scholarly journals The effect of N-methylprotoporphyrin IX on the synthesis of photosynthetic pigments in Cyanidium caldarium. Further evidence for the role of haem in the biosynthesis of plant bilins

1982 ◽  
Vol 208 (2) ◽  
pp. 487-491 ◽  
Author(s):  
Stanley B. Brown ◽  
J. Andrew Holroyd ◽  
David I. Vernon ◽  
Robert F. Troxler ◽  
Kevin M. Smith
Keyword(s):  
Chlorophyll A ◽  
Photosynthetic Pigments ◽  
Control Mechanism ◽  
Cyanidium Caldarium

N-Methylprotoporphyrin IX strongly inhibits synthesis of phycocyanobilin, but not chlorophyll a, in the dark. In the light, both phycocyanin and chlorophyll a synthesis are inhibited in parallel. These results are consistent with the intermediacy of haem in algal bilin synthesis and suggest a control mechanism for chlorophyll a synthesis, previously unknown.

Role of the Cilia Membrane in Control of Microtubule Sliding

1980 ◽  
Vol 38 ◽  
pp. 612-615
Author(s):  
Edna S. Kaneshiro
Keyword(s):  
Control Mechanism ◽  
Beat Frequency ◽  
Surface Membrane ◽  
Ciliary Membrane ◽  
Ciliary Beating ◽  
Ciliary Reversal ◽  
Voltage Dependent ◽  
Reversal Mechanism ◽  
And Function

It is currently believed that ciliary beating results from microtubule sliding which is restricted in regions to cause bending. Cilia beat can be modified to bring about changes in beat frequency, cessation of beat and reversal in beat direction. In ciliated protozoans these modifications which determine swimming behavior have been shown to be related to intracellular (intraciliary) Ca2+ concentrations. The Ca2+ levels are in turn governed by the surface ciliary membrane which exhibits increased Ca2+ conductance (permeability) in response to depolarization. Mutants with altered behaviors have been isolated. Pawn mutants fail to exhibit reversal of the effective stroke of ciliary beat and therefore cannot swim backward. They lack the increased inward Ca2+ current in response to depolarizing stimuli. Both normal and pawn Paramecium made leaky to Ca2+ by Triton extrac¬tion of the surface membrane exhibit backward swimming only in reactivating solutions containing greater than IO-6 M Ca2+ Thus in pawns the ciliary reversal mechanism itself is left operational and only the control mechanism at the membrane is affected. The topographic location of voltage-dependent Ca2+ channels has been identified as a component of the ciliary mem¬brane since the inward Ca2+ conductance response is eliminated by deciliation and the return of the response occurs during cilia regeneration. Since the ciliary membrane has been impli¬cated in the control of Ca2+ levels in the cilium and therefore is the site of at least one kind of control of microtubule sliding, we have focused our attention on understanding the structure and function of the membrane.

Role of fibrinopeptide B release: comparison of fibrins produced by thrombin and Ancrod

1977 ◽  
Vol 232 (6) ◽  
pp. H629-H633 ◽  
Author(s):  
L. L. Shen ◽  
J. Hermans ◽  
J. McDonagh ◽  
R. P. McDonagh
Keyword(s):  
Elastic Moduli ◽  
Slow Release ◽  
Control Mechanism ◽  
Gelation Time ◽  
Fibrin Gels ◽  
Lateral Association ◽  
Complete Digestion ◽  
Low Ionic Strength

The gelation time, opacity, light scattering, and elastic moduli of human fibrin gels clotted in the presence of thrombin, Ancrod, and Reptilase have been compared. At low ionic strength lateral association to thick fibers is observed in all cases. At all ionic strengths thrombin fibrin forms thicker fibers than does Ancrod fibrin. We have demonstrated that an increase in the extent of lateral association is linked to an increase in its velocity and to a decrease in the gelation time. One may consider the removal of fibrinopeptide B to act as a switch: after it is removed fibrin assembles rapidly to thick fibers and gelation is fast; but when this peptide is still attached, there is a slow assembly of thin fibers, and gelation, especially of dilute fibrin, is delayed. We believe that this delay is critical for the complete digestion by plasmin of fibrin formed during in vivo defibrination with Ancrod and of fibrin produced by very small amounts of thrombin (which would still contain fibrinopeptide B), and that slow release of fibrinopeptide B is part of a control mechanism for the regulation of fibrin formation and the prevention of intravascular coagulation.

