Acta Bot. Neerl.
Polar
ions
June
21(3),
1972,
211-218
p.
transport
across
the
labelled rubidium
of
leaf
of
Potamogeton
lucens
R.J.
Helder
and
Boerma
J.
Laboratorium, Universiteit, Groningen
Botanisch
SUMMARY
of
Leaves
ions
Potamogeton lucens,
at their
small
Only
greater
The
part
amounts of the
of the rubidium
above-mentioned
it also
However,
occurs
by
surrounded
lower surface and release
ions
ions
taken
are
1
a
these ions
mM
remain
up
transported
on
bicarbonate
within
the
the leaf in
light
is
solution,
take up
rubidium
solution.
upper
fixed
across
polar transport depends
when rubidium
rubidium
into the
leaf
one
and the
tissue,
presence
only applied to
so
that the
direction.
of bicarbonate.
the lower
surface of the
leaves.
The results
gradients
bonate
are
ions
far obtained
so
be
to
accompanied by
lower
1.
and
taken
the
explained by
to the
and the
up
rubidium
So, according to
is involved.
are
developed owing
polarity
upper
layers
following simple hypothesis.
assimilation
ions
hydroxyl
formed
to
in
the
Concentration
the
light, causing
be released.
These
bicar-
anions
are
ions.
hypothesis
The
the
bicarbonate
a
completely inactive
of the process is due to
a
movement of cations
difference
in anion
as
well
as
anions
permeability between
the
of the leaf tissue.
INTRODUCTION
A number of
aquatics
carbon dioxide.
when the leaves
containing
On
hand,
This is
a
a
increases
assimilate in
stream
also accompanied
small
above 9.
is
amount
appears
Similarly,
use
if
containing
reached in this way
dioxide
to
pH
a
the
to
in addition
value of 10
restricted
normal
to
or
volume of
a
11
even
solution
of
free from
nitrogen
bicarbonate
as
well
as
carbon
carbon
dioxide is led
dioxide,
all of the
carbon dioxide is removed.
gaseous
such
allowed
are
solution
a
the
bicarbonate.
the other
through
assimilate bicarbonate ions
can
Consequently,
to
some
by
a
rise of the pH.
approximately
However,
of free carbon dioxide that any
be
the
highest
value
9. At this value the solution will contain
further removal of carbon
practically negligible.
species
Apparently they
of
aquatics
assimilate
are
unable
to
only free carbon
the bicarbonate ions for this purpose
(Ruttner
raise the value of the
dioxide and
are
pH
unable
to
1948, Steemann Nielsen
1960).
Additionalevidence for bicarbonate assimilation
He found the
exceptional
which
contact
It is
was
in
unlikely
increase of the
pH
value
was
found
to occur
by
only
Arens
(1933).
in the solution
with the upper side of the leaves.
that gaseous carbon dioxide can
only penetrate the upper surface.
212
R.
Further this release
As
depends
the bicarbonate
apply
result
a
surface.
valent
Hardly
presence of bicarbonate and
Under natural conditions there will be
release into the upper solution,
earlier,
causes
The
point
resulting polar transport
for
centrated
on
the
experiments
and extended the
Besides
they
carbonate
oxygen,
We
the
transport,
the results
MATERIAL
the
Single
leaves
actual
experiment.
basin
measuring
The
to
clearly
Depending
or
0.8
X
growing
months
cold
So,
Attempts
treatment
plants
were
mentioned
pH
aquatics.
the
was
starting
con-
have corroborated
on
medium,
the
exchange,
and
the
bi-
evolution of
in due time.
plant physiologist
have had
think,
we
of
to
the
little attention.
too
in
the
open
before the
day
one
air in
large
a
concrete
metres.
from the
rhizomes in
within the
carbonate
that
indicating
space
the
on
and formed
May
of
a
upper surface
bicarbonate
a
dense
month. At that time
of the
assimilation
leaves
and
polar
a start.
