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Full text of "The antagonistic action of magnesium and potassium"

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AGRICULTURa? 
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UNIVKRSITv 

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Reprinted from the Botanical Gazette 45: 11 7-1 24, Febniar 1908 

CALTFOP> 

Main Mb, 
\"ric. DtviL 

THE ANTAGONISTIC ACTION OF MAGNESIUM AND 

POTASSIUM 

W. J. V. OSTERHOTJT 

(with three figures) 

It has been previously pointed out^ that potassium may inhibit 
more or less fully the poisonous effects of magnesium and that the 
abundance of potassium in the soil makes this inhibitory action of 
importance in soil investigations. Loew and Aso^ have criticized 
this statement. Their objections are that only chlorids were used 
and that no flowering plants were investigated. In the present paper 
these objections are fully met. The experiments extend over a wide 
range of forms and their general agreement furnishes conclusive proof 
of the above-mentioned action of potassium. 

The technique employed has already been described in previous 
papers in this journal.^ The material was placed in glass dishes con- 
taining 100-300'^'^ of the solution and was covered with glass plates to 
exclude dust and hinder evaporation. Water twice distilled and salts 
which were tested for purity were used throughout. The results given 
in the tables are in all cases averages of several series of experiments. 

The first experiments were made upon a marine alga, Entero- 
morpha Hopkirkii, which is able to live in both sea water and dis- 
tilled water. It was taken from the sea water, rinsed in distilled 
water, and placed directly in the solutions. The solutions used were 
of the concentration 0.37 5 w, which has the same osmotic pressure 
as the sea water in which the plants naturally grow. 

In pure MgCl^ .0375 w they lived but four days; in pure KCl .0375 w 
seven days; while in distilled water and sea water they were alive 
and vigorous at the end of twenty days when the experiment was dis- 
continued. It is evident therefore that both KCl and MgCl^ have a 
poisonous action. 

This poisonous effect largely disappears if we mix the two salts 

I OsTERHouT, University of California Publications, Botany 2:235. 1906. 
' Loew and Aso, Bull. Imp. Coll. Agr. Tokyo 7:395. 1907. 

3 OSTERHOUT, Box. GAZETTE 42:127-134. 1906; 44:259-272. 1907. 

117] [Botanical Gazette, vol. 45 



272648 



ii8 



BOTANICAL GAZETTE 



[FEBRUARY 



(MgClj and KCl) in proper proportions. In the mixture 100*=*= MgCl, 
+40*^*^ KCl, the plants were alive and in good condition at the end of 
twenty days, when the experiment was discontinued. It is evident 
therefore that in the mixture of magnesium and potassium chlorids 
the plants live five times as long as in pure magnesium chlorid and 
three times as long as in pure potassium chlorid. 

TABLE I 

Marine Algae 

All quantities given are cubic centimeters of o . 37SW solutions 



Coltuie solution 



KCl 

100 KCl I 

40 MgCla S 

MgCl, 

Distilled water 

Sea water (total salts = 2. 7 per cent.) 
Artificial sea water (total salts = 
2.7 per cent.): 
100 NaCl \ 

7.8MgCU / 

a.SMgSO^J 

2.2 KCl 1 
I CaCla ' 



Duration of life in 

days: Entero- 
tnorpha Hopkirkii 



7 
20 + 

4 

20+ 
20+ 



20+ 



The plus agn indicates that the plants were ali\-e at the end of the experiment. 

The results obtained from the study of Vaucheria were even more 
striking. Zoospores were allowed to attach themselves to slides. 
These were then rinsed in distilled water and placed in the solutions. 
The results are shown in the following table and also in ^^. i. 

TABLE II 
Fresh-water Algae 
All quantities given are cubic centimeters of .oiw solutions 




i9o8] OSTERHOUT— ACTION OF MAGNESIUM AND POTASSIUM iig 

A large Spirogyra of the majuscula type was used for experiments 
with the stronger solutions. The results are given in Table III. 



TABLE III 

Fresh-water Algae 

All quantities given are cubic centimeters of .0937W 

solutions 







Culture solution 


Duration of life in days: 
Spirogyra species 


KCl 


i 

13 


100 KCl I 


40 MgCla S 

MgCla 


25 + 


Distilled water 





The plus sign indicates that the plants were alive at the end of the 
experiment. 

A series of experiments was next made with 
the gemmae of Lunularia. These were allowed 
to float on the surface of the solutions. A 
large number was used and the average results 
given in the following table. 

