Plant Physiol, January 2002, Vol. 128, pp. 212-222
Effect of Temperature on Rates of Alternative and Cytochrome
Pathway Respiration and Their Relationship with the Redox Poise of the
Quinone Pool1
Owen K.
Atkin,*
Qisen
Zhang, and
Joe T.
Wiskich
Department of Biology, The University of York, P.O. Box 373, York,
YO10 5YW United Kingdom (O.K.A.); Department of Plant Sciences,
University of Adelaide, South Australia 5005, Australia (Q.Z.); and
School of Biological Sciences, Flinders University of South Australia,
South Australia 5042, Australia (J.T.W.)
We investigated the effect of short-term changes in
temperature on alternative (Alt) and cytochrome (Cyt) pathway
respiration, both in intact tissues and isolated mitochondria of
14-d-old cotyledons of soybean (Glycine max L. cv
Stevens). We also established the extent to which temperature alters
the interaction between the oxidizing pathways and the level of
ubiquinone (UQ) reduction (UQr/UQt). No
difference was found between the temperature coefficient of respiration
(Q10; proportional change per 10°C) of Alt
and Cyt pathway respiration in cotyledon slices
(Q10 = 1.92 and 1.86, respectively). In
isolated mitochondria, the Q10 of the fully activated Alt pathway (Q10 = 2.24-2.61) was always equal to, or higher than, that of Cyt
c oxidase (COX) alone
(Q10 = 2.08) and the complete Cyt
pathway (Q10 = 2.40-2.55). This was
true regardless of substrate or whether ADP was present. There was
little difference in the Q10 of the Cyt
pathway with or without ADP; however, the Q10 of COX was substantially lower in the
presence of an uncoupler (Q10 = 1.61)
than its absence (Q10 = 2.08). The
kinetics of Alt and Cyt pathway activity in relation to
UQr/UQt were not affected by temperature. For a
given UQr/UQt value, the proportion of maximum flux taking place was similar at all temperatures for both pathways (±ADP). However, the Q10 of the Alt and the
Cyt pathways (+ADP) increased with increasing
UQr/UQt. We conclude that the Alt pathway is
not less temperature sensitive than the Cyt pathway or COX per se and
that changes in the degree of control exerted by individual steps in
the respiratory apparatus could result in changes in the
Q10 of mitochondrial O2 uptake.
1
This work was supported by a Royal Society
Research Grant and Australian Research Council Postdoctoral Fellowship
(to O.K.A.) and by an Australian Research Council Grant (to
J.T.W.).
*
Corresponding author; e-mail oka1{at}york.ac.uk; fax
44-1904-432860.
© 2002 American Society of Plant Physiologists
