638 Journal of Agricultural Research voi. xxxi, no. 7 
WEATHER CONDITIONS A FACTOR IN ALKALI TOLERANCE 
The wide fluctuations in the percentage of survivors on different 
dates were apparently due to changes in weather conditions, while 
the seedlings were exposed to the salt solutions. No detailed notes 
were taken on the daily behayior and appearance of the seedlings 
in relation to weather conditions, but it was noted when making 
the counts that the number of survivors was likely to be small if 
exceptionally high temperature in combination with high wind 
velocity and. low relative humidity prevailed during a considerable 
part of the time when the seedlings were being tested. It was also 
observed that when cloudy weather, with high relative humidity 
prevailed during one or more days of the test, the number of sur¬ 
viving seedlings usually increased. 
Fig. 1The four stages of plumule development at which maize seedlings were subjected to concen¬ 
trated sodium-chloride solutions. Stage No. 2 illustrates that of greatest resistance, and stage 
No. 4 that of least resistance 
The mean maximum and minimum temperatures, relative humid¬ 
ity, and wind velocity, during the three and four day periods while 
the seedlings were being tested are given in Table IV. 
The data in Tables III and IV indicate that the high relative hu¬ 
midity occurring during the period May 28 to June 3 apparently 
affected an increase in the seedlings which were counted on May 31 
and June 3. During June 6 to 9 there occurred a period of low rela¬ 
tive humidity accompanied by unusually high wind velocity and its 
effect is reflected in the relatively small percentage of survivors re¬ 
corded on June 9. 
There were indications also that seasonal changes influenced, the 
resistance of the seedlings to the salt solutions, and some adjust¬ 
ments were made in the method in order to meet these conditions. 
It was found that the plants developed more rapidly and showed 
distress more quickly during the hot months of summer than during 
the spring and autumn. 
