Fleming, A.L.

Noggle, J.C.

Wit, C.T., de

de Wit, C.T.

NARCIS 

Interrelations of Calcium and Rubidium Absorption by Excised Roots of Barley and Plantain

Name not available

Wageningen Yield 

Reprinted from SOIL SCIENCE SOCIETY OF AMERICA PROCEEDINGS 
Vol. 28, No. 1, January-February 1964, pages 97-100 
677 South Segoe Road, Madison 11, '''isconsin 
Interrelations of Calcium and Rubidium Absorption by Excised 
Roots of Barley and Plantain1 
J. c. NoGGLE2, c. T. DE vVITS, AND A. L. FLE:NHNG4 
ABSTRACT 
The uptake rates of Rb and Ca, applied alone or 
together, by excised barley and plantain roots were com-
pared. The barley roots absorbed Rb at a faster rate than 
Ca, whereas the reverse was true for plantain roots. The 
presence of Ca increased the rate of Rb uptake by barley 
roots, but the presence of Rb had very little effect upon 
the Ca uptake. The uptake rate of either ion by plantain 
was reduced by the presence of the other ion. 
Calculations indicate that the depressing effect of one 
ion on the uptake of the other by plantain was due pre-
dominantly to ionic competition when the ions were 
present in the concentration range of I0- 2N, but factors 
in addition to competition were responsible in the concen-
tration range of I0- 4N. The significance of the differences 
in response of the two species is discussed. 
C OLLANDER ( 3) GREW DIFFERENT species of plants in solutions containing equivalent amounts of K and Ca 
and found that oats accumulate much more K than Ca 
while Plantago lanceolata accumulates K and Ca in about 
equal amounts. This difference in cation selectivity between 
plant species, which has been confirmed by de Wit and 
Dijkshoorn (unpublished) for Dactylis glomerata and P. 
lanceolata, may be associated with the utilization of the 
ions during growth or related to the cation uptake mecha-
nism by the roots. With the assumption that the uptake of 
cations by exised roots is affected to only a small extent by 
cation utilization, the interrelations between Ca and Rb 
uptake by excised roots of barley (Hordeum vulgare) and 
plantain (P. lanceolata) were compared. 
1Contribution from the U. S. Soils Laboratory, Soil and ·water 
Conservation Research Division, ARS, USDA, Beltsville, Md. 
Presented before Div. IV, Soil Sci. Soc. Am., Ithaca, N. Y. 
Aug. 20, 1962. Received Mar. 4, 1963. Approved May 13, 1963. 
2Soil Scientist. 
3Formerly Visiting Soil Scientist, Present Address: Institute 
for Biological and Chemical Research on Field Crops and 
Herbage, Bornse steeg 65, vVageningen, The Netherlands. 
4Physical Science Aid. 
Competitive Relations 
The n equations 
r. = 
1 [1} 
vvith proper designations for the symbols are widely used 
to describe competitive phenomena in physical and 
chemical engineering, physical chemistry, biochemistry, 
plant ecology, and animal ecology. 
In the case of ionic uptake CI>-Ci>-Cn represent con-
centrations of ions of the same sign in the root medium 
and ri> the absorption, adsorption, or sorption of the 
ionic species by roots, and bi and Ri are constants for 
each ionic species. Ri is the value of ri for infinite con-
centration of Ci. Epstein and Hagen ( 6), Fried and Noggle 
(7), and others used these equations to evaluate whether 
two ions affect each other competitively. 
If one of the ions, in a n-ion system, is varied and the 
others are kept constant, equation [ 1] reduces to 
[ 2] 
in which 
n 
K ;:: 1 + L:; b1· C1· = constant. i;::2 . 
Fried and Noggle (7) tested the validity of this equation 
over a wide concentration range and found that for 
barley roots the results can be described with two 
equations [2], one being predominant at concentrations 
in the order of 10-4 equivalents (eq.) per liter and 
the other at concentrations around 10-2 eq. per liter. 
Bear (I), Dijkshoom (5), Sutcliffe (10), and Said (9) 
used replacement series to study the effect of one ion on 
the other. These are series of treatments in which the 
