"In chloroplasts, limitation of CO2 fixation coupled with
over-reduction of the electron transport chain(in other words, too much light) is the
main cause of Reactive Oxygen Species(ROS) production."
This leads to stress and reduced metabolic efficacy, reduced growth and stunting of growth if severe. This can occur over an hour or perhaps weeks etc, depending on the aquarist habits and set up.
Perhaps the CO2 takes a long time to get non limiting when the lights come.
Perhaps they think they have 40ppm when it's really 8ppm.
Perhaps they think they have low light when it's really quite high.
Perhaps their fish are stressed if they try and add more CO2, so they do not add enough, due to other factors like low O2, poor current etc.
"Essential for ROS detoxification during normal metabolism, and
particularly during stress, are antioxidants such as ascorbic
acid and glutathione, and ROS-scavenging enzymes
such as superoxide dismutase (SOD), ascorbate peroxidase
(APX), catalase (CAT), glutathione peroxidase (GPX), and peroxiredoxin (PrxR) (Asada and Takahashi
1987, Iba 2002, Mittler et al. 2004). These have been found in almost all cellular compartments, demonstrating the importance of ROS detoxification for cellular survival (Mittler et al. 2004)."
From:
http://www.plantstress.com/Articles/up_general_files/Reactive_Oxygen_2006.pdf
When these systems are stressed further and limited strongly by CO2, this system cannot maintain itself and a cascade begins that leads to stunted growth. The plant can and may recover if good CO2 is added.
CO2 is central to plant growth and metabolism.
This is a good simple figure that explains the overall approach:
http://www.agresponse.com/images/plantmetabolism.gif
So what happens without CO2 or a limitation?
Plants have suddenly much less energy, since the energy comes from the same things that we eat:
carbohydrates, sugars, starch etc............
If the plants suddenly lack Carbon to make the sugars, starches etc, then they have no food, like us, we get tired and go after our fat reserves. Plants do not have much fat reserves etc, but tend to translocate older leaves which act as their fat reserves.
The other effect is no new growth at the active meristematic tips.
Not enough CO2 to keep things going.
Okay, say now you add more CO2 back...........it takes awhile for the metabolic pathways to re machine and get chugging along like they once where. Unlike say PO4 or N, that plants have extra of for a few days, CO2 runs out fast and is a much larger fraction of the total biomass, 40X more than N.
It's not just the fixing of Carbon that needs up regulated once you bottom things out, it's also things like the mitochondria that produce the energy required for growth as well. These pathways can be quite long and involved. ROS(Reacive oxygen species) often damage many of the enzymes and machinery, compartments etc inside each cell when the CO2 is suddenly limited.
Why does ROS play a role when CO2 is limited?
Well, all that chemical reducing power that was suppose to go to reducing CO2 into sugar is left backing up, much like a traffic jam. Many of these ROS end up crashing into the machinery, destroying them. So even when the CO2 is added back, the effects are long and permanent. The cell has to make entirely new enzymes to process the CO2 and light.
It's basically like pouring herbicides such as "diquat" at low levels on the plants.
This herbicide decouples the electron transport in the light reactions and stops CO2 fixation.
The ROS back up and start frying everything inside the chloroplast, so light and the the photosynthic pathway destroys the plant by blockage. CO2 limitation can do a milder effect.
Given enough time to adapt and if the stress is milder, then plants can adapt to such CO2 changes.
Slow mild changes can be tolerated fairly well. Plants can adjust and the ROS production is mild.
Some plants are going to be worse than others at this adaptation, some will be heavily competitive compared to other species as well.
So they will remove most of the CO2 limited supply, leaving very little for the other species.
Since Carbon is the backbone for virtually all components in the plant cell, it makes good sense to treat it with the upmost respect and care. All the fats, cell wall, enzymes, membranes, all sugars, use massive amounts.
Regards,
Tom Barr
over-reduction of the electron transport chain(in other words, too much light) is the
main cause of Reactive Oxygen Species(ROS) production."
This leads to stress and reduced metabolic efficacy, reduced growth and stunting of growth if severe. This can occur over an hour or perhaps weeks etc, depending on the aquarist habits and set up.
Perhaps the CO2 takes a long time to get non limiting when the lights come.
Perhaps they think they have 40ppm when it's really 8ppm.
Perhaps they think they have low light when it's really quite high.
Perhaps their fish are stressed if they try and add more CO2, so they do not add enough, due to other factors like low O2, poor current etc.
"Essential for ROS detoxification during normal metabolism, and
particularly during stress, are antioxidants such as ascorbic
acid and glutathione, and ROS-scavenging enzymes
such as superoxide dismutase (SOD), ascorbate peroxidase
(APX), catalase (CAT), glutathione peroxidase (GPX), and peroxiredoxin (PrxR) (Asada and Takahashi
1987, Iba 2002, Mittler et al. 2004). These have been found in almost all cellular compartments, demonstrating the importance of ROS detoxification for cellular survival (Mittler et al. 2004)."
From:
http://www.plantstress.com/Articles/up_general_files/Reactive_Oxygen_2006.pdf
When these systems are stressed further and limited strongly by CO2, this system cannot maintain itself and a cascade begins that leads to stunted growth. The plant can and may recover if good CO2 is added.
CO2 is central to plant growth and metabolism.
This is a good simple figure that explains the overall approach:
http://www.agresponse.com/images/plantmetabolism.gif
So what happens without CO2 or a limitation?
Plants have suddenly much less energy, since the energy comes from the same things that we eat:
carbohydrates, sugars, starch etc............
If the plants suddenly lack Carbon to make the sugars, starches etc, then they have no food, like us, we get tired and go after our fat reserves. Plants do not have much fat reserves etc, but tend to translocate older leaves which act as their fat reserves.
The other effect is no new growth at the active meristematic tips.
Not enough CO2 to keep things going.
Okay, say now you add more CO2 back...........it takes awhile for the metabolic pathways to re machine and get chugging along like they once where. Unlike say PO4 or N, that plants have extra of for a few days, CO2 runs out fast and is a much larger fraction of the total biomass, 40X more than N.
It's not just the fixing of Carbon that needs up regulated once you bottom things out, it's also things like the mitochondria that produce the energy required for growth as well. These pathways can be quite long and involved. ROS(Reacive oxygen species) often damage many of the enzymes and machinery, compartments etc inside each cell when the CO2 is suddenly limited.
Why does ROS play a role when CO2 is limited?
Well, all that chemical reducing power that was suppose to go to reducing CO2 into sugar is left backing up, much like a traffic jam. Many of these ROS end up crashing into the machinery, destroying them. So even when the CO2 is added back, the effects are long and permanent. The cell has to make entirely new enzymes to process the CO2 and light.
It's basically like pouring herbicides such as "diquat" at low levels on the plants.
This herbicide decouples the electron transport in the light reactions and stops CO2 fixation.
The ROS back up and start frying everything inside the chloroplast, so light and the the photosynthic pathway destroys the plant by blockage. CO2 limitation can do a milder effect.
Given enough time to adapt and if the stress is milder, then plants can adapt to such CO2 changes.
Slow mild changes can be tolerated fairly well. Plants can adjust and the ROS production is mild.
Some plants are going to be worse than others at this adaptation, some will be heavily competitive compared to other species as well.
So they will remove most of the CO2 limited supply, leaving very little for the other species.
Since Carbon is the backbone for virtually all components in the plant cell, it makes good sense to treat it with the upmost respect and care. All the fats, cell wall, enzymes, membranes, all sugars, use massive amounts.
Regards,
Tom Barr
