Epinasty is the one of the effects caused by flooding the roots of
plants with water. It is produced by the hormone Ethylene. What it
looks like is the leaves are wilting just as if the plant had not
enough water. What has been shown though is that Ethylene causes the
upper part of the leaf stem to grow or grow faster than the bottom,
thus the leaf droops down in a purposeful way. The reason for this
effect has puzzled scientists.

Suggestion: Epinasty during flooding is adaptive because the downward
directed leaves act as sails in the wind, and the wind action on the
leaf acts on the plant and leaf stems like somebody working a lever
water pump.

That is there is a physical mechanism within the stem similar to a
lever water pump which is activated by the up and down movements of
Epinastic leaves blown in the wind. There should then be structure
analogous to those in a lever pump, for example pistons, diaphragms,
valves etc. I don't know how these pumps really work.

The idea is that a flooded plant needs to pump water out of space
surrounding the roots as quickly as possible. Epinasty then does this
through ramped up transpiration induced by a higher water pressure from
a lever pump action. (Maybe downward directed leaves transpire more
quickly in the wind even without pump action because when they become
perpendicular to it or when the plant makes sure to epinastically grow
perpendicular to the most common prevailing wind - this makes
transpiration faster than if the leaves are parallel to the wind as the
are on the most part during normal conditions.)

Since I believe these is nothing new under the sun, I'm sure this idea
has been around before.