total cation content of the solution is constant but the 
ratios of the cations vary. 
For a replacement series of the ions 1 and 2, equation 
[ 1] can be simplified by substituting the identity 
98 SOIL SCIENCE SOCIETY PROCEEDINGS 1964 
K = K C1 + C2 = K C1 + C2 forK= 1 + .£ bi ci =constant 
c1 + c2 a 1=3 
in equation [1]. 
This gives 
and 
with 
[ 3] 
b/K + (1/a) 
1 
brfK b/K 
k12 = bz/K + (1/a)' R1 = b1/K + (1/a) R1 and Rz' = bz/K + (1/a) R2. 
Hence a competitive relation as described by equation 
[1] may exist if for any concentration ratio within a re-
placement series, the sum rdR1' + r2/R2' == 1, that is, if 
the curves rdR1' vs. C1 and r2/R2' vs. C2 are both curved 
to the same extent but in opposite directions. A detailed 
discussion of the interrelations for this type of competition 
was given by De Wit ( 4). A more critical test of the ap-
plicabilitr of equation [1] involves calculation of the con-
stants b/K and R for both ions by matching equation [2] 
to the observations from a concentration series and check-
ing whether substituting these values into equations [ 3] 
will yield curves to fit the observed data of the replace-
ment series. 
It is often supposed that the first step in ionic uptake 
is an exchange reaction. This being the case, it may be that 
the competitive interrelations between a monovalent ion 
and a divalent ion are more complicated than indicated 
by equation [1]. For resin systems this has been analyzed 
by Heald et al. ( 8) . Their treatment and data show that 
experiments must be executed rather accurately over a 
wide concentration range to show these complications. 
Neither the accuracy nor the range of concentrations used 
in the present study permit the use of an equation other 
than [1]. 
EXPERIMENTAL TECHNIQUES 
Barley roots were obtained from 7 -day-old seedlings grown 
in a solution of 4 X I0-4 eq. CaS04 per liter, as described 
by Epstein and Hagen ( 6). About 24 hours before the begin-
ning of an experiment, the CaS04 solution was replaced by 
demineraliz·ed water. 
Plantain was removed from the field and the roots and tops 
were clipped. The plants were allowed to regrow for 3 to 4 
weeks in a half-strength Hoagland nutrient solution with 
micro-nutrients and iron chelate as developed by Said ( 9). 
About 48 hours before beginning the experiment, the nutrient 
solution was replaced by demineralized water in order to 
remove Ca from the surface of the roots. After removal of 
the roots the tops were clipped and the plants were returned 
to the nutrient solution for regrowth and use in subsequent 
experiments. 
The roots were excised shortly before the beginning of an 
experiment and washed in demineralized water. Samples of 
an estimated 0.5 g. were transferred to the treatment solutions 
at the beginning of the sorption period. The treatment solution 
was decanted at the end of the sorption period and adhering 
solution was removed by washing one minute with deminer-
alized water. The adhering water was removed by blotting 
the roots with tissue paper before determining the fresh 
weight. Roots containing Ca45 were ashed at 400°C. before 
Ca45 was determined. 
Chloride salts of Ca and Rb were used in all cases. \i\Then 
both Ca and Rb uptake were to be determined from a mixture 
of the two ions, sufficient solution was prepared and divided 
into two portions. One portion was tagged with Rb86 and the 
other with Ca45 • Solution volume to root ratios were sufficientlv 
large to limit exhaustion to within 25%. · 
Fried and Noggle ( 7) shO\ved that Rb and K are practically 
indistinguishable by excised barley roots in short-time sorption 
studies so that within rather narrow limits it is allowed to 
read K uptake for Rb uptake. 
RESULTS AND DISCUSSIONS 
Time Series 
The uptake of Rb by barley from a solution with 10-4 
eq. RbCl per liter in the absence and presence of 10-3 
eq. CaCl2 per liter is given in figure 1, left; figure 1, 
right, represents the data during the first 40 minutes of 
