Carbon Fixation Profiles Do Reflect Light Absorption Profiles in Leaves

1995 ◽  
Vol 22 (6) ◽  
pp. 865 ◽  
Author(s):  
JR Evans
Keyword(s):  
Light Absorption ◽  
Carbon Fixation ◽  
Protein Complexes ◽  
Lower Surface ◽  
High Irradiance ◽  
Absorption Profile ◽  
Light Gradient ◽  
Pigment Protein Complexes ◽  
Leaf Space ◽  
Leaf Photosynthetic Rate

Bifacial leaves contain an array of chloroplasts which are aligned along cell walls adjacent to intercellular airspaces. Cells beneath the adaxial (upper) surface are generally cylindrical in shape, forming palisade tissue and contain chloroplasts that have characteristics associated with acclimation to high irradiance. Conversely, cells near the abaxial (lower) surface are irregular in shape, forming spongy tissue and contain chloroplasts that have characteristics associated with acclimation to low irradiance. This results in a gradient of declining photosynthetic capacity per unit chlorophyll with increasing depth into the leaf. Space irradiance declines dramatically through the leaf. The profile of light absorption through the leaf has yet to be measured, but should approximate the product of space irradiance and pigment profiles. Since pigment content is highest in the middle of the leaf, light absorption peaks about one quarter of the way through the leaf. The response of leaf photosynthetic rate to irradiance reflects the interaction between the profiles of light absorption and chloroplast characteristics. Quantum yield (mol CO2 mol-1 quanta absorbed) varies for different layers in the leaf because the profile of Rubisco content per unit chlorophyll is not as steep as the light absorption profile. This skews the profile of carbon fixation away from the light absorption profile, favouring greater fixation in deeper layers. Nishio, Sun and Vogelmann (1993, Plant Cell 5, 953-961) measured profiles of 14C fixation across spinach leaves and concluded that carbon fixation was disconnected from the light gradient. Reanalysis of their data shows that carbon fixation is remarkably consistent with light absorption obeying the Beer- Lambert law when allowance is made for chlorophyll and Rubisco profiles through the leaf. This interpretation is supported by chlorophyll fluorescence properties of adaxial and abaxial surfaces. An apparent extinction coefficient of about 1500 m2 (mol Chl)-1 could be derived from leaf data which compares with 2230 m2 (mol Chl)-1 for pigment-protein complexes in solution. A possible test for this analysis would be to measure the 14C fixation profile of leaves illuminated on their abaxial surface.

Partitioning of Nitrogen Between and Within Leaves Grown Under Different Irradiances

1989 ◽  
Vol 16 (6) ◽  
pp. 533 ◽  
Author(s):  
JR Evans
Keyword(s):  
Nitrogen Content ◽  
Photosynthetic Rate ◽  
Protein Complexes ◽  
Leaf Nitrogen ◽  
High Irradiance ◽  
Leaf Nitrogen Content ◽  
Unit Leaf ◽  
Growth Irradiance ◽  
Pigment Protein Complexes ◽  
Nitrogen Contents

The distribution of nitrogen between leaves on individual plants of Phaseolus vulgaris and Cucumis sativus which were grown under different irradiances was examined. For Phaseolus, shading treatments were imposed on individual leaflets when they had reached one-third of full expansion. Adjacent leaflets were either grown under the same irradiance or had different irradiances imposed on them. The nitrogen content of leaves depended on their growth irradiance and not on the growth irradiance of adjacent leaflets, with more nitrogen being found in leaves grown under higher irradiance compared to those grown in shade. For Cucumis, the nitrogen contents of the leaves changed following the imposition of shading treatments. The experiment was repeated four times with different nitrate nutrient treatments, twice in combination with a pretreatment growth irradiance of 40% sunlight. The relative changes in leaf nitrogen content for each irradiance treatment were independent of changes to the leaf nitrogen content of the plant and of the growth irradiance prior to the shading treatments. Again, nitrogen contents were highest in leaves grown at high irradiance. Acclimation of individual leaves to their irradiance treatment was seen for both Phaseolus and Cucumis. Growth under shade resulted in lower rates of oxygen evolution per unit of chlorophyll, when measured at high irradiance, and increased partitioning of nitrogen into pigment-protein complexes. These two changes working in opposition to each other meant that for Cucumis, the relationship between photosynthetic capacity and nitrogen content was similar between irradiance treatments. For Phaseolus, the increased partitioning of nitrogen into pigment-protein complexes at low irradiance was not as great as the reduction in photosynthetic rate per unit of chlorophyll, so that the photosynthetic rate per unit leaf nitrogen was less for leaves grown under low irradiance compared to those grown under high irradiance. It is shown that acclimation to lower irradiance can increase the potential daily photosynthesis for a given leaf nitrogen content.

