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Relationship between stem CO 2 efflux, stem sap velocity and xylem CO 2 concentration in young loblolly pine trees
Author(s) -
MAIER CHRIS A.,
CLINTON BARTON D.
Publication year - 2006
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.1365-3040.2006.01511.x
Subject(s) - diel vertical migration , xylem , vitis vinifera , canopy , phloem , botany , respiration , cambium , chemistry , horticulture , biology , ecology
We measured diel patterns of stem surface CO 2 efflux ( E s , µ mol m −2 s −1 ), sap velocity ( v s , mm s −1 ) and xylem CO 2 concetration ([CO 2 ]) ( X s , %) in 8‐year‐old loblolly pine trees during the spring to determine how v s and X s influence E s . All trees showed a strong diel hysteresis between E s and stem temperature, where at a given temperature, E s was lower during the day than at night. Diel variations in temperature‐independent E s were correlated with v s ( R 2 = 0.54), such that at maximum v s , E s was reduced between 18 and 40%. However, this correlation may not represent a cause‐and‐effect relationship. In a subset of trees, v s was artificially reduced by progressively removing the tree canopy. Reducing v s to near zero had no effect on E s and did not change the diel hysteretic response to temperature. Diel X s tended to decrease with v s and increase with E s , however, in defoliated trees, large increases in X s , when v s ≈ 0, had no effect on E s . We conclude that at this time of the year, E s is driven primarily by respiration of cambium and phloem tissues and that sap flow and xylem transport of CO 2 had no direct influence on E s .