This seedling stretching too much?

cannabineer

cannabineer

Ursus marijanus
Horselover fat said:
Yeah, please read what I write or read the khan article you posted. It explains phototespiration very well. Actually let me quote the very beginning of the article:

"Photorespiration
Photorespiration is a wasteful pathway that competes with the Calvin cycle. It begins when rubisco acts on oxygen instead of carbon dioxide."
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You are making my point for me, thank you
 
Horselover fat

Horselover fat

Well-Known Member
cannabineer said:
Your confirmation bias blinds you to the third option: you could be wrong.
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Sure, but the fact that you are not pointing out what's wrong in my understanding speaks volumes.

Let's explain the dark cycle / calvin cycle: It is when rubisco fixes carbon and energy is produced. That's it. Then it cycles again. Sometimes rubisco cocks up and it grabs an oxygen instead of a co2 and oxygen is cycled instead. That's called photorespiration. This process happens the same whether it's day or night.
 
cannabineer

cannabineer

Ursus marijanus
Horselover fat said:
Sure, but the fact that you are not pointing out what's wrong in my understanding speaks volumes.

Let's explain the dark cycle / calvin cycle: It is when rubisco fixes carbon and energy is produced. That's it. Then it cycles again. Sometimes rubisco cocks up and it grabs an oxygen instead of a co2 and oxygen is cycled instead. That's called photorespiration. This process happens the same whether it's day or night.
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My Ph.D is in organic chemistry. So why don’t you, using the chemicalliest of chemical language, my preferred dialect - expound upon your failed logic?
 
cannabineer

cannabineer

Ursus marijanus
Horselover fat said:
Uhm, I think you're confused. I could be too, but I think it's you. In my understanding photosynthesis consists of the light cycle and the dark cycle. In the light cycle light is harvested and atp & nadph are produced. Those are used to power the dark cycle, in which rubisco is used to fix carbon. Instead of co2 rubisco sometimes fixes oxygen and it is a wasted cycle, because no energy is produced and that is called photorespiration. Despite the name dark reactions take place in the light too. They are light independent. During the night the dark cycle continues on stored atp and nadph.
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My disagreement is with your last sentence. During the night the dark cycle shuts off. The photorespirative cycle continues, powering the plant’s metabolism in the dark.

You cannot use those two terms interchangeably. “The photorespiration when the dark cycle” told me that that is what you’re doing.

That’s as far as I can think of breaking it down. If there is something specific that you don’t understand, please tell me.
 
curious2garden

curious2garden

Well-Known Mod
Staff member
Horselover fat said:
Awesome! I'm thinking of going back to uni to study biochem. Why don't you explain this for us then? Wouldn't that have been a lot faster and easier? I mean I want to learn. I'm sure others would too.
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We certainly could use more biochemists. It's a nice area of study especially if you focused that on so much of the research we need done. Because here we sit with an implied truth but we won't know until we do the research.
 
Horselover fat

Horselover fat

Well-Known Member
cannabineer said:
My disagreement is with your last sentence. During the night the dark cycle shuts off. The photorespirative cycle continues, powering the plant’s metabolism in the dark.

You cannot use those two terms interchangeably. “The photorespiration when the dark cycle” told me that that is what you’re doing.

That’s as far as I can think of breaking it down. If there is something specific that you don’t understand, please tell me.
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Ok, excellent. I thought the calvin cycle would continue in the dark on atp reserves, but that was obviously wrong. But now I can't understand how the photorespiration can continue in the dark then? How does the rubisco only fix oxygen at night?

Edit: or rather where does the oxygen come from? If stomata are closed then no co2, but no oxygen either?
 
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Horselover fat

Horselover fat

Well-Known Member
curious2garden said:
We certainly could use more biochemists. It's a nice area of study especially if you focused that on so much of the research we need done. Because here we sit with an implied truth but we won't know until we do the research.
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Ha, I dunno. We don't have to pay for studying at the uni so I'm thinking of taking it up. It's certainly fascinating. I'm 39 and thinking of it more like a possible hobby than a career. I did sign up for plant physiology class and chemistry for this semester.
 
curious2garden

curious2garden

Well-Known Mod
Staff member
Horselover fat said:
Ha, I dunno. We don't have to pay for studying at the uni so I'm thinking of taking it up. It's certainly fascinating. I'm 39 and thinking of it more like a possible hobby than a career. I did sign up for plant physiology class and chemistry for this semester.
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Nice, university for free! So many great classes to take. Why not try it. I enjoyed my inorganic and organic chemistry classes. I found bio to be a bit of a chore but I did ok. Definitely go for it.
 
cannabineer

cannabineer

Ursus marijanus
Horselover fat said:
Ok, excellent. I thought the calvin cycle would continue in the dark on atp reserves, but that was obviously wrong. But now I can't understand how the photorespiration can continue in the dark then? How does the rubisco only fix oxygen at night?

Edit: or rather where does the oxygen come from? If stomata are closed then no co2, but no oxygen either?
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Yeah, photorespiration sounds like it is light-mediated, but it helps me to think of it as photosynthesis run in reverse, using Rubisco to turn sugar and oxygen into ATP and carbon dioxide, which the authors could measure. Helps explain that photo- prefix.

The link that Annie put up shows that the plant in the dark produces considerable carbon dioxide. This suggests to me that there is gas diffusion even with most or all stomata closed. Stomata are diffusion accelerators but they’re not the sole diffusion locus, I think.
 
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