1021-4437/05/5205- © 2005
Russian Journal of Plant Physiology, Vol. 52, No. 5, 2005, pp. 629–634. Translated from Fiziologiya Rastenii, Vol. 52, No. 5, 2005, pp. 708–714.
Original Russian Text Copyright © 2005 by Cherkozianova, Vysotskaya, Veselov, Kudoyarova.
A deﬁciency of water and mineral nutrients in soil is
known to result in root growth acceleration [1, 2]. It
seems evident that a predominant development of the
organ supplying the plant with water and ions provides
for its survival under stress conditions. A physiological
importance of this plant growth response determined an
interest of researchers to its studying. In these studies,
a great attention was paid to the hormone involvement
[3–5]. It was shown that a deﬁciency of water and ions
in soil resulted in cytokinin depletion and ABA accu-
mulation in plants [6, 7]. Cytokinins are known to acti-
vate shoot growth and to retard root elongation .
Therefore, it was supposed that a decrease in the cyto-
kinin content induced by water and ion deﬁciencies
could facilitate relative root-growth acceleration .
According to some published data, ABA accumulation
can also favor root growth [3, 5, 9]. Since predominant
root growth occurs under deﬁciency of not only mineral
nutrients but also water, the attention of researchers was
attracted to the fact of reduced hydraulic conductivity
under nutrient stress [10, 11].
The objective of this work was to check whether dis-
turbances in water regime mediate the effects of deﬁ-
cient nutrition on plant growth and hormonal balance.
MATERIALS AND METHODS
Experiments were performed on durum wheat
Desf., cv. Bezenchukskaya 139)
plants grown on 10% Hoagland–Arnon nutrient
medium. Earlier, we have found that this medium is
the best for wheat growth . Plant were grown
under an irradiance of 90 W/m
, a 14-h photoperiod,
and a temperature of
. Seven days after seed
germination, the nutrient medium was diluted to 1%.
At this time, plants were actively developing the ﬁrst
true leaf. At this developmental stage, we divided the
shoot into two parts: (1) unfolded blade of the ﬁrst
leaf (mature leaf zone) and (2) the base of the ﬁrst
leaf, the coleoptile, and the primordium of the sec-
ond leaf (growing part of the shoot). Preliminary
experiments with India ink marks showed that a
growing leaf zone was within the coleoptile. After
one and two days, we determined fresh and dry
weights of shoots and roots. Simultaneously and at
the same time of the day, we measured the rate of
transpiration (a loss in the weight of the glass, con-
taining 50 ml of nutrient medium and ten seedlings,
for 10 min). To prevent water evaporation from the
surface of nutrient medium, the glass was covered
with aluminum foil with the holes for seedlings.
Hormonal Control of the Shoot-to-Root Ratio
Is Not Related to Water Deficiency in Wheat Plants
under Mineral Deficiency
A. V. Cherkozianova*, L. B. Vysotskaya*, S. Yu. Veselov**, and G. R. Kudoyarova*
*Institute of Biology, Ufa Research Center, Russian Academy of Sciences,
pr. Oktyabrya 69, Ufa, 450054 Russia;
**Bashkortostan State University,
ul. Frunze 32, Ufa, 450074 Russia
Received June 24, 2004
—We measured the content of hormones, the rate of growth, and some parameters of water regime
(water content, transpiration, and stomatal and hydraulic conductivities) one and two days after wheat plant
transfer from 10 to 1% Hoagland–Arnon nutrient medium. It was shown that, a day after dilution of nutrient
solution, the content of various cytokinin forms decreased in the xylem sap, shoots, and roots. This decrease
was most pronounced in the case of zeatin in the xylem sap and zeatin riboside in the mature zone of the ﬁrst
leaf. ABA was found to accumulate in shoots. A day after dilution of nutrient solution, we observed root elon-
gation evidently induced by mineral nutrient deﬁciency, and this accelerated root growth was maintained later.
Two days after dilution of nutrient solution, we observed the slowing of shoot weight accumulation, whereas
root weight remained unchanged. Plant growth response could be related to ABA accumulation in shoots and
cytokinin depletion in the whole plant. A reduced hydraulic conductivity and water content in the growing leaf
zone was detected only two days after dilution of nutrient solution. Thus, changes in the growth rates and hor-
mone contents could not result from disturbances in water regime induced by mineral nutrient deﬁciency.
Key words: Triticum durum - mineral nutrition - cytokinins - ABA - growth - water regime