scholarly journals The Light Dependence of Mesophyll Conductance and Relative Limitations on Photosynthesis in Evergreen Sclerophyllous Rhododendron Species

Plants ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 1536
Author(s):  
Ying-Jie Yang ◽  
Hong Hu ◽  
Wei Huang
Keyword(s):  
Light Intensity ◽  
Negative Relationship ◽  
Light Response ◽  
Co2 Concentration ◽  
Limiting Factor ◽  
Mesophyll Conductance ◽  
Co2 Diffusion ◽  
Rate Limiting Step ◽  
Internal Cavities ◽  
Rate Limiting

Mesophyll conductance (gm) limits CO2 diffusion from sub-stomatal internal cavities to the sites of RuBP carboxylation. However, the response of gm to light intensity remains controversial. Furthermore, little is known about the light response of relative mesophyll conductance limitation (lm) and its effect on photosynthesis. In this study, we measured chlorophyll fluorescence and gas exchange in nine evergreen sclerophyllous Rhododendron species. gm was maintained stable across light intensities from 300 to 1500 μmol photons m−2 s−1 in all these species, indicating that gm did not respond to the change in illumination in them. With an increase in light intensity, lm gradually increased, making gm the major limiting factor for area-based photosynthesis (AN) under saturating light. A strong negative relationship between lm and AN was found at 300 μmol photons m−2 s−1 but disappeared at 1500 μmol photons m−2 s−1, suggesting an important role for lm in determining AN at sub-saturating light. Furthermore, the light-dependent increase in lm led to a decrease in chloroplast CO2 concentration (Cc), inducing the gradual increase of photorespiration. A higher lm under saturating light made AN more limited by RuBP carboxylation. These results indicate that the light response of lm plays significant roles in determining Cc, photorespiration, and the rate-limiting step of AN.

scholarly journals Physiological and Transcriptomic Analyses Revealed the Implications of Abscisic Acid in Mediating the Rate-Limiting Step for Photosynthetic Carbon Dioxide Utilisation in Response to Vapour Pressure Deficit in Solanum Lycopersicum (Tomato)

2021 ◽  
Vol 12 ◽  
Author(s):  
Dalong Zhang ◽  
Qingjie Du ◽  
Po Sun ◽  
Jie Lou ◽  
Xiaotian Li ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Vapour Pressure Deficit ◽  
Plant Water ◽  
Mesophyll Conductance ◽  
Tomato Plants ◽  
Plant Water Stress ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Photosynthetic Carbon ◽  
Rate Limiting

The atmospheric vapour pressure deficit (VPD) has been demonstrated to be a significant environmental factor inducing plant water stress and affecting plant photosynthetic productivity. Despite this, the rate-limiting step for photosynthesis under varying VPD is still unclear. In the present study, tomato plants were cultivated under two contrasting VPD levels: high VPD (3–5 kPa) and low VPD (0.5–1.5 kPa). The effect of long-term acclimation on the short-term rapid VPD response was examined across VPD ranging from 0.5 to 4.5 kPa. Quantitative photosynthetic limitation analysis across the VPD range was performed by combining gas exchange and chlorophyll fluorescence. The potential role of abscisic acid (ABA) in mediating photosynthetic carbon dioxide (CO2) uptake across a series of VPD was evaluated by physiological and transcriptomic analyses. The rate-limiting step for photosynthetic CO2 utilisation varied with VPD elevation in tomato plants. Under low VPD conditions, stomatal and mesophyll conductance was sufficiently high for CO2 transport. With VPD elevation, plant water stress was gradually pronounced and triggered rapid ABA biosynthesis. The contribution of stomatal and mesophyll limitation to photosynthesis gradually increased with an increase in the VPD. Consequently, the low CO2 availability inside chloroplasts substantially constrained photosynthesis under high VPD conditions. The foliar ABA content was negatively correlated with stomatal and mesophyll conductance for CO2 diffusion. Transcriptomic and physiological analyses revealed that ABA was potentially involved in mediating water transport and photosynthetic CO2 uptake in response to VPD variation. The present study provided new insights into the underlying mechanism of photosynthetic depression under high VPD stress.

