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The quote “Natural photosynthesis is not efficient because it has evolved merely to survive so it makes the bare minimum amount of energy needed – around 1-2 pe

by gns24 8y ago

The quote “Natural photosynthesis is not efficient because it has evolved merely to survive so it makes the bare minimum amount of energy needed – around 1-2 per cent of what it could potentially convert and store” makes no sense to me; plants are usually in massive competition for access to light, so in what sense is there no need for it to be more efficient?

ben_w 8y ago
As a hypothesis (because I’m not a biologist) it might be important to optimise for other things at the expense of efficiency. Disease resistance, for example. Or perhaps absorbing more sunlight will cause them to overheat (is that why the leaves are not black?)
vixen99 8y ago
Unless we know all the factors involved in 'survival' we can't assume that it's enhanced by greater energy efficiency. The latter may be counter-productive in ways that are not immediately obvious. Given the state of inefficiency of conversion that's evolved (survived), clearly there has not been a need for efficiency besting 1-2 per cent.
- AllegedAlec 8y ago
  That's not generally not how evolution works. Sure, a plant will do fine with the current efficiency of photosynthesis, but intuition would tell us that a plant would do more fine if its leaves were more efficient. It would grow faster, have more or better seed and would generally outcompete other plants of its species. That the efficiency is not higher than this leads us to believe that either: - there are strong evolutionary imperatives to not raise the efficiency any further (ie: "there has been a need not to", rather than "there has not been a need to). This could be due to a lot of reasons; oxidative stress, a plant's 'desire' to have a large leaf surface, a tendency to dry out the soil too quickly, etc etc. - With the current 'design' of chlorophyl, it is not possible to increase efficiency further, and it's quite hard to get out of the local optimum.
  - Drakim 8y ago
    The higher amount of energy (sugar?) might make the plant more prone to predation.
    - AllegedAlec 8y ago
      That would also be a possibility, yeah.
    - chopin 8y ago
      That could be countered with venom, especially if you have plenty of energy available. Many plants already go that route, even now.
hinkley 8y ago
In full sun a plant can absorb far more light than it can handle. Apparently one of the little tricks of chloroplasts is how they shunt that power away without sustaining damage. Could we just do something with that power? It’s a bit like turning the rotor blades when the wind is too high to keep the thing from ripping itself apart. But imagine if you could make a turbine that generated tons more electricity in a gale force wind. Think what you could do with that much concentrated power.
- pjc50 8y ago
  In both cases it's a straightforward cost-benefit tradeoff: sure, you can build a turbine that works in gales. But they're rare. So in practice the turbine design is tuned against a statistical model of expected wind speeds to deliver the best $/kWh ratio over its design life. > Think what you could do with that much concentrated power. That sounds more like a headache (now you have to uprate the whole power-handling systems) than a benefit.
- SuoDuanDao 8y ago
  I've not been able to kill the idea of a plant that uses excess energy to create hydrogen which it uses to float its seeds far and yonder. Didn't know that there's already a lot of excess energy that could be used for such a project, though I suspect the knowledge of genegeneering needed to make it happen is a ways off still.
  - sofon 8y ago
    That's such a neat idea. I wonder why floating plants don't already exist. I'm also surprised that I've not seen it in Scifi.
    - adrianN 8y ago
      How would an evolutionary pathway to floating look like?
      - stephengillie 8y ago
skookumchuck 8y ago
Plants turn their leaves throughout the day to fully face the sun. It seems they can't afford to be less efficient.
21 8y ago
It's called photoprotection: > High sunlight can raise plant growth rates but can potentially cause cellular damage. The likelihood of deleterious effects is lowered by a sophisticated set of photoprotective mechanisms, one of the most important being the controlled dissipation of energy from chlorophyll within photosystem II (PSII) measured as non-photochemical quenching (NPQ). Although ubiquitous, the role of NPQ in plant productivity remains uncertain because it momentarily reduces the quantum efficiency of photosynthesis. https://en.wikipedia.org/wiki/Photoprotection https://en.wikipedia.org/wiki/Photoprotection https://en.wikipedia.org/wiki/Non-photochemical_quenching https://en.wikipedia.org/wiki/Non-photochemical_quenching
scotty79 8y ago
Optimisation methods tend to get stuck in local optima. I'm sure nature sqeezed out every ounce of possible performance out of the current photosynthesis but that doesn't mean there can't be vastly superior process doing basically same thing but different enough that it won't spontaneously get discovered by evolution in next billion years.
strainer 8y ago
That statement makes no sense to me but neither does the popular idea that species evolve to compete with each other limited only by immediate material resources. I imagine some mechanism of foresight or conservatism must develope in a diverse population for the population to survive in total. Such a mechanism may have had to be present in the earliest lifeforms or else long periods of accumulating complexity and diversity, seem open to frequent and potentially unrecoverable upheaval, by the temporary competitiveness of mutations fit only for immediate material demands.
wahern 8y ago
I think the particular hypothesis in the following has been rejected, but the article introduces some of the interesting variations in photosynthesis and hints at different evolutionary pressures behind their emergence. To the point about the efficiency of chlorophyll-based photosynthesis, Chlorophyll, the main photosynthetic pigment of plants, absorbs mainly blue and red wavelengths from the Sun and reflects green ones, and it is this reflected light that gives plants their leafy color. This fact puzzles some biologists because the sun transmits most of its energy in the green part of the visible spectrum. -- https://www.livescience.com/1398-early-earth-purple-study-suggests.html https://www.livescience.com/1398-early-earth-purple-study-su...

by gns24 8y ago

ben_w 8y ago

As a hypothesis (because I’m not a biologist) it might be important to optimise for other things at the expense of efficiency. Disease resistance, for example. Or perhaps absorbing more sunlight will cause them to overheat (is that why the leaves are not black?)

vixen99 8y ago

Unless we know all the factors involved in 'survival' we can't assume that it's enhanced by greater energy efficiency. The latter may be counter-productive in ways that are not immediately obvious. Given the state of inefficiency of conversion that's evolved (survived), clearly there has not been a need for efficiency besting 1-2 per cent.

