Premium
Light Absorption by the Chlorophyll a–b Complexes of Photosystem II in a Leaf with Special Reference to LHCII ¶
Author(s) -
Rivadossi Andrea,
Zucchelll Giuseppe,
Gariaschi Flavio M.,
Jennigns Robert C.
Publication year - 2004
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2004.tb00120.x
Subject(s) - absorption (acoustics) , photosystem ii , chlorophyll a , absorption spectroscopy , chemistry , chlorophyll , light harvesting complex , photosystem i , photosynthesis , photochemistry , physics , optics , biochemistry , organic chemistry
Abstract To investigate the light‐harvesting properties of the Photsystem II chlorophyll (chl) a‐b complexes (major light‐harvesting complex of Photosystem II [LHCII], CP24, CP26, CP29) in a mature leaf under natural “daylight” illumination, the absorption spectra of the isolated complexes were converted into the photon absorption spectrum (1‐T) within a leaf, using the approach of Rivadossi et al . ([1991] Photosynth. Res. 60, 209–215). In the Q y region, significant enhancement of light harvesting by the chl b electronic transitions, with respect to the absorption spectra (optical density [od]), as well as a large and generalized increase (between two‐ and four‐fold) associated with the vibrational bands of both chl a and b , was observed, which acquires an important light‐harvesting role (approximately 30–40% of total). In the Soret region, a small increase in light harvesting by chlb was indicated. To gain more detailed information on these aspects the light harvesting of LHCII in a leaf was investigated. This required describing the pigment absorption (chla and b , carotenoids) in the LHCII OD spectrum in therms of spectral subbands, which were subsequently used to estimate the relative light harvesting of each pigment type in LHCLL in leaf. When the entire visible spectral interval between 400 and 730nm is considered, the chl a light harvesting is essentially unchanged with respect to the absorption spectrum (OD) of isolated LHCII, whereas the chl b contribution is 20% higher and the carotenoids are 33% lower. The relative enhancement of chl b absorption is principally associated wiht the Q y electronic transition region, the light‐harvesting contribution of which becomes prominent in the leaf.