sorption plotted on a larger scale. The uptake rate in the 
presence of Ca does not change appreciably during the 
3 hours, but in the absence of Ca a much smaller rate is 
established after 50 minutes. Although the amount of Rb 
associated with the roots is lower during the first 40 
minutes, the rate of uptake (slope of line) between 5 
and 180 minutes is higher in the presence than in the ab-
sence of Ca. The uptake of Rb by plantain roots from a 
solution with 10-4 eq. RbCl per liter in the absence and 
presence of 10-4 eq. CaCl2 per liter during 3 hours is 
given in figure 2, left. A steady uptake rate is reached 
after half an hour. Calcium appears to depress the uptake 
of Rb during the entire 3-hour period. 
The uptake of Ca from a solution with 10-4 eq. 
CaCl2 per liter by plantain is given in figure 2, right. 
After 40 minutes a steady uptake rate is established which 
is small compared with the sorption before that time. The 
sorption of Ca by barley roots before 40 minutes is often 
so high, compared with the sorption between 40 and 180 
minutes, that it is difficult to establish an uptake rate after 
40 minutes. 
lo-6·~ Rb 
20 Q. 
Barley 
10 
100 
Minutes 
I 
25 
OL-------·L-------~-
200 0 20 40 
Minutes 
Figure 1-The uptake of Rb by barley roots from a solu-
tion with l X I0-4 eq. Rb/liter. 
10-e eq Rb 
100 ---g-.-
A 
Plantain 
:-: ~~}:q. Co/X0 0 
. 0 
0 0 501/ ,..,~~ 
,_........--~·----'~ 
o. ' I 
0 100 200 
to-7 eq. Co 
)00 --g-.-
'50 
e 
Plantain 
10- 4 eq Call 
Figure 2-The uptake of Rb (left) and Ca (right) by 
plantain roots from a solution with 1 X I0- 4 eq./liter. 
XOGGLE ET AL. : CALCIUM AND RUBIDIUM ABSORPTION BY EXCISED ROOTS 99 
Table !-Concentrations of RbCI and CaCI2 used 
in uptake rate studies. 
Concentration series 
RbCI RbCl CnCl~ 
----------10 4 eq, /lill'l'----------
0, 33 0, 00 1. 00 0. 00 
o. 67 0, 00 0, 67 o .. 3:1 
1, 00 0, 00 0, 33 IJ, 67 
0, 00 1. 00 0, 00 1. 00 
0, 00 o. 67 
0, 00 0, 33 
These time studies show a steady rate of Rb and Ca 
uptake between 40 and 180 minutes. Therefore, in 
subsequent experiments the sorption of Rb and Ca per 
gram of fresh roots was determined in duplicate after 
40 and 180 minutes. The value for the rate of uptake, ex-
pressed as equivalents per gram fresh root per 140 minutes, 
was obtained by subtracting the sorption for 40 minutes 
from the sorption for 180 minutes. 
Experiments at Concentrations Around I0- 4 eq. per liter 
The uptake of Rb and Ca was studied at the concentra-
tions and combinations as shown in table 1. It should be 
noted that only one cation, either Rb or Ca, is present in 
a solution of the concentration series, but both Rb and 
Ca may be present in the same solution of a replacement 
series. The sum of Rb and Ca is constant in all solutions 
of a replacement. 
The uptake rates for Rb and Ca by barley are presented 
in figure 3 and by plantain in figure 4. The concentrations 
of Rb and Ca, expressed in a scale from 0 to 1 X 10-4 
eq. per liter, are given along the abscissa in opposite 
directions. Increasing Ca concentrations are plotted from 
right to left on the concentration series so that the uptake 
rates are more easily compared with the uptake rates of 
the replacement series. 
Concentration 
Serres 
Barley 
0 
0 
o~~==~==~~~~~ 
0 (),33 0,67 1.00 Rb 
1,00 0,67 0,33 0 Ca 
eq./1. (x 10 4) 
Replacement 
Serres 
Barley 
1.00 Rb 
0 Ca 
Figure 3-The uptake rate of Rb and Ca by barley roots 
from solutions with a concentration around I0- 4 
eq./liter. 
Concenlralion 
I0'7e 
Series 
40 ~ 40 
~k Plantain 
0 
0 
0 0 
0 0.33 0.67 1.00 Rb 
1,00 0.66 0.33 0 Co 
eq./1 (kl04 l 
Figure 4-The uptake rate of Rb and Ca by plantain roots 
from solutions with a concentration around I0-4 
eq./liter. 
The uptake rate of Ca by barley roots is negligible com-
pared with the uptake rate of Rb, figure 3, left. The 
rate of Rb uptake appears to double in the presence of 
CaCl2, figure 3, right. It has been suggested by Briggs, 
