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Just what the title states.

Given identical, necessary and favourable conditions (Probably nutrients, humidity, and light but what I mean is all necessary requirements are fulfilled) - Is photosynthesis equally efficient in terms of the amount of sugar/carbohydrates generated by all plants/trees, or are some plants/trees more adept at it?

My background in biology/botany is high-school, so my list of necessary requirements may be lacking for which I crave your indulgence

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I think you would have to define the conditions. Even a single plant will vary in photosynthetic output over the course of a single day. Would maximal photosynthetic output be sufficient? –  kmm Jun 23 '12 at 15:29
    
It should also be clarified how exactly you define efficiency. Photosynthesis on a molecular level is likely highly efficient because the pigments exploit a quantum mechanical property called quantum coherence. On a macroscopic level, looking at the overall organism, there must certainly be a range of efficiency when measuring incident photons relative to carbon fixation. –  leonardo Jun 23 '12 at 16:47
    
Define efficiency: carbon fixed per unit of what [h2o, nitrogen, light, CO2]? Any way you look at it, the answer will be "no". –  David Jun 23 '12 at 17:39
    
@Kevin: Yes, assuming that maximal photosynthetic output refers to the quantity of food available after the process completes –  Everyone Jun 23 '12 at 17:57
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Zhu et al, 2008 provide a review titled "What is the maximum efficiency with which photosynthesis can convert solar energy into biomass?" in the Journal Current Opinion in Biotechnology. –  David Jun 27 '12 at 17:00
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up vote 7 down vote accepted

If you mean the efficiency at which plants convert light energy to chemical energy (in sugar or other reduced C compounds) then there is definitely variability between plants, both at the species and individual level. The photosynthetic efficiency WP page gives ranges of between 0.1 and 8% of total solar radiation converted to "biomass", but these values are not cited. In their review, (Zhu et al, 2008) state that the maximum maximum efficiency with which photosynthesis can convert solar energy into biomass is 3.5% and 4.3% for C3 and C4 plants (both observed for crops), respectively. Biomass is not a measure of energy, but perhaps they mean potential chemical energy in that biomass.

Its a pretty complicated question though. Photosynthesis is a complex process involving many interdependent chemical reactions and physical processes. All species (or even individuals) of plants have different morphology, physiology, and biochemistry that influences overall photosynthetic efficiency. In addition, they each inhabit different ecological niches and climate space. Therefore, all species or individuals would have a slightly unique maximum potential efficiency. Here are a couple other efficiency related concepts to consider:

There are 2 systems in photosynthesis that work in tandem, the light reaction and the dark reaction. The light reaction uses light energy, pigments like chlorophyll, and a bunch of electron transport chain proteins to generate ATP and NADPH. These 2 molecules then provide the reducing power for use in the dark reaction (the Calvin Cycle). In the dark reaction, the enzyme RuBisCO joins CO2 and RuBP, creating simple reduced carbon chains which are then used to assemble sugars. This is an over-simplification, as both reactions are very complex systems with lots of biochemical machinery, but this is the basic process used to convert light energy to chemical energy. To operate at peak efficiency, the entire process must not be limited by incoming energy (light), substrate supply (CO2, RuBP), or nutrients used to construct all the needed cellular and molecular machinery (N, P, K, and many others). In reality, there are limits that vary from plant to plant, species to species. For example, a species or individual with a very reflective leaf surface converts less of the light reaching the leaf surface to chemical energy, thus lowering the output of ATP and NADPH. This reduces the chemical energy supplied to the dark reaction and limits the amount of carbon fixed by RuBisCO. So the reflective surface of the leaf, which might be advantageous to the plant in other ways, has a large impact on overall photosynthetic efficiency (compared to a less reflective leaf or leaves).

If you want to search for more information, there are a number of terms that plant physiologists and ecologists use when describing a plant's (or communities of plants) photosynthetic efficiency. Each of these is used in different ways and can have many variations in units.

  • Light use efficiency: The amount of carbon fixed per unit of light incident.
  • Water use efficiency: The amount of carbon fixed per unit of water transpired
  • Nutrient use efficiency: The amount of carbon fixed per unit of nutrient concentration (usually in leaves).

reference:

Zhu, Ort, and Long 2008 "What is the maximum efficiency with which photosynthesis can convert solar energy into biomass?" Current Opinion in Biotechnology.

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According to Zhu et al,, 2008 the maximum observed conversion of photosynthetic energy to biomass is 6% at 30C. I am not sure why there is a discrepancy, but Wikipedia has no citation nor reference temperature and Zhu et al do not consider CAM plants or algae. –  David Jun 27 '12 at 16:59
    
Great reference that I wish I had seen before posting. If I'm reading it right, the 4.6 and 6% figures are theoretical. They give the highest observed efficiencies as 3.4 and 4.3% (C3 and C4 respectively), so values in the WP article are very high. –  gremau Jun 27 '12 at 22:52
    
Yep, you are correct, I read a good bit of the article, but when it came to writing down the numbers I just grabbed them from the Abstract where they are called "maximum conversion efficiency of solar energy to biomass", in the text they explain that this is the theoretical max. The numbers you give are short term max reported values (for the record, the C3 value is 3.5%, second line of p 157). I changed your answer. –  David Jun 27 '12 at 23:38
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