Spatio-temporal decoupling of stomatal and mesophyll conductance induced by vein cutting in leaves of Helianthus annuus

Reduction of hydraulic conductance to the canopy has been shown to result in stomatal responses to limit transpiration. To test for similar responses to perturbations of the hydraulic network in leaves, we simultaneously measured leaf gas exchange with spatially explicit chlorophyll-a fluorescence a...

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Main Authors: David Thomas Hanson, Laura E Green, William ePockman
Format: Article
Language:English
Published: Frontiers Media S.A. 2013-09-01
Series:Frontiers in Plant Science
Subjects:
Online Access:http://journal.frontiersin.org/Journal/10.3389/fpls.2013.00365/full
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spelling doaj-3b25a7aff65640cf8335679ee4f117062020-11-24T23:24:41ZengFrontiers Media S.A.Frontiers in Plant Science1664-462X2013-09-01410.3389/fpls.2013.0036552140Spatio-temporal decoupling of stomatal and mesophyll conductance induced by vein cutting in leaves of Helianthus annuusDavid Thomas Hanson0Laura E Green1William ePockman2University of New MexicoUniversity of New MexicoUniversity of New MexicoReduction of hydraulic conductance to the canopy has been shown to result in stomatal responses to limit transpiration. To test for similar responses to perturbations of the hydraulic network in leaves, we simultaneously measured leaf gas exchange with spatially explicit chlorophyll-a fluorescence and leaf temperature to examine the effects of cutting a primary leaf vein in Helianthus annuus. We repeated the leaf treatment at each of three different vapor pressure deficits and monitored the short-term dynamics of gas exchange following the treatment. Immediately after treatment, photosynthesis and stomatal conductance showed a transient wrong-way response in which photosynthesis declined despite increased stomatal conductance. Comparisons of fluorescence and temperature across the leaf showed that both photosynthesis and stomatal conductance were transiently patchy across the measured leaf area, but that the patchiness of the two processes did not correspond in space or time. This suggests that photosynthesis and stomatal conductance respond to vein cutting-induced cavitation via different mechanisms. Because the stomatal response varied by VPD condition but photosynthesis did not, it is likely that stomatal conductance, but not photosynthesis, responded to a hydraulic signal. In contrast, we hypothesize that photosynthesis declined due to a wound-induced electrical signal that has recently been shown to transiently decrease mesophyll conductance to CO2. The interaction of epidermal hydraulics and the electrical signal across the leaf likely created a patchy pattern of chlorophyll fluorescence and leaf temperature that cannot be explained through the action of a single signal.http://journal.frontiersin.org/Journal/10.3389/fpls.2013.00365/fullPhotosynthesiscavitationtranspirationStomatal conductancemesophyll conductancestomatal patchiness
collection DOAJ
language English
format Article
sources DOAJ
author David Thomas Hanson
Laura E Green
William ePockman
spellingShingle David Thomas Hanson
Laura E Green
William ePockman
Spatio-temporal decoupling of stomatal and mesophyll conductance induced by vein cutting in leaves of Helianthus annuus
Frontiers in Plant Science
Photosynthesis
cavitation
transpiration
Stomatal conductance
mesophyll conductance
stomatal patchiness
author_facet David Thomas Hanson
Laura E Green
William ePockman
author_sort David Thomas Hanson
title Spatio-temporal decoupling of stomatal and mesophyll conductance induced by vein cutting in leaves of Helianthus annuus
title_short Spatio-temporal decoupling of stomatal and mesophyll conductance induced by vein cutting in leaves of Helianthus annuus
title_full Spatio-temporal decoupling of stomatal and mesophyll conductance induced by vein cutting in leaves of Helianthus annuus
title_fullStr Spatio-temporal decoupling of stomatal and mesophyll conductance induced by vein cutting in leaves of Helianthus annuus
title_full_unstemmed Spatio-temporal decoupling of stomatal and mesophyll conductance induced by vein cutting in leaves of Helianthus annuus
title_sort spatio-temporal decoupling of stomatal and mesophyll conductance induced by vein cutting in leaves of helianthus annuus
publisher Frontiers Media S.A.
series Frontiers in Plant Science
issn 1664-462X
publishDate 2013-09-01
description Reduction of hydraulic conductance to the canopy has been shown to result in stomatal responses to limit transpiration. To test for similar responses to perturbations of the hydraulic network in leaves, we simultaneously measured leaf gas exchange with spatially explicit chlorophyll-a fluorescence and leaf temperature to examine the effects of cutting a primary leaf vein in Helianthus annuus. We repeated the leaf treatment at each of three different vapor pressure deficits and monitored the short-term dynamics of gas exchange following the treatment. Immediately after treatment, photosynthesis and stomatal conductance showed a transient wrong-way response in which photosynthesis declined despite increased stomatal conductance. Comparisons of fluorescence and temperature across the leaf showed that both photosynthesis and stomatal conductance were transiently patchy across the measured leaf area, but that the patchiness of the two processes did not correspond in space or time. This suggests that photosynthesis and stomatal conductance respond to vein cutting-induced cavitation via different mechanisms. Because the stomatal response varied by VPD condition but photosynthesis did not, it is likely that stomatal conductance, but not photosynthesis, responded to a hydraulic signal. In contrast, we hypothesize that photosynthesis declined due to a wound-induced electrical signal that has recently been shown to transiently decrease mesophyll conductance to CO2. The interaction of epidermal hydraulics and the electrical signal across the leaf likely created a patchy pattern of chlorophyll fluorescence and leaf temperature that cannot be explained through the action of a single signal.
topic Photosynthesis
cavitation
transpiration
Stomatal conductance
mesophyll conductance
stomatal patchiness
url http://journal.frontiersin.org/Journal/10.3389/fpls.2013.00365/full
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