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 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 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 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.

Modelling photosynthesis in fluctuating light with inclusion of stomatal conductance, biochemical activation and pools of key photosynthetic intermediates

Planta ◽  
1997 ◽  
Vol 204 (1) ◽  
pp. 16-26 ◽  
Author(s):  
M. U. F. Kirschbaum ◽  
M. Küppers ◽  
H. Schneider ◽  
C. Giersch ◽  
S. Noe
Keyword(s):  
Stomatal Conductance ◽  
Fluctuating Light ◽  
Biochemical Activation

Regulation of cytochrome oxidase redox state during umbilical cord occlusion in preterm fetal sheep

2007 ◽  
Vol 292 (4) ◽  
pp. R1569-R1576 ◽  
Author(s):  
Laura Bennet ◽  
Vincent Roelfsema ◽  
Justin M. Dean ◽  
Guido Wassink ◽  
Gordon G. Power ◽  
...  
Keyword(s):  
Cytochrome Oxidase ◽  
Umbilical Cord ◽  
Redox State ◽  
Cerebral Oxygenation ◽  
Cerebral Metabolism ◽  
Electron Flow ◽  
Initial Response ◽  
Severe Hypoxia ◽  
Fetal Sheep ◽  
Severe Hypotension

The preterm fetus is capable of surviving prolonged periods of severe hypoxia without neural injury for much longer than at term. To evaluate the hypothesis that regulated suppression of brain metabolism contributes to this remarkable tolerance, we assessed changes in the redox state of cytochrome oxidase (CytOx) relative to cerebral heat production, and cytotoxic edema measured using cerebral impedance, during 25 min of complete umbilical cord occlusion or sham occlusion in fetal sheep at 0.7 gestation. Occlusion was followed by rapid, profound reduction in relative cerebral oxygenation and EEG intensity and an immediate increase in oxidized CytOx, indicating a reduction in electron flow down the mitochondrial electron transfer chain. Confirming rapid suppression of cerebral metabolism there was a loss of the temperature difference between parietal cortex and body at a time when carotid blood flow was maintained at control values. As occlusion continued, severe hypotension/hypoperfusion developed, with a further increase in CytOx levels to a plateau between 8 and 13 min and a progressive rise in cerebral impedance. In conclusion, these data strongly suggest active regulation of cerebral metabolism during the initial response to severe hypoxia, which may help to protect the immature brain from injury.

scholarly journals Response of Acer saccharum seedlings to elevated O3 and CO2 concentrations

2005 ◽  
Vol 86 (1) ◽  
pp. 7-17
Author(s):  
Catherine Gaucher ◽  
Pierre Dizengremel ◽  
Yves Mauffette ◽  
Normand Chevrier
Keyword(s):  
Stomatal Conductance ◽  
Acer Saccharum ◽  
Sugar Maple ◽  
Growing Season ◽  
Growth Conditions ◽  
High Light ◽  
Assimilation Rate ◽  
Competitive Growth ◽  
Elevated O3 ◽  
Fertilizing Effect

The effects of three times ambient [O3] (3x) and high [CO2] (650 µL L-1 CO2) alone and in combination were studied on 2-yr-old sugar maple (Acer saccharum) seedlings for 86 days in open top chambers. Sugar maple net CO2 assimilation rate and growth were not decreased by the O3 treatment after one growing season, and the epicuticular wax was not damaged compared with the control. The absence of response to the O3 treatment is attributable to the low stomatal conductance of this species resulting in a low O3 uptake, together with the succession of periods of high and low [O3], which allowed the seedlings to alleviate the oxidative stress. At the end of August, under high [CO2], the growth of the seedlings and net CO2 assimilation to stomatal conductance to CO2 ratio in the second flush of leaves had doubled. Under the environmental growth conditions of the chambers (high light, nutrients and water availabilities), the seedlings may benefit from the availability of CO2. Sugar maple seedlings may have a competitive growth advantage under elevated CO2 conditions and three times ambient [O3] did not decreased the fertilizing effect of CO2.

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