Oct. 6, 1923 
Temperature of the Leaves of Crop Plants 
37 
TabtE VII .—Average temperature of the upper and lower surfaces of the leaves of plants 
under different conditions of light intensity 1 
Time. 
Kind of plant. 
June 15: 
9.30 to 10.00 a. m., 
July 3: 
10.05 to 10.20 a. m. 
10.30 to 10.4s a. m. 
July 26: 
10.40 to 11.00 a. m, 
11.05 to 11.15 a. m, 
1.20 to 1.30 p. m.. 
1.35 to 1.45 P* m.. 
2.00 to 2.10 p. m.. 
2.15 to 2.25 p. m.. 
3.05 to 3.30 p. m.. 
3.45 to 3.55 P- m.. 
4.05 to 4.20 p. m.. 
4.30 to 4.40 p. m.. 
6.10 to 6.20 p. m.. 
6.30 to 6.40 p. m.. 
6.45 to 6.55 p. m.. 
July 28: 
2.05 to 2.15 p. m.. 
2.20 to 2.30 p. m.. 
Aug. 8: 
3.00 to 3.30 p. m.. 
3.40 to 3.55 p. m.. 
4.10 to 4.25 p. m.. 
Aug. 9: 
2.00 to 2.15 p. m.. 
2.20 to 2.35 p. m.. 
Aug. 10: 
8.50 to 9.05 a. m.. 
9.10 to 9.25 a. m.. 
10.10 to 10.25 a - m 
10.30 to 10.45 a - m 
2.30 to 2.45 p. m.. 
2-55 to 3.10 p. m.. 
Aug. 12: 
8.45 to 9.00 a. m.. 
9.02 to 9.15 a. m.. 
Aug. 14: 
8.45 to 9.00 a. m.. 
9.50 to 10.05 a - m. 
11.15 to 11.30 a. m 
1.40 to 1.55 p. m.. 
4.40 to 4.55 p. m.. 
Aug. 15: 
1.45 to 2.00 p. m.. 
Aug. 16: 
8.35 to 8.50 a. m.. 
8.55 to 9.10 a. m.. 
9.25 to 9.40 a. m.. 
9.45 to 10.00 a. m. 
Feterita. 
Cane, Freed. 
Corn, Pride of Saline. 
Cowpeas, New Era. 
Pumpkin, Cheese. 
Cowpeas, New Era.... 
Pumpkin, Cheese. 
Cowpeas, New Era. 
Pumpkin, Cheese. 
Watermelon, Cobs Gem. 
.do. 
Sudan grass. 
.do..... 
Cowpeas, New Era. 
Watermelon, Cobs Gem. 
Sudan grass. 
Com, Kansas Sunflower. 
.do. 
Alfalfa, Common. 
.do. 
.do. 
.do. 
.do. 
.do. 
.do. 
.do. 
.do. 
.do. 
.do. 
.do. 
.do. 
Kafir, Blackhull. 
.do. 
.do. 
Sudan grass. 
Corn (Reid Yellow Dent)... 
Corn, Commercial White_ 
Bean, Velvet.. 
.do. 
.do. 
.do. 
Num¬ 
ber of 
deter¬ 
mina¬ 
tions. 
Conditions. 
Average temperature 
of— 
Air. 
Upper. 
Tower. 
•c. 
°C. 
°C. 
20 
In sunshine... 
27. 6 
26.8 
26.5 
20 
.do. 
25.6 
25.1 
20 
.do. 
25* 7 
25.4 
10 
Shaded. 
30-3 
29.4 
29-3 
10 
.do. 
30-9 
29.9 
30.0 
10 
In sunshine... 
35 -1 
35 -x 
34-4 
10 
.do. 
35*4 
35-7 
35-4 
10 
Shaded. 
31-9 
• 30- 8 
30 * 7 
10 
.do. 
3 i- 7 
30-5 
30-4 
20 
In sunshine... 
35-4 
35-9 
35 - I 
10 
Shaded. 
29-4 
28.5 
28. 5 
10 
In sunshine... 
30. 6 
30. 6 
30. 2 
10 
Shaded. 
28. 7 
27. 7 
2 7. 7 
10 
In sunshine... 
28. 2 
27.1 
27.1 
10 
.do. 
27 - 5 
26. 9 
26.9 
10 
.do. 
27. 2 
26. 9 
26- 9 
10 
.do. 
35-4 
34-9 
34-7 
10 
Shaded. 
34-3 
33-8 
33-8 
20 
In sunshine... 
26. 4 
25. 8 
25-7 
20 
26.6 
26.0 
25 * 9 
20 
.do. 
26.6 
26.1 
26- O 
20 
3 °- 7 
29. 7 
29 - 5 
20 
Shaded. 
29.1 
28.3 
28. 3 
20 
In sunshine... 
26. 7 
26.4 
25. 8 
20 
Shaded. 
26. 0 
25. 2 
25*1 
20 
In sunshine... 
29 - 2 
28. 0 
27. 7 
20 
Shaded. 
28. O 
27.1 
26.9 
20 
In sunshine... 
32-5 
31-6 
31-3 
20 
Shaded. 
30*3 
29.1 
29. 0 
20 
In sunshine... 
27. 7 
26.8 
26.6 
20 
' Shaded. 
26. 5 
25.6 
25-5 
20 
In sunshine... 
29 - 7 
30-4 
29. 7 
20 
Shaded. 
30 - 5 
30.1 
30.0 
20 
In sunshine... 
32.0 
32. 6 
32. 2 
20 
.do. 
32 . 5 
32.4 
32.1 
20 
Shaded. 
30-4 
3°-3 
30-3 
20 
In sunshine... 
32-9 
32.1 
31-7 
20 
28.6 
28. 5 
28. 5 
20 
Shaded. 
28. 5 
28.1 
28.1 
20 
In sunshine... 
29-3 
29. 6 
29.6 
20 
Shaded. 
30. 2 
29.9 
29.9 
1 The conditions of diffuse light for the experiments reported in this table were obtained by shading the 
entire plant, or that portion of it under observation, by an ordinary umbrella. 
given in Tables VIII and IX, and the results of the experiments are illus¬ 
trated by graphs in figures 6 and 7. Some observations were made on 
the temperature of different leaves of the same plant, some of which 
were in direct sunlight and some shaded by other leaves of the plant. 
An example of the behavior of the temperature of the leaves of cowpeas 
under these conditions during a 20-minute period is shown in Table X, 
and is illustrated by graphs in figure 8. The data obtained show that in 
diffuse light the temperature of attached turgid leaves of the plants 
studied is always consistently lower than the temperature of the sur¬ 
rounding air. The average temperature differences between the turgid 
leaves and the surrounding air under conditions of diffuse light varied 
from 0.1 0 to 3 0 C. In a large number of cases the difference was less than 
