Photoinhibition

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Photoinhibition of Photosystem II (PSII) leads to loss of PSII electron transfer activity. PSII is continuously repaired via degradation and synthesis of the D1 protein. Lincomycin can be used to block protein synthesis Photoinhibition.svg
Photoinhibition of Photosystem II (PSII) leads to loss of PSII electron transfer activity. PSII is continuously repaired via degradation and synthesis of the D1 protein. Lincomycin can be used to block protein synthesis

Photoinhibition is light-induced reduction in the photosynthetic capacity of a plant, alga, or cyanobacterium. Photosystem II (PSII) is more sensitive to light than the rest of the photosynthetic machinery, and most researchers define the term as light-induced damage to PSII. In living organisms, photoinhibited PSII centres are continuously repaired via degradation and synthesis of the D1 protein of the photosynthetic reaction center of PSII. Photoinhibition is also used in a wider sense, as dynamic photoinhibition, to describe all reactions that decrease the efficiency of photosynthesis when plants are exposed to light.

Contents

History

The first measurements of photoinhibition were published in 1956 by Bessel Kok. [1] Even in the very first studies, it was obvious that plants have a repair mechanism that continuously repairs photoinhibitory damage. In 1966, Jones and Kok measured the action spectrum of photoinhibition and found that ultraviolet light is highly photoinhibitory. [2] The visible-light part of the action spectrum was found to have a peak in the red-light region, suggesting that chlorophylls act as photoreceptors of photoinhibition. In the 1980s, photoinhibition became a popular topic in photosynthesis research, and the concept of a damaging reaction counteracted by a repair process was re-invented. Research was stimulated by a paper by Kyle, Ohad and Arntzen in 1984, showing that photoinhibition is accompanied by selective loss of a 32-kDa protein, later identified as the PSII reaction center protein D1. [3] The photosensitivity of PSII from which the oxygen evolving complex had been inactivated with chemical treatment was studied in the 1980s and early 1990s. [4] [5] A paper by Imre Vass and colleagues in 1992 described the acceptor-side mechanism of photoinhibition. [6] Measurements of production of singlet oxygen by photoinhibited PSII provided further evidence for an acceptor-side-type mechanism. [7] The concept of a repair cycle that continuously repairs photoinhibitory damage, evolved and was reviewed by Aro et al. in 1993. [8] Many details of the repair cycle, including the finding that the FtsH protease plays an important role in the degradation of the D1 protein, have been discovered since. [9] In 1996, a paper by Tyystjärvi and Aro showed that the rate constant of photoinhibition is directly proportional to light intensity, a result that opposed the former assumption that photoinhibition is caused by the fraction of light energy that exceeds the maximum capability of photosynthesis. [10] The following year, laser pulse photoinhibition experiments done by Itzhak Ohad's group led to the suggestion that charge recombination reactions may be damaging because they can lead to production of singlet oxygen. [11] The molecular mechanism(s) of photoinhibition are constantly under discussion. The newest candidate is the manganese mechanism suggested 2005 by the group of Esa Tyystjärvi. [12] A similar mechanism was suggested by the group of Norio Murata, also in 2005. [13]

What is inhibited

Cyanobacteria photosystem II, dimer, PDB 2AXT Photosystem-II 2AXT.PNG
Cyanobacteria photosystem II, dimer, PDB 2AXT

Photoinhibition occurs in all organisms capable of oxygenic photosynthesis, from vascular plants to cyanobacteria. [14] [15] In both plants and cyanobacteria, blue light causes photoinhibition more efficiently than other wavelengths of visible light, and all wavelengths of ultraviolet light are more efficient than wavelengths of visible light. [14] Photoinhibition is a series of reactions that inhibit different activities of PSII, but there is no consensus on what these steps are. The activity of the oxygen-evolving complex of PSII is often found to be lost before the rest of the reaction centre loses activity. [12] [13] [16] [17] However, inhibition of PSII membranes under anaerobic conditions leads primarily to inhibition of electron transfer on the acceptor side of PSII. [6] Ultraviolet light causes inhibition of the oxygen-evolving complex before the rest of PSII becomes inhibited. Photosystem I (PSI) is less susceptible to light-induced damage than PSII, but slow inhibition of this photosystem has been observed. [18] Photoinhibition of PSI occurs in chilling-sensitive plants and the reaction depends on electron flow from PSII to PSI.

