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1 December 2004 Light Absorption by the Chlorophyll a–b Complexes of Photosystem II in a Leaf with Special Reference to LHCII
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To investigate the light-harvesting properties of the Photosystem 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. ([1999] Photosynth. Res. 60, 209–215). In the Qy 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 chl b 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 (chl a and b, carotenoids) in the LHCII OD spectrum in terms of spectral subbands, which were subsequently used to estimate the relative light harvesting of each pigment type in LHCII of a leaf. When the entire visible spectral interval between 400 and 730 nm 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 the chl b absorption is principally associated with the Qy electronic transition region, the light-harvesting contribution of which becomes prominent in the leaf.

Andrea Rivadossi, Giuseppe Zucchelli, Flavio M. Garlaschi, and Robert C. Jennings "Light Absorption by the Chlorophyll a–b Complexes of Photosystem II in a Leaf with Special Reference to LHCII," Photochemistry and Photobiology 80(3), 492-498, (1 December 2004).<0492:LABTCA>2.0.CO;2
Received: 16 April 2004; Accepted: 1 August 2004; Published: 1 December 2004

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