scholarly journals Variations of Chlorophyll Content at Abies alba and Nepeta pannonica Species According to Phenophase and Harvesting Area

2019 ◽  
Vol 52 (1) ◽  
pp. 74-78
Author(s):  
S. Buhăianu ◽  
Doina Carmen Jităreanu
Keyword(s):  
Chlorophyll Content ◽  
Chlorophyll A ◽  
Photosynthetic Pigments ◽  
Photosynthetic Activity ◽  
Abies Alba ◽  
Chlorophyll B ◽  
Green Color ◽  
Yellow Coloration ◽  
Chlorophyll A And B ◽  
Chlorophyll A Content

Abstract Chlorophylls from plants are photosynthetic pigments. Their quantity offers valuable informations about photosynthetic activity, growing and developing of plants. Photosynthetic pigments decrease quantitatively during senescence process or in stress conditions. The present study has been realized in laboratory conditions with material harvested from spontaneous flora. The purpose of this research was the investigation of variations of chlorophyll content from samples of biological material collected from Nepeta pannonica L. and Abies alba Mill. plants, from Câmpulung Moldovenesc and Cacica areas, Suceava county, Romania. The targeted phenophases were growth and flowering. There were realized acetonic extracts from samples for spectrophotometric determinations. Obtained data were processed to estabilish chlorophyll a and b content. There were observed that at Abies alba species, from both locations, the chlorophyll a content grew during flowering phenophase, while the chlorophyll b content had little variations. At Nepeta pannonica species, the chlorophyll a and b content decreased visibly during the flowering, due to stress. Leaves of plants from this species presented a intense green color in the growing phenophase, while during flowering phenophase they had a purple or yellow coloration. Obtained results revealed a different dynamics of chlorophyll content at studied species.

scholarly journals INFLUENCE OF PRE-SOWING TREATMENT OF SEEDS WITH COMPOSITIONS OF METABOLICALLY ACTIVE SUBSTANCES ON THE CONTENT OF PHOTOSYNTHETIC PIGMENTS IN THE LEAVES OF WINTER RYE PLANTS OF SYNTHETIC 38 AND ZABAVA VARIETIES AT DIFFERENT STAGES OF ONTOGENESIS

2021 ◽  
Vol 4 (11(75)) ◽  
pp. 11-16
Author(s):  
А. Kurylenko ◽  
O. Kurylenko ◽  
О. Kuchmenko ◽  
V. Havii
Keyword(s):  
Vitamin E ◽  
Chlorophyll A ◽  
Photosynthetic Pigments ◽  
Total Content ◽  
Winter Rye ◽  
Plant Leaves ◽  
Active Compounds ◽  
Chlorophyll A And B ◽  
Ubiquinone 10 ◽  
Active Substances

Purpose. The aim of the study is to investigate the effect of pre-sowing treatment of winter rye seeds of Synthetic 38 and Zabava with compositions of metabolically active substances on the content of photosynthetic pigments in plant leaves at different phases of ontogenesis. Materials and methods. The research materials were winter rye varieties Synthetic 38 and Zabava, and combinations of metabolically active substances: vitamin E (10-8M), paraoxybenzoic acid (0,001%), methionine (0,001%), ubiquinone-10 (10-8M) and MgSO4 (0,001%). The research scheme provided 4 options: 1) control (untreated seeds); 2) seeds, treated with a composition of substances: vitamin E + paraoxybenzoic acid + methionine + MgSO4; 3) seeds treated with a composition of substances: vitamin E + paraoxybenzoic acid + methionine; 4) seeds, processing by composition of substances: vitamin E + ubiquinone-10. Studies were conducted in the following phases of rye development: tillering, tubing, earing, flowering. The content of pigments - chlorophyll a, b and the total content of chlorophyll in the leaves of rye plants was determined by spectrophotometric method. Results and conclusions. It was demonstrated for the first time that the use of compositions of metabolically active compounds for pre-sowing treatment of winter rye varieties Synthetic 38 and Zabava leads to an increase of main chlorophyll, chlorophyll a and b in plant leaves in the dynamics from tillering to flowering. The composition consisting of vitamin E, para-oxybenzoic acid, methionine and MgSO4 showed the greatest efficiency. The effectiveness of this composition may be due to the complex action of all metabolically active compounds that are part of it. The obtained results may indicate a potentially more efficient absorption and conversion of energy by plants and the positive effect of these compositions on the photosynthesis of winter rye plants. Substances that have shown their effectiveness can be used as components of stimulants.

