Ask a Question forum: Does This sound Reasonable?

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BeKind
Nov 27, 2015 7:47 PM CST
Consider: By day, plants convert atmospheric carbon dioxide into starch and sugars. During the night, many species consume the starch stored during the day, thus avoiding starvation and maintaining plant productivity, including growth. Moreover, they process the stored starch at just the right rate​—not too quickly and not too slowly—​so that they use about 95 percent of it by dawn, when they start making more.
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bitbit
Dec 1, 2015 2:46 PM CST
Your first two sentences are spot-on. I think the rate of starch usage really depends on the plant and growing conditions, and can't be generalized so easily. After all, if a potato plant went through 95% of its starch reserves every night, we'd never get a harvest!
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gemini_sage
Dec 1, 2015 2:55 PM CST
I agree with bitbit. Perhaps somewhat true with annuals, but perennials store food (starch) to sustain during dormancy and regrowth. Most manufacture and store more than they need and contribute to the food chain while surviving and reproducing.
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William
Dec 2, 2015 2:21 PM CST
BeKind said:Consider: By day, plants convert atmospheric carbon dioxide into starch and sugars. During the night, many species consume the starch stored during the day, thus avoiding starvation and maintaining plant productivity, including growth. Moreover, they process the stored starch at just the right rate​—not too quickly and not too slowly—​so that they use about 95 percent of it by dawn, when they start making more.

I heard a short version about this a while back, but never got around to reading up on it, so thanks for posting.

Short version here: https://www.jic.ac.uk/news/2013/06/plants-do-sums-to-get-thr...
More in depth here: http://elifesciences.org/content/2/e00669

Pretty fascinating stuff really. 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?

Name: Rick Corey
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RickCorey
Dec 2, 2015 4:58 PM CST
Hi William

>> 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/content/2/e00669#sthash.3wbZqGFG.dp...

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.

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