How often does damage occur?

Photosystem II is damaged by light irrespective of light intensity. [16] The quantum yield of the damaging reaction in typical leaves of higher plants exposed to visible light, as well as in isolated thylakoid membrane preparations, is in the range of 10−8 to 10−7 and independent of the intensity of light. [10] [19] This means that one PSII complex is damaged for every 10-100 million photons that are intercepted. Therefore, photoinhibition occurs at all light intensities and the rate constant of photoinhibition is directly proportional to light intensity. Some measurements suggest that dim light causes damage more efficiently than strong light. [11]

Molecular mechanism(s)

The mechanism(s) of photoinhibition are under debate, several mechanisms have been suggested. [16] Reactive oxygen species, especially singlet oxygen, have a role in the acceptor-side, singlet oxygen and low-light mechanisms. In the manganese mechanism and the donor side mechanism, reactive oxygen species do not play a direct role. Photoinhibited PSII produces singlet oxygen, [7] and reactive oxygen species inhibit the repair cycle of PSII by inhibiting protein synthesis in the chloroplast. [20]

Acceptor-side photoinhibition

Strong light causes the reduction of the plastoquinone pool, which leads to protonation and double reduction (and double protonation) of the QA electron acceptor of Photosystem II. The protonated and double-reduced forms of QA do not function in electron transport. Furthermore, charge recombination reactions in inhibited Photosystem II are expected to lead to the triplet state of the primary donor (P680) more probably than same reactions in active PSII. Triplet P680 may react with oxygen to produce harmful singlet oxygen. [6]

Donor-side photoinhibition

If the oxygen-evolving complex is chemically inactivated, then the remaining electron transfer activity of PSII becomes very sensitive to light. [4] [19] It has been suggested that even in a healthy leaf, the oxygen-evolving complex does not always function in all PSII centers, and those ones are prone to rapid irreversible photoinhibition. [21]

Manganese mechanism

A photon absorbed by the manganese ions of the oxygen-evolving complex triggers inactivation of the oxygen-evolving complex. Further inhibition of the remaining electron transport reactions occurs like in the donor-side mechanism. The mechanism is supported by the action spectrum of photoinhibition. [12]

Singlet oxygen mechanisms

Inhibition of PSII is caused by singlet oxygen produced either by weakly coupled chlorophyll molecules [22] or by cytochromes or iron–sulfur centers. [23]

Low-light mechanism

Charge recombination reactions of PSII cause the production of triplet P680 and, as a consequence, singlet oxygen. Charge recombination is more probable under dim light than under higher light intensities. [11]

Kinetics and action spectrum

Photoinhibition follows simple first-order kinetics if measured from a lincomycin-treated leaf, cyanobacterial or algal cells, or isolated thylakoid membranes in which concurrent repair does not disturb the kinetics. Data from the group of W. S. Chow indicate that in leaves of pepper ( Capsicum annuum ), the first-order pattern is replaced by a pseudo-equilibrium even if the repair reaction is blocked. The deviation has been explained by assuming that photoinhibited PSII centers protect the remaining active ones. [24] Both visible and ultraviolet light cause photoinhibition, ultraviolet wavelengths being much more damaging. [12] [23] [25] Some researchers consider ultraviolet and visible light induced photoinhibition as a two different reactions, [26] while others stress the similarities between the inhibition reactions occurring under different wavelength ranges. [12] [13]

PSII repair cycle

Photoinhibition occurs continuously when plants or cyanobacteria are exposed to light, and the photosynthesizing organism must, therefore, continuously repair the damage. [8] The PSII repair cycle, occurring in chloroplasts and in cyanobacteria, consists of degradation and synthesis of the D1 protein of the PSII reaction centre, followed by activation of the reaction center. Due to the rapid repair, most PSII reaction centers are not photoinhibited even if a plant is grown in strong light. However, environmental stresses, for example, extreme temperatures, salinity, and drought, limit the supply of carbon dioxide for use in carbon fixation, which decreases the rate of repair of PSII. [27]

In photoinhibition studies, repair is often stopped by applying an antibiotic (lincomycin or chloramphenicol) to plants or cyanobacteria, which blocks protein synthesis in the chloroplast. Protein synthesis occurs only in an intact sample, so lincomycin is not needed when photoinhibition is measured from isolated membranes. [27] The repair cycle of PSII recirculates other subunits of PSII (except for the D1 protein) from the inhibited unit to the repaired one.

