Relaciones entre cavitación y cierre estomático en vides sometidas a déficit hídrico
Cavitation is a physiological dysfunction that takes place in the xylem of plants under water stress. It leads to a loss of hydraulic conductance as the vessels are filled with air. This has a negative impact on water supply and affects ΨL and canopy hydration. Stomatal clossure is an effective res...
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2011
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| Acceso en línea: | https://bdigital.uncu.edu.ar/fichas.php?idobjeto=4290 |
| Sumario: | Cavitation is a physiological dysfunction that takes place in the xylem of plants under water stress. It leads to a loss of hydraulic conductance as the vessels are filled with air. This has a negative impact on water supply and affects 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. A not vulnerable to cavitation plant may maintain higher stomatal conductances (gs) and therefore greater photosynthesis, by keeping opened stomata for longer periods of time. On the other hand, vulnerable plants should close their stomata in order to prevent runaway embolism and lost of hydraulic conductance.
This research intended to understand how stomatal control acts upon cavitation events in four contrasting grapevine varieties (Grenache, Syral, Malbec and Chardonnay).
We hypothesized that water stressed grapevines, reduce gs in order to avoid catastrophic embolism, and that some varieties, when grown under water stress, may acclimatize themselves by the development of a precise stomatal control, or a less vulnerable xylem, or both.
A randomized experimental plot inside a greenhouse was conducted (two FTSW treatmentes were determined, 100% and 50%). Quantitative measurements of gs, transpiration, photosynthesis and stem water potential were assessed from predawn to 4 pm, every one our. Two months later, cavitation curves were constructed, and the level of embolism reached along the day and plant hydraulic conductance, were calculated. Finally the relationship among gs, kL and embolism was determined.
By means of a mechanistical model that was constructed based on the water and vapour fluxes, kL, gs, and the vulnerability to cavitation of the xylematic tissue, we probed that gs is not the only variable that controls cavitation. It was determined that gs is coupled with kL, and this coupling is the responsible mechanism that achieves embolism control. This leaded us to conclude that grapevines under mild water stress, do not need to close their stomata in order to avoid cavitation. They only need a midmorning decrease in the difference between gs and kL (Δgs), therefore, no cost in terms of carbon assimilation is required. |
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