It does not follow, however, that the
more vigorously a crop grows, the more rapidly does it transpire
water, for it is well known that the most luxuriant plant growth
occurs in the tropics, where the transpiration is exceedingly low.
It seems to be true that under the same conditions, plants that grow
most vigorously tend to use proportionately the smallest amount of
water.
Tenth, the root system--its depth and manner of growth--influences
the rate of transpiration. The more vigorous and extensive the root
system, the more rapidly can water be secured from the soil by the
plant.
The conditions above enumerated as influencing transpiration are
nearly all of a physical character, and it must not be forgotten
that they may all be annulled or changed by a physiological
regulation. It must be admitted that the subject of transpiration is
yet poorly understood, though it is one of the most important
subjects in its applications to plant production in localities where
water is scaree. It should also be noted that nearly all of the
above conditions influencing transpiration are beyond the control of
the farmer.
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