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  • 1
    Online Resource
    Online Resource
    The difficulty of estimating the electron transport rate at photosystem I
    Springer Science and Business Media LLC ; 2022
    In:  Journal of Plant Research Vol. 135, No. 4 ( 2022-07), p. 565-577
    Details
    In: Journal of Plant Research, Springer Science and Business Media LLC, Vol. 135, No. 4 ( 2022-07), p. 565-577
    Type of Medium: Online Resource
    ISSN: 0918-9440 , 1618-0860
    URL: Article
    DOI: 10.1007/s10265-021-01357-6
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 2077362-6
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Photosynthetic Parameters Show Specific Responses to Essential Mineral Deficiencies
    MDPI AG ; 2021
    In:  Antioxidants Vol. 10, No. 7 ( 2021-06-23), p. 996-
    Details
    In: Antioxidants, MDPI AG, Vol. 10, No. 7 ( 2021-06-23), p. 996-
    Abstract: In response to decreases in the assimilation efficiency of CO2, plants oxidize the reaction center chlorophyll (P700) of photosystem I (PSI) to suppress reactive oxygen species (ROS) production. In hydro-cultured sunflower leaves experiencing essential mineral deficiencies, we analyzed the following parameters that characterize PSI and PSII: (1) the reduction-oxidation states of P700 [Y(I), Y(NA), and Y(ND)]; (2) the relative electron flux in PSII [Y(II)] ; (3) the reduction state of the primary electron acceptor in PSII, QA (1 − qL); and (4) the non-photochemical quenching of chlorophyll fluorescence (NPQ). Deficiency treatments for the minerals N, P, Mn, Mg, S, and Zn decreased Y(II) with an increase in the oxidized P700 [Y(ND)], while deficiencies for the minerals K, Fe, Ca, B, and Mo decreased Y(II) without an increase in Y(ND). During the induction of photosynthesis, the above parameters showed specific responses to each mineral. That is, we could diagnose the mineral deficiency and identify which mineral affected the photosynthesis parameters.
    Type of Medium: Online Resource
    ISSN: 2076-3921
    URL: Article
    DOI: 10.3390/antiox10070996
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2704216-9
    SSG: 15,3
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  • 3
    Online Resource
    Online Resource
    Intrinsic Fluctuations in Transpiration Induce Photorespiration to Oxidize P700 in Photosystem I
    MDPI AG ; 2020
    In:  Plants Vol. 9, No. 12 ( 2020-12-12), p. 1761-
    Details
    In: Plants, MDPI AG, Vol. 9, No. 12 ( 2020-12-12), p. 1761-
    Abstract: Upon exposure to environmental stress, the primary electron donor in photosystem I (PSI), P700, is oxidized to suppress the production of reactive oxygen species that could oxidatively inactivate the function of PSI. The illumination of rice leaves with actinic light induces intrinsic fluctuations in the opening and closing of stomata, causing the net CO2 assimilation rate to fluctuate. We examined the effects of these intrinsic fluctuations on electron transport reactions. Under atmospheric O2 conditions (21 kPa), the effective quantum yield of photosystem II (PSII) (Y(II)) remained relatively high while the net CO2 assimilation rate fluctuated, which indicates the function of alternative electron flow. By contrast, under low O2 conditions (2 kPa), Y(II) fluctuated. These results suggest that photorespiration primarily drove the alternative electron flow. Photorespiration maintained the oxidation level of ferredoxin (Fd) throughout the fluctuation of the net CO2 assimilation rate. Moreover, the relative activity of photorespiration was correlated with both the oxidation level of P700 and the magnitude of the proton gradient across the thylakoid membrane in 21 kPa O2 conditions. These results show that photorespiration oxidized P700 by stimulating the proton gradient formation when CO2 assimilation was suppressed by stomatal closure.
    Type of Medium: Online Resource
    ISSN: 2223-7747
    URL: Article
    DOI: 10.3390/plants9121761
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2704341-1
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  • 4
    Online Resource
    Online Resource
    Higher Reduced State of Fe/S-Signals, with the Suppressed Oxidation of P700, Causes PSI Inactivation in Arabidopsis thaliana
    MDPI AG ; 2022
    In:  Antioxidants Vol. 12, No. 1 ( 2022-12-22), p. 21-
    Details
    In: Antioxidants, MDPI AG, Vol. 12, No. 1 ( 2022-12-22), p. 21-
    Abstract: Environmental stress increases the risk of electron accumulation in photosystem I (PSI) of chloroplasts, which can cause oxygen (O2) reduction to superoxide radicals and decreased photosynthetic ability. We used three Arabidopsis thaliana lines: wild-type (WT) and the mutants pgr5hope1 and paa1-7/pox1. These lines have different reduced states of iron/sulfur (Fe/S) signals, including Fx, FA/FB, and ferredoxin, the electron carriers at the acceptor side of PSI. In the dark, short-pulse light was repetitively illuminated to the intact leaves of the plants to provide electrons to the acceptor side of PSI. WT and pgr5hope1 plants showed full reductions of Fe/S during short-pulse light and PSI inactivation. In contrast, paa1-7/pox1 showed less reduction of Fe/S and its PSI was not inactivated. Under continuous actinic-light illumination, pgr5hope1 showed no P700 oxidation with higher Fe/S reduction due to the loss of photosynthesis control and PSI inactivation. These results indicate that the accumulation of electrons at the acceptor side of PSI may trigger the production of superoxide radicals. P700 oxidation, responsible for the robustness of photosynthetic organisms, participates in reactive oxygen species suppression by oxidizing the acceptor side of PSI.
