scholarly journals Different Strategies for Photosynthetic Regulation under Fluctuating Light in Two Sympatric Paphiopedilum Species

Cells ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1451
Author(s):  
Jing-Qiu Feng ◽  
Wei Huang ◽  
Ji-Hua Wang ◽  
Shi-Bao Zhang
Keyword(s):  
Abrupt Change ◽  
Electron Flux ◽  
Water Cycle ◽  
Electron Flow ◽  
High Light ◽  
Orchid Species ◽  
Redox Kinetics ◽  
Fluctuating Light ◽  
Transport Chain ◽  
Photosynthetic Regulation

Fluctuating light can cause selective photoinhibition of photosystem I (PSI) in angiosperms. Cyclic electron flow (CEF) around PSI and electron flux from water via the electron transport chain to oxygen (the water-water cycle) play important roles in coping with fluctuating light in angiosperms. However, it is unclear whether plant species in the same genus employ the same strategy to cope with fluctuating light. To answer this question, we measured P700 redox kinetics and chlorophyll fluorescence under fluctuating light in two Paphiopedilum (P.) Pftzer (Orchidaceae) species, P. dianthum and P. micranthum. After transition from dark to high light, P. dianthum displayed a rapid re-oxidation of P700, while P. micranthum displayed an over-reduction of P700. Furthermore, the rapid re-oxidation of P700 in P. dianthum was not observed when measured under anaerobic conditions. These results indicated that photo-reduction of O2 mediated by the water-water cycle was functional in P. dianthum but not in P. micranthum. Within the first few seconds after an abrupt transition from low to high light, PSI was highly oxidized in P. dianthum but was highly reduced in P. micranthum, indicating that the different responses of PSI to fluctuating light between P. micranthum and P. dianthum was attributed to the water-water cycle. In P. micranthum, the lack of the water-water cycle was partially compensated for by an enhancement of CEF. Taken together, P. dianthum and P. micranthum employed different strategies to cope with the abrupt change of light intensity, indicating the diversity of strategies for photosynthetic acclimation to fluctuating light in these two closely related orchid species.

scholarly journals Diurnal Response of Photosystem I to Fluctuating Light Is Affected by Stomatal Conductance

Cells ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 3128
Author(s):  
Ting-Yu Li ◽  
Qi Shi ◽  
Hu Sun ◽  
Ming Yue ◽  
Shi-Bao Zhang ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Redox State ◽  
Electron Flow ◽  
High Light ◽  
Primary Metabolism ◽  
Diurnal Changes ◽  
Late Afternoon ◽  
Fluctuating Light ◽  
Photosynthetic Regulation ◽  
Sudden Transition

Upon a sudden transition from low to high light, electrons transported from photosystem II (PSII) to PSI should be rapidly consumed by downstream sinks to avoid the over-reduction of PSI. However, the over-reduction of PSI under fluctuating light might be accelerated if primary metabolism is restricted by low stomatal conductance. To test this hypothesis, we measured the effect of diurnal changes in stomatal conductance on photosynthetic regulation under fluctuating light in tomato (Solanum lycopersicum) and common mulberry (Morus alba). Under conditions of high stomatal conductance, we observed PSI over-reduction within the first 10 s after transition from low to high light. Lower stomatal conductance limited the activity of the Calvin–Benson–Bassham cycle and aggravated PSI over-reduction within 10 s after the light transition. We also observed PSI over-reduction after transition from low to high light for 30 s at the low stomatal conductance typical of the late afternoon, indicating that low stomatal conductance extends the period of PSI over-reduction under fluctuating light. Therefore, diurnal changes in stomatal conductance significantly affect the PSI redox state under fluctuating light. Moreover, our analysis revealed an unexpected inhibition of cyclic electron flow by the severe over-reduction of PSI seen at low stomatal conductance. In conclusion, stomatal conductance can have a large effect on thylakoid reactions under fluctuating light.

scholarly journals Drought stress delays photosynthetic induction and accelerates photoinhibition of photosystem I under fluctuating light

2021 ◽  
Author(s):  
Hu Sun ◽  
Qi Shi ◽  
Ning-Yu Liu ◽  
Shi-Bao Zhang ◽  
Wei Huang
Keyword(s):  
Drought Stress ◽  
Gas Exchange ◽  
Photosystem I ◽  
Co2 Fixation ◽  
Electron Flow ◽  
Photosynthetic Performance ◽  
High Light ◽  
Carbon Gain ◽  
Photosynthetic Induction ◽  
Fluctuating Light

Fluctuating light (FL) and drought stress usually occur concomitantly. However, whether drought stress affects photosynthetic performance under FL remains unknown. Here, we measured gas exchange, chlorophyll fluorescence, and P700 redox state under FL in drought-stressed tomato (Solanum lycopersicum) seedlings. Drought stress significantly affected stomatal opening and mesophyll conductance after transition from low to high light and thus delayed photosynthetic induction under FL. Therefore, drought stress exacerbated the loss of carbon gain under FL. Furthermore, restriction of CO2 fixation under drought stress aggravated the over-reduction of photosystem I (PSI) upon transition from low to high light. The resulting stronger FL-induced PSI photoinhibition significantly supressed linear electron flow and PSI photoprotection. These results indicated that drought stress not only affected gas exchange under FL but also accelerated FL-induced photoinhibition of PSI. Furthermore, drought stress enhanced relative cyclic electron flow in FL, which partially compensated for restricted CO2 fixation and thus favored PSI photoprotection under FL. Therefore, drought stress has large effects on photosynthetic dark and light reactions under FL.