TABLE IV 

Liverworts 

All quantities given are cubic centimeters of .0937W 

solutions 



Culture solution 


Duration of life 

in days: 

genunae of Lunularia 


KCl 


12 


100 KCl ) 


120 + 


so MgCl, ) 

100 KCl I 


120 + 


100 MgCla S 

50 KCl ) 




100 MgClj ) 

MgCU 


4 


Distilled water 







<?. 





3 



The plus sign indicates that the plants were alive at the end of the 
experiment. 



Fig. I. — Growth 
of Vaucheria during 
45 days in . 01m solu- 
tions. I, KCl, gain 
o; 2, ioqcc KCl 
-I-40CC MgClj, gain 
4200%; 3, MgCla, 
gain o. X 25. 



I20 



BOTANICAL GAZETTE 



[FEBRUARY 



It will be noticed even when magnesium greatly preponderates in 
the mixed solutions the plants live twenty-five times as long as in pure 
MgClj, and over eight times as long as in pure KCl. Increasing the 
proportion of potassium increases the length of life. 

The same relation is seen more completely in the next table (Table 
V). Decreasing the amount of Mg causes increased growth up to a 
certain point (loo K + io Mg). StUl further decrease of the relative 
amount of Mg beyond this point is imfavorable. The optimum 
relation is therefore not far from lo Mg + loo K. 

TABLE V 

Liverworts 

All quantities given axe cubic centimeters of .037SW solutions 



CUVrtTKE SOLUTION 



KCl 

100 KCl ) 

5MgCla5 

100 KCl I 
10 MgCla S 

100 KCl I 
25MgClJ 

MgCU 

Distilled water 



Growth in 150 days: geioiae 
of lunulakia 



Length of 
thallus 



0-5 
3-3° 

3-41 

2.6 

o-S 
6.60 



Percentage of 

gain in length 

of thallus 



O 
560 

582 

420 



It will be noticed also that the gemmae made no growth whatever 
in pure MgClj or pure KCl, while in mixtures of the two a good growth 
occurred. 

For the study of flowering plants wheat was chosen. The seeds 
were supported in the solutions on strips of filter paper as described 
in a previous paper.'* The results agree with those already given. 
Table VI shows that certain mixtures of potassium chlorid and mag- 
nesium chlorid are much more favorable than cither of the pure salts 
(see also figs. 2, j). 



4 0STERH0TJT, BOT. GAZETTE 44:259-272. 1907. 



i9o8] OSTERHOUT— ACTION OF MAGNESIUM AND POTASSIUM 12 1 



^ 



1 





Turning now to the experiments with sulfates and nitrates, we 
see entirely similar results, save that the mixed solutions, while better 
than pure magnesium salts, 
are not better than pure potas- 
sium salts. The question 
might then arise whether the 
favorable result is due in this 
case to mere dilution of mag- 
nesium salts with less poison- 
ous ones. This, however, is 
not the case. We are dealing 
with a true antagonistic action. 
This is shown by the fact that 
addition of the potassium salt 
in solid form likewise pro- 
duces a favorable result, and 
also by the fact that the 
addition of pure water does 
not produce anything like 
the improvement seen on the addition of the same amount of a 
solution of a potassium salt. 

.0937 m 



Fig. 2. — Growth of wheat roots during 
40 days in .og^ym solutions: I, MgClj, 
aggregate length of roots io""n; 2, loocc 
KCl + 2SCC MgClj, aggregate length of roots 
153™™; 3, KCl, aggregate length of roots 
no™™. X§. 




.05 m- 



,037&m 

a bed 

Fig. 3. — Curves showing growth of wheat roots in salt solutions. The ordinates 
represent concentrations (parts molecular); the abscissae represent the aggregate 
length of roots per plant in millimeters, a, loocc KCl+ioocc MgCU; 6, loocc KCl 
+ SOCC MgClj; c, KCl; d, ioqcc KCI + 25CC MgClj. 



122 



BOTANICAL GAZETTE 

TABLE VI 
Wheat 



[FEBRUARY 



Culture solution 


Growth during 60 days 
aggregate length of roots per plant dj lof . 