Protective mechanisms

The xanthophyll cycle is important in protecting plants from photoinhibition Violaxanthin cycle.png
The xanthophyll cycle is important in protecting plants from photoinhibition

Plants have mechanisms that protect against adverse effects of strong light. The most studied biochemical protective mechanism is non-photochemical quenching of excitation energy. [28] Visible-light-induced photoinhibition is ~25% faster in an Arabidopsis thaliana mutant lacking non-photochemical quenching than in the wild type. It is also apparent that turning or folding of leaves, as occurs, e.g., in Oxalis species in response to exposure to high light, protects against photoinhibition.

The PsBs Protein

Because there are a limited number of photosystems in the electron transport chain, organisms that are photosynthetic must find a way to combat excess light and prevent photo-oxidative stress, and likewise, photoinhibition, at all costs. In an effort to avoid damage to the D1 subunit of PSII and subsequent formation of ROS, the plant cell employs accessory proteins to carry the excess excitation energy from incoming sunlight; namely, the PsBs protein. Elicited by a relatively low luminal pH, plants have developed a rapid response to excess energy by which it is given off as heat and damage is reduced.

The studies of Tibiletti et al. (2016) found that PsBs is the main protein involved in sensing the changes in the pH and can therefore rapidly accumulate in the presence of high light. This was determined by performing SDS-PAGE and immunoblot assays, locating PsBs itself in the green alga, Chlamydomonas reinhardtii . Their data concluded that the PsBs protein belongs to a multigene family termed LhcSR proteins, including the proteins that catalyze the conversion of violaxanthin to zeaxanthin, as previously mentioned. PsBs is involved in the changing the orientation of the photosystems at times of high light to prompt the arrangement of a quenching site in the light harvesting complex.

Additionally, studies conducted by Glowacka et al. (2018) show that a higher concentration of PsBs is directly correlated to inhibiting stomatal aperture. But it does this without affecting CO2intake and it increases water use efficiency of the plant. This was determined by controlling the expression of PsBs in Nicotinana tabacum by imposing a series of genetic modifications to the plant in order to test for PsBs levels and activity including: DNA transformation and transcription followed by protein expression. Research shows that stomatal conductance is heavily dependent on the presence of the PsBs protein. Thus, when PsBs was overexpressed in a plant, water uptake efficiency was seen to significantly improve, resulting in new methods for prompting higher, more productive crop yields.

These recent discoveries tie together two of the largest mechanisms in phytobiology; these are the influences that the light reactions have upon stomatal aperture via the Calvin Benson Cycle. To elaborate, the Calvin-Benson Cycle, occurring in the stroma of the chloroplast obtains its CO2 from the atmosphere which enters upon stomatal opening. The energy to drive the Calvin-Benson cycle is a product of the light reactions. Thus, the relationship has been discovered as such: when PsBs is silenced, as expected, the excitation pressure at PSII is increased. This in turn results in an activation of the redox state of Quinone A and there is no change in the concentration of carbon dioxide in the intracellular airspaces of the leaf; ultimately increasing stomatal conductance. The inverse relationship also holds true: when PsBs is over expressed, there is a decreased excitation pressure at PSII. Thus, the redox state of Quinone A is no longer active and there is, again, no change in the concentration of carbon dioxide in the intracellular airspaces of the leaf. All these factors work to have a net decrease of stomatal conductance.