Hope, and Robertson (2) that the enhancement effect of 
Ca on the uptake of Rb is due to the uptake of the anion 
which is associated with the Ca. The Cl concentra-
tion is constant in the replacement series which 
eliminates any effect that the anion might have on the 
uptake of the Rb. The uptake rate of Rb from solutions 
of 0.33 and 0.67 X 10-4 eq. Rb per liter in the presence 
of Ca is higher than the uptake rate from a solution of 
1 X 10-4 eq. Rb per liter in the absence of Ca while the 
Cl concentration is constant in the three solutions. This 
agrees with the results of Viets ( 11) who found the effect 
by adding CaS04, while the uptake rate of S04 is slow 
compared to Cl. It is useless trying to recognize competi-
tion in these data because of the enhancement effect of 
Ca on Rb uptake. 
The uptake rate of Ca by plantain roots is about 10 
times larger than Rb uptake rate (different scales, figure 
4, left) , but it is apparent that Ca and Rb decrease the 
sorption of each other, figure 4, right. Using the uptake 
rates from the concentration curves in figure 4, a value of 
about 2.3 for kcaRb is calculated. The values for the uptake 
rate in a replacement series, calculated with this constant 
and equation [3], are represented by the dotted lines on 
the replacement series graph of figure 4. The observed 
depressing effect of each ion on the uptake rate of the 
other is larger than the calculated effect, and since both 
measured replacement curves are not bent to the same ex-
tent, it must be concluded that although competitive 
effects may play a role some other effect is also present. 
Experiments at Concentrations Around 1 X I0-2 
eq. per liter 
The experiments of figures 3 and 4 were repeated at 
100-times higher concentrations. 
The results are represented in figures 5 and 6. 'Vith 
Rb 
Barley 
0o~--~0~.3~3----~0~67~--~I.OO Rb 
1,00 0,67 0,33 0 Co 
eq/1 (k lo2) 
Replocemenl 
Serres 
Rb 
Barley 
1.00 Rb 
0 Co 
Figure 5-The uptake rate of Rb and Ca by barley roots 
from solutions with a concentration around I0-2 
eq./liter. 
I0'6eq C oncentrolion 
7 ~ Series 
Plonloin 
~~. 
0.67 
0,33 
eq/1 (xi02 ) 
~ Replacement 
g.Y~O mm. Series 
Figure 6-The uptake rate of Rb and Ca by plantain roots 
from solutions with a concentration around I0-2 
eq./liter. 
100 SOIL SCIENCE SOCIETY PROCEEDINGS 1964 
140 
ro·7 eq. Rb 
g. x 140 min. 
Barley I I 
/ 
~ x _.x 
/ 
( 
1 
o-----o no Co 
x-x +2xi0-4eq. Ca/1 
0 
ro·5 ro·4 ro·3 ro·2 
eq. Rb/1. 
80 
0 
ro·7 eq. Rb 
g. x 140 min. 
Planlain 
I 
I 
0 /x 
/ 
..-
IV 
~ 
ro·4 10·3 rcr 2 
eq. Rb/1. 
Figure 7-The uptake rate of Rb by barley (left) and plan~ 
tain (right) from solutions with 2 X 10--1 eq. Ca/liter 
and varying Rb concentrations. 
ro·s eq. Rb 
10 ~ ' 140 mio. ' / 
/~loy 
10-4 eq. Rb/1. 
0 
o 1o·s ro·5 10-4 10-3 1o·2 
eq. Co/1. 
ro·7 eq. Rb 
24 g. x 140 min. 
--p~ 
I o·3 eq. Rb/ I. 
0 
o ro·s 1o·5 ro·4 ro·3 
eq. Ca/1. 
Figure 8-The uptake rate of Rb by barley (left) and plan-
tain (right) from solutions with constant Rb concentra-
tions and varying Ca concentrations. 
barley (figure 5) , the enhancing effect of Ca is still present, 
although it is much smaller than at 1 X 10-4 eq. per liter. 
The data indicate that, although Ca promotes the up-
take of Rb, Rb suppresses the uptake of Ca. There are 
insufficient data to calculate whether this may be a com-
petitive effect. 
At concentrations around 1 X 10-4 eq. per liter, the 
Ca uptake by plantain roots was about 10 times the Rb 
uptake. At concentrations around 10-2 eq. per liter 
(figure 6) , the uptake of both ions are the same order if 
the ions are given alone. From the concentration curves 
it is calculated that kcaRb is about 4.9 for the uptake rates, 
and the replacement curves calculated with this value and 
equation [3] match very well the measured replacement 
curves. Hence, competition seems to be the predominate 
effect at these concentrations. 
Experiments at Constant Ca Concentration 
Since with both barley and plantain other than competi-
