Jan, 12, 1924 
Anchorage and Extent of Corn Root Systems 
77 
Additional data from a comparative study of root systems of plants 
from a good strain and two strains susceptible to rootrot are given in 
Table VII. Differences in the number of main roots, 6.1 ± 2.0 roots and 
10.2 ± 1.2 roots, were marked. The latter difference, being 8.5 times its 
probable error, is very significant. Both differences in mean total 
number and mean total length of all laterals on equal lengths of main 
roots are very significant. The greatest and most important difference 
between the good strain and the strains susceptible to rootrot, however, 
lay in the mean total lengths of all laterals per plant on healthy roots 
only in a horizontal 6-inch section 6 to 12 inches below the surface. In 
one comparison the difference was 7.2 times the probable error, and in 
the other comparison, 7.0 times the probable error. 
The significance of such differences in root systems is still further 
emphasized by the fact that plants of the strains susceptible to rootrot 
were considerably taller than plants of the good strain. The importance 
of such differences in ratio of lengths of roots which function to those of 
parts above ground is plainly evident. 
Additional data on the relation of extent of root system to pulling 
resistance and lodging in the good strain and the strain susceptible to 
rootrot are presented in Table VIII. The difference of 6, or 16.2 per 
cent, in number of main roots, although not large, was very consistent 
and significant. Differences both in mean total number of lateral roots 
and mean total length of lateral roots were very marked. The strain 
susceptible to rootrot had a lower pulling resistance and more leaning 
plants than the good strain. 
Tabl£ VIII .—Data from a comparative study of plants from a good inbred strain and 
plants from an unrelated inbred strain susceptible to rootrot, the corn being planted 
May 22, IQ 22 , in adjacent rows, near Bloomington, III., on brown sill loam soil on 
which the three previous crops were corn, 10 plants from each strain being excavated 
September 16-18 , and ij erect plants with green stalks from each strain being pulled 
September 28 and 2Q 
Percentage of 
30° or more in 
years. 
plants leaning 
l a period of six 
Character of strain. 
1917 
1918 
1919 
1920 
1921 
1922 
Mean 
resist¬ 
ance 
per 
plant 
to a 
vertical 
pull. 
Mean 
number 
of main 
roots per 
plant. 
Good.. . . .. 
Per 
cent. 
0.0 
Per 
cent. 
8.0 
Per 
cent. 
0.0 
Per 
cent. 
0.0 
Per 
cent . 
7.8 
83-3 
Per 
cent. 
2-5 
20.0 
Pounds. 
2 5 I -5 
198.5 
53-0 
21. I 
37 
3 i 
6 
Susceptible to rootrot. 
0.0 
• y 
7.1 
31-8 
10.1 
Difference between good 
and susceptible strains.. 
Percentage difference 
based on good strain.... 
16.2 
Odds. 
322U 
3 . 332 :i 
Mean 
total 
number 
of 
lateral 
roots 
per 
plant 
on six 
6-inch 
pieces 
of main 
roots 
6 to 12 
inches 
below 
surface. 
318.4 
212.7 
«> 5-7 
33-2 
SS4U 
Mean 
total 
length 
of 
lateral 
roots 
per 
plant 
on six 
6-inch 
pieces 
of main 
roots 
6 to 12 
inches 
below 
surface. 
Inches • 
434-5 
217.4 
217.1 
50.0 
908:1 