experimental
to
lucens
Potamogeton
grown
completely
extend this
by growing
or
experiments
the
published
the weather conditions,
October.
only.
of
which,
of calcium
visible,
on
they
as
draw the attention of the
from
cation transport had made
tember
equi-
an
observed in
commonly
so
for
point
will be
plants
the basin
slight precipitate
became
1
x
started
plants
vegetation filling
a
The
2
by
some
lower
METHODS
picked
were
the
at
abundance of calcium ions. Their
an
of calcium and other cations
pH changes
of which
AND
release of
accompanied
are
with labelled rubidium,
older papers mentioned above
2.
to a
absorption.
precipitate,
starting
in this article
hope
to
known from literature.
findings
were
BOERMA
part of which will be discussed here. We have
experiments,
our
J.
it suffices
observed
with the increase of the
together
the formation of a
is
pH
bicarbonate ions
of cations in the process of
is due
pH
of the
change
any
This indicates that the
amount
HELDER AND
the lower surface of the leaves.
to
conclude that the rise of the
one can
alkaline substance.
the
on
J.
shoots
period
in
plants
the
material
a
started
dying
available for
was
by subjecting
greenhouse
were
off in
Sep-
about
four
the rhizomes
not
succesful
to
a
until
now.
The second
the
or
third leaf from the top
It is very active and
ments.
experimental
set-up
whereas older leaves
less
perforated owing
After
leaves
order
picking,
to
aid
the
placed
were
to
described below.
not
flat
the
activity
precipitate
enough.
was
of
a
water-tight.
suitable for these
experi-
Younger
Moreover,
leaves
often
are
too
the latter are often
small
more or
of snails.
on
the
in aerated distilled
then mounted between
mixture of vaseline and
The details of the
most
and flat which renders it ideal for
leaves
water
vessels,
two
was
and
get rid of any calcium carbonate left
A leaf
the
are
proved
sufficiently large
on
removed
kept
in
gently.
the dark
wax
which
the
in
the leaves.
experimental absorption
bees’
Then
overnight
to
were
ensure
that
vessels
the set-up
made of perspex,
can
be
with
was
seen
POLAR
in fig.
I. The leaf
side of the
For
by
the
as
added
the
mistake.
the
1. Absorption
onto the
is used
in
area
are
an
not
cm
?
either
on
a
the
and
the
springs
to the
the
D:
the vessels
of ion
ensure
The
experimental
light
results
the
1 mM solution
transport
was
inlet
on
even
the
few
leaves
side
pressure
outlet.
and
of
the
Potamogeton
contact the
of the leaf and
of the vessels
For the
aerated
opening
times,
may
the upper side
and the
is stirred
via
across
a
volume.
to
that its lower
so
placed
solution
washed
made up
a more
solution
at
light.
one-hour intervals. At the end of
opening
via
the
on
3
off,
study
renewed
up-right position.
be directed towards the
to
labelled RbHC0
afterwards. B. The
upper vessel
exposed
with
upright position
have any influence
during regular
drained
was
used for
added
an
the direction of the
by
itself 5 ml of
lower vessel. The
C: Solutions
in
placed
50 ml volumetric flask and
a
vessels
screwed
The leaf
solution is 5
experimental
happened
vessel. A leaf is put onto
administered
was
by
the
on
purpose
an
the
the
air stream.
same i.e.
5
2
cm
experiments.
The
of
the
source.
induced
not
solution
solution
all
to
213
POTAMOGETON
OF
however, did
experiment
A: The lower
in
light
This,
is
collected in
liquid
set-up
exposed
either side of the leaf
to
each interval the
leaf.
LEAF
of convenience the leaf is
facing
polarity
During
Fig.
area
THE
few instances the lower side
a
source
all
IN
leaf.
reasons
upper side
In
RB*
TRANSPORT OF
other dimensions
clarity
the
bigger
of the vessels
ones
of
10 ml
varied, however,
capacity
are
shown
and
here.
so
did their
capacity.
