Oct. 1, 1925 
Resistance o f Maize to Sodium Chloride 
639 
Table IV .—Mean maximum and minimum temperatures, relative humidity, wind 
velocity, and total precipitation, during the three and four day periods while seed¬ 
lings were exposed to sodium-chloride solutions 
Period 
Mar. 27 to 29___ 
Mar. 29 to 31...... 
Apr. 3 to 5. 
Apr. 4 to 6... 
Apr. 12 to 14... 
Apr. 19 to 21.... 
May 20 to 22.. 
May 28 to 31__ 
May 31 to June 3... 
June 6 to 9... 
June 12 to 15... 
June 22 to 25__ 
June 28 to July 1.. 
July 3 to 6__.. 
July 19-22___ 
Mean 
maximum 
tempera¬ 
ture 
Mean 
minimum 
tempera¬ 
ture 
Mean 
relative 
humidity 
Mean wind 
velocity 
Rainfall 
during 
period 
66 
43 
54 
2.4 
0.44 
66 
41 
58 
1.9 
79 
46 
48 
2.1 
.03 
80 
50 
64 
3.6 
.13 
78 
51 
60 
2.6 
90 
44 
33 
2.1 
98 
58 
31 
2.1 
91 
61 
49 
2.9 
.51 
98 
61 
51 
1.8 
98 
56 
29 
3.7 
109 
70 
38 
1.9 
106 
67 
42 
1.6 
106 
79 
45 
2.0 
101 
75 
56 
2.2 
.04 
101 
62 
40 
1.8 
SUMMARY 
The use of water cultures in breeding alkali-resistant strains of 
maize, by selecting individual seedlings which survived strong salt 
solutions, was studied and various modifications were tested. 
The stage of development of the seedlings was found to be an 
important factor in determining the amount of salt in solution which 
they were able to withstand. 
In testing the youngest stages of seedling development, using 
various lengths of radicles as a basis of grouping, the resistance in¬ 
creased up to certain limits in proportion to the length of the radicles. 
The greatest number were killed by strong salt solutions when the 
radicles were 25 millimeters long, and the smallest number when the 
radicles were 100 millimeters long. 
The extent of the development of the plumule was found to be the 
most satisfactory indicator for preparing uniform groups of seedlings 
in the older stages of growth. 
The stage at which the older seedlings were most resistant to 
sodium chloride was just prior to the unfolding of the first true leaf. 
Young seedlings with short radicles and undeveloped plumules were 
found to be most susceptible; the oldest plants with two seed leaves 
were the next in susceptibility; and the intermediate stages were the 
most resistant. 
Seedlings whose radicles were destroyed earliest by the salt solution 
made the most rapid plumule growth, due to the rapid development 
and early functioning of the permanent roots. 
Artificial excision of the radicles increased the resistance of the 
seedlings to a marked degree, causing a prompt and comparatively 
rapid development of permanent roots and plumule, even while 
exposed to a strong salt solution. 
it was found impossible to obtain consistent results when comparing 
the.behavior of seedlings subjected to salt solutions on different dates, 
the resistance of the seedlings apparently being influenced profoundly 
by changes in weather conditions. 