Measurement

Effect of illumination on the ratio of variable to maximum fluorescence (FV/FM) of ground-ivy (Glechoma hederacea) leaves. Photon flux density was 1000 mmol m s , corresponding to half of full sunlight. Photoinhibition damages PSII at the same rate whether the leaf stalk is in water or lincomycin, but, in the "leaf stalk in water" sample, repair is so rapid that no net decrease in (FV/FM) occurs Photoinhibition in Glechoma hederacea.jpg
Effect of illumination on the ratio of variable to maximum fluorescence (FV/FM) of ground-ivy (Glechoma hederacea) leaves. Photon flux density was 1000 μmol m s , corresponding to half of full sunlight. Photoinhibition damages PSII at the same rate whether the leaf stalk is in water or lincomycin, but, in the “leaf stalk in water” sample, repair is so rapid that no net decrease in (FV/FM) occurs

Photoinhibition can be measured from isolated thylakoid membranes or their subfractions, or from intact cyanobacterial cells by measuring the light-saturated rate of oxygen evolution in the presence of an artificial electron acceptor (quinones and dichlorophenol-indophenol have been used).

The degree of photoinhibition in intact leaves can be measured using a fluorimeter to measure the ratio of variable to maximum value of chlorophyll a fluorescence (FV/FM). [16] This ratio can be used as a proxy of photoinhibition because more energy is emitted as fluorescence from Chlorophyll a when many excited electrons from PSII are not captured by the acceptor and decay back to their ground state.

When measuring FV/FM, the leaf must be incubated in the dark for at least 10 minutes, preferably longer, before the measurement, in order to let non-photochemical quenching relax.

Flashing light

Photoinhibition can also be induced with short flashes of light using either a pulsed laser or a xenon flash lamp. When very short flashes are used, the photoinhibitory efficiency of the flashes depends on the time difference between the flashes. [11] This dependence has been interpreted to indicate that the flashes cause photoinhibition by inducing recombination reactions in PSII, with subsequent production of singlet oxygen. The interpretation has been criticized by noting that the photoinhibitory efficiency of xenon flashes depends on the energy of the flashes even if such strong flashes are used that they would saturate the formation of the substrate of the recombination reactions. [12]

Dynamic photoinhibition

Some researchers prefer to define the term “photoinhibition” so that it contains all reactions that lower the quantum yield of photosynthesis when a plant is exposed to light. [29] [30] In this case, the term "dynamic photoinhibition" comprises phenomena that reversibly down-regulate photosynthesis in the light and the term "photodamage" or "irreversible photoinhibition" covers the concept of photoinhibition used by other researchers. The main mechanism of dynamic photoinhibition is non-photochemical quenching of excitation energy absorbed by PSII. Dynamic photoinhibition is acclimation to strong light rather than light-induced damage, and therefore "dynamic photoinhibition" may actually protect the plant against "photoinhibition".

Ecology of photoinhibition

Photoinhibition may cause coral bleaching. [27]

See also

Related Research Articles

<span class="mw-page-title-main">Photosynthesis</span> Biological process to convert light into chemical energy

Photosynthesis is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their activities. Photosynthetic organisms use intracellular organic compounds to store the chemical energy they produce in photosynthesis within organic compounds like sugars, glycogen, cellulose and starches. Photosynthesis is usually used to refer to oxygenic photosynthesis, a process that produces oxygen. To use this stored chemical energy, the organisms' cells metabolize the organic compounds through another process called cellular respiration. Photosynthesis plays a critical role in producing and maintaining the oxygen content of the Earth's atmosphere, and it supplies most of the biological energy necessary for complex life on Earth.

<span class="mw-page-title-main">Thylakoid</span> Membrane enclosed compartments in chloroplasts and cyanobacteria

Thylakoids are membrane-bound compartments inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen. Chloroplast thylakoids frequently form stacks of disks referred to as grana. Grana are connected by intergranal or stromal thylakoids, which join granum stacks together as a single functional compartment.

<span class="mw-page-title-main">Photosystem</span> Structural units of protein involved in photosynthesis

Photosystems are functional and structural units of protein complexes involved in photosynthesis. Together they carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons. Photosystems are found in the thylakoid membranes of plants, algae, and cyanobacteria. These membranes are located inside the chloroplasts of plants and algae, and in the cytoplasmic membrane of photosynthetic bacteria. There are two kinds of photosystems: PSI and PSII.

