Botanical authorities agree that transpiration is of value to plant
growth, first, because it helps to distribute the mineral nutrients
necessary for plant growth uniformly throughout the plant; secondly,
because it permits an active assimilation of the carbon by the
leaves; thirdly, because it is not unlikely that the heat required
to evaporate water, in large part taken from the plant itself,
prevents the plant from being overheated. This last mentioned value
of transpiration is especially important in dry-farm districts,
where, during the summer, the heat is often intense. Fourthly,
transpiration apparently influences plant growth and development in
a number of ways not yet clearly understood.
Conditions influencing transpiration
In general, the conditions that determine the evaporation of water
from the leaves are the same as those that favor the direct
evaporation of water from soils, although there seems to be
something in the life process of the plant, a physiological factor,
which permits or prevents the ordinary water-dissipating factors
from exercising their full powers.
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