Originally posted by humy
Similarly, if the temperature is too low (and sometimes if it is too high but usually it is how low it is that really counts unless you are talking about it being so high as to begin to harm the plants ) this slows down photosynthesis (because most chemical reactions are slowed by lower temperatures ) and then temperature becomes the dominant limiting factor.

From what little I know about the chemistry involved, I would say this is the only effect that would be reversed by enzymes.

Originally posted by humy
yes, it is a significant limiting factor at least usually during when there is direct sunlight and the temperature is very roughly in about the right range for optimum efficiency of photosynthesis.

This is because those conditions produce what is called a high "carbon dioxide gradient" that has the effect of greatly reducing efficiency of photosynthesis (we ...[text shortened]...
( I have studied all of this pretty intensely so I know exactly what I am talking about here )

This is the thing. Cyanobacteria are single celled so the gas transport problem doesn't exist for them - unless they are capable of photosynthesising so fast that they drain all the dissolved carbon dioxide out of the small volume of sea around them. A leaf is something like 12 orders of magnitude larger. If the problem is gas transport in the leaf then that would be the thing to attempt to alter, rather than starting with the actual photosynthesis process.

It seems a little like building a train that can do 250 mph when the tracks can only cope with 125.

Incidentally, your last post was perfectly plausible to me and didn't require the appeal to authority at the end.

Originally posted by DeepThought
If the problem is gas transport in the leaf then that would be the thing to attempt to alter, rather than starting with the actual photosynthesis process.

Of course there is no harm in trying and seeing what happens. It will certainly teach us more about photosynthesis and what the limiting factors are. What I objected to was the article practically assuming that larger yields was a done deal.

Originally posted by DeepThought
This is the thing. Cyanobacteria are single celled so the gas transport problem doesn't exist for them - unless they are capable of photosynthesising so fast that they drain all the dissolved carbon dioxide out of the small volume of sea around them. A leaf is something like 12 orders of magnitude larger. If the problem is gas transport in the leaf t ...[text shortened]... r last post was perfectly plausible to me and didn't require the appeal to authority at the end.

If the problem is gas transport in the leaf then that would be the thing to attempt to alter,

I think this would be an insolvable problem because it is at a result of what is called “transpiration” through what is called the “stomatal pores”.
The problem is that the plant looses water by evaporation through the stomatal pores on the surface of the leaf and the simplest way the plant can decrease the CO2 gradient (some plants do it by another way but there is always a biological cost in doing so ) is by making those pores either open up wider or have more of them; either way, this would dramatically increase the rate of water loss. Even if the roots have plenty of water and when there is no risk of drought, if you greatly reduce the CO2 gradient by having the leaf with more pores (or widen them ) , a point will be reached where the loss of water through these pores would be so great that even a well watered plant would be unlikely in most natural conditions to make the amount of water transportation up its stems and through its leaves keep up with that water loss and then all the leaves will just dry up and die. Even before you go to that extreme, you would have the problem that your crop would have dramatically greater water needs and you may have to irrigate it a lot more just to keep it alive.

So, we have two mutually exclusive possible optimum conditions; either have optimum photosynthesis by having lots of pores but extremely poor water retention (with likely fatal results ) or have optimum water retention by having very few pores but then have extremely inefficient photosynthesis due to a massive CO2 gradient even when the light is dim. Thus, most higher plants have therefore been forced to evolve to exercise a trade-off; a compromise between the two extremes of maximizing photosynthesis at the expense of much greater water loss and minimizing water loss at the expense of reducing photosynthesis.

Personally I don't see any easy way around that one! do you?
I guess if there was an easy simple solution to that, plants would have probably already evolved to have it.
The fact that they haven't in billions of years is then perhaps an indicator that there is no simple solution.
Pity.

Originally posted by humy

If the problem is gas transport in the leaf then that would be the thing to attempt to alter,

I think this would be an insolvable problem because it is at a result of what is called “transpiration” through what is called the “stomatal pores”.
The problem is that the plant looses water by evaporation through the stomatal pores on the surf ...[text shortened]... ven't in billions of years is then perhaps an indicator that there is no simple solution.
Pity.

Possibly, given we are talking about crops then they could be grown in water beds or via hydroponics. The CO2 needs could be met by dissolving it in the water they're given. No idea how practicable that is.