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Decoupling the influence of leaf and root hydraulic conductances on stomatal conductance and its sensitivity to vapour pressure deficit as soil dries in a drained loblolly pine plantation
Author(s) -
DOMEC JEANCHRISTOPHE,
NOORMETS ASKO,
KING JOHN S.,
SUN GE,
MCNULTY STEVEN G.,
GAVAZZI MICHAEL J.,
BOGGS JOHNNY L.,
TREASURE EMRYS A.
Publication year - 2009
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2009.01981.x
Subject(s) - stomatal conductance , vapour pressure deficit , transpiration , hydraulic conductivity , botany , elongation , horticulture , chemistry , water content , water potential , agronomy , soil water , environmental science , biology , photosynthesis , soil science , geology , materials science , geotechnical engineering , ultimate tensile strength , metallurgy
The study examined the relationships between whole tree hydraulic conductance ( K tree ) and the conductance in roots ( K root ) and leaves ( K leaf ) in loblolly pine trees. In addition, the role of seasonal variations in K root and K leaf in mediating stomatal control of transpiration and its response to vapour pressure deficit ( D ) as soil‐dried was studied. Compared to trunk and branches, roots and leaves had the highest loss of conductivity and contributed to more than 75% of the total tree hydraulic resistance. Drought altered the partitioning of the resistance between roots and leaves. As soil moisture dropped below 50%, relative extractable water (REW), K root declined faster than K leaf . Although K tree depended on soil moisture, its dynamics was tempered by the elongation of current‐year needles that significantly increased K leaf when REW was below 50%. After accounting for the effect of D on g s , the seasonal decline in K tree caused a 35% decrease in g s and in its sensitivity to D , responses that were mainly driven by K leaf under high REW and by K root under low REW. We conclude that not only water stress but also leaf phenology affects the coordination between K tree and g s and the acclimation of trees to changing environmental conditions.