Measurements of Phytoplankton Absorption Other Than Per Unit of Chlorophyll a

Ocean Optics ◽  
1994 ◽  
Author(s):  
Mary Jane Perry
Keyword(s):  
Primary Production ◽  
Chlorophyll A ◽  
Photosynthetic Pigments ◽  
Critical Role ◽  
Specific Effect ◽  
Water Volume ◽  
Phytoplankton Abundance ◽  
Chlorophyll A Concentration ◽  
Total Irradiance ◽  
Phytoplankton Absorption

Phytoplankton plays a critical role in determining light fields of the world’s oceans, primarily through absorption of light by photosynthetic pigments (see Chapters 1 to 5). Consequently there has been considerable interest from optical researchers in determining phytoplankton absorption. Conversely, from the biological point of view, this absorption assumes paramount importance because it is the sole source of energy for photosynthesis and thus should be central to direct estimates of primary production. There are two logical parts in determining this effect of phytoplankton and in estimating primary production. One is the estimation of abundance, and the other is estimation of specific effect or specific production rate. The earliest estimates of phytoplankton abundance were based on cell counts. From the time of Francis A. Richards’ Ph.D. dissertation, however, measurement of chlorophyll a concentration per unit of water volume, because of its relative ease, has assumed a central role in abundance estimation. Physiological studies and technological advances in optical instrumentation over the last decade lead me to question whether the continued use of chlorophyll a concentration to estimate phytoplankton abundance was wise either from the viewpoint of narrowing confidence intervals on estimates of absorption and production or from the viewpoint of mechanistic understanding of the processes involved. The measurement of chlorophyll a has become such a routine tool of biological oceanography, however, that the reasons for my heresy require elaboration. Some of the reasons are not too subtle. Chlorophyll a exists with other photosynthetic pigments in organized arrays associated with photosynthetic membranes. The function of these arrays is to harvest photons and transfer their energy to the specialized reaction center complexes that mediate photochemistry (see Chapter 9). The size of the arrays or packages and the ratio of chlorophyll a molecules to other light-harvesting pigments within the packages vary with phytoplankton cell size, total irradiance and its spectral distribution, as well as with other environmental parameters. It is well known that dark-adapted (= light-limited) cells increase their complements of photopigments. This plasticity in pigment packaging is evidenced in the variability of chlorophyll a-specific absorption coefficients. Simple optical models based only on chlorophyll a concentrations cannot be accurate or precise unless the effects of pigment packaging are considered.

Interactions between Photosynthetic Pigments Bound to Lipid and Protein Particles. Spectroscopic Properties

1979 ◽  
Vol 34 (7-8) ◽  
pp. 582-587
Author(s):  
Framçoise Techy ◽  
Monique Dinant ◽  
Jacques Aghion
Keyword(s):  
Chlorophyll A ◽  
Photosynthetic Pigments ◽  
Relative Concentration ◽  
Spectroscopic Properties ◽  
Chlorophyll B ◽  
Pheophytin A ◽  
Chlorophylls A And B ◽  
Protein Particles ◽  
Β Carotene

Abstract The spectroscopic (visible) properties of pigment-bearing lipid and protein particles extract­ ed from milk show that: 1) chlorophylls a and b bound to separate particles can form aggregates provided their relative concentration is high enough. Neither pheophytin a nor β-carotene, in the same conditions, form observable aggregates. 2) Chlorophylls a and b can co-aggregate when they are bound to the same particles. Pheophytin a as well as β-carotene seem to prevent the aggregation of chlorophyll a. β-carotene has no effect on the aggregation of chlorophyll b.

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