Not relying on anything but intuition, my first though was this is a hoax. If the gel is so hydrophilic that it can harvest water from the air, yet be less hydrophilic than plant roots (otherwise, the gel would not release the water to the roots), then..... being more hydrophilic than the gel, why can't the plant roots just grab water from air, too?
So I had to read more. Sorry to say, I don't have too much time now to do so, but I did find a satisfying answer: the gel is not a single substance, but interacting components that are thermodynamic, with properties that change with temperature. Hard to envision, though, how such a comparatively small temp range could be beneficial in wide applications. But... we have to start somewhere!
