> I suspect that the stalk should
> bend most strongly at the base, because of (a) the wind acting not only
> on the tip of the stalk, but also on lower portions, so that the wind
> force affecting the bending of any given point increases downward along
> the stalk,

I would say that it decreases as you approach the ground.  See Alain's comments,
although I would say that the maximum force/curvature would be near the top.
There is the shielding effect, the tapering effect, the higher surface area due
to flowering, and also the laminar flow issues.

> (b) the stalk acting as a lever, further amplifying the
> bending force exerted on any given point on the stalk based on how far
> it is from the tip

True, but it's all to easy to "reason in reverse" and come up with exactly the
opposite conclusion.   Can't tell you how many times I've done that.  :\

>(c) the wind force acting upon a near-vertical
> portion of the stalk being stronger than that acting upon a
> near-horizontal portion.

?  Not sure what you meant by that.

>
> The reeds should bend in a single direction only (albeit at different
> amplitudes) - the primary direction of the wind.

True, but often there is some asymmetry to the stalk - they might be elliptic in
cross-section, and sometimes IIRC they are almost tear-shaped, with a thin rigid
rib at the thinnest portion.  Depending upon the orientation of that and the
direction of the wind, that could give rise to a twisting effect.
I suppose searching for some IRL video would be in order.

> As for the waves, I guess they are not from turbulences already present
> in the wind, but rather from upright reeds "shadowing" those further
> downwind causing them to rise again, while themselves being exposed to
> the wind and beginning to move downward; this effect might be initiated
> and amplified by the individual reeds also resonating in the wind due to
> (c).

I'm not quite sure exactly what the waves are a result of, but anyone who's done
and has studied long-range ballistics knows that wind speed and direction can be
all over the place between you and what you're looking at 400 yards away.
What's going on where you are, what's going on at where you're looking, and
what's going on at various places in between can vary and even be in complete
opposition.
Consider a tornado, where on one side the air is moving North, and on the other
side it's moving South.  Ditto East & West.
The same kind of thing can happen in vertical strata as well.

I think Thomas needs funding to study the issue....    ;)

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