ISSN 10214437, Russian Journal of Plant Physiology, 2011, Vol. 58, No. 1, pp. 109–117. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © I.V. Seregin, A.D. Kozhevnikova, V.V. Gracheva, E.I. Bystrova, V.B. Ivanov, 2011, published in Fiziologiya Rastenii, 2011, Vol. 58, No.1, pp. 85–94.
Zinc (Zn) is an essential micronutrient because it is
a cofactor of many enzymes involved in nitrogen
metabolism, photosynthesis, auxin biosynthesis, the
synthesis of nucleic acids and proteins, and many
other processes . However, like other heavy metals,
high Zn concentrations could be toxic for diverse
physiological processes, which could result in the dis
turbances of plant growth and morphogenesis [1, 2].
In connection with uneven accumulation of heavy
metals in different plant tissues and organs, the prob
lem of their compartmentation deserves an attention
at investigation of metal toxicity and the mechanisms
of plant tolerance to them. Most of numerous studies
of Zn accumulation, concern aboveground organs of
excluders and hyperaccumulators, the two contrasting
plant groups accumulating metals in underground and
aboveground organs, respectively [3–5].
Much less is known about tissue Zn distribution in
the root system [3, 6], although just the analysis of
heavy metal distribution in the root tissues is required
for understanding the mechanisms of their toxicity
and morphological and physiological mechanisms of
their detoxification. The limited amount of such data
is related to insufficient development of histochemical
methods for heavy metal detection. Elaboration and
modification of such methods of Zn detection and also
the analysis of its tissue distribution in different root
parts is one of the tasks of this work. To check and con
firm the results of histochemical analysis, the content
of Zn in shoots and different root zones of maize seed
lings was determined.
Heavy metals penetrate the plant mainly through
its root system. Therefore, the primary plant response
to their action occurs just in the root, and this is clearly
manifested in growth suppression. In this connection,
the root is often used as a testsystem for investigation
of toxic effects of various heavy metals [7–14].
Tissue Zinc Distribution in Maize Seedling Roots
and Its Action on Growth
I. V. Seregin, A. D. Kozhevnikova, V. V. Gracheva, E. I. Bystrova, and V. B. Ivanov
Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya ul. 35, Moscow, 127276 Russia;
fax: 7 (495) 9778018; email: email@example.com
Received March 23, 2010
—Zinc (Zn) distribution over tissues and organs of maize (
L.) seedlings and its action on
root growth, cell division, and cell elongation were studied. Twodayold seedlings were incubated in the
0.25strength Hoagland solution containing 2 or 475
. Zn toxicity was assessed after the inhi
bition of primary root increment during the first and second days of incubation. The content of Zn was deter
mined by atomic absorption spectrometry in the apical (the first centimeter from the root tip) and basal (the
third centimeter from the kernel) root parts. Zn distribution in various tissues was studied by histochemical
methods, using a metallochromic indicator zincon and fluorescent indicator Zinpyr1 and light and confocal
scanning fluorescent light microscopy, respectively. To evaluate Zn effects on growth processes, the average
length of the meristem; the length of fully elongated cells; the number of meristematic cells in the cortex row;
and duration of the cell cycle were measured. When the Zn concentration in the solution was high, the Zn
content per weight unit was higher in the basal root part due to its accumulation in lateral root primordial. Zn
was also accumulated in both the meristem apoplast and cell protoplasts. In the basal and middle root parts,
Zn was detected essentially in all tissues predominantly in the apoplast. Zn inhibited both cell division and
elongation. Under Zn influence, the size of the meristem and the number of meristematic cells decreased,
which was determined by an increase in the cell cycle duration. The length of the fully elongated cells was also
reduced. A comparison of Zn distribution and growthsuppressing activity with other heavy metals studied
earlier allows a conclusion that toxic action of heavy metals is mainly determined by physical and chemical
properties of their ions and specific patterns of their transport and distribution. As a result, two basic processes
determining root growth, e.g., cell division and elongation, could be affected differently.
Keywords: Zea mays
, zinc, root, growth, cell division, cell elongation.
—time of the cell life in the meristem.