scholarly journals LIMITING FACTORS IN PHOTOSYNTHESIS: LIGHT AND CARBON DIOXIDE

1938 ◽  
Vol 22 (1) ◽  
pp. 21-35 ◽  
Author(s):  
Emil L. Smith
Keyword(s):  
Carbon Dioxide ◽  
Light Intensity ◽  
Large Range ◽  
Co2 Concentration ◽  
Order Reaction ◽  
First Order Reaction ◽  
Limiting Factors ◽  
Limiting Factor ◽  
First Order ◽  
Families Of Curves

1. Extensive measurements have been obtained (a) relating photosynthesis and light intensity for a large range of CO2 concentrations and (b) relating photosynthesis and CO2 at different light intensities. From these families of curves, the limiting factor relationship can be secured for any value of the photosynthesis rate. 2. In terms of previous work an equation has been derived for describing these relations between the intensity and CO2 concentration necessary to produce a definite amount of photosynthesis. This equation furnishes an exact description for all the data, except those for low rates of photosynthesis where a slightly different equation is required. The nature of the two equations suggests that a simple first order reaction determines the velocity of the light process at low photosynthesis rates, but that at high rates the mechanism is complicated by another factor.

scholarly journals The rate-limiting step for photosynthetic CO2 utilization under varying atmospheric evaporative demand in Solanum lycopersicum (tomato)

2020 ◽  
Author(s):  
Dalong Zhang ◽  
Qingming Li ◽  
Wataru Yamori ◽  
Min Wei
Keyword(s):  
Carbon Fixation ◽  
Vapour Pressure Deficit ◽  
Photosynthetic Performance ◽  
Mesophyll Conductance ◽  
Evaporative Demand ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Photosynthetic Potential ◽  
Rate Limiting ◽  
Mesophyll Resistance

Abstract Background: Despite atmospheric vapour pressure deficit (VPD) was demonstrated as significant environmental factors affecting plant photosynthesis and productivity, the regulating mechanism under varying atmospheric evaporative demand was still unclarified. The contribution of stomatal, mesophyll resistance and biochemical limitation imposed on photosynthesis in tomato under varying evaporative demand was highlighted in the present study. Quantitative photosynthetic limitation analysis across a series of VPD was performed in well-watered tomato, by combining gas exchange and chlorophyll fluorescence. Results: Photosynthetic performance in tomato was gradually depressed with increasing in VPD. Under low VPD condition, stomatal and mesophyll conductance were sufficiently high for CO2 transport, which facilitated high chloroplast CO2 concentration for carbon fixation. Stomatal and mesophyll limitation accounted a low fraction, and photosynthetic potential was mostly constrained by biochemical limitation inside chloroplasts under low VPD condition. With increasing in VPD, plant water stress was gradually pronounced and triggered declines in stomatal and mesophyll conductance. Contribution of stomatal and mesophyll limitation on photosynthesis increased gradually with rise in VPD. Consequently, the low CO2 availability inside chloroplast substantially constrained photosynthesis under high VPD condition. Conclusion: Photosynthetic potential in tomato was mostly constrained by biochemical limitation inside chloroplasts under low VPD condition. CO2 diffusion limitation in series of stomatal and mesophyll resistance was the key rate-limiting step for photosynthesis under high VPD condition.

scholarly journals Post-translational regulation of retinal IMPDH1 in vivo to adjust GTP synthesis to illumination conditions

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Anna Plana-Bonamaisó ◽  
Santiago López-Begines ◽  
David Fernández-Justel ◽  
Alexandra Junza ◽  
Ariadna Soler-Tapia ◽  
...  
Keyword(s):  
Translational Regulation ◽  
De Novo ◽  
Bright Light ◽  
Atp Synthesis ◽  
Light Response ◽  
Photoreceptor Cells ◽  
Aggregate Formation ◽  
Rate Limiting Step ◽  
Rate Limiting

