Efficiency of photosynthesis

The specific carbon dioxide-fixing mechanism used by a plant will affect the efficiency of photosynthesis, so from an energy utilization standpoint, it... 

When plants receive more light energy than can be used for photochemistry, they show a characteristic decline in the quantum efficiency of photosynthesis, termed photoinhibition (reviewed in Ref. 110). Most plants experience photoinhibition at some point over the course of their lives, often on a regular or even a daily basis. The excess quanta from photoinhibitory... 

The action spectrum of photosynthesis, which describes the efficiency of photosynthesis as a function of the wavelength of incident light, has a valley around 550 nm. Why ... 

Explain why in green plants, the quantum efficiency of photosynthesis drops sharply at wavelengths longer than 680 nm. 

In a measurement of the quantu efficiency of photosynthesis in green plants, it was found that 8 quanta of red light at 685nm were needed to evolve one molecule of 02. The average energy storage in the photosynthetic process is 469... 

It is well known that the high quantum efficiency of photosynthesis is provided, first of all, by minimizing a useless dissipation of electron excitation energy in... 

Photorespiration reduces the efficiency of photosynthesis for a couple of reasons. First, oxygen is added to carbon. In other words, the carbon is oxidized, which is the reverse of photosynthesis—the reduction of carbon to carbohydrate. Secondly, it is now necessary to resynthesize the ribulose bisphosphate and to reduce the phosphoglycolate. 

This set of reactions is very detrimental to the efficiency of photosynthesis. Oxygen is added to carbon, CO2 is lost, energy is consumed, and ribulose bisphosphate is destroyed. For a plant to be able to increase the discrimination of Rubisco for CO2 would obviously be advantageous, but that hasn t happened, either naturally or through the efforts of scientists. An increased concentration of CO2 in the atmosphere may lead to increased photosynthesis and decreased photorespiration, but high CO2 concentrations would also contribute to global warming (and the increased photosynthetic carbon fixation would not likely reduce the amount of CO2 in any event). 

Table 11.2 Comparison of predicted efficiencies of photosynthesis with measured values at various values of diffusion coefficients...

Figure 5-12. Efficiency of photosynthesis at various PPF levels directly incident on a chloroplast. The lines were calculated assuming 250 chlorophyll molecules per reaction center, 30% absorption of the incident PPF, and a 5 ms processing time for the biochemical reactions (see text). Under these specific assumptions, below a PPF of 160 pmol m-2 s l, all excitations are used photo-chemically (solid line) and the fraction of the time that the biochemical reactions are used increases with the PPF (dashed line) above this PPF, the biochemical reactions are used all of the time (dashed line) but the fraction of excitations processed photochemically decreases (solid line).

It is not possible to give a single value for the energy storage efficiency of photosynthesis. Almost any value from 0... 

Photosynthetic efficiency. Use the following information to estimate the efficiency of photosynthesis. 

I. The electrons given up by photosystem I are replenished by photosystem II, which needs to absorb an equal number of photons. Hence, eight photons are needed to generate the required NADPH. The energy input of 8 moles of photons is 381 kcal. Thus, the overall efficiency of photosynthesis under standard conditions is at least 114/381, or 30%. 

The C02-fixing pathways used by a specific biomass species will affect the efficiency of photosynthesis, so from a biomass energy standpoint, it is desirable to choose species that exhibit high photosynthesis rates to maximize the yields of biomass in the shortest possible time. Obviously, however, there are numerous factors that affect the efficiency of photosynthesis other than the... 

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