Oct. 1, 1925 
Resistance of Maize to Sodium Chloride 
635 
mine the highest concentration of salt to which a plant can be exposed 
without showing injury to any of its organs or without seriously 
affecting its ordinary behavior or growth. In this experiment the 
purpose was to kill off a greater part of the plant population in order 
to isolate those individuals which showed a marked resistance. It will 
Tie seen that salt concentrations used in this experiment are consider¬ 
ably higher than those used by most of the other investigators, who 
have seldom carried the concentration to the point where the entire 
plant was killed. 
RESISTANCE OF SEEDLINGS WITH DIFFERENT LENGTHS OF 
RADICLES 
At the beginning of the experiment seedlings were used which had 
developed radicles only 25 to 50 millimeters long with plumules still 
encased in the coleoptyles. It soon was discovered that seedlings of 
this size were unsatisfactory for use in the higher concentrations of 
salt, for, where the percentage of salt was as great as 1.8 per cent, no 
further elongation of the radicle was observed after a few hours in 
solution. A few of the seedlings developed a hardened bulbous en¬ 
largement just behind the tip of the radicle, and in such cases the root 
remained turgid and healthy but without further growth of radicle 
or coleoptyle. On most of the seedlings, however, the radicle be¬ 
came flaccid during the first 24 hours in the salt solution, and at the 
end of 72 hours many of the primary roots had sloughed off, leaving 
only a stub attached to the mesocotyl (£). At the end of this period 
the coleoptyles of many of the seedlings had assumed a yellowish 
color and showed signs of decomposition. A few seedlings however, 
after losing their radicles began to develop secondary roots from 
the base of the mesocotyl or laterally' from the remaining stub of 
the radicle. In such cases there occurred a guick response in growth 
of the plumule, and development was continued though slowly for 
several days while exposed to the salt solution. Inasmuch as the 
primary or axial root soon dies undei* field conditions in the early 
stages of development of the maize plant, it was decided that the most 
valuable test of resistance should occur after the brace roots or 
permanent roots had begun to function. 
The percentage of seedlings with radicles of various lengths which 
survived after 72 hours in the salt solutions are shown in Table I. 
Table I. — Percentage of maize seedlings surviving after 72 hours in salt solution , 
when the primary radicles were at different lengths between 25 and 100 millimeters 
Date 
Percentage 
of sodium 
chloride 
Length of radicle (percentage of seedlings surviving °) 
25 mm. 
38 mm. 
42 mm. 
51 mm 
88 mm. 
100 mm. 
1924 
Mar 29 
2.0 
2.2 
2.0 
2.0 
2.2 
2.2 
2.2 
2.2 
11.7±2.33 
11.2±2.18 
ATar 31 
A pr H 
6.9dbl. 76 
- 
A pr fi 
6.9±1.76 
18.4±2.48 
14.8±2.33 
11.4±2.45 
Do 
A pr 14 
3.3±1.20 
11.2±2.13 
4.9±1.47 
8.9±2.04 
Apr 21 
8.6±2.00 
12.8±2.35 
May 22__ 
3.1±1.169 
22.8±2.84 
23. Idb2.84 
•The irregular growth of the radicles made it impracticable to select a sufficient number of seedlings of 
the various radicle lengths to represent each group for comparison on the same day. 
