Effects of enhanced hydraulic supply for foliage on stomatal responses in little-leaf linden (<Emphasis Type="Italic">Tilia cordata</Emphasis> Mill.) |
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Authors: | Arne Sellin Priit Kupper |
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Institution: | (1) Institute of Botany and Ecology, University of Tartu, Lai 40, 51005 Tartu, Estonia |
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Abstract: | Responses of leaf conductance (g
L) to variation in environmental and plant hydraulic factors were examined on intact and detached shoots of little-leaf linden
(Tilia cordata Mill.) with respect to branch position in the crown. Using detached shoots, we manipulated leaf water supply and light availability
in order to separate the effects of insufficient hydraulic supply and low irradiance. The intact upper-crown leaves demonstrated
2.0–2.2 times higher (P < 0.001) daily maxima of g
L compared to the lower-crown leaves growing in the shadow of upper branches. Mean soil-to-leaf conductance (G
T) was 1.9 times higher (P < 0.001) for the upper-crown foliage compared to that of the lower crown. The total hydraulic resistance was distributed:
soil to distal shoots—41–51%, 25-cm distal shoots—10–15% and leaves—39–44%. In lower branches, g
L was constrained by both low light availability and limited water supply; in upper branches, only by irradiance. Artificial
reduction of hydraulic constraints raised bulk leaf water potential (Ψ
L) and made g
L less sensitive to changes in both atmospheric and plant factors. Stomatal responses to leaf-to-air vapour pressure difference
(VPD) were significantly modified by leaf water status: high Ψ
L seemingly inverted the g
L versus VPD relationship. Enhanced water supply increased g
L and transpiration rate (E) in the lower-crown foliage, but not in the upper-crown foliage. The results support the idea that leaves in the lower canopy
are hydraulically more constrained than those in the upper canopy. |
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Keywords: | Hydraulic conductance Hydraulic constraints Irradiance Leaf conductance Leaf water potential Light availability Soil-to-leaf conductance Tilia cordata Vapour pressure difference Water supply |
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