1021-4437/01/4805- $25.00 © 2001
Russian Journal of Plant Physiology, Vol. 48, No. 5, 2001, pp. 595–600. From Fiziologiya Rastenii, Vol. 48, No. 5, 2001, pp. 692–697.
Original English Text Copyright © 2001 by Kong, Zhou, Wang.
Mitochondria are major organelles in the metabolic
production of energy and electron transport in cells.
Mitochondrial electron transport from ubiquinone to O
via the CP (cytochrome pathway) is coupled to ATP
synthesis, and its terminal oxidase (cytochrome oxi-
dase) is sensitive to KCN. Another electron ﬂow via the
AP (alternative pathway) is not coupled to ATP produc-
tion, and its terminal oxidase (alternative oxidase) is
sensitive to SHAM . Although AP is found in all
plants investigated to date, its only conﬁrmed function
is the thermogenesis in the inﬂorescences of the
Araceae plants [1, 2].
Stress conditions, such as low temperature [3–5],
drought  and plant pathogen attack , appear to
inﬂuence the AP activity, thus indicating that the AP
may take part in stress response of plants [8, 9]. For
example, abundant evidence has been accumulated
upon the relationship between AP and low temperature.
However, knowledge about respiratory metabolism
under saline stress conditions is still lacking .
Under saline stress, ion uptake by cells is an integral
component of osmotic adjustment necessary for adap-
tion to salt . Because of the deleterious effects of
high ion concentrations on cytosolic metabolism, pre-
cise regulation of intracellular ion accumulation and
vacuolar compartmentation are needed . This regu-
lation requires energy mainly in the form of ATP gener-
ated from respiration . The production of solutes is
linked not only to the supply of reducing power and car-
bon skeletons by respiration, but also to the energy pro-
duction which depends on the efﬁciency of the phos-
phorylation . In this context, the role of the non-
phosphorylating AP, which is a common feature of
higher plant respiration [2, 15], has not been elucidated.
In the present paper, two wheat cultivars, 89122 and
Longchun13, differing in salt tolerance were used to
determine the effects of salt stress on dry matter pro-
contents, ATP content, proline
concentration, yield and respiratory pathways, espe-
cially the alternative pathway, in leaves. The objective
of the experiments reported here was to investigate the
possible participation of AP in total respiration of
spring wheat leaves, and to assess the correlation
between the respiratory pattern and some physiological
processes during salt acclimation.
MATERIALS AND METHODS
Plant growth and stress treatments.
Seeds of two
spring wheat cultivars (89122 and Longchun13)
imbibed for 12 h and then germinated in trays of ver-
Physiological Characteristics and Alternative Respiratory
Pathway under Salt Stress in Two Wheat Cultivars Differing
in Salt Tolerance*
Y. Kong, G. Zhou, and Y. Wang
The State Key Laboratory of Arid Agroecology, Lanzhou University, Lanzhou, 730000 P.R. China;
fax: +86-0931-8912823; e-mail: firstname.lastname@example.org
Received October 5, 2000
—Changes in respiratory pathway, dry weight, contents of proline, ATP, Na
under ﬁve salinity treatments in the leaves of plants of spring wheat (
L.). Two cultivars dif-
fering in salt resistance, namely, 89122 (salt-tolerant) and Longchun13 (salt-sensitive), were used. The decrease
in dry weight and K
content was observed with the increasing NaCl concentrations, but more in cv. 89122
plants than in Longchun13 plants. Contents of proline and Na
in both cvs increased greatly, but the former
increased more in 89122 while the latter more in Longchun13 plants. In all salinity treatments tested, a salt-
induced increase in the activity of the alternative pathway was found, although cytochrome pathway (CP) still
remained the main electron transport pathway. ATP production changed in parallel with CP operation. Cv.
89122 plants could produce more ATP than cv. Longchun13 plants exposed to each salinity treatment and their
ATP generation could even be stimulated in contrast to its rapidly decline in Longchun13 plants with increased
salinity stress. The possible relationship between respiration metabolism and above mentioned physiological
changes is discussed.
Key words: Triticum aestivum - salt stress - salt-tolerant - respiratory pathways
* This article was submitted by the authors in English.
: AP—alternative pathway; CP—cytochrome path-
way; SHAM—salicylhydroxamic acid.