Plant and Soil 226: 113–116, 2000.
© 2000 Kluwer Academic Publishers. Printed in the Netherlands.
113
Diverse responses of root cell structure to aluminium stress
M.
ˇ
Ciamporov
´
a
Institute of Botany, Slovak Academy of Sciences, D´ubravsk´a cesta 14, 842 23 Bratislava, Slovak Republic
Key words: aluminium, root cells, stress adaptation, structural response, Zea mays
Abstract
Plant cells respond to a certain stress factor in different ways depending on their developmental stage and type of
tissue. Structural damage may be severe or even lethal in individual cells within a tissue that exhibits moderate
or no effects of stress. In the case of aluminium toxicity, detailed observations of root tips of 3 day old Zea
mays L., cv. TO360 seedlings revealed differences in the response of some cells. Two different structural changes
appeared within root epidermis just behind the root cap. Cells with dark and shrunken cytoplasm occurred next to
swollen cells with preserved cellular compartments. Within the root cortex, individual cells or a few cells of a file
have severely damaged cytoplasm, in contrast to almost undisturbed cytoplasm of adjacent cells. Such extremely
sensitive cells appear irregularly within the root apex. Their structural similarity with cells that are observed after
a hypersensitive response in infected plant tissues suggests a role to accumulate aluminium, in order to allow the
surrounding tissue to survive the stress.
Introduction
Stress-induced alterations of cell ultrastructuredepend
on both developmental and functional cell features.
There are numerous examples of differences in struc-
tural responses to a certain stress factor, between cells
of different age as well as between the cells belong-
ing to different tissues. Cells of maize root epidermis
were severely damaged while the neighbouring hypo-
dermal cells revealed undisturbed structural integrity
under copper stress (Ouzounidou et al., 1995). Simil-
arly, structure of the cells of epidermis and peripheral
cortex layers suffered more from aluminium than the
cells in the central cylinder (Budíková et al., 1997).
However, these responses could be ascribed to the loc-
ation of the tissues on the root periphery and their
immediate contact with the stress source, rather than
to the abilities of the tissue to respond specifically.
Along the root axis of aluminium stressed maize seed-
lings, the younger epidermal cells at about 2–20 mm
from the root tip undergo serious structural damage
while the older cells more proximally located do not
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75829
accumulate aluminium or callose, and their structure
remains unaffected (Budíková, 1999).
In our previous experiments, individual severely
damaged cells with prominent deposits in their cell
walls appeared within the cortex and stelar par-
enchyma of maize roots exposed to copper stress
(Ouzounidou et al., 1995). Increased concentration of
Al
3+
in the root medium induced severe damage to
the ultrastructure of peripheral root cap cells, cells of
epidermis and of peripheral cortical layers within the
meristematic and elongation root zones, while the cells
of more centripetally located tissues revealed only
higher vacuolation and irregularly thickened cell walls
(Bennet et al., 1985; Ikeda and Tadano, 1993; Mari-
enfeld et al., 1995). The aim of this paper is to point
to the phenomenon of diverse stress responses in in-
dividual cells within the tissues of aluminium stressed
maize roots.
Material and methods
Seeds of Zea mays L., cv. TO360 germinated on filter
paper at 25
◦
C for 72 h in darkness. Seedlings with
primary roots 40–50 mm long were transferred into
the solution of 0.1 mM CaCl
2
, (control) or exposed to