For
reasons
214
R.
obvious
For
there
of the
calcium
reasons
in
concentrations
Rb*
calculated
as
well
the
as
results could be checked
that purpose the
learned that all
As
light
a
source
Light intensity
vessels
number of
a
was
leaf tissue.
the end of the
The
latter
For
experiment.
150 W
light
to
incandescent
was
adjusted
with
lamp
passed through
was
be done very
accurately
which
simplicity.
a
5
cm
that
so
period.
collected
As 5 ml of
adjusted by inserting simple
measured
amounted
to
by
at
a
internal reflecting
an
of a copper
layer
sulphate
of the infrared radia-
most
neutral
Braun
a
filters in
glass
meter
the
at
place
hol-
a
of the
greenish-bluish light.
RESULTS
the
experiments
behaviour of the rubidium
fresh
On
the hour
the
end of each
1
a
3000 lux of
conditions of temperature
constant
9 hours
of their
intensity
EXPERIMENTAL
under
had
measurements
of which
was
maximum
absorption
In
at
scintillation
simple
absorbed.
was
der. The
3.
by
and release of Rb* could be
uptake
the leaf
by analysing
spite
a
strength
solution the
tion
although
benefit to the condition
accumulation within the
net
activity
used. The
was
used,
BOERMA
leaf was extracted with hot dilute nitric acid. From this check
made them tedious in
surface
determined
were
From this data the simultaneous
counting.
liquids
some
J.
material.
plant
Changes
we
omitted from all
was
be little doubt that it would have been of
can
HELDER AND
J.
a
solution
hour and
mM Rb* HC0
leaf, exactly
ions
was
studied
light (3000 lux) during
a
added and the old solution
was
analysed.
solution
3
the lower sides of the
and
(20 °C)
applied
was
5 [xeq Rb*
to both the upper and
available for
was
absorption
on
either side of the leaf. In all instances the concentration of the lower solution
whereas the
decreased,
increase will be
As
is illustrated
increased
little
a
slightly, during
The
release
was
to
by fig.
during
the
of the upper solution increased. This decrease and
2 the
the
uptake
second
across
the
show
retained
the
At the
equal.
uptake
release, respectively.
high
was
hour,
a
similar
exceeded the release
by
the
as
well
as
picture. During
figures,
indicating
no
the
significant
release
of the
experiment,
steadily, though
very
the first
that
a
the
hours
two
small
amount
of
During
represent the polar
this
transport
leaf tissue.
start
of each hour the concentrations
However,
place against
some
start
differences occurred.
figures
because
of
polar transport
on
the
solution exceeds the concentration of the lower
In
the
at
and decreased
leaf tissue.
From the third hour onwards
period
and
uptake
as
remaining experimental period.
figures
uptake figures
rubidium
one
referred
a
concentration
no
polar transport was
within the leaves
were
concentration of the
one,
so
that
were
upper
transport takes
gradient.
preliminary experiments,
tested. Here
both sides of the leaves
solutions of rubidium chloride
observed and the
smaller than in the
case
net
amounts
were
also
accumulated
of bicarbonate solutions.
POLAR TRANSPORT
Fig.
2.
RB*
OF
The influence
of
IN
THE
light
LEAF
OF
215
POTAMOGETON
on the course of the rubidium
transport
j
across a leaf of Potamo-
geton lucens.
A
set
1 mM labelled
up shown
Uptake
release
The
figure
1.
the
the
differences
showing
rubidium
fig.
refers to
refers to
accumulation
The
in
bicarbonate
The solutions
drop
observed
between
within
is based
of the
was
renewed
rubidium
increase
the
solution
were
and
to both
sides of
a
leaf, using
the
hour.
concentration
of the
upper
release
added
each
of the
lower
solution,
whereas
solution.
uptake
values
represent
the
rate
of
rubidium
the leaf tissue.
on
the results
about the same rate
of
of three selected
transport during
experiments
with
the first two hours
three
of the
different
leaves,
experiment.
216
R.
