Structural and functional organization of the photosystems in spinach chloroplasts. Antenna size, relative electron-transport capacity, and chlorophyll composition
- 1 September 1983
- journal article
- research article
- Published by Elsevier BV in Biochimica et Biophysica Acta (BBA) - Bioenergetics
- Vol. 724 (3), 473-484
- https://doi.org/10.1016/0005-2728(83)90108-1
Abstract
The structural and functional organization of the spinach chloroplast photosystems (PS) I, IIα and IIβ was investigated. Sensitive absorbance difference spectrophotometry in the ultraviolet (▵A320) and red (▵A700) regions of the spectrum provided information on the relative concentration of PS II and PS I reaction centers. The kinetic analysis of PS II and PS I photochemistry under continuous weak excitation provided information on the number (N) of chlorophyll (Chl) molecules transferring excitation energy to PS IIα, PS IIβ and PS I. Spinach chloroplasts contained almost twice as many PS II reaction centers compared to PS I reaction centers. The number Nα of chlorophyll (Chl) molecules associated with PS IIα was 234, while Nβ = 100 and NPS I = 210. Thus, the functional photosynthetic unit size of PS II reaction centers was different from that of PS I reaction centers. The relative electron-transport capacity of PS II was significantly greater than that of PS I. Hence, under light-limiting green excitation when both Chl a and Chl b molecules are excited equally, the limiting factor in the overall electron-transfer reaction was the turnover of PS I. The Chl composition of PS I, PS IIα and PS IIβ was analyzed on the basis of a core Chl a reaction center complex component and a Chl component. There is a dissimilar Chl composition in the three photosystems with 77% of total Chl b associated with PS IIα only. The results indicate that PS IIα, located in the membrane of the grana partition region, is poised to receive excitation from a wider spectral window than PS IIβ and PS I.Keywords
This publication has 36 references indexed in Scilit:
- Characterization of a resolved oxygen-evolving Photosystem II preparation from spinach thylakoidsBiochimica et Biophysica Acta (BBA) - Bioenergetics, 1983
- A highly resolved, oxygen‐evolving photosystem II preparation from spinach thylakoid membranesFEBS Letters, 1981
- Consequences of spatial separation of photosystem 1 and 2 in thylakoid membranes of higher plant chloroplastsFEBS Letters, 1981
- Chlorophyll—protein complexes of higher plant thylakoids: distribution, stoichiometry and organization in the photosynthetic unitFEBS Letters, 1980
- A Developmental Study of Photosystem I Peripheral Chlorophyll ProteinsPlant Physiology, 1980
- The kinetic relationship between the C-550 absorbance change, the reduction of Q(ΔA320) and the variable fluorescence yield change in chloroplasts at room temperatureBiochimica et Biophysica Acta (BBA) - Bioenergetics, 1979
- Analysis of the Light-harvesting Pigment-Protein Complex of Wild Type and a Chlorophyll-b-less Mutant of BarleyPlant Physiology, 1979
- BIPHASIC ENERGY CONVERSION KINETICS AND ABSORBANCE DIFFERENCE SPECTRA OF PHOTOSYSTEM II OF CHLOROPLASTS. EVIDENCE FOR TWO DIFFERENT PHOTOSYSTEM II REACTION CENTERSPhotochemistry and Photobiology, 1979
- Photosynthesis in TreesPlant Physiology, 1976
- The flattering of the absorption spectrum of suspensions, as compared to that of solutionsBiochimica et Biophysica Acta, 1956