OTHEK FACTOKS INFLUENCING WATER REQUIREMENT. 67 
OTHER FACTORS INFLUENCING THE WATER REQUIREMENT. 
THE EFFECT OF RELATIVE LEAF AREA ON THE WATER REQUIREMENT. 
Montgomery's experiments. 
Montgomery (1911) has investigated the influence of the leaf area 
of corn on its water requirement, using for this purpose selected 
strains having a high leaf area and a low leaf area, respectively. 
The plants were grown in large potometers of two sizes, one con- 
taining 1,000 pounds and the other 350 pounds of soil. The larger 
potometers contained two plants each, the smaller ones a single 
plant. The results of the experiments, which cover a period of 
three years, are given in Table LVIII, and show that, with an average 
difference in relative leanness of 14 per cent, the more leafy type 
had a water requirement 7 per cent higher than the less leafy strain. 
The leafy plants required 16 per cent more water to produce an 
equal weight of ear. 
Table LVIII. — Effect of relative leaf area on the water requirement of corn, according 
to Montgomery (1911, p. 150). 
Year. 
Ratio of leaf area 
to dry weight. 
Ratio of 
high to 
low. 
Water require- 
ment. 
Ratio of 
high to 
low. 
Low leaf 
area. 
High leaf 
area. 
Low 
leaf. 
High 
leaf. 
1907 
2.31 
2.33 
2.10 
2.65 
2.73 
2.36 
1.14 
1.17 
1.12 
220 
263 
236 
242 
287 
240 
1.10 
1909 
1.09 
1910 
1.02 
Mean 
1.14±.01 
1.07±.02 
1 
The transpiration per unit area of leaf was higher in the less leafy 
types, the ratio of low to high leaf area for the three years being 1 .04, 
1.07, 1.10. But some transpiration takes place also from the stalk, 
which would be relatively greater in the type with low leaf area, and 
the effect of this would be to make the transpiration of the low leaf- 
area strain per unit area appear higher than it really is. This effect 
is not sufficient, however, to account for the differences found between 
high leaf- area and low leaf- area types. From a computation made 
by the writers it appears that, in order to account for the observed 
differences in transpiration per unit area of leaf, the stalk would have 
to possess an area which is the equivalent as regards transpiration 
of 20 to 40 per cent of the total leaf area. 
Montgomery's results indicate that the transpiration loss of corn 
in proportion to the growth made is decreased by a decreased leaf 
area. It is possible, however, that the narrow-leaved type developed 
through selection possessed also a varietal efficiency in the use of 
285 
