398 
Journal of Agricultural Research 
Vol. XXXI, No. 4 
In the majority of cases the equilibrium point reached with soy¬ 
bean root tips under the foregoing conditions was P H 6.18 to 6.49. 
The lowest equilibrium point reached from the alkaline side was P H 
5.89, and the highest from the acid side was P H 6.44. 
When allowed to stand quietly in larger quantities of the buffer 
mixtures, the equilibrium point reached, as determined colorimetri- 
cally, was P H 5.9; as determined electrometrically, P H 6.72 to 6.85. 
When the mycelium of Gibberella saubinetii was placed in small 
quantities of dilute buffer mixtures, and the reaction determined 
electrometrically, solutions of P H 5.88 or less became more alkaline, 
and solutions of P H 6.88 or greater became more acid. The lowest 
equilibrium reached from the alkaline side was P H 6.21, and the 
highest from the acid side was P H 6.25. 
When the mycelium of Fusarium lycopersici was treated in the 
same way, solutions of P H 5.43 or less became more alkaline, and 
solutions of P H 6.66 or greater became more acid. The lowest 
equilibrium point reached from the alkaline side was P H 5.52, and the 
highest from the acid side, with one exception, was P H 5.50. 
When the mycelium of Fusarium oxysporum was treated in the same 
way, solutions of P H 4.73 or less became more alkaline, and solutions of 
P H 5.06 or greater became more acid. The lowest equilibrium point 
reached from the alkaline side was P H 4.71, and the highest from the 
acid side was P H 4.94. 
It is concluded that, under the particular conditions of these exper¬ 
iments, these plant tissues act much like amphoteric colloids, with 
isoelectric points as follows: For potato-tuber tissue at P H 6.4; for 
soy-bean root tips (variety Virginia) at 6.2 to 6.44; for the mycelium of 
Gibberella saubinetii at 6.2; for the mycelium of Fusarium lycopersici 
at 5.5; and for the mycelium of Fusarium oxysporum at 4.9. 
LITERATURE CITED 
(1 ) Arrhenius, O. 
1920. OCOLOGISCHE STUDIEN IN DEN STOCKHOLMER SCHAREN. 123 p., 
illus. Stockholm. 
(2) Hopkins, E. F. 
1922. hydrogen-ion concentration in its relation to wheat scab. 
Amer. Jour. Bot. 9: 159-179, illus. 
(3) Michaelis, L. 
1922. DIE WASSERSTOFFIONENKONZENTRATION. TEIL I. DIE THEORETI- 
schen grundlagen. AufL 2, BcL 1, illus. Berlin. 
(4) Pearsall, W. H., and Priestley, J. H. 
1923. MERISTEMATIC TISSUES AND PROTEIN ISO-ELECTRIC POINTS. New 
Phytol. 22: 185-191. 
(5) Robbins, W. J. 
1923. AN ISOELECTRIC POINT FOR PLANT TISSUE AND ITS SIGNIFICANCE. 
Amer. Jour. Bot. 10: 412-439, illus. 
1924. ISOELECTRIC POINTS FOR THE MYCELIUM OF FUNGI. Jour. Gen. 
Physiol. 6 : 259-271, illus. 
(7) Rohde, K. 
1917. untersuchungen uber den einfluss der freien h-ionen im 
INNERN LEBENDER ZELLEN AUF DEN VORGANG DER VITALEN 
fXrbung. Arch. Physiol. [Pfluger] 168: 411-433, illus. 
(8) Scott, I. T. 
1924. THE INFLUENCE OF HYDROGEN-ION CONCENTRATION ON THE GROWTH 
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