The eﬀect of nickel phytotoxicity on photosystem II activity  and antioxidant enzymes in barley

In this study, the eﬀect of mild (100 µM), moderate (300 µM) and severe (500 µM) nickel (NiSO4.7H2O) toxicity on the photosynthetic activity, photosynthetic pigment content and some antioxidant enzymes in the leaves of a barley cultivars (Hordeum vulgare L. cv. Tarm-92) was investigated. Moderate and severe nickel toxicity decreased root length while shoot length was not aﬀected by nickel stress, probably due to over accumulation of nickel in roots. Similarly, biomass accumulation was declined by moderate and severe nickel toxicity as reﬂected by the lowered fresh and dry weight. Chlorophyll a, chlorophyll b and consequently total chlorophyll content decreased by all nickel applications, presumably because the reduced level of carotenoids. Chlorophyll a ﬂuorescence measurements showed that nickel toxicity blocked electron movement in some speciﬁc points of the photosynthetic electron transport system. The constant Fo value indicated that PSII reaction centers was not damaged in the leaves of barley under nickel toxicity while the reduced Fm value showed that acceptor side of PSII was more sensitive to nickel toxicity as compared to donor side. Changes in JIP test parameters in the leaves of barley showed that primary photochemical reactions are reduced, and thermal dissipation of excess energy is increased. SOD and CAT activity is elevated in the leaves of barley under moderate and severe nickel toxicity which demonstrate an eﬃcient superoxide dismutation. Severe nickel toxicity, however, did not aﬀect SOD and CAT activity. The ascorbate-glutathione cycle was activated in the leaves of barley plants under nickel toxicity, probably indicating an eﬃcient H2O2 detoxiﬁcation. However, considerable H2O2 and MDA accumulation was observed in the leaves of barley under nickel stress. As a result, it may be concluded that the barley genotype Tarm-92 is moderately tolerant to nickel toxicity.

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Light Absorption and Partitioning in Response to Nitrogen in Apple Leaves

HortScience ◽

10.21273/hortsci.33.3.541a ◽

1998 ◽

Vol 33 (3) ◽

pp. 541a-541

Author(s):

Lailiang Cheng ◽

Leslie H. Fuchigami ◽

Patrick J. Breen

Keyword(s):

High Light ◽

Thermal Dissipation ◽

Photochemical Quenching ◽

Light Conditions ◽

Psii Efficiency ◽

Fluorescence Measurements ◽

Free Radical Formation ◽

Highly Correlated ◽

Non Photochemical Quenching ◽

Leaf N

Bench-grafted Fuji/M26 apple trees were fertigated with different concentrations of nitrogen by using a modified Hoagland solution for 6 weeks, resulting in a range of leaf N from 1.0 to 4.3 g·m–2. Over this range, leaf absorptance increased curvilinearly from 75% to 92.5%. Under high light conditions (1500 (mol·m–2·s–1), the amount of absorbed light in excess of that required to saturate CO2 assimilation decreased with increasing leaf N. Chlorophyll fluorescence measurements revealed that the maximum photosystem II (PSII) efficiency of dark-adapted leaves was relatively constant over the leaf N range except for a slight drop at the lower end. As leaf N increased, non-photochemical quenching under high light declined and there was a corresponding increase in the efficiency with which the absorbed photons were delivered to open PSII centers. Photochemical quenching coefficient decreased significantly at the lower end of the leaf N range. Actual PSII efficiency increased curvilinearly with increasing leaf N, and was highly correlated with light-saturated CO2 assimilation. The fraction of absorbed light potentially used for free radical formation was estimated to be about 10% regardless of the leaf N status. It was concluded that increased thermal dissipation protected leaves from photo-oxidation as leaf N declined.

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Effects of Different Planting Densities on Photosynthesis in Maize Determined via Prompt Fluorescence, Delayed Fluorescence and P700 Signals

Plants ◽

10.3390/plants10020276 ◽

2021 ◽

Vol 10 (2) ◽

pp. 276

Author(s):

Wanying Chen ◽

Bo Jia ◽

Junyu Chen ◽

Yujiao Feng ◽

Yue Li ◽

...

