Basal
Roots
Zobel,
R
.
W
.
USDA
-
ARS,
Cornell
University,
Ithaca,
NY
For
the
last
100
years
or
so,
plant
scientists
have
been
investigating
plant
root
systems
to
improve
growth,
reduce
sensitivity
to
stressful
conditions,
or
improve
tolerance
to
pathogens
like
nematodes,
Fusarium,
etc
.
During
this
time
the
plant
anatomists
characterized
the
plant
root
system
as
having
three
types
of
root:
the
radicle
or
tap
-
root
which
is
the
first
to
emerge,
lateral
roots
(branches
off
other
roots),
and
adventitious
roots
(roots
originating
from
non
-
root,
non
-
meristematic
tissues)
.
Because
ail
three
types
of
root
are
virtually
identical
in
their
anatomy,
root
researchers
assumed
that
they
were
also
functionally
(physiologically)
equivalent
-
paradigm:
Although
most
plant
root
systems
consist
of
three
developmentally
distinct
types
of
root
(radicle
or
tap
root,
lateral
roots
and
adventitious
roots),
their
virtually
identical
anatomy
and
morphology
suggests
that
these
three
types
are
functionally
(physiologically)
equivalent
.
In
the
1970's
we
hybridized
the
diageotropica
(
dgt
)
mutant
with
the
rosette
(
ro
)
mutant
and
obtained
the
double
homozygote
shown
on
the
cover
of
this
issue
of
the
TGC
Reports
.
Since
dgt
does
not
develop
lateral
roots,
and
ro
does
not
develop
adventitious
roots,
the
resulting
homozygote
should
have
had
only
a
tap
root
-
indeed
this
was
the
original
intent
.
Morphologically,
the
segregating
F
2
seedlings
showed
a
ratio
of
9:3:4
(+:dgt
.
ro
)
for
shoot
characteristics,
and
3:1
(+:dgt
)
for
root
characteristics
.
The
seedlings
which
were
classified
as
ro
segregated
3:1
(+:dgt
)
for
the
lateral
-
less
characteristic
of
dgt
-
double
homozygotes
.
When
tested
for
adventitious
rooting,
none
of
the
ro
plants
developed
adventitious
roots,
and
the
double
homozygotes
did
not
develop
lateral
roots
.
The
additional
roots
on
the
double
homozygote
have
been
termed
'Basal
Roots"
because
of
their
location
at
the
base
of
the
hypocotyl
(Zobel,
1975)
.
These
results
suggested
that
there
were
four
types
of
root
rather
than
the
classical
three
.
Further
research
with
other
plant
species
has
confirmed
the
existence
of
four
types,
and
evidence
dating
back
to
the
1800's
(Weinhold,
1967)
demonstrate
the
development
of
these
basal
roots
on
all
plant
species
.
This
article
is
placed
in
this
issue
of
the
reports,
because
new
data
from
our
lab
.
,
with
other
species,
demonstrates
that
these
four
types
of
root
are
functionally
distinct
as
well
as
developmentally
distinct
.
The
following
note
describes
a
short
experiment
where
we
demonstrated
the
physiological
distinctness
of
the
tap,
basal,
and
lateral
roots
of
tomato
in
terms
of
nutrient
uptake
.
Literature
Cited:
Weinhold
L
1967
Beitr
.
Biol
.
Pflanzen
.
43,
387
-
454
.
Zobel,
R
.
W
.
1975
.
In
.
The
development
and
function
of
roots
.
Academic
Press,
London
p
.
261
-
275
.
Spatial
and
temporal
characteristics
of
nutrient
uptake;
root
type
differences
Zobel,
R
.
W
.
,
L
.
V
.
Kochian
and
T
.
K
.
Toulemonde
USDA
-
ARS
&
Cornell
Univ
.
,
Ithaca
NY
Using
ion
specific
microelectrode
technology
(Toulemonde,
1992),
we
investigated
the
spatial
and
temporal
characteristics
of
several
different
root
-
types
on
seedlings
of
cv
.
VFN8
(Zobel
et
al
.
1992)
.
We
measured
the
rate
of
potassium
(K*)
uptake
by
tap
roots
at
7
and
14
days
after
germination
and
by
basal
roots
at
14
days
after
germination
.
At
7
days
the
tap
root
was
8
cm
long
and
at
14
days
the
basal