New Phytol.
(1992),
120,
453^57
Adventitious root formation
in
hypocotyl
cuttings
of
Picea sitchensis
(Bong.) Carr.
—
the influence
of
plant growth regulators
BY
C.
S E L B Y \
S.
J.
KENNEDY^
AND
B. M. R.
HARVEY^
^Agricultural Botany Research Division, Department
of
Agriculture for Northern Ireland
and The Queen's University
of
Belfast, Newforge Lane, Belfast,
BT9
5PX,
UK
^
Greenmount College
of
Agriculture and Horticulture,
22
Greenmount Road,
Antrim
BT41 4PU,
UK
{Received 28 June 1991; accepted
3
December
1991)
SUMMARY
A simple method
for the
study
of
adventitious root initiation
on
Sitka spruce
[Picea
sitchensis
(Bong.) Carr.]
hypocotyl cuttings is described and was used to examine the effects of plant growth regulators. Twenty-one-day-
old seedlings, grown at a low light intensity (15-20
fimol
m~^
s~^) to stimulate hypocotyl elongation, provided easy
to handle tissues which were responsive to root inducing treatments. Spontaneous rooting only occurred
at
a low
frequency
on
untreated cuttings and reliable rooting depended upon auxin treatment. When continuous auxin
treatment was used, indole-3-butyric acid (IBA) was more effective than either indole-3-acetic acid (IAA)
or 1-
naphthaleneacetic acid (NAA), and was optimal between
lO"""
and
10~*
M.
Pulse treatments with
10~^
M
IBA
for
as little as 10 min were sufficient to stimulate rooting. All other growth regulators examined were inhibitory to IBA
induced rooting. 6-benzylaminopurine (BA) was
the
most active being inhibitory down
to a
concentration
of
3
X
10"'
M
when it was applied
in
a mixture with IBA. Pre-treatment of hypocotyl cuttings with BA prior to auxin
treatment demonstrated strong cytokinin 'carry-over' inhibitory effects
on
rooting. Gibberellic acid Ag (GAg),
abscisie acid (ABA) and 2-chloroethyl-phosphoric acid (ethrel) were less potent inhibitors
of
rooting.
Keywords:
Picea
sitchensis,
adventitious roots, auxins, cytokinins.
INTRODUCTION
Cuttings prepared from young conifer seedlings
have frequently been used
to
study
the
processes
Rooting gymnosperm shoots on tissue culture media
involved
in
root induction (Smith & Thorpe, 1975
a,
has been widely recognized
to be
both difficult
to 6;
Gronroos
& von
Arnold, 1987). Similarly,
a
achieve
and
unreliable (Minocha
1980;
Mott
&
bioassay employing mung bean seedling cuttings
Amerson, 1981; Amerson & Mott, 1982; Bornman,
has
been widely used
to
detect rooting factors
and
1983;
Abo
El-Nil, 1987). Spontaneous rooting
of
cofactors (Bassuk & Howard, 1981;Bassuk, Hunter
cultured shoots without
the aid
of
growth regulator
& Howard, 1981).
In
this paper, a simple method
for
compounds only occurs
at low
frequencies
with
studying root induction
in
Picea sitchensis
seedling
Picea
sitchensis
(Webb & Street, 1977; Webb, 1978;
hypocotyl tissues
is
reported and used
to
investigate
John,
1983) and
with
a
wide
range
of
other
the
influence
of
exogenous growth regulator
com-
gymnosperm species (Sommer, Brown & Kormanik,
pounds
on
adventitious rooting.
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