Plant Physiol, November 2001, Vol. 127, pp. 1279-1286
An Off-Line Implementation of the Stable Isotope Technique for
Measurements of Alternative Respiratory Pathway
Activities1
Oscar W.
Nagel,*
Susan
Waldron, and
Hamlyn G.
Jones
Division of Environmental and Applied Biology, School of Life
Sciences, University of Dundee, Dundee DD1 4HN, United Kingdom (O.W.N.,
H.G.J); and Life Sciences Community Stable Isotope Facility, Scottish
Universities Environmental Research Centre, East Kilbride, Glasgow G75
0QF, United Kingdom (S.W.)
In situ measurements of alternative respiratory pathway
activity are needed to provide insight into the energy efficiency of
plant metabolism under various conditions in the field. The only
reliable method at present to measure alternative oxidase (AOX)
activity is through measurement of changes in
18O(O2), which to date has only been used in
laboratory environments. We have developed a cuvette system to measure
partitioning of electrons to AOX that is suitable for off-line use and
for field experiments. Plant samples are enclosed in airtight cuvettes
and O2 consumption is monitored. Gas samples from the
cuvette are stored in evacuated gas containers until measurement of
18O(O2). We have validated this method using
differing plant material to assess AOX activity. Fractionation factors
were calculated from 18O(O2) measurements,
which could be measured with an accuracy and precision to 0.1
and
0.3, respectively. Potential sources of error are discussed and
quantified. Our method provides results similar to those obtained with
laboratory incubations on-line to a mass spectrometer but greatly
increases the potential for adoption of the stable isotope method.
1
This work was supported by the UK National
Environmental Research Council (grant no. 9/04503).
*
Corresponding author; e-mail o.w.nagel{at}dundee.ac.uk; fax
44-1382-344275.
© 2001 American Society of Plant Physiologists
