is an
effective response upon diminishing momentary or seasonal foliar hydraulic contents.
Depending on each type of plant, stomata may close preventing catastrophic cavitations.
This research intended to understand how stomatal control acts upon cavitation
events in two contrasting grapevine varieties, Syrah and Grenache. A mechanistic was
developed model based on the water and vapour fluxes, kL, stomata conductance (gs),
and the vulnerability to cavitation of the xylematic tissue. The theoretical model explains
how plants respond to drought and avoid catastrophic cavitation. Water stressed grapevines
couple their gs with their kL in order to avoid embolism. It is not stomatal closure,
by istself, the controlling mechanism. Grapevines under mild water stress, do not need
to completely close their stomata in order to avoid cavitation, therefore, photosynthesis
is not completely impeded, and the cost in terms of carbon assimilation is less than
expected for other species.
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Biblioteca Digital de Vanguardia