Hjacking Photosynthesis

[brewer]

Yes-ish and no-mostly.  It's technically possible to micromanage exposure but it's not practical or cost effective.  You'd have to draw and retract shade constantly, as often as clouds roll across the sky.  Widening the thresholds and increasing response time, even if you did that (draw and retract shade), would still be beneficial, but the response time of the leaf is a more cost effective solution in the broadest number of scenarios and applications.  

There's already a pretty cost effective way to convert cellulose into sugar.  Integrated sugar beet production.  Probably not what you had in mind, lol.  You're thinking more along the lines of cellulosic ethanol commercialization, with an edible byproduct, yeah?  Food or fuel carbon nuetral.

I think photochromic panels for the greenhouse ceiling/walls might work. 

As far as cellulose, not alcohol production, conversion to edible sugar. The termite gut does it.