AllegedAlec 8y ago
That's not generally not how evolution works. Sure, a plant will do fine with the current efficiency of photosynthesis, but intuition would tell us that a plant would do more fine if its leaves were more efficient. It would grow faster, have more or better seed and would generally outcompete other plants of its species. That the efficiency is not higher than this leads us to believe that either: - there are strong evolutionary imperatives to not raise the efficiency any further (ie: "there has been a need not to", rather than "there has not been a need to). This could be due to a lot of reasons; oxidative stress, a plant's 'desire' to have a large leaf surface, a tendency to dry out the soil too quickly, etc etc. - With the current 'design' of chlorophyl, it is not possible to increase efficiency further, and it's quite hard to get out of the local optimum.
- Drakim 8y ago
  The higher amount of energy (sugar?) might make the plant more prone to predation.
  - AllegedAlec 8y ago
    That would also be a possibility, yeah.
  - chopin 8y ago
    That could be countered with venom, especially if you have plenty of energy available. Many plants already go that route, even now.

hinkley 8y ago

In full sun a plant can absorb far more light than it can handle. Apparently one of the little tricks of chloroplasts is how they shunt that power away without sustaining damage. Could we just do something with that power? It’s a bit like turning the rotor blades when the wind is too high to keep the thing from ripping itself apart. But imagine if you could make a turbine that generated tons more electricity in a gale force wind. Think what you could do with that much concentrated power.

pjc50 8y ago
In both cases it's a straightforward cost-benefit tradeoff: sure, you can build a turbine that works in gales. But they're rare. So in practice the turbine design is tuned against a statistical model of expected wind speeds to deliver the best $/kWh ratio over its design life. > Think what you could do with that much concentrated power. That sounds more like a headache (now you have to uprate the whole power-handling systems) than a benefit.
SuoDuanDao 8y ago
I've not been able to kill the idea of a plant that uses excess energy to create hydrogen which it uses to float its seeds far and yonder. Didn't know that there's already a lot of excess energy that could be used for such a project, though I suspect the knowledge of genegeneering needed to make it happen is a ways off still.
- sofon 8y ago
  That's such a neat idea. I wonder why floating plants don't already exist. I'm also surprised that I've not seen it in Scifi.
  - adrianN 8y ago
    How would an evolutionary pathway to floating look like?
    - stephengillie 8y ago

skookumchuck 8y ago

Plants turn their leaves throughout the day to fully face the sun. It seems they can't afford to be less efficient.

21 8y ago

It's called photoprotection: > High sunlight can raise plant growth rates but can potentially cause cellular damage. The likelihood of deleterious effects is lowered by a sophisticated set of photoprotective mechanisms, one of the most important being the controlled dissipation of energy from chlorophyll within photosystem II (PSII) measured as non-photochemical quenching (NPQ). Although ubiquitous, the role of NPQ in plant productivity remains uncertain because it momentarily reduces the quantum efficiency of photosynthesis. https://en.wikipedia.org/wiki/Photoprotection https://en.wikipedia.org/wiki/Photoprotection https://en.wikipedia.org/wiki/Non-photochemical_quenching https://en.wikipedia.org/wiki/Non-photochemical_quenching

scotty79 8y ago

Optimisation methods tend to get stuck in local optima. I'm sure nature sqeezed out every ounce of possible performance out of the current photosynthesis but that doesn't mean there can't be vastly superior process doing basically same thing but different enough that it won't spontaneously get discovered by evolution in next billion years.

strainer 8y ago

That statement makes no sense to me but neither does the popular idea that species evolve to compete with each other limited only by immediate material resources. I imagine some mechanism of foresight or conservatism must develope in a diverse population for the population to survive in total. Such a mechanism may have had to be present in the earliest lifeforms or else long periods of accumulating complexity and diversity, seem open to frequent and potentially unrecoverable upheaval, by the temporary competitiveness of mutations fit only for immediate material demands.

wahern 8y ago

I think the particular hypothesis in the following has been rejected, but the article introduces some of the interesting variations in photosynthesis and hints at different evolutionary pressures behind their emergence. To the point about the efficiency of chlorophyll-based photosynthesis, Chlorophyll, the main photosynthetic pigment of plants, absorbs mainly blue and red wavelengths from the Sun and reflects green ones, and it is this reflected light that gives plants their leafy color. This fact puzzles some biologists because the sun transmits most of its energy in the green part of the visible spectrum. -- https://www.livescience.com/1398-early-earth-purple-study-suggests.html https://www.livescience.com/1398-early-earth-purple-study-su...