22 
Journal^ of Agricultural Research 
Vol. XXV, No. x 
Inspection of the climatic data shows that while the absolute extremes 
of temperature varied much more at the higher range than at the lower 
one, the daily average temperature varied only 4.5° in the former case 
and 3 0 in the latter. On the average, a difference of about 5.3 0 C. was 
maintained fairly continuously between the two chambers. The total 
evaporation during the growth of the cultures, as measured by the black 
atmometers, was only 6.5 per cent greater at the higher temperature 
than at the lower one. As measured by the white atmometers the 
difference of evaporation was 7.2 per cent. Had the mass of water 
remained the same at the former average temperature of 22.8° C. as at 
the latter average of 17.5 0 C, with the relative humidity at 70 per cent 
in the latter case, the saturation deficits would have been 10.32 mm. 
and 4.50 mm., respectively. Thus, if uncontrolled, the evaporation 
would have been 129 per cent greater at the higher than at the lower 
temperature. The normal tendency for difference in evaporation with 
uniform water supply was therefore greatly reduced in this experiment. 
As indicated by the ratio of water loss between the black and the white 
atmometers, the intensity of solar radiation was nearly the same in the 
two culture chambers. 
Table IV. —Climatic records of plant chambers in experiment of IQ20 
Designation of temperature 
range. 
Absolute 
maximum 
tempera¬ 
ture. 
Daily aver¬ 
age max¬ 
imum tem¬ 
perature. 
Absolute 
minimum 
tempera¬ 
ture. 
Daily aver¬ 
age min¬ 
imum tem¬ 
perature. 
Total evap¬ 
oration 
standard 
black 
atmometer. 
Ratio of 
evapora¬ 
tion black 
to white 
atmometer. 
°c. 
°c. 
°c. 
°c. 
Cc. 
High. 
33 -o 
25.0 
10. 0 
20. 5 
769 
I. 083 
Tow. 
23. 0 
19. 0 
14. 0 
l6. O 
721 
I. 086 
Table V.— Yield and composition of buckwheat, soil cultures of climatic chambers 
in IQ 20 
| 
Range of temperature 
(daily average). 
Number 
of seeds 
! at har¬ 
vest. 1 
Dry matter of tissues. 
Dry matter yield. 2 
Leaf. 
Stem. 
Leaf. 
Stem. 
Seed. 
°c. 
Per cent. 
Per cent. 
Gm. 
Gm. 
Gm. 
20.5 to 25. 
73 
14.7 
II. 2 
5-36 
9 - 52 
2. 03 
16 to 19. 
57 
15*9 
13*9 
5 - 26 
9-15 
I. 82 
Composition of dry matter. 
Range of tem¬ 
perature (daily 
average). 
Ether extract. 
Polysaccharids.* 
Nitrogen. 
j Leaf. 
! 
Stem. 
Seed. 
Leaf. 
Stem. 
Seed. 
Leaf. 
Stem. 
Seed. 
°C. 
20.5 to 25- 
16.0 to 19. ... 
j Per cent. 
: 9 - 7 
8.5 
Per cent. 
I. O 
•9 
Per cent. 
3-2 
3-2 
Per cent. 
18. 2 
22.6 
Per cent. 
33 -o 
38.2 
Per cent. 
39.6 
45-4 
Per cent. 
5 * 1 
4 - 5 
Per cent. 
1.8 
1.4 
Per cent. 
2.6 
2. 8 
1 Broken parts removed before harvest contained 2 immature seeds at higher and 11 at lower temper* 
2 Dry weight of broken parts: Leaf at high temperature c.41 gm., low temperature 0.46 gm.; stem at 
high temperature 0.32 gm., low temperature 0.30 gm. 
3 Hemicellulose of leaf and stem determined by hydrolysis with 4 per cent HC 1 3 hours; starch of seed 
determined by digestion with saliva. 
