Chl a is present in the reaction center and light-harvesting complexes of almost all oxygenic photosynthetic organisms including cyanobacteria, algae, and embryophytes. By contrast, marine organisms possess a range of Chls (e.g., Chls a, b, c 1, c 2, c 3, d, and f) and a larger number of accessory pigments, such as carotenoids and/or biliproteins, to allow them to acclimate to the prevailing blue–green light that is found at greater depths (Croce and van Amerongen 2014 Kirk 2011).įunctional groups (mainly formyl group) at different positions cause different spectral properties, and the absorption maxima of Chls are significantly shifted. Although several light-harvesting pigments exist, most terrestrial plants use specific Chls ( a and b) and carotenoids to construct pigment-protein complexes (Björn et al. Various taxa of photosynthetic organisms contain different sets of light-harvesting chlorophylls (Chl). Knowledge of the relationship between the spectrum of incident radiation and the light-harvesting pigments that are found in organisms is crucial for understanding life on Earth and photosynthesis. These findings indicate that the spectra of the photosynthetic pigments and constructed photosystems and antenna proteins significantly align with the terrestrial solar spectra to allow the safe and efficient use of solar radiation. The absorption spectra of photosynthetic complexes were negatively correlated with SPFD spectra, but LHCs with low a/ b ratios were more positively correlated with SIR spectra. In contrast, Chl a effectively avoided the high SPFD and/or high SIR waveband. 460 nm, making it suitable for absorbing the PAR diff, but not suitable for avoiding the high spectral irradiance (SIR) waveband of PAR dir. The absorption peak in the short wavelength region of Chl b in the proteinaceous environment occurred at c. The spectral absorbance spectra of Chls a and b functioned complementary to each other, and the absorbance peaks of Chl b were nested within those of Chl a. 680 and 460 nm, respectively, during the daytime. We found that direct and diffuse solar radiation (PAR dir and PAR diff, respectively) have different spectral distributions, showing maximum spectral photon flux densities (SPFD) at c. Here, we investigated why Chl b is used in LHCs rather than other light-absorbing pigments that can be used for photosynthesis by considering the solar radiation spectrum under field conditions. 20 nm, and the ratio between them (the a/ b ratio) is an important determinant of the light absorption efficiency of photosynthesis (i.e., the antenna size). The peak wavelengths of the absorption spectra of Chls a and b differ by c. The two pigments form light-harvesting Chl a/ b-binding protein complexes (LHC), which absorb most of the light. There are several types of Chls but terrestrial plants only possess two of these: Chls a and b. Chlorophylls (Chl) are important pigments in plants that are used to absorb photons and release electrons.
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