>> I'm assuming that the starch in the leaves that is consumed during night is somewhat separate from the starch content in say a root?
I assume the same thing. They said:
"Photosynthetic starch reserves that accumulate in Arabidopsis leaves
during the day decrease approximately linearly with time at night to support metabolism and growth."
- See more at: http://elifesciences.org/conte...
I didn't read past the point where they said they constructed some models, and that the measurements fit one or both of their models. That told me that they were not going to even speculate on the real
mechanism, so I lost interest.
Whether or not Arabidopsis can or does mobilize [u]any[/y] starch reserves from stems or roots at night, or perhaps on nights where their "planning ahead" fell short, I don't know.
But "it makes sense" for a plant to have some long-term energy storage, and some short-term energy storage, and little reason they should both work the same way.
Elsewhere the authors say that daily-varying starch is stored "in plants" rather than saying "in plants' leaves", so I'm guessing there is variation in where "daily starch reserves" are stored, in different plants, or in genera other than Arabidopsis.
But we're both speculating.