<span class="mw-page-title-main">Photosystem II</span> First protein complex in light-dependent reactions of oxygenic photosynthesis

Photosystem II is the first protein complex in the light-dependent reactions of oxygenic photosynthesis. It is located in the thylakoid membrane of plants, algae, and cyanobacteria. Within the photosystem, enzymes capture photons of light to energize electrons that are then transferred through a variety of coenzymes and cofactors to reduce plastoquinone to plastoquinol. The energized electrons are replaced by oxidizing water to form hydrogen ions and molecular oxygen.

<span class="mw-page-title-main">Photosystem I</span> Second protein complex in photosynthetic light reactions

Photosystem I is one of two photosystems in the photosynthetic light reactions of algae, plants, and cyanobacteria. Photosystem I is an integral membrane protein complex that uses light energy to catalyze the transfer of electrons across the thylakoid membrane from plastocyanin to ferredoxin. Ultimately, the electrons that are transferred by Photosystem I are used to produce the moderate-energy hydrogen carrier NADPH. The photon energy absorbed by Photosystem I also produces a proton-motive force that is used to generate ATP. PSI is composed of more than 110 cofactors, significantly more than Photosystem II.

Chlorophyll <i>a</i> Chemical compound

Chlorophyll a is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light, and it is a poor absorber of green and near-green portions of the spectrum. Chlorophyll does not reflect light but chlorophyll-containing tissues appear green because green light is diffusively reflected by structures like cell walls. This photosynthetic pigment is essential for photosynthesis in eukaryotes, cyanobacteria and prochlorophytes because of its role as primary electron donor in the electron transport chain. Chlorophyll a also transfers resonance energy in the antenna complex, ending in the reaction center where specific chlorophylls P680 and P700 are located.

<span class="mw-page-title-main">Light-harvesting complexes of green plants</span> Component of photosynthesis

The light-harvesting complex is an array of protein and chlorophyll molecules embedded in the thylakoid membrane of plants and cyanobacteria, which transfer light energy to one chlorophyll a molecule at the reaction center of a photosystem.

<span class="mw-page-title-main">Photosynthetic reaction centre</span> Molecular unit responsible for absorbing light in photosynthesis

A photosynthetic reaction center is a complex of several proteins, pigments, and other co-factors that together execute the primary energy conversion reactions of photosynthesis. Molecular excitations, either originating directly from sunlight or transferred as excitation energy via light-harvesting antenna systems, give rise to electron transfer reactions along the path of a series of protein-bound co-factors. These co-factors are light-absorbing molecules (also named chromophores or pigments) such as chlorophyll and pheophytin, as well as quinones. The energy of the photon is used to excite an electron of a pigment. The free energy created is then used, via a chain of nearby electron acceptors, for a transfer of hydrogen atoms (as protons and electrons) from H2O or hydrogen sulfide towards carbon dioxide, eventually producing glucose. These electron transfer steps ultimately result in the conversion of the energy of photons to chemical energy.

Photoprotection is the biochemical process that helps organisms cope with molecular damage caused by sunlight. Plants and other oxygenic phototrophs have developed a suite of photoprotective mechanisms to prevent photoinhibition and oxidative stress caused by excess or fluctuating light conditions. Humans and other animals have also developed photoprotective mechanisms to avoid UV photodamage to the skin, prevent DNA damage, and minimize the downstream effects of oxidative stress.

<span class="mw-page-title-main">Pheophytin</span> Chlorophyll molecules lacking a central Mg2+ ion

Pheophytin or phaeophytin is a chemical compound that serves as the first electron carrier intermediate in the electron transfer pathway of Photosystem II in plants, and the type II photosynthetic reaction center found in purple bacteria. In both PS II and RC P870, light drives electrons from the reaction center through pheophytin, which then passes the electrons to a quinone (QA) in RC P870 and RC P680. The overall mechanisms, roles, and purposes of the pheophytin molecules in the two transport chains are analogous to each other.

<span class="mw-page-title-main">Photosynthetic reaction centre protein family</span>

Photosynthetic reaction centre proteins are main protein components of photosynthetic reaction centres (RCs) of bacteria and plants. They are transmembrane proteins embedded in the chloroplast thylakoid or bacterial cell membrane.