The effect of bicarbonate is
undoubtedly
This is also apparent from the other
the
light intensity
reduced
was
to
related
J. HELDER
the third and
J. BOERMA
assimilation in the
light.
in fig. 2, in which
experiments represented
during
AND
fourth hour of the
experi-
ment.
If the leaf
The
uptake
at
much
a
first hour.
in the
placed
was
from the lower
reduced
dark, polar transport
and
level,
the
Consequently,
came to
stand-still
a
rubidium
to an
came
continued for
solution, however,
content
while, although
before the end
not
of the
immediate stop.
a
of the
leaf must
have increased
and
release started
in the dark.
the
If, however,
but
afresh,
light.
As
light
was
release
the
now
turned
both
again,
on
the
surpassed
uptake
result the Rb*-content of the leaf decreased
a
the
uptake during
first
during
hour in
the
this part of the
experiment.
This increase
after
of
and
uptake
complete
in
a treatment
the level in the first
release
hours of the
two
continued
was
during
darkness. The level reached
experiment,
the
before the
second hour
almost
was
light
equal
to
switched
was
off.
In
number of
a
In
the
by
this
The
a
water
gradual
a
light,
administered
was
the
virtually
were
slowing
could be
rubidium bicarbonate solution.
and darkness
light
down,
observed.
the
to
upper
The results
same
con-
may be illu-
as
following experiment.
experiment
second two-hours
the
liquids
the leaf
period
rubidium solution
0-2
Period
were
was
renewed every
at
water
the lower side
h.
at
were
hours.
During
the upper side and
uptake
4-6
dark
h.
6-8
light
h.
light
Release
2.1
0.7
1.3
3.5 p
Uptake
2.7
1.2
1.4
3.6(xeqRb*
These
in the
even
figures
experiments
more
reached,
is
In other
rubidium
contrast
In
solution,
(0.3
m
upper solution.
dark
2.
treatment
reduced the
The induction
whereas the
the
experiments
slight
a
high
period
rate
at
eq
polar transport
after
the dark
Rb*
as
it did
treatment
which the transport is
is
finally
striking.
most
but
at
upper side of the leaf
was
the lower side the solution
left in
was
contact
for
changed
with the
water.
In
previous experiments polar transport stopped altogether.
experiment,
a
to water
of fig.
pronounced,
with the
one
Rb*/h,
show that
the
obtained:
2-4 h.
light
two
in the dark.
kept
for the release into
following figures
from the
experiment
distilled
experiments
leaf instead of
the effect of
cerning
of the
hours
that found under conditions of continuous
to
side of the
strated
remaining
the
During
similar
in which the
amount
eq),
of Rb*
whereas there
The
amount
rate of transport
previously
can
was
a
hardly
was
absorbed
very
by
of the order of 3 meq
the leaf
slight uptake (0.1
be considered
was
m
eq)
significant.
given
off
from the
POLAR
TRANSPORT
We
RB*
OF
these
repeated
experiments by using
of distilled water. The results
the effects obtained
Polar transport
tion present
at
quite
were
due
mainly
were
the lower side
a
rubidium
similarto those
water
replaced by
was
or
the
had been somewhat harmful
treatments
resistance
such
against
the rubidium
to
solu-
sulphate
that the
and
water
the leaf. We concluded that
varied from leaf
treatments
that
the normal rubidium bicarbonate
solution. However, in many instances the results suggested
sulphate
solution instead
sulphate
discussed, indicating
the absence of bicarbonate.
to
resumed when the
was
217
THE LEAF OF POTAMOGETON
IN
to
leaf,
depending
on
their internal conditions.
4.
DISCUSSION
The
the
findings concerning
of Arens
older results
leaves. However,
from
a
of rubidium ions corroborate the
polar transport
(1933)
the
on
behaviour
quantitative point
of cations
of view
in
Potamogeton
details have become
more
available.
