Search results for "PHOTOS"
showing 10 items of 701 documents
The Effect of Different Light Intensities on the Frequency and Size of Stomata, the Size of Cells, the Number, Size and Chlorophyll Content of Chloro…
1980
Summary Plants of Sinapis alba were cultivated under high light (60 W m -2 PhAR) and low light (6 W m -2 PhAR) conditions. High light intensity during growth increased the stomatal frequency but there were only small changes in the length of the stomatal pore. High-light leaves had more than twice as many stomata per unit area as low-light leaves. The decrease of stomatal diffusive resistance in high-light leaves is primarily caused by the increase in stomatal density. There were striking changes in stomatal frequency during the ontogeny of primary leaves. High light caused a stronger development of the assimilating mesophyll. The volume of the palisade cells increased to a much higher exte…
Light-harvesting chlorophyll a/b-binding protein stably inserts into etioplast membranes supplemented with Zn-pheophytin a/b.
1997
Light-harvesting chlorophyll a/b-binding protein, LHCP, or its precursor, pLHCP, cannot be stably inserted into barley etioplast membranes in vitro. However, when these etioplast membranes are supplemented with the chlorophyll analogs Zn-pheophytin a/b, synthesized in situ from Zn-pheophorbide a/b and digeranyl pyrophosphate, pLHCP is inserted into a protease-resistant state. This proves that chlorophyll is the only component lacking in etioplast membranes that is necessary for stable LHCP insertion. Synthesis of Zn-pheophytin b alone promotes insertion of LHCP in vitro into a protease-resistant state, whereas synthesis of Zn-pheophytin a alone does not. Insertion of pLHCP into etioplast me…
Determination of relative chlorophyll binding affinities in the major light-harvesting chlorophyll a/b complex.
2002
The major light-harvesting complex (LHCIIb) of photosystem II can be reconstituted in vitro from its recombinant apoprotein in the presence of a mixture of carotenoids and chlorophylls a and b. By varying the chlorophyll a/b ratio in the reconstitution mixture, the relative amounts of chlorophyll a and chlorophyll b bound to LHCIIb can be changed. We have analyzed the chlorophyll stoichiometry in recombinant wild type and mutant LHCIIb reconstituted at different chlorophyll a/b ratios in order to assess relative affinities of the chlorophyll-binding sites. This approach reveals five sites that exclusively bind chlorophyll b. Another site exhibits a slight preference of chlorophyll b over ch…
Chlorophyll b is involved in long-wavelength spectral properties of light-harvesting complexes LHC I and LHC II.
2001
AbstractChlorophyll (Chl) molecules attached to plant light-harvesting complexes (LHC) differ in their spectral behavior. While most Chl a and Chl b molecules give rise to absorption bands between 645 nm and 670 nm, some special Chls absorb at wavelengths longer than 700 nm. Among the Chl a/b-antennae of higher plants these are found exclusively in LHC I. In order to assign this special spectral property to one chlorophyll species we reconstituted LHC of both photosystem I (Lhca4) and photosystem II (Lhcb1) with carotenoids and only Chl a or Chl b and analyzed the effect on pigment binding, absorption and fluorescence properties. In both LHCs the Chl-binding sites of the omitted Chl species…
Random mutations directed to transmembrane and loop domains of the light-harvesting chlorophyll a/b protein: impact on pigment binding.
1999
The major light-harvesting complex of photosystem II (LHCII) can be reconstituted in vitro by folding its bacterially expressed apoprotein, Lhcb, in detergent solution in the presence of chlorophylls and carotenoids. To compare the impact of alpha-helical transmembrane domains and hydrophilic loop domains of the apoprotein on complex formation and stability, we introduced random mutations into a segment of the protein comprising the stromal loop, the third (C-proximal) transmembrane helix, and part of the amphipathic helix in the C-terminal domain. The mutant versions of Lhcb were screened for the loss of their ability to form stable LHCII upon reconstitution in vitro. Most steps during the…
The energy distribution between the photosystems and light-induced changes in the stoichiometry of system I and II reaction centers in the chlorophyl…
1988
The chlorophyll b-containing alga Mantoniella squamata was analyzed with respect to its capacity to balance the energy distribution from the light-harvesting antenna to photosystem I or photosystem II. It was shown, that this alga is unable to alter the absorption cross section of the two photosystems in terms of short-time regulations (state transitions). The energy absorbed by the LHC, which contains 60% of total photosynthetic pigments, is transferred to both photosystems without any preference. The stoichiometry of the two photosystems is found to be extremely unequal and variable during light adaptation. In high light, the molar ratio of P-680 per P-700 is found to be two, whereas unde…
Chlorophyll-Protein Complexes of Chlorella fusca
1980
Chlorophyll-protein complexes from thylakoids of the normal type and two mutants of Chlorella fusca were separated using sodium dodecyl sulfate acrylamide gel electrophoresis (PAGE). The properties of the chlorophyll-protein complexes of the three strains of Chlorella were compared. Standard curves were set up for the characterization of the chlorophyll-proteins. In every electrophoretic separation of chlorophyll-protein complexes, a certain amount of pigment is separated from the protein. We tried to keep that amount as low as possible by mild solubilization and by working in low temperature. Under these conditions, we obtained several new chlorophyll-proteins in addition to the P-700-chl…
Chlorophyll-protein-complexes of thylakoids of wild type and chlorophyll b mutants of Arabidopsis thaliana
1983
Pigment-protein-complexes of two chlorophyll b deficient mutants of Arabidopsis and from the wild type were separated electrophoretically. Light-harvesting proteins were absent in the chlorophyll b free mutant ch(1) and their amount was reduced in the mutant ch(2) which has a reduced content of chlorophyll b. The ratio of CPa:CP I increased with decreasing chlorophyll b content which indicated that the stoichiometry of photosystem II to photosystem I is not constant.
Pigment Assembly—Transport and Ligation
2006
The ligation of pigments to proteins involved in photosynthesis appears to be strictly regulated and, in turn, to have an important regulatory impact on the biogenesis of the photosynthetic apparatus. Even so, the molecular mechanism of pigment-protein assembly is largely unknown. However, data are now accumulating on the co-translational transport of chlorophyll a proteins and the post-translational transport of chlorophyll a/b proteins into the thylakoid membrane. The molecular apparatus in the thylakoid membrane presumably occupied with protein insertion may also be involved in pigment ligation. Similarly, the last steps of pigment biosynthesis, whose location has not been fully establis…
Plant chlorophyll fluorescence: active and passive measurements at canopy and leaf scales with different nitrogen treatments
2015
Highlight We studied for the first time the temporal and spatial limits within which active and passive chlorophyll fluorescence measurements are comparable.