Down-Regulation of Photosynthetic Electron Transport and Decline in CO<sub>2</sub> Assimilation under Low Frequencies of Pulsed Lights
The decline in CO<sub>2</sub> assimilation in leaves exposed to decreasing frequencies of pulsed light is well characterized, in contrast to the regulation of photosynthetic electron transport under these conditions. Thus, we exposed sunflower leaves to pulsed lights of different frequen...
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MDPI AG
2021-09-01
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| Series: | Plants |
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| Online Access: | https://www.mdpi.com/2223-7747/10/10/2033 |
| _version_ | 1797513317204361216 |
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| author | Marguerite Cinq-Mars Guy Samson |
| author_facet | Marguerite Cinq-Mars Guy Samson |
| author_sort | Marguerite Cinq-Mars |
| collection | DOAJ |
| description | The decline in CO<sub>2</sub> assimilation in leaves exposed to decreasing frequencies of pulsed light is well characterized, in contrast to the regulation of photosynthetic electron transport under these conditions. Thus, we exposed sunflower leaves to pulsed lights of different frequencies but with the same duty ratio (25%) and averaged light intensity (575 μmoles photons m<sup>−2</sup> s<sup>−1</sup>). The rates of net photosynthesis P<i>n</i> were constant from 125 to 10 Hz, and declined by 70% from 10 to 0.1 Hz. This decline coincided with (1) a marked increase in nonphotochemical quenching (NPQ), and (2) the completion after 25 ms of illumination of the first phase of P<sub>700</sub> photooxidation, the primary electron donor of PSI. Under longer light pulses (<5 Hz), there was a slower and larger P<sub>700</sub> photooxidation phase that could be attributed to the larger NPQ and to a resistance of electron flow on the PSI donor side indicated by 44% slower kinetics of a P<sub>700</sub><sup>+</sup> dark reduction. In addition, at low frequencies, the decrease in quantum yield of photochemistry was 2.3-times larger for PSII than for PSI. Globally, our results indicate that the decline in CO<sub>2</sub> assimilation at 10 Hz and lower frequencies coincide with the formation of NPQ and a restriction of electron flows toward PSI, favoring the accumulation of harmless P<sub>700</sub><sup>+</sup>. |
| first_indexed | 2024-03-10T06:14:53Z |
| format | Article |
| id | doaj.art-01280311e90f4b71ad7b1de826722b03 |
| institution | Directory Open Access Journal |
| issn | 2223-7747 |
| language | English |
| last_indexed | 2024-03-10T06:14:53Z |
| publishDate | 2021-09-01 |
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| record_format | Article |
| series | Plants |
| spelling | doaj.art-01280311e90f4b71ad7b1de826722b032023-11-22T19:42:40ZengMDPI AGPlants2223-77472021-09-011010203310.3390/plants10102033Down-Regulation of Photosynthetic Electron Transport and Decline in CO<sub>2</sub> Assimilation under Low Frequencies of Pulsed LightsMarguerite Cinq-Mars0Guy Samson1Département des Sciences de l’Environnement, Groupe de Recherche en Biologie Végétale, Université du Québec à Trois-Rivières, Trois-Rivières, QC G8Z 4M3, CanadaDépartement des Sciences de l’Environnement, Groupe de Recherche en Biologie Végétale, Université du Québec à Trois-Rivières, Trois-Rivières, QC G8Z 4M3, CanadaThe decline in CO<sub>2</sub> assimilation in leaves exposed to decreasing frequencies of pulsed light is well characterized, in contrast to the regulation of photosynthetic electron transport under these conditions. Thus, we exposed sunflower leaves to pulsed lights of different frequencies but with the same duty ratio (25%) and averaged light intensity (575 μmoles photons m<sup>−2</sup> s<sup>−1</sup>). The rates of net photosynthesis P<i>n</i> were constant from 125 to 10 Hz, and declined by 70% from 10 to 0.1 Hz. This decline coincided with (1) a marked increase in nonphotochemical quenching (NPQ), and (2) the completion after 25 ms of illumination of the first phase of P<sub>700</sub> photooxidation, the primary electron donor of PSI. Under longer light pulses (<5 Hz), there was a slower and larger P<sub>700</sub> photooxidation phase that could be attributed to the larger NPQ and to a resistance of electron flow on the PSI donor side indicated by 44% slower kinetics of a P<sub>700</sub><sup>+</sup> dark reduction. In addition, at low frequencies, the decrease in quantum yield of photochemistry was 2.3-times larger for PSII than for PSI. Globally, our results indicate that the decline in CO<sub>2</sub> assimilation at 10 Hz and lower frequencies coincide with the formation of NPQ and a restriction of electron flows toward PSI, favoring the accumulation of harmless P<sub>700</sub><sup>+</sup>.https://www.mdpi.com/2223-7747/10/10/2033photosystemcyclic electron flowphotoprotectionnonphotochemical quenchingLEDs |
| spellingShingle | Marguerite Cinq-Mars Guy Samson Down-Regulation of Photosynthetic Electron Transport and Decline in CO<sub>2</sub> Assimilation under Low Frequencies of Pulsed Lights Plants photosystem cyclic electron flow photoprotection nonphotochemical quenching LEDs |
| title | Down-Regulation of Photosynthetic Electron Transport and Decline in CO<sub>2</sub> Assimilation under Low Frequencies of Pulsed Lights |
| title_full | Down-Regulation of Photosynthetic Electron Transport and Decline in CO<sub>2</sub> Assimilation under Low Frequencies of Pulsed Lights |
| title_fullStr | Down-Regulation of Photosynthetic Electron Transport and Decline in CO<sub>2</sub> Assimilation under Low Frequencies of Pulsed Lights |
| title_full_unstemmed | Down-Regulation of Photosynthetic Electron Transport and Decline in CO<sub>2</sub> Assimilation under Low Frequencies of Pulsed Lights |
| title_short | Down-Regulation of Photosynthetic Electron Transport and Decline in CO<sub>2</sub> Assimilation under Low Frequencies of Pulsed Lights |
| title_sort | down regulation of photosynthetic electron transport and decline in co sub 2 sub assimilation under low frequencies of pulsed lights |
| topic | photosystem cyclic electron flow photoprotection nonphotochemical quenching LEDs |
| url | https://www.mdpi.com/2223-7747/10/10/2033 |
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