scholarly journals Drought stress delays photosynthetic induction and accelerates photoinhibition of photosystem I under fluctuating light

2021 ◽  
Author(s):  
Hu Sun ◽  
Qi Shi ◽  
Ning-Yu Liu ◽  
Shi-Bao Zhang ◽  
Wei Huang
Keyword(s):  
Drought Stress ◽  
Gas Exchange ◽  
Photosystem I ◽  
Co2 Fixation ◽  
Electron Flow ◽  
Photosynthetic Performance ◽  
High Light ◽  
Carbon Gain ◽  
Photosynthetic Induction ◽  
Fluctuating Light

Fluctuating light (FL) and drought stress usually occur concomitantly. However, whether drought stress affects photosynthetic performance under FL remains unknown. Here, we measured gas exchange, chlorophyll fluorescence, and P700 redox state under FL in drought-stressed tomato (Solanum lycopersicum) seedlings. Drought stress significantly affected stomatal opening and mesophyll conductance after transition from low to high light and thus delayed photosynthetic induction under FL. Therefore, drought stress exacerbated the loss of carbon gain under FL. Furthermore, restriction of CO2 fixation under drought stress aggravated the over-reduction of photosystem I (PSI) upon transition from low to high light. The resulting stronger FL-induced PSI photoinhibition significantly supressed linear electron flow and PSI photoprotection. These results indicated that drought stress not only affected gas exchange under FL but also accelerated FL-induced photoinhibition of PSI. Furthermore, drought stress enhanced relative cyclic electron flow in FL, which partially compensated for restricted CO2 fixation and thus favored PSI photoprotection under FL. Therefore, drought stress has large effects on photosynthetic dark and light reactions under FL.

scholarly journals A novel PSII photosynthetic control is activated in anoxic cultures of green algae

2021 ◽  
Author(s):  
Yuval Milrad ◽  
Valeria Nagy ◽  
Szilvia Toth ◽  
Iftach Yacoby
Keyword(s):  
Green Algae ◽  
Electron Flow ◽  
Spectroscopic Techniques ◽  
Rate Limiting Step ◽  
Fluctuating Light ◽  
Photosynthetic Complexes ◽  
Photosynthetic Control ◽  
Control Set ◽  
Photosynthetic Regulation ◽  
Rate Limiting

Photosynthetic green algae face an ever-changing environment of fluctuating light as well as unstable oxygen levels, which via the production of free radicals constantly challenges the integrity of the photosynthetic complexes. To face such challenges, a complex photosynthetic control network monitors and tightly control the membrane redox potential. Here, we show that not only that the photosynthetic control set the rate limiting step of photosynthetic linear electron flow, but also, upon its ultimate dissipation, it triggers intrinsic alternations in the activity of the photosynthetic complexes. These changes have a grave and prolonged effect on the activity of photosystem II, leading to a massive 3-fold decrease in its electron output. We came into this conclusion via studying a variety of green algae species and applying advance mass-spectrometry and diverse spectroscopic techniques. Our results shed new light on the mechanism of photosynthetic regulation and provide new target for improving photosynthesis.

scholarly journals ROS signalling requires uninterrupted electron flow and is lost during ageing in flies

2021 ◽  
Author(s):  
Charlotte Graham ◽  
Rhoda Stefanatos ◽  
Angeline E.H. Yek ◽  
Ruth V. Spriggs ◽  
Samantha H.Y. Loh ◽  
...  
Keyword(s):  
Electron Transport ◽  
Electron Flux ◽  
Electron Flow ◽  
Oxygen Species ◽  
Transport Chain ◽  
Response To Stress ◽  
Respiratory Complex I ◽  
Flow Through ◽  
Ros Signalling ◽  
Reverse Electron Transport

Mitochondrial Reactive Oxygen Species (mtROS) are cellular messengers essential for cellular homeostasis. In response to stress, reverse electron transport (RET) by respiratory complex I generates high levels of mtROS. Suppression of ROS produced via RET (ROS-RET) reduces survival under stress, while activation of ROS-RET extends lifespan in basal conditions. Here, we demonstrate that ROS-RET signalling requires increased electron entry and uninterrupted electron flow through the electron transport chain (ETC). We found that ROS-RET is abolished in old fruit flies where electron flux is reduced. Instead, mitochondria in aged flies produce consistently high levels of mtROS. Finally, we demonstrate that in young flies reduction of electron exit from the ETC, but not electron entry, phenocopies mtROS generation observed in old individuals. Our results define the mechanism by which ROS signalling is lost during ageing.

scholarly journals Photosynthetic induction upon transfer from low to high light is affected by leaf nitrogen content in tomato

