1021-4437/04/5103- © 2004
Russian Journal of Plant Physiology, Vol. 51, No. 3, 2004, pp. 342–347. Translated from Fiziologiya Rastenii, Vol. 51, No. 3, 2004, pp. 383–389.
Original Russian Text Copyright © 2004 by Bragina, Ponomareva, Drozdova, Grinieva.
Plants often experience various types of ﬂooding in
their natural habitats. It is thought that the lack of oxy-
gen is the main injuring factor of submergence [1–3].
Flooding of the root system arrests growth and dimin-
ishes the productivity in the majority of terrestrial
plants . Being a self-regulating system, the plant is
capable of developing a survival strategy under stress-
ful conditions. It should be borne in mind that the action
of stress factor on the underground plant part causes a
series of physiological changes in the aboveground
organs; these changes reﬂect either plant adaptation or
damage. The responses of leaf machinery to waterlog-
ging of the root system are studied much less than the
adaptive mechanisms operating in roots. Moreover, the
stress responses in leaves of different ages remain com-
pletely uninvestigated, even though such leaves are
often considered as different organs .
It is known that plant adaptation to stress conditions
requires additional material and energy resources, mak-
ing processes such as photosynthesis and respiration
more signiﬁcant . The dynamics of photosynthetic
activity in plants exposed to hypoxic stress depends to
a large extent on species-speciﬁc tolerance and duration
of stress treatment [4, 7–9]. According to Kozlowsky
and Pallardy , who studied a number of resistant
and nonresistant species, the photosynthetic rates in
plants susceptible to O
deﬁcit decreased by 10–90%
under root hypoxia . At the same time, a prolonged
period of O
deﬁciency may have a hardening effect on
photosynthesis, even in nonresistant plants .
The physiological regulation of photosynthesis
involves stomata. It is commonly accepted that the
decrease in stomatal conductance upon soil ﬂooding
decelerates transpiration [12–14], thus helping plants to
prevent wilting. On the other hand, the decrease in sto-
matal aperture under these conditions may restrict the
photosynthetic activity . The parallel studying of
transpiration and photosynthesis may clarify the role of
stomata in CO
uptake under ﬂooding.
The study of respiration under oxygen deﬁciency is
particularly important in relation to speciﬁcity of the
stress treatment. We showed earlier that changes in
oxygen content in water medium during a 15-day
waterlogging of maize roots resulted in a gradual
decline of dark respiration in leaves . According to
other studies, the soil ﬂooding stimulated dark respira-
tion in sunﬂower leaves  but inhibited O
tomato leaves . The controversial data on the
dynamics of dark respiration in leaves of waterlogged
plants necessitate further careful investigations.
Presently, much interest is focused on primary
responses to adverse environmental cues. These
responses are often opposite to secondary changes
caused by a prolonged action of a stress factor [11, 14].
One may expect that studying the effects of prolonged
root ﬂooding will disclose the primary and secondary
responses of leaves of different ages and reveal tempo-
ral changes in the whole plant resistance.
Photosynthesis and Dark Respiration in Leaves of Different Ages
of Partly Flooded Maize Seedlings
T. V. Bragina, Yu. V. Ponomareva, I. S. Drozdova, and G. M. Grinieva
Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya ul. 35, Moscow, 127276 Russia;
fax: 7 (095) 977-8018; e-mail: email@example.com
Received August 15, 2002
—Maize seedlings were ﬂooded for periods from 1 to 15 days, and the leaves of different ages were
then taken to examine photosynthesis, dark respiration, transpiration, chlorophyll content, and some morpho-
metric parameters. The responses of leaves to root submergence essentially depended on the leaf layer and the
treatment duration. A short-term ﬂooding (1–24 h) induced primary stress responses in the ﬁrst leaf. Photosyn-
thesis and respiration in this leaf oscillated around the control levels with amplitudes of
60%, respectively. After a longer ﬂooding, the CO
exchange in the second leaf was suppressed, while oxygen
uptake was stimulated. In the third leaf, which was formed during submergence, the photosynthetic rate
increased and the respiratory activity decreased. The transpiration rate did not change in these leaves for 15 days
of ﬂooding. The hypoxic treatment, at its early stages, retarded growth and disturbed the source–sink relations.
At later stages the plants adapted to hypoxic environment: the seedling growth was restored, which elevated the
demand for assimilates and stimulated photosynthesis. It is concluded that plants overcome negative impact of
the root hypoxia at the systemic level.
Key words: Zea mays - ﬂooding - photosynthesis - respiration - transpiration - leaf layers