Why is chlorophyll b only used in light-harvesting systems?

Chlorophylls (Chl) are important pigments in plants that are used to absorb photons and release electrons. There are several types of Chls but terrestrial plants only possess two of these: Chls a and b . The two pigments form light-harvesting Chl a / b -binding protein complexes (LHC), which absorb...

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Vydáno v:	Journal of plant research Ročník 131; číslo 6; s. 961 - 972
Hlavní autoři:	Kume, Atsushi, Akitsu, Tomoko, Nasahara, Kenlo Nishida
Médium:	Journal Article
Jazyk:	angličtina
Vydáno:	Tokyo Springer Japan 01.11.2018 Springer Nature B.V
Témata:	Absorbance Absorption Absorption spectra Biomedical and Life Sciences Chlorophyll Chlorophyll - radiation effects diffuse solar radiation Electromagnetic absorption electrons Irradiance Life Sciences light harvesting complex light intensity Light-Harvesting Protein Complexes Photons Photosynthesis Photosynthetic pigments Pigments Plant Biochemistry Plant Ecology Plant Physiology Plant Sciences Plants plants (botany) Proteins Regular Paper Solar radiation Solar spectra spectral analysis Sunlight Wavelengths Chlorophyll Spectroradiometer Carotenoids Atmospheric optics Terrestrial photosynthesis Chlorophyll d Chlorophyll c
ISSN:	0918-9440, 1618-0860, 1618-0860
On-line přístup:	Získat plný text
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Popis
Shrnutí:	Chlorophylls (Chl) are important pigments in plants that are used to absorb photons and release electrons. There are several types of Chls but terrestrial plants only possess two of these: Chls a and b . The two pigments form light-harvesting Chl a / b -binding protein complexes (LHC), which absorb most of the light. The peak wavelengths of the absorption spectra of Chls a and b differ by c. 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). 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. 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. 680 and 460 nm, respectively, during the daytime. 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 . The absorption peak in the short wavelength region of Chl b in the proteinaceous environment occurred at c. 460 nm, making it suitable for absorbing the PAR diff , but not suitable for avoiding the high spectral irradiance (SIR) waveband of PAR dir . In contrast, Chl a effectively avoided the high SPFD and/or high SIR waveband. 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. 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.
Bibliografie:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 14 content type line 23
ISSN:	0918-9440 1618-0860 1618-0860
DOI:	10.1007/s10265-018-1052-7