<span class="mw-page-title-main">Cytochrome b559</span> Family of protein complexes

Cytochrome b559 is an important component of Photosystem II (PSII) is a multisubunit protein-pigment complex containing polypeptides both intrinsic and extrinsic to the photosynthetic membrane. Within the core of the complex, the chlorophyll and beta-carotene pigments are mainly bound to the antenna proteins CP43 (PsbC) and CP47 (PsbB), which pass the excitation energy on to chlorophylls in the reaction centre proteins D1 and D2 that bind all the redox-active cofactors involved in the energy conversion process. The PSII oxygen-evolving complex (OEC) provides electrons to re-reduce the PSII reaction center, and oxidizes 2 water molecules to recover its reduced initial state. It consists of OEE1 (PsbO), OEE2 (PsbP) and OEE3 (PsbQ). The remaining subunits in PSII are of low molecular weight, and are involved in PSII assembly, stabilisation, dimerization, and photoprotection.

<span class="mw-page-title-main">Photosystem II light-harvesting protein</span> Biological protein

Photosystem II light-harvesting proteins are the intrinsic transmembrane proteins CP43 (PsbC) and CP47 (PsbB) occurring in the reaction centre of photosystem II (PSII). These polypeptides bind to chlorophyll a and β-Carotene and pass the excitation energy on to the reaction centre.

Non-photochemical quenching (NPQ) is a mechanism employed by plants and algae to protect themselves from the adverse effects of high light intensity. It involves the quenching of singlet excited state chlorophylls (Chl) via enhanced internal conversion to the ground state, thus harmlessly dissipating excess excitation energy as heat through molecular vibrations. NPQ occurs in almost all photosynthetic eukaryotes, and helps to regulate and protect photosynthesis in environments where light energy absorption exceeds the capacity for light utilization in photosynthesis.

<span class="mw-page-title-main">Light-dependent reactions</span> Photosynthetic reactions

Light-dependent reactions are certain photochemical reactions involved in photosynthesis, the main process by which plants acquire energy. There are two light dependent reactions: the first occurs at photosystem II (PSII) and the second occurs at photosystem I (PSI).

<span class="mw-page-title-main">Anoxygenic photosynthesis</span> Process used by obligate anaerobes

Anoxygenic photosynthesis is a special form of photosynthesis used by some bacteria and archaea, which differs from the better known oxygenic photosynthesis in plants in the reductant used and the byproduct generated.

<span class="mw-page-title-main">Chlorophyll fluorescence</span> Light re-emitted by chlorophyll molecules during return from excited to non-excited states

Chlorophyll fluorescence is light re-emitted by chlorophyll molecules during return from excited to non-excited states. It is used as an indicator of photosynthetic energy conversion in plants, algae and bacteria. Excited chlorophyll dissipates the absorbed light energy by driving photosynthesis, as heat in non-photochemical quenching or by emission as fluorescence radiation. As these processes are complementary processes, the analysis of chlorophyll fluorescence is an important tool in plant research with a wide spectrum of applications.

<span class="mw-page-title-main">Ycf9 protein domain</span> Plastid protein involved in photosynthesis

In molecular biology, the PsbZ (Ycf9) is a protein domain, which is low in molecular weight. It is a transmembrane protein and therefore is located in the thylakoid membrane of chloroplasts in cyanobacteria and plants. More specifically, it is located in Photosystem II (PSII) and in the light-harvesting complex II (LHCII). Ycf9 acts as a structural linker, that stabilises the PSII-LHCII supercomplexes. Moreover, the supercomplex fails to form in PsbZ-deficient mutants, providing further evidence to suggest Ycf9's role as a structural linker. This may be caused by a marked decrease in two LHCII antenna proteins, CP26 and CP29, found in PsbZ-deficient mutants, which result in structural changes, as well as functional modifications in PSII.

<span class="mw-page-title-main">Orange carotenoid protein</span>

Orange carotenoid protein (OCP) is a water-soluble protein which plays a role in photoprotection in diverse cyanobacteria. It is the only photoactive protein known to use a carotenoid as the photoresponsive chromophore. The protein consists of two domains, with a single keto-carotenoid molecule non-covalently bound between the two domains. It is a very efficient quencher of excitation energy absorbed by the primary light-harvesting antenna complexes of cyanobacteria, the phycobilisomes. The quenching is induced by blue-green light. It is also capable of preventing oxidative damage by directly scavenging singlet oxygen (1O2).

