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Cost and color of photosynthesis.

Marosvölgyi MA, van Gorkom HJ - Photosyn. Res. (2010)

Bottom Line: The expectation is incorrect, however, because it fails to take the energy cost of the photosynthetic apparatus into account.The optimization predicts a strong influence of Fraunhofer lines in the solar irradiance on the spectral shape of the optimized absorption band, which appears to be correct.It does not predict any absorption at other wavelengths.

View Article: PubMed Central - PubMed

Affiliation: Department of Biophysics, Huygens Laboratory, Leiden University, The Netherlands. marosvolgyi@physics.leidenuniv.nl

ABSTRACT
The question of why plants are green has been revisited in several articles recently. A common theme in the discussions is to explain why photosynthesis appears to absorb less of the available green sunlight than expected. The expectation is incorrect, however, because it fails to take the energy cost of the photosynthetic apparatus into account. Depending on that cost, the red absorption band of the chlorophylls may be closely optimized to provide maximum growth power. The optimization predicts a strong influence of Fraunhofer lines in the solar irradiance on the spectral shape of the optimized absorption band, which appears to be correct. It does not predict any absorption at other wavelengths.

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The absorptance spectra of Fig. 4 calculated for the irradiance spectrum selected in Fig. 5. Growth power optimized absorptance spectra for the same relative cost values as in Figs. 3 and 4. The gray shaded spectrum is an absorptance plot of the absorption spectrum of Rhodobacter sphaeroides chromatophores, arbitrarily normalized to obtain an absorptance at the red maximum corresponding to that of the most similar theoretical curve
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Fig6: The absorptance spectra of Fig. 4 calculated for the irradiance spectrum selected in Fig. 5. Growth power optimized absorptance spectra for the same relative cost values as in Figs. 3 and 4. The gray shaded spectrum is an absorptance plot of the absorption spectrum of Rhodobacter sphaeroides chromatophores, arbitrarily normalized to obtain an absorptance at the red maximum corresponding to that of the most similar theoretical curve

Mentions: In order to determine if the similarity between real and predicted spectra in Fig. 4 is merely a coincidence, we applied the same analysis to one of the “colorful spectral niches” at the bottom of the photic zone described by Stomp et al. (2007). Figure 5 shows the solar irradiance under 5 cm of water with a high concentration of organic matter. At the same relative cost that yielded a good approximation of the red band of photosynthesis in non-attenuated sunlight, optimization for growth power in this spectral niche yields an absorptance spectrum that resembles the QY absorption of bacteriochlorophyll A in purple non-sulfur bacteria (Fig. 6). The lower and upper bounds of the spectral range depend on the arbitrary choice of water depth and organic matter concentration. The fact that the deep trough around 820 nm is reproduced by the effect of a minor atmospheric H2O absorption band on the optimization, however, does provide independent evidence for the validity of the analysis presented here.Fig. 5


Cost and color of photosynthesis.

Marosvölgyi MA, van Gorkom HJ - Photosyn. Res. (2010)

The absorptance spectra of Fig. 4 calculated for the irradiance spectrum selected in Fig. 5. Growth power optimized absorptance spectra for the same relative cost values as in Figs. 3 and 4. The gray shaded spectrum is an absorptance plot of the absorption spectrum of Rhodobacter sphaeroides chromatophores, arbitrarily normalized to obtain an absorptance at the red maximum corresponding to that of the most similar theoretical curve
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2807594&req=5

Fig6: The absorptance spectra of Fig. 4 calculated for the irradiance spectrum selected in Fig. 5. Growth power optimized absorptance spectra for the same relative cost values as in Figs. 3 and 4. The gray shaded spectrum is an absorptance plot of the absorption spectrum of Rhodobacter sphaeroides chromatophores, arbitrarily normalized to obtain an absorptance at the red maximum corresponding to that of the most similar theoretical curve
Mentions: In order to determine if the similarity between real and predicted spectra in Fig. 4 is merely a coincidence, we applied the same analysis to one of the “colorful spectral niches” at the bottom of the photic zone described by Stomp et al. (2007). Figure 5 shows the solar irradiance under 5 cm of water with a high concentration of organic matter. At the same relative cost that yielded a good approximation of the red band of photosynthesis in non-attenuated sunlight, optimization for growth power in this spectral niche yields an absorptance spectrum that resembles the QY absorption of bacteriochlorophyll A in purple non-sulfur bacteria (Fig. 6). The lower and upper bounds of the spectral range depend on the arbitrary choice of water depth and organic matter concentration. The fact that the deep trough around 820 nm is reproduced by the effect of a minor atmospheric H2O absorption band on the optimization, however, does provide independent evidence for the validity of the analysis presented here.Fig. 5

Bottom Line: The expectation is incorrect, however, because it fails to take the energy cost of the photosynthetic apparatus into account.The optimization predicts a strong influence of Fraunhofer lines in the solar irradiance on the spectral shape of the optimized absorption band, which appears to be correct.It does not predict any absorption at other wavelengths.

View Article: PubMed Central - PubMed

Affiliation: Department of Biophysics, Huygens Laboratory, Leiden University, The Netherlands. marosvolgyi@physics.leidenuniv.nl

ABSTRACT
The question of why plants are green has been revisited in several articles recently. A common theme in the discussions is to explain why photosynthesis appears to absorb less of the available green sunlight than expected. The expectation is incorrect, however, because it fails to take the energy cost of the photosynthetic apparatus into account. Depending on that cost, the red absorption band of the chlorophylls may be closely optimized to provide maximum growth power. The optimization predicts a strong influence of Fraunhofer lines in the solar irradiance on the spectral shape of the optimized absorption band, which appears to be correct. It does not predict any absorption at other wavelengths.

Show MeSH