from the surfaces of open bodies of water, and from the land. We have
all seen “steam” rising from lakes and roadways, but the majority
rises invisible, except as a component of “haze”. And vast
amounts more stream skyward from the billions of open stomata of plants,
which use water as both structure and conveyance.
Sessile organisms by human classification, plants still move, not just
swayed by wind, but actually covering distance by growing, and by sending
out roots or rhizomes in search of water or new territory. They can recreate
themselves by the same processes, as well as by seeds, which are carried
elsewhere by wind and animals, and yes, water. By movements both passive
and self-actuated, plants spread outwards and upwards, going everywhere
they can, dying on inhospitable substrates, but thriving where they meet
the minimal requirements of soil (or that which they can convert to soil),
sunlight and water. They take on every form from single-celled algae to
huge, buoyant kelp beds in water, and from moss to massive firs on land.
Water or other plants may even supplant soil in many instances, leaving
some plants dependent on just two elements, light and water. Plants actively
seek the solar energy they absorb, and a plant’s use of water is
neither passive nor static. Take water away, and plants wilt, their leaves,
or even their whole structure sagging earthwards as internal pressures
drop. Trees, “woody” plants, and many grasses have enough
of a skeleton of lignin to stand aloft a time beyond death, but without
water coursing through them, no plant remains “alive”, never
mind upright. Crystal clear structural blood, with no heart to pump it,
just the willing complicity of the properties of the blood itself.
“Stoma” means “mouth” in Greek, “stomata”
small mouths. With a microcope one would see millions of them on the undersides
of most leaves. Hormonally controlled pressures in the cells that thicken
to form the “lips” of these tiny openings swell them shut,
relax them open. And through these stomata a plant “breathes”.
When open, water evaporates into the air, carrying both the fire of all
carbon-based life, oxygen, as well as this crystal blood, an invisible
vapor off to become cloud.
And a structural miracle keeps the cycle flowing. The cohesive forces
of water rival that of steel in the right conditions, and those conditions
are embodied in a plant’s vascular sytem, in particular the xylem.
Thousands of towers of tiny tubes with closed end walls set at what a
carpenter would call a scarf-joint angle extend root to leaftip. Those
end walls are permeable to water, and they assure the chain links are
not too long and never have an opportunity to break. In the reverse of
the desktop ball-bearing swing toy, as one molecule leaves, the capillary
force draws another up, and the cohesion of that chain extends to the
roots, where water is drawn from that collected by the ambitious, patient
root system. The pressure of this flow keeps many plants upright, and
its release contributes mightily to the clouds through which I so recently
This tense but graceful exploitation of the physics of water takes place
in a war zone. Outwardly trees embody patient peace to the humans
who read poetry under their branches, photograph their fall colors.
But no Shakespearean plot that might be read under any tree’s cool
shade ever had as many eager, rightful heirs held under such a delicately
balanced tyranny as a tree. It seems “right” that plants
use gravity as a reference to balance their quest for the sky. Sunflowers
track the motion of the sun across the sky with shifts in water pressure
and seem beatific in their serene, glacially-paced cycle of sun-worship.
But most plants -- and especially trees -- have many parts, all just as
intent on success as their nearest siblings. A slow-motion race
is in progress, the combatants of similar ability, but over time unequally
armed with chemical weaponry.