We report the in vivo regulation of Inosine-5´-monophosphate dehydrogenase 1 (IMPDH1) in the retina. IMPDH1 catalyzes the rate-limiting step in the de novo synthesis of guanine nucleotides, impacting the cellular pools of GMP, GDP and GTP. Guanine nucleotide homeostasis is central to photoreceptor cells, where cGMP is the signal transducing molecule in the light response. Mutations in IMPDH1 lead to inherited blindness. We unveil a light-dependent phosphorylation of retinal IMPDH1 at Thr159/Ser160 in the Bateman domain that desensitizes the enzyme to allosteric inhibition by GDP/GTP. When exposed to bright light, living mice increase the rate of GTP and ATP synthesis in their retinas; concomitant with IMPDH1 aggregate formation at the outer segment layer. Inhibiting IMPDH activity in living mice delays rod mass recovery. We unveil a novel mechanism of regulation of IMPDH1 in vivo, important for understanding GTP homeostasis in the retina and the pathogenesis of adRP10 IMPDH1 mutations.

Ornithine Decarboxylase Activity in Cultured Endothelial Cells Stimulated by Serum, Thrombin and Serotonin

1978 ◽  
Vol 39 (02) ◽  
pp. 496-503 ◽  
Author(s):  
P A D’Amore ◽  
H B Hechtman ◽  
D Shepro
Keyword(s):  
Endothelial Cells ◽  
Ornithine Decarboxylase ◽  
Decarboxylase Activity ◽  
Aortic Endothelial Cells ◽  
Ornithine Decarboxylase Activity ◽  
Rate Limiting Step ◽  
Bovine Aortic Endothelial Cells ◽  
Limiting Step ◽  
Rate Limiting ◽  
Serum Serotonin

SummaryOrnithine decarboxylase (ODC) activity, the rate-limiting step in the synthesis of polyamines, can be demonstrated in cultured, bovine, aortic endothelial cells (EC). Serum, serotonin and thrombin produce a rise in ODC activity. The serotonin-induced ODC activity is significantly blocked by imipramine (10-5 M) or Lilly 11 0140 (10-6M). Preincubation of EC with these blockers together almost completely depresses the 5-HT-stimulated ODC activity. These observations suggest a manner by which platelets may maintain EC structural and metabolic soundness.

Dynamics of hepatic and peripheral insulin effects suggest common rate-limiting step in vivo

Diabetes ◽  
1993 ◽  
Vol 42 (2) ◽  
pp. 296-306 ◽  
Author(s):  
D. C. Bradley ◽  
R. A. Poulin ◽  
R. N. Bergman
Keyword(s):  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Cobalt/Lewis Acid Catalysis for Hydrocarbofunctionalization of Alkynes via Cooperative C–H Activation

2020 ◽  
Author(s):  
Chang-Sheng Wang ◽  
Sabrina Monaco ◽  
Anh Ngoc Thai ◽  
Md. Shafiqur Rahman ◽  
Chen Wang ◽  
...  
Keyword(s):  
Catalytic System ◽  
Lewis Acid ◽  
Hydrogen Transfer ◽  
Acid Catalysis ◽  
Rate Limiting Step ◽  
Site Selectivity ◽  
Set Up ◽  
Site Selective ◽  
First Time ◽  
Rate Limiting

A catalytic system comprised of a cobalt-diphosphine complex and a Lewis acid (LA) such as AlMe3 has been found to promote hydrocarbofunctionalization reactions of alkynes with Lewis basic and electron-deficient substrates such as formamides, pyridones, pyridines, and azole derivatives through site-selective C-H activation. Compared with known Ni/LA catalytic system for analogous transformations, the present catalytic system not only feature convenient set up using inexpensive and bench-stable precatalyst and ligand such as Co(acac)3 and 1,3-bis(diphenylphosphino)propane (dppp), but also display distinct site-selectivity toward C-H activation of pyridone and pyridine derivatives. In particular, a completely C4-selective alkenylation of pyridine has been achieved for the first time. Mechanistic stidies including DFT calculations on the Co/Al-catalyzed addition of formamide to alkyne have suggested that the reaction involves cleavage of the carbamoyl C-H bond as the rate-limiting step, which proceeds through a ligand-to-ligand hydrogen transfer (LLHT) mechanism leading to an alkyl(carbamoyl)cobalt intermediate.

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