AGE OF SEEDLINGS AS A FACTOR IN THE RESISTANCE 
OF MAIZE TO SODIUM CHLORIDE 1 
By G. J. Harrison, Senior Scientific Aidj Office of Alkali and Drought-Resistant 
Plant Investigations, and C. J. King, Associate Agronomist, Office of Crop Acclir 
matization, Bureau of Plant Industry, United States Department of Agriculture 
INTRODUCTION 
Much work has been done in recent years in comparing different 
genera, species, varieties,, and strains of plants as to their resistance 
to the effect of salt solutions. Harter (3), 2 Kearney and Harter (5) 
and others have called attention to the opportunity for selecting and 
breeding the most resistant strains for alkali soils common in the arid 
portions of the United States, but apparently little has been accom¬ 
plished along such lines. 
The work of the writers, the results of which are presented in this 
paper, was taken up in 1923 at the suggestion of G. N. Collins, 
botanist in charge of biophysical investigations of the Bureau of 
Plant Industry, United States Department of Agriculture, who sug¬ 
gested the water-culture method, whereby great numbers of indi¬ 
viduals could be handled and observed in a short time, as a means of 
segregating individuals showing marked resistance to the effects of 
the salts contained in alkali soils. 
Since sodium chloride is a predominating salt in the southern Ari¬ 
zona valleys, 3 it was decided to make use oi this salt alone in the pre¬ 
liminary experiments ( 6 ). Corn was chosen as the crop to use be¬ 
cause of the ease of handling and transplanting the seedlings and its 
suitability for genetic studies. Extreme variation in tolerance of 
seedlings of different sizes to the effects of sodium chloride was en¬ 
countered soon after the investigations were started, and the results 
obtained in this phase of the work are presented and discussed in 
this paper. 
EXPERIMENTAL METHODS 
The seeds were sprouted on a lime-sawdust germinating table (4), 
and allowed to remain until the radicles had attained convenient 
length for suspending in the salt solutions, then the seedlings were 
transferred to perforated aluminum disks which were floated by means 
of sealed glass buoys on the surface of the solutions contained in 
enameled milk pans (I). 4 These culture pans contained 3 liters of 
the salt solution, and the volume was kept constant by the use of 
Mariotte flasks suspended above each pan. In all of the work prior 
to May 22 the seedlings were assorted according to the length of the 
primary radicle, and 100 plants of uniform radicle length were placed 
1 Received for publication Jan. 7, 1925; issued December. 
2 Reference is made by number (italic) to “Literature cited,” p. 640. 
2 The results of analyses by the Bureau of Soils, U. S. Department of Agriculture ( 6 ), indicate that sodium 
and chlorine comprise on an average 56.3 per cent of the total alkali salts in the soils of the U. S. Field Sta¬ 
tion at Sacaton, Ariz. (Na 31.9 and Cl 24.4). , _ _ 
4 The writers gratefully acknowledge the helpful assistance rendered by J. F. Breazeale, associate 
biochemist in the Office of Western Irrigation Agriculture, Bureau of Plant Industry, U. S. Department 
of Agriculture, who performed work along similar lines in 1921 and 1922. 
Journal of Agricultural Research, 
Washington, D. C. 
( 633 ) 
Vol. XXXI, No. 7 
Oct. 1, 1925 
Key No. G-483 