<span class="mw-page-title-main">Photoautotrophism</span> Organisms that use light and inorganic carbon to produce organic materials

Photoautotrophs are organisms that can utilize light energy from sunlight and elements from inorganic compounds to produce organic materials needed to sustain their own metabolism. This biological activity is known as photosynthesis, and examples of such photosynthetic organisms include plants, algae and cyanobacteria.

References

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  19. 1 2 Eckert HJ; Geiken B; Bernarding J; Napiwotzki A; Eichler HJ; Renger G (1991). "Two sites of photoinhibition of the electron-transfer in oxygen evolving and Tris-treated PS-II membrane-fragments from spinach". Photosynthesis Research. 27 (2): 97–108. doi:10.1007/BF00033249. PMID   24414573. S2CID   38944774.
  20. ↑ Nishiyama Y, Allakhverdiev SI & Murata N (2006). "A new paradigm for the action of reactive oxygen species in the photoinhibition of photosystem II". Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1757 (7): 742–749. doi:10.1016/j.bbabio.2006.05.013. PMID   16784721.
  21. ↑ Anderson JM, Park Y-I & Chow WS (1998). "Unifying model for the photoinactivation of Photosystem II in vivo: a hypothesis". Photosynthesis Research. 56: 1–13. doi:10.1023/A:1005946808488. S2CID   31724011.
  22. ↑ Santabarbara S; Cazzalini I; Rivadossi A; Garlaschi FM; Zucchelli G; Jennings RC (2002). "Photoinhibition in vivo and in vitro involves weakly coupled chlorophyll-protein complexes". Photochemistry and Photobiology. 75 (6): 613–618. doi:10.1562/0031-8655(2002)0750613PIVAIV2.0.CO2. PMID   12081323. S2CID   222101185.
  23. 1 2 Jung J, Kim HS (1990). "The chromophores as endogenous sensitizers involved in the photogeneration of singlet oxygen in spinach thylakoids". Photochemistry and Photobiology. 52 (5): 1003–1009. doi:10.1111/j.1751-1097.1990.tb01817.x. S2CID   83697536.
  24. ↑ Lee HY, Hong YN & Chow WS (2001). "Photoinactivation of photosystem II complexes and photoprotection by non-functional neighbours in Capsicum annuum L. leaves". Planta. 212 (3): 332–342. doi:10.1007/s004250000398. PMID   11289597. S2CID   8399980.
  25. ↑ Sarvikas P; Hakala M; Pätsikkä E; Tyystjärvi T; Tyystjärvi E (2006). "Action spectrum of photoinhibition in leaves of wild type and npq1-2 and npq4-1 mutants of Arabidopsis thaliana". Plant and Cell Physiology. 47 (3): 391–400. doi:10.1093/pcp/pcj006. PMID   16415063.
  26. ↑ Sicora C, Mate Z & Vass I (2003). "The interaction of visible and UV-B light during photodamage and repair of Photosystem II". Photosynthesis Research. 75 (2): 127–137. doi:10.1023/A:1022852631339. PMID   16245083. S2CID   22151214.
  27. 1 2 3 Takahashi S, Murata N (2008). "How do environmental stresses accelerate photoinhibition". Trends in Plant Science. 13 (4): 178–182. doi:10.1016/j.tplants.2008.01.005. PMID   18328775.
  28. ↑ Krause GH & Jahns P (2004) "Non-photochemical energy dissipation determined by chlorophyll fluorescence quenching: Characterization and function" in Papageorgiou GC & Govindjee (eds.) "Chlorophyll Fluorescence: A Signature of Photosynthesis". pp. 463–495. Springer, The Netherlands. ISBN   978-1-4020-3217-2
  29. ↑ Powles SB (1984). "Photoinhibition of photosynthesis induced by visible light". Annual Review of Plant Physiology and Plant Molecular Biology. 35: 15–44. doi:10.1146/annurev.pp.35.060184.000311.
  30. ↑ Hall DO, Rao KK (1999). Photosynthesis. Cambridge University Press, Cambridge. ISBN   978-0-521-64497-6.

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