The
increase of the
cluded,
as
there
seems
be
to
Nielsen
(Steemann
process. However, this
against
concentration
It shows that the
rate
rubidium concentration
electrical
no
potential
that the
1960),
statement
does
not
the cation transport will prove
analysis,
a
by changing
transport
It
gradient.
difference
be
across
possibility that,
coupled
to
active
an
is
no
the
highly
be
can
polar transport represents
exclude the
to
of
and
gradient
of transport could be obtained
water.
prevailing
of the
independent
place
rate
rubidium solution for
upper
tissue
take
transport could
significant
con-
the leaf
an
on
active
further
transport of
anions.
Clearly, light
with
is the
primary
in this paper. But,
rubidium
at
the
than did the
The
upper
uptake
at
release represents the
the transport
source
the
of energy for active cation
dealt
transport
light
leaf surface
was
switched
responded
more
on
and
rapidly
to
the
release of
light
conditions
off,
the
the lower surface.
conclusion
simplest
words,
if
at
which
one can
arrive from this evidence is that the
active part of the transport
truly
depends
active secretion
on
by
across
the leaf.
the upper cell
In other
layers
of the
leaf tissue.
This
idea
secretion
has
activity
been
advocated
other, mainly animal,
tissues.
claims that it is the
hydroxyl
which
actively.
are
secreted
According
which in
turn
However,
take
to
processes
becomes
this
Lowenhaupt
(1956),
can
who
the
other
as
a
hand,
also
in
the
to
relates
this
be present in
Steemann Nielsen
(1960)
result of bicarbonate assimilation
content
of the leaf
the lower surface of the leaf.
uptake
at
explain
the different responses of the release and up-
by assuming
depleted
On
ions formed
view the secretion lowers the rubidium
induces the
one
by
with the well-known sodium pump, assumed
that the
dark
uptake depends
more
slowly
than
on an
the
energy
source
source
for
the
which
release
process.
The
polar
cation transport
depends
on
the
availability
of bicarbonate in the
218
R.
lower solution. As
is also
light
required,
of bicarbonate represents the crucial
HELDER
AND
J.
BOERMA
there is little doubt that the assimilation
active process
for the
responsible
pheno-
observed.
mena
One
can
imagine
that the assimilation is the
observed. That
phenomena
the
was
active
only
processes discussed here. We think it also leads
the
J.
reason
the
to
for
of the
part
transport
for
simplest explanation
accepting this idea
as
a
part
following hypothesis.
of the
The
of bicarbonate
consumption
the bicarbonate and the
creates
a
concentration
for both
gradient
ions between leaf tissue and the
hydroxyl
surrounding
solution.
If the lower cell
layers
ions and the upper cell
will
ions
hydroxyl
This leads
the tissue
It
tissue
ence
to
the
to
be
might
a
upper
enter
we
at
permeable
to
hydroxyl ions,
to
the lower surface
bicarbonate
the
gradients
of the
leaf,
the
will be
by equivalent
assumed differences in
of the
response
discussed
simple
accompanied
amounts
of
across
solution.
that the
before,
believe that much
discount the
more
transport of the cations from the lower solution
bicarbonate and hydroxyl ions
between the
Still,
to
to
argued
light conditions,
rather
be released into the upper solution.
to
The anions moved in this way
cations.
to
are
permeable
more
bicarbonate ions
the
cause
of the leaf
layers
uptake
are
more
somewhat
are
and that of the
somewhat
convincing
explanation given
permeability
at
of the
release
variance with
to
our
leaf
the differ-
unlikely. Also
changes
in
hypothesis.
evidence is needed
experimental
here.
ACKNOWLEDGEMENTS
The
authors
are
much
indebted
to
Mrs.
Shephaly
Ides-Shorter for
her
correcting
the
English
text.
REFERENCES
Arens,
K.
mersen
—
Wasserpflanzen
(1936a); Physiologisch
Die
—
(1933): Physiologisch polarisierter
Ca(HC0
20:
polarisierter
)2-Assimilation.
3
(1936b): Photosynthese
Bot.
I. Planla
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