Stomatal conductance and photosynthesis vary linearly with plant hydraulic conductance in ponderosa pine
Year: 2001
Type: article
Abstract: Recent work has shown that stomatal conductance (gs) and assimilation (A) are responsive to changes in the hydraulic conductance of the soil to leaf pathway (KL), but no study has quantitatively described this relationship under controlled conditions where steady‐state flow is promoted. Under steady‐state conditions, the relationship betweengs, water potential (Ψ) andKLcan be assumed to follow the Ohm's law analogy for fluid flow. When boundary layer conductance is large relative togs, the Ohm's law analogy leads togs=KL(Ψsoil−Ψleaf)/D, whereDis the vapour pressure deficit. Consequently, if stomata regulate Ψleafand limitA, a reduction inKLwill causegsandAto decline. We evaluated the regulation of ΨleafandAin response to changes inKLin well‐watered ponderosa pine seedlings (Pinus ponderosa). To varyKL, we systematically reduced stem hydraulic conductivity (k) using an air injection technique to induce cavitation while simultaneously measuring Ψleafand canopy gas exchange in the laboratory under constant light andD. Short‐statured seedlings (< 1 m tall) and hour‐long equilibration times promoted steady‐state flow conditions. We found that Ψleafremained constant near − 1·5 MPa except at the extreme 99% reduction ofkwhen Ψleaffell to − 2·1 MPa. Transpiration,gs,AandKLall declined with decreasingk(P< 0·001). As a result of the near homeostasis in bulk Ψleaf,gsandAwere directly proportional toKL(R2> 0·90), indicating that changes inKLmay affect plant carbon gain.
Source: Plant Cell & Environment
Authors: R. M. Hubbard, M. G. Ryan, V. Stiller, J. S. Sperry
Institutions: US Forest Service, University of Utah
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2171608029