2021 ◽  
Author(s):  
Hu Sun ◽  
Yu-Qi Zhang ◽  
Shi-Bao Zhang ◽  
Wei Huang
Keyword(s):  
Electron Flow ◽  
Co2 Assimilation ◽  
High Light ◽  
Carbon Gain ◽  
Leaf Nitrogen Content ◽  
Photosynthetic Induction ◽  
N Content ◽  
Fluctuating Light ◽  
Leaf N Content ◽  
Leaf N

The response of photosynthetic CO2 assimilation to changes of illumination affects plant growth and crop productivity under natural fluctuating light conditions. However, the effects of nitrogen (N) supply on photosynthetic physiology after transition from low to high light are seldom studied. To elucidate this, we measured gas exchange and chlorophyll fluorescence under fluctuating light in tomato (Solanum lycopersicum) seedlings grown with different N conditions. After transition from low to high light, the induction speeds of net CO2 assimilation (AN), stomatal conductance (gs) and mesophyll conductance (gm) delayed with the decline in leaf N content. The times to reach 90% of maximum AN, gs and gm were negatively correlated to leaf N content. This delayed photosynthetic induction in plants grown under low N concentration was mainly caused by the slow induction response of gm rather than that of gs. Furthermore, the photosynthetic induction upon transfer from low to high light was hardly limited by photosynthetic electron flow. These results indicate that decreased leaf N content declines carbon gain under fluctuating light in tomato. Increasing the induction kinetics of gm has the potential to enhance the carbon gain of field crops grown in infertile soil.

scholarly journals Coordination of Cyclic Electron Flow and Water–Water Cycle Facilitates Photoprotection under Fluctuating Light and Temperature Stress in the Epiphytic Orchid Dendrobium officinale

Plants ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 606
Author(s):  
Hu Sun ◽  
Qi Shi ◽  
Shi-Bao Zhang ◽  
Wei Huang
Keyword(s):  
Water Cycle ◽  
Electron Flow ◽  
Reducing Power ◽  
Cyclic Electron Flow ◽  
Dendrobium Officinale ◽  
Sudden Increase ◽  
Temperature Stresses ◽  
Electrochromic Shift ◽  
Photosynthetic Organisms ◽  
Fluctuating Light

Photosystem I (PSI) is the primary target of photoinhibition under fluctuating light (FL). Photosynthetic organisms employ alternative electron flows to protect PSI under FL. However, the understanding of the coordination of alternative electron flows under FL at temperature stresses is limited. To address this question, we measured the chlorophyll fluorescence, P700 redox state, and electrochromic shift signal in leaves of Dendrobium officinale exposed to FL at 42 °C, 25 °C, and 4 °C. Upon a sudden increase in illumination at 42 °C and 25 °C, the water–water cycle (WWC) consumed a significant fraction of the extra reducing power, and thus avoided an over-reduction of PSI. However, WWC was inactivated at 4 °C, leading to an over-reduction of PSI within the first seconds after light increased. Therefore, the role of WWC under FL is largely dependent on temperature conditions. After an abrupt increase in light intensity, cyclic electron flow (CEF) around PSI was stimulated at any temperature. Therefore, CEF and WWC showed different temperature responses under FL. Furthermore, the enhancement of CEF and WWC at 42 °C quickly generated a sufficient trans-thylakoid proton gradient (ΔpH). The inactivation of WWC at 4 °C was partially compensated for by an increased CEF activity. These findings indicate that CEF and WWC coordinate to protect PSI under FL at temperature stresses.

Changes in the Stoichiometry of Photosystem II Components as an Adaptive Response to High-Light and Low-Light Conditions during Growth

1986 ◽  
Vol 41 (5-6) ◽  
pp. 597-603 ◽  
Author(s):  
Aloysius Wild ◽  
Matthias Höpfner ◽  
Wolfgang Rühle ◽  
Michael Richter
Keyword(s):  
Photosystem Ii ◽  
Functional Organization ◽  
Photosynthetic Apparatus ◽  
High Light ◽  
Molar Ratio ◽  
Light Conditions ◽  
Low Light ◽  
Pigment System ◽  
Transport Chain ◽  
The One

The effect of different growth light intensities (60 W·m-2, 6 W·m-2) on the performance of the photosynthetic apparatus of mustard plants (Sinapis alba L.) was studied. A distinct decrease in photosystem II content per chlorophyll under low-light conditions compared to high-light conditions was found. For P-680 as well as for Oᴀ and Oв protein the molar ratio between high-light and low-light plants was 1.4 whereas the respective concentrations per chlorophyll showed some variations for P-680 and Oᴀ on the one and Oв protein on the other hand.In addition to the study of photosystem II components, the concentrations of PQ, Cyt f, and P-700 were measured. The light regime during growth had no effect on the amount of P-700 per chlorophyll but there were large differences with respect to PQ and Cyt f. The molar ratio for Cyt f and PQ between high- and low-light leaves was 2.2 and 1.9, respectively.Two models are proposed, showing the functional organization of the pigment system and the electron transport chain in thylakoids of high-light and low-light leaves of mustard plants.

Sign in / Sign up

Export Citation Format

Share Document