100 Nebraska Agricultural Exp. Station, Research Bui. 6. 
VARIATION IN THE DAILY TRANSPIRATION RATE AS INFLUENCED BY THE SOIL- 
MOISTURE CONTENT. 
During two years, 1913 and 1914, eight plants of Hogue's 
Yellow Dent corn were grown in each of several different degrees 
of soil moisture. Summary data of the results secured relative 
to the growth and water requirements are included in Tables 
56, 57, and 58, pages 137, 138, and 139. The average daily loss 
during about one month for the plants in each degree of soil 
moisture is recorded in Tables 29 and 30 and Charts XII and XIV. 
The plants were full grown and the leaf-area was practically con- 
stant during this period. 
The relative daily transpiration in the different degrees of 
soil moisture is also shown in these tables by regarding the loss 
under the optimum moisture conditions (70 per cent saturation) 
as 100 per cent. The object is to show to what extent the fluctu- 
ations in the daily transpiration rates are independent of the 
soil-moisture content, under the conditions of these tests. These 
data are shown graphically in Charts XIII and XV. With a 
few exceptional days, the rates of water loss from plants in dif- 
ferent degrees of soil moisture, altho markedly different in 
amount because of smaller plant development, are seen to be 
rather parallel in their daily fluctuation. There is no consistent 
or striking tendency for the plants lacking moisture to transpire 
a relatively large amount on days of low climatic values or 
relatively small amounts when climatic values are high, as 
measured in per cent of the loss from plants with ample soil 
moisture. 
These facts, together with the failure of transpiration to lag 
behind free water surface evaporation in the heat of the day as 
shown in Charts VIII and IX, are contrary to the observations 
termed incipient drying by Livingston, B. E., and Brown, W. 
H., 1912. It seems entirely probable that had the water supply 
been sufficiently low to cause prolonged wilting, the transpiration 
would have been relatively low during the wilted condition. 
Wilting is accompanied by a reduced turgidity or a relatively 
low moisture content in the leaf. It is a principle in physics that 
water evaporates less readily from an object with a low moisture 
content than from one containing much moisture. Microscopic 
examination has shown that with a collapse of leaf tissue which 
accompanies wilting, the stomata are in a fairly closed condition, 
thus reducing the opportunity for diffusion. 