Carotenoidless pigment-protein complexes of the sulfur photosynthetic bacterium Ectothiorhodospira haloalkaliphila

2013 ◽  
Vol 453 (1) ◽  
pp. 304-307 ◽  
Author(s):  
A. A. Ashikhmin ◽  
Yu. E. Erokhin ◽  
Z. K. Makhneva ◽  
A. A. Moskalenko
Keyword(s):  
Protein Complexes ◽  
Photosynthetic Bacterium ◽  
Pigment Protein Complexes

Biogenesis of Chloroplasts and Pigment-Protein Complexes in Barley Seedlings with Blocked Biosynthesis of Carotenoids

1992 ◽  
pp. 349-354
Author(s):  
Navassard V. Karapetyan ◽  
Marina G. Rakhimberdieva ◽  
Yulia V. Bolychevtseva ◽  
Andrei A. Moskalenko ◽  
Nina Yu. Kuznetsova ◽  
...  
Keyword(s):  
Protein Complexes ◽  
Pigment Protein Complexes

scholarly journals The role of LHCBM1 in non-photochemical quenching in Chlamydomonas reinhardtii

2022 ◽  
Author(s):  
Xin Liu ◽  
Wojciech J Nawrocki ◽  
Roberta Croce
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Protein Complexes ◽  
Ph Sensor ◽  
High Light ◽  
Photochemical Quenching ◽  
Knock Out ◽  
Photosynthetic Organisms ◽  
Pigment Protein Complexes ◽  
Non Photochemical Quenching

Non-photochemical quenching (NPQ) is the process that protects photosynthetic organisms from photodamage by dissipating the energy absorbed in excess as heat. In the model green alga Chlamydomonas reinhardtii, NPQ was abolished in the knock-out mutants of the pigment-protein complexes LHCSR3 and LHCBM1. However, while LHCSR3 was shown to be a pH sensor and switching to a quenched conformation at low pH, the role of LHCBM1 in NPQ has not been elucidated yet. In this work, we combine biochemical and physiological measurements to study short-term high light acclimation of npq5, the mutant lacking LHCBM1. We show that while in low light in the absence of this complex, the antenna size of PSII is smaller than in its presence, this effect is marginal in high light, implying that a reduction of the antenna is not responsible for the low NPQ. We also show that the mutant expresses LHCSR3 at the WT level in high light, indicating that the absence of this complex is also not the reason. Finally, NPQ remains low in the mutant even when the pH is artificially lowered to values that can switch LHCSR3 to the quenched conformation. It is concluded that both LHCSR3 and LHCBM1 need to be present for the induction of NPQ and that LHCBM1 is the interacting partner of LHCSR3. This interaction can either enhance the quenching capacity of LHCSR3 or connect this complex with the PSII supercomplex.

scholarly journals Structure of the stress-related LHCSR1 complex determined by an integrated computational strategy

2021 ◽  
Author(s):  
Ingrid Guarnetti Prandi ◽  
Vladislav Sláma ◽  
Cristina Pecorilla ◽  
Lorenzo Cupellini ◽  
Benedetta Mennucci
Keyword(s):  
Structural Model ◽  
Light Harvesting ◽  
Structural Information ◽  
Protein Complexes ◽  
Complex Stress ◽  
Main Function ◽  
Light Harvesting Complexes ◽  
Light Harvesting Complex ◽  
Pigment Protein Complexes ◽  
Computational Strategy

Light-harvesting complexes (LHCs) are pigment-protein complexes whose main function is to capture sunlight and transfer the energy to reaction centers of photosystems. In response to varying light conditions, LH complexes also play photoregulation and photoprotection roles. In algae and mosses, a sub-family of LHCs, Light-Harvesting complex stress related (LHCSR), is responsible for photoprotective quenching. Despite their functional and evolutionary importance, no direct structural information on LHCSRs is available that can explain their unique properties. In this work we propose a structural model of LHCSR1 from the moss P. Patens, obtained through an integrated computational strategy that combines homology modeling, molecular dynamics, and multiscale quantum chemical calculations. The model is validated by reproducing the spectral properties of LHCSR1. Our model reveals the structural specificity of LHCSR1, as compared with the CP29 LH complex, and poses the basis for understanding photoprotective quenching in mosses.

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