ISSN 1021-4437, Russian Journal of Plant Physiology, 2009, Vol. 56, No. 4, pp. 488–494. © Pleiades Publishing, Ltd., 2009.
Published in Russian in Fiziologiya Rastenii, 2009, Vol. 56, No. 4, pp. 539–545.
Phytohormones greatly affect root growth and
development [1-4]. There have been numerous and
often contradictory reports concerning the effects of
ethylene on root growth. Ethylene tends to be regarded
as a regulator of root growth in response to environ-
mental stimuli. In some cases, it has been suggested
that ethylene is not the main regulatory factor of root
growth and that its action probably occurs only at early
stages of development . Nevertheless, there is
emerging evidence that ethylene could act in more pro-
cesses than it was previously thought and even as a
root-generated signal .
Most experimental studies on ethylene effects on
root growth chieﬂy analyze the response to ethylene
after prolonged treatments. To the best of our knowl-
edge, only a limited number of reports refers to the
early response of roots to ethylene [6-8]. In long-term
This text was submitted by the authors in English.
(many hours or days) experiments, low concentrations
may enhance root elongation, whereas high concentra-
tions inhibit it and simultaneously enlarge root diame-
ter [7, 9].
Ethylene is also involved in a diverse array of cellu-
lar, developmental and stress-related processes in
plants. A number of examples of the role played by eth-
ylene in the morphogenesis in plants have been
described. The ethylene participates, for example, in
the control of the formation of reaction wood, ﬂoral
induction, sex determination, ﬂooding-induced shoot
elongation and leaf abscission . At the cellular
level, ethylene may be necessary for the formation of a
functional root cap , controls the differentiation of
root hairs [12, 13] and probably regulates the ﬁnal
length attained by root cells .
An important research topic concerns the precise
role of plant hormones in cell diferentiation. In many
instances, it is not clear whether the hormones prima-
rily inﬂuence differentiation by early regulating cell
fate or by acting during relatively later development.
Ethylene action during the differentiation of root hairs
Response of Maize Seedling Roots to Changing Ethylene
M. V. Alarcon
, P. G. Lloret
, D. J. Iglesias
, M. Talon
, and J. Salguero
Departamento de Anatomia, Biologia Celular y Zoologia, Facultad de Ciencias,
Universidad de Extremadura, Badajoz, Spain
Departamento de Hortofruticultura, Centro de Investigacion “La Orden-Valdesequera”, Badajoz, Spain
Departamento de Genomica y Postcosecha, Instituto Valenciano de Investigaciones Agrarias, Valencia, Spain
Departamento de Biologia Vegetal, Ecologia y Ciencias de la Tierra,
Universidad de Extremadura, E-06071, Badajoz, Spain
Receved April 11, 2008
—Maize roots (
, cv. DK 626) growing in aerated solutions showed striking variations in the
amount of ethylene produced during different stages of development. As endogenous ethylene increases, root
elongation decreases. Exogenous 1-aminocyclopropane-1-carboxylic acid (ACC) supplied to these roots also
inhibited their elongation and increased both the fresh weight of the apex and the ethylene produced. The inhib-
itor of ethylene biosynthesis, 2-aminoethoxyvinyl glycine (AVG), and the inhibitor of ethylene action, silver
thiosulfate (STS), also reduced growth and increased swelling. As growth diminishes at reduced ethylene con-
centrations or with impeded ethylene action, these results support the view that ethylene is necessary for root
growth. As ACC treatment also inhibited root elongation, it appears that ethylene was inhibitory at both low and
high concentrations. Whereas ACC stimulated ethylene production 4 h after the beginning of treatment, inhibi-
tion of root elongation and promotion of fresh weight advanced slowly and needed 24 h to be established. At
that time, root elongation reached a maximum response of 60% inhibition and 50% increase in weight. At 48 h,
higher doses of ACC were required to provoke the same response as at 24 h. This suggests that the root growth
progressively accomodates to higher ethylene concentrations.
Key words: Zea mays - root elongation - ethylene inhibitors - ethylene - ACC
: ACC—1-aminocyclopropane-1-carboxylic acid;
AVG—2-aminoethoxyvinyl glycine; STS—silver thiosulfate.