tive phenomena are observed, it is necessary to check 
whether the effect of Ca can be overcome by increasing 
Rb concentrations. The graphs in figure 7, with the Rb 
concentration along the abscissa in logarithmic progression, 
represent these results. The enhancing effect of 2 X 10-4 
eq. Caper liter on the rate of Rb uptake by barley occurs 
over a large range of concentrations of Rb. The sigmoid 
shape of the curves indicates again that at least two 
equations [2] are needed to describe the relation between 
concentrations and uptake. Increasing the Rb concentration 
did not overcome the effect of 2 X 10--1 eq. Caper liter 
on the uptake rate of Rb by plantain roots, although a 
calculation based on the data of figure 4 (kcaRb == 2.3) 
shows that the depressing effect of 2 X 10-4 eq. Ca per 
liter due to competition should be negligible at con-
centrations of 1 X 10-2 eq. Rb per liter. This indicates 
that something other than competitive effects of Ca may 
decrease the Rb uptake. 
Experiments at Constant Rb Concentrations 
The preceding data do not exclude the possibility that 
beyond a certain minimum concentration the effect of 
Ca on the Rb sorption is independent of Ca concentration. 
The graphs in figure 8, with the Ca concentration along 
the abscissa in logarithmic progression, and the Rb uptake 
rates from 1 X 10-4 eq. Rb per liter (barley) or 1 X 
10-3 eq. Rb per liter (plantain) along the ordinate, show 
that this is not the case. The enhancing effect of Ca on 
the Rb uptake by barley and the depressing effect of Ca 
on the Rb uptake by plantain increases with increasing Ca 
concentrations up to 1 X 10-2 eq. Ca per liter (barley) 
and up to 1 X 10-3 eq. Ca per liter (plantain). 
CONCLUDING RE:MARKS 
The results of this series of experiments show that the 
effect of Ca on the uptake of Rb by excised roots of 
barley and plantain is not consistent. Although competition 
between Ca and Rb exists with plantain roots, other inter-
actions also occur. These observations place more rigid 
requirements on any explanation of the interactions of Ca 
and Rb uptake by excised roots. 
The relative uptake rates of Ca and Rb by excised roots 
of barley and plantain are similar to the relative Ca and 
K contents of the whole plants. A test of whether Ca in-
creases the uptake of K in growing plants is difficult be-
cause plants will not grow in a nub·ient medium that does 
not contain Ca. 
LITERATURE CITED 
1. Bear, F. E. Cation and anion relationships in plants and 
their bearing on crop quality. Agron. J. 42:176-178. 1950. 
2. Briggs, G. E., Hope, A. B., and Robertson, R. N. Electro-
lytes and plant cells. Oxford, 1961. 
3. Callander, R. Selective absorption of cations by higher 
plants. Plant Physiol. 16:691-720. 1941. 
4. De Wit, C. T. On competition. Verslagen Landb. Onderz. 
66.8: 82 p. 1960. 
5. Dijkshoorn, vV. The rate of uptake of chloride, phosphate, 
and sulphate in perennial ryegrass. Neth. J. Agr. Sci. 7: 
194-201. 1959. 
6. Epstein, E., and Hagen, C. E. A kinetic study of the ab-
sorption of alkali cations by barley roots. Plant Physiol. 
27: 457-474. 1952. 
7. Fried, M., and Noggle, J. C. Multiple site uptake of in-
dividual cations by roots as affected by hydrogen ion. 
Plant Physiol. 33: 139-144. 1958. 
8. Heald, vV., Frere, M., and de vVit, C. T. Ion adsorption 
on charged surfaces. In press. 
9. Said, I. M. Cation selectivity and cation-anion balance 
as factors governing the mineral composition of pasture 
herbage. Verslagen Landb. Onderz. 65.16: 64 p. 1959. 
10. Sutcliffe, J. F. The selective uptake of alkali cations by 
red beet tissue. J. Exp. Bot. 8: 36-49. 1957. 
11. Viets, Frank G., Jr. Calcium and other polyvalent cations 
as accelerators of ion accumulation by excised barley roots. 
Plant Physiol. 19: 466-480. 1944_. 


Interrelations of Calcium and Rubidium Absorption by Excised Roots of Barley and Plantain

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