1021-4437/05/5204- © 2005
Russian Journal of Plant Physiology, Vol. 52, No. 4, 2005, pp. 459–462. Translated from Fiziologiya Rastenii, Vol. 52, No. 4, 2005, pp. 518–521.
Original Russian Text Copyright © 2005 by Chikov, Bakirova, Batasheva, Sergeeva.
Investigation of the role of source–sink relations in
the regulation of photosynthesis has shown that they
signiﬁcantly affect the direction of carbon photosyn-
thetic metabolism in the leaves . The consequences
of such inﬂuences also affect the relationships between
the plant shoots and roots: the removal of some above
ground organs, which consume assimilates, stimulates
the inﬂux of photosynthetic products to the roots and
partial defoliation has an opposite effect [2, 3]. Such a
change in the provision of the root system with assimi-
lates affects its operation. It was assumed that, when the
mass of sink organs reduces, the additional provision of
the roots with the products of photosynthesis stimulates
the uptake of mineral substances from soil and their
arrival from the roots in the leaves and therefore pro-
longs an active state of the photosynthetic apparatus.
This activates growth processes (especially in roots) 
and elevates the yield . However, it is so far unknown
how quickly and for how long the changes in the con-
tent of assimilates produced in the leaves affect the
operation of the root system and what products of plant
photosynthesis are most important for the interaction
between the leaf and root.
In this work we studied the effect of disturbance in
the source–sink relations (caused by the removal of the
growing axillary shoots or mature source leaves) on the
content and composition of labeled photosynthetic
products in the xylem sap after assimilation of
by the mature leaf in the light.
MATERIALS AND METHODS
Kidney bean (
L.) plants were
grown in the open air on leached chernozem at opti-
mum water supply. During the mass formation of grow-
ing axillary shoots and ﬁrst ﬂower buds, which
occurred when the plants were 50–55 cm in height, tip
leaﬂets of mature middle leaves of 40 plants were fed
in the light using a photosynthetic clip chamber.
was supplied to the chamber within 2 min in a
period from 10:00 to 12:00 a.m.
Fifteen minutes after
feeding, some leaves
C-assimilates were detached in order to
determine their initial radioactivity. A 15-min delay
was necessary for a complete release from the leaf of
produced in the course of photorespiration
because the emanation of
formed during photores-
piration is known to last for 10–15 min .
Effect of Defoliation or Excision of Growing Axillary Shoots
on the Composition of Labeled Products of Photosynthesis
in the Leaves and Xylem Sap of Kidney Bean
V. I. Chikov, G. G. Bakirova, S. N. Batasheva, and A. A. Sergeeva
Institute of Biochemistry and Biophysics, Kazan Research Center, Russian Academy of Sciences,
ul. Lobachevskogo 2/31, Kazan, 420111 Tatarstan, Russia;
fax: 7 (8432) 92-7747; e-mail: firstname.lastname@example.org
Received October 15, 2004
—The content of
C in the products of photosynthesis of the source leaf and xylem sap was investi-
gated in kidney bean (
L.) plants during the stage of mass tillering.
C partition was mea-
sured a day after two-minute photoassimilation of
by an individual mature leaf located in the middle part
of the shoot. The source–sink relations were disturbed by the excision of all mature leaves (except the source
leaf) or all growing axillary shoots. The leaves or growing axillary shoots were excised 15 min after leaf feeding
. A day later, in plants with excised growing axillary shoots, the content of
C in the source leaf was
by 18% higher and in those with removed leaves by 15% lower than in control plants. The next day after the
excision of growing axillary shoots, radioactivity of the xylem sap increased; after defoliation, both the volume
of the xylem sap and its speciﬁc radioactivity decreased. In the xylem sap of defoliated plants, the proportion
C in malate decreased more than six times, whereas the proportion of
C in amino acids somewhat
increased (1.5 times). In two days, the volume of the xylem sap exuded by treated plants became the same as
in control plants and its radioactivity decreased almost by an order of magnitude but essentially did not differ
in the both types of treatment. It is concluded that the processes occurring in the roots are governed by photo-
synthesis but its regulatory effect is limited by a photoperiod and largely depends on changes in the ratio
between biosynthesis of amino acids in the roots and leaves.
Key words: Phaseolus vulgaris - assimilate transport - roots - symplast - apoplast