    Type of Medium: Online Resource
    ISSN: 2076-3921
    URL: Article
    DOI: 10.3390/antiox12010021
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2704216-9
    SSG: 15,3
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  • 5
    Online Resource
    Online Resource
    Oxidation of P700 Induces Alternative Electron Flow in Photosystem I in Wheat Leaves
    MDPI AG ; 2019
    In:  Plants Vol. 8, No. 6 ( 2019-06-05), p. 152-
    Details
    In: Plants, MDPI AG, Vol. 8, No. 6 ( 2019-06-05), p. 152-
    Abstract: Oxygen (O2)-evolving photosynthetic organisms oxidize the reaction center chlorophyll, P700, in photosystem I (PSI) to suppress the production of reactive oxygen species. The oxidation of P700 is accompanied by alternative electron flow in PSI (AEF-I), which is not required for photosynthetic linear electron flow (LEF). To characterize AEF-I, we compared the redox reactions of P700 and ferredoxin (Fd) during the induction of carbon dioxide (CO2) assimilation in wheat leaves, using dark-interval relaxation kinetics analysis. Switching on an actinic light (1000 μmol photons m−2 s−1) at ambient CO2 partial pressure of 40 Pa and ambient O2 partial pressure of 21 kPa gradually oxidized P700 (P700+) and enhanced the reduction rate of P700+ (vP700) and oxidation rate of reduced Fd (vFd). The vFd showed a positive linear relationship with an apparent photosynthetic quantum yield of PSII (Y[II]) originating at point zero; the redox turnover of Fd is regulated by LEF via CO2 assimilation and photorespiration. The vP700 also showed a positive linear relationship with Y(II), but the intercept was positive, not zero. That is, the electron flux in PSI included the electron flux in AEF-I in addition to that in LEF. This indicates that the oxidation of P700 induces AEF-I. We propose a possible mechanism underlying AEF-I and its physiological role in the mitigation of oxidative damage.
    Type of Medium: Online Resource
    ISSN: 2223-7747
    URL: Article
    DOI: 10.3390/plants8060152
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2704341-1
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  • 6
    Online Resource
    Online Resource
    Image_1.tif
    Frontiers Media SA ; 2022
    In:  Frontiers in Plant Science Vol. 13 ( 2022-6-2)
    Details
    In: Frontiers in Plant Science, Frontiers Media SA, Vol. 13 ( 2022-6-2)
    Abstract: The photosynthetic electron transport chain is mineral rich. Specific mineral deficiencies can modify the electron transport chain specifically. Here, it is shown that on the basis of 2 short Chl fluorescence and P700 + measurements (approx. 1 s each), it is possible to discriminate between 10 out of 12 different mineral deficiencies: B, Ca, Cu, Fe, K, Mg, Mn, Mo, N, P, S, and Zn. B- and Mo-deficient plants require somewhat longer measurements to detect the feedback inhibition they induce. Eight out of twelve deficiencies mainly affect PS I and NIR measurements are, therefore, very important for this analysis. In Cu- and P-deficient plants, electron flow from the plastoquinone pool to PS I, is affected. In the case of Cu-deficiency due to the loss of plastocyanin and in the case of P-deficiency probably due to a fast and strong generation of Photosynthetic Control. For several Ca-, K-, and Zn-deficient plant species, higher levels of reactive oxygen species have been measured in the literature. Here, it is shown that this not only leads to a loss of Pm (maximum P700 redox change) reflecting a lower PS I content, but also to much faster P700 + re-reduction kinetics during the I 2 -P (~30–200 ms) fluorescence rise phase. The different mineral deficiencies affect the relation between the I 2 -P and P700 + kinetics in different ways and this is used to discuss the nature of the relationship between these two parameters.
    Type of Medium: Online Resource
    ISSN: 1664-462X
    URL: Article
    URL: Article
    DOI: 10.3389/fpls.2022.894607
    DOI: 10.3389/fpls.2022.894607.s001
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2022
    detail.hit.zdb_id: 2687947-5
    detail.hit.zdb_id: 2613694-6
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