In .og37w solutions 


In .05 m solutions 


In .o3^sm solutions 


KCl 


no 
66 

72 

153 

10 

80 

36 
48 
60 

4 

114 

12 

32 
80 

35 


268 
170 

224 

312 

20 

216 

112 

148 

166 
10 

275 
76 

144 

224 
8 


340 


loo KCl ) 


loo MgCU ) 

loo KCl \ 


294 

388 
28 


50 MgCla S 

100 KCl \ 


25 MgCl, 5 

MgClj 


SO K,S04 I 


276 

144 

190 

240 
24 


50 H,0 S 

5oK,S04 ) 


100 Mgso^ 5 

5oK,S04 ) 


SO MgS04 ) 

SoKjS04 I 


25 MgS04 5 

MgSO. 


KNO, 


345 
104 


100 KNO3 ) 


100 MgCNOj), J 

100 KNO3 ) 


198 

290 

10 


5oMg(N03),5 

100 KNO3 I 


2sMg(N03),i 

MeOSIO,), 






Distilled water 


lAO 











Since each molecule of K,S04 yields two K ions, half as much K.SO^ is used as KCl or KNO, . 
The figures for 50 K.SO4+S0 H.O are comparable with the corresponding figures for KCl and KNOj, 
though the concentration of the solution is only half as great. For example, the roots reach a length 
of 8o""» in so« K,S04 .o937»» + soee H.O; a length of 216"" in 50" K,S04 .osw + so" H.O; and 
a length of 276"™ in 50" KaS04 .037sm+so« H.O. 

It will be noticed that these antagonistic effects are less marked as 
the concentration is lowered. This is of course true of all antago- 
nistic action, since as the concentration is lowered toxicity diminishes 
and the effect of its inhibition is consequently less striking. 

It is observed that those parts which are in direct contact with 
solutions always show their effects much more plainly than those 



1908] OSTERHOUT— ACTION OF MAGNESIUM AND POTASSIUM 123 

(e. g., leaves and stems) which are raised above them. It seemed 
desirable therefore to find out how sections of stems and roots would 
behave in the solutions. The answer to this question is given in 
Table VII. Transverse sections of the stem of Tradescantia and the 
root of the common red beet were employed. They were cut on a 
microtome and were of considerable but uniform thickness. 



TABLE VII 

Cuttings and Sections 
All quantities given are cubic centimeters of .o937ffi solutions 



Culture solution 



Duration of life in days 



Microtome sections 

of stem of 
Tropaeolum majus 



Microtome sections 

of root of 

Beta vulgaris 



Develophent 



Cuttings IS'" 

long of 
Tradescantia 



KCl 

ICO KCl ) 
40 MgCU ) ■ 

MgCU 

Distilled water. 



20 

28 + 

20 
28 + 



14 
27 

18 
28 + 



No roots 

Short roots 

No roots 
Long roots 



A plus sign indicates that the plants were alive at the end of the experiment. 

In both cases the color and microscopic appearance served as the 
criterion of death. As is seen in Table VII, the results agree with 
those already obtained. The table likewise shows the results obtained 
from cuttings of Tradescantia (about 15'^™ long) which were placed 
with their lower ends in the solutions. 

In view of the striking agreement of results obtained from such a 
variety of material, it seems useless to seek for further proof. The 
experiments of Loew and Aso also show antagonism between potas- 
sium and magnesium, as far as they go. They do not, however, 
employ sufficient potassium (nor sufiiciently strong solutions) to bring 
out the results clearly. The use of percentage solutions (rather 
than molecular solutions) likewise obscures their results. More funda- 
mental is their confusion of physiologically balanced solutions with 
ordinary nutrient solutions.^ 

As for the theory of Loew and Aso that the inhibitory action of 
potassium on magnesium is due to the formation of a double salt; I; 

s Cf. Osterhout, On nutrient and balanced solutions. University of California. 
Publications, Botany 2:317. 1907; also, BoT. Gazette 44:259-272. 1907. •* * .'. 



134 BOTANICAL GAZETTE [February 

need merely say that it cannot be true because this inhibitory action 
is seen in mixtures of potassium nitrate and magnesium nitrate where 
no double salt is formed. Moreover, even in the chlorids and sulfates 
the formation of a double salt cannot much affect the result, since the 
double salt, at the concentrations here used, dissociates and sets free 
magnesium and potassium ions to almost the same extent as the 
simple salts. 

RESULTS 

Magnesium salts and potassium salts, used separately, are poison- 
ous to plants, but when mixed together (in suitable proportions) the 
poisonous effects more or less completely disappear. These results 
are of importance in soil investigations. 

• University of California 
Berkeley 



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