TY  - JOUR
AU  - Jahnke, S.
AU  - Pieruschka, R.
TI  - Air pressure in clamp-on leaf chambers: a neglected issue in gas exchange measurements
JO  - The journal of experimental botany
VL  - 57
SN  - 0022-0957
CY  - Oxford
PB  - Univ. Press
M1  - PreJuSER-52636
SP  - 2553 - 2561
PY  - 2006
N1  - Record converted from VDB: 12.11.2012
AB  - Air pressure in leaf chambers is thought to affect gas exchange measurements through changes in partial pressure of the air components. However, other effects may come into play when homobaric leaves are measured in which internal lateral gas flow may occur. When there was no pressure difference between the leaf chamber and ambient air (DeltaP=0), it was found in previous work that lateral CO(2) diffusion could affect measurements performed with clamp-on leaf chambers. On the other hand, overpressure (DeltaP>0) in leaf chambers has been reported to minimize artefacts possibly caused by leaks in chamber sealing. In the present work, net CO(2) exchange rates (NCER) were measured under different DeltaP values (0.0-3.0 kPa) on heterobaric and homobaric leaves. In heterobaric leaves which have internal barriers for lateral gas movement, changes in DeltaP had no significant effect on NCER. For homobaric leaves, effects of DeltaP>0 on measured NCER were significant, obviously due to lateral gas flux inside the leaf mesophyll. The magnitude of the effect was largely defined by stomatal conductance; when stomata were widely open, the impact of DeltaP on measured NCER was up to 7 mumol CO(2) m(-2) s(-1) kPa(-1). Since many other factors are also involved, neither DeltaP=0 nor DeltaP>0 was found to be the 'one-size fits all' solution to avoid erroneous effects of lateral gas transport on measurements with clamp-on leaf chambers.
KW  - Air Pressure
KW  - Artifacts
KW  - Botany: instrumentation
KW  - Botany: methods
KW  - Botany: standards
KW  - Carbon Dioxide: chemistry
KW  - Carbon Dioxide: metabolism
KW  - Diffusion
KW  - Photosynthesis
KW  - Plant Leaves: metabolism
KW  - Plant Transpiration: physiology
KW  - Carbon Dioxide (NLM Chemicals)
KW  - J (WoSType)
LB  - PUB:(DE-HGF)16
C6  - pmid:16820393
UR  - <Go to ISI:>//WOS:000239901500009
DO  - DOI:10.1093/jxb/erl003
UR  - https://juser.fz-juelich.de/record/52636
ER  -