Keyword(s):

Electron Transport ◽

Chlorophyll A ◽

Chlorophyll A Fluorescence ◽

Electron Transport Chain ◽

Plant Density ◽

Photosynthetic Electron Transport ◽

Planting Density ◽

Strong Impact ◽

Photosynthetic Electron Transport Chain ◽

Transport Chain

The mutual shading among individual field-grown maize plants resulting from high planting density inevitably reduces leaf photosynthesis, while regulating the photosynthetic transport chain has a strong impact on photosynthesis. However, the effect of high planting density on the photosynthetic electron transport chain in maize currently remains unclear. In this study, we simultaneously measured prompt chlorophyll a fluorescence (PF), modulated 820 nm reflection (MR) and delayed chlorophyll a fluorescence (DF) in order to investigate the effect of high planting density on the photosynthetic electron transport chain in two maize hybrids widely grown in China. PF transients demonstrated a gradual reduction in their signal amplitude with increasing planting density. In addition, high planting density induced positive J-step and G-bands of the PF transients, reduced the values of PF parameters PIABS, RC/CSO, TRO/ABS, ETO/TRO and REO/ETO, and enhanced ABS/RC and N. MR kinetics showed an increase of their lowest point with increasing high planting density, and thus the values of MR parameters VPSI and VPSII-PSI were reduced. The shapes of DF induction and decay curves were changed by high planting density. In addition, high planting density reduced the values of DF parameters I1, I2, L1 and L2, and enhanced I2/I1. These results suggested that high planting density caused harm on multiple components of maize photosynthetic electron transport chain, including an inactivation of PSII RCs, a blocked electron transfer between QA and QB, a reduction in PSI oxidation and re-reduction activities, and an impaired PSI acceptor side. Moreover, a comparison between PSII and PSI activities demonstrated the greater effect of plant density on the former.

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Chlorophyll a fluorescence as an indicator of water stress in Calophyllum brasiliense

Notulae Botanicae Horti Agrobotanici Cluj-Napoca ◽

10.15835/nbha48111757 ◽

2020 ◽

Vol 48 (1) ◽

pp. 210-220 ◽

Cited By ~ 2

Author(s):

Lucas C. REIS ◽

Silvana P.Q. SCALON ◽

Daiane DRESCH ◽

Andressa Caroline FORESTI ◽

Cleberton C. SANTOS ◽

...

Keyword(s):

Water Deficit ◽

Chlorophyll A ◽

Chlorophyll A Fluorescence ◽

Stress Condition ◽

Water Status ◽

Photosynthetic Apparatus ◽

Stress Indicator ◽

Fluorescence Measurements ◽

Calophyllum Brasiliense ◽

And Function

The objective of this study was to evaluate chlorophyll a fluorescence as a stress indicator in Calophyllum brasiliense Cambess seedlings grown with different concentrations of abscisic acid (ABA) under intermittent water deficit condition: daily irrigation without ABA (I); daily irrigation + 10 μM ABA (I 10); daily irrigation + 100 μM ABA (I 100); suspension of daily irrigation without ABA (SI); suspension of daily irrigation + 10 μM ABA (SI 10) and suspension of daily irrigation + 100 μM ABA (SI 100). The intermittent water deficit reduces water status and impairs the photochemical apparatus functioning and seedling quality. The fluorescence measurements helped identify the stress condition of water deficit in the cultivation of C. brasiliense and the beneficial effect of the application of 10 μM of ABA in minimizing stress and facilitating the recovery of seedlings after re-irrigation, while maintaining the integrity and function of the photosynthetic apparatus.

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Photosystem Disorder Could be the Key Cause for the Formation of Albino Leaf Phenotype in Pecan

International Journal of Molecular Sciences ◽

10.3390/ijms21176137 ◽

2020 ◽

Vol 21 (17) ◽

pp. 6137

Author(s):

Ji-Yu Zhang ◽

Tao Wang ◽

Zhan-Hui Jia ◽

Zhong-Ren Guo ◽

Yong-Zhi Liu ◽

...

Keyword(s):

Chlorophyll A ◽

Molecular Mechanisms ◽

Chlorophyll Biosynthesis ◽

Protoporphyrin Ix ◽

Photosynthetic Electron Transport ◽

Chlorophyll Degradation ◽

Pheophorbide A ◽

Leaf Phenotype ◽

Photosynthesis Pathway ◽

Almost All

Pecan is one of the most famous nut species in the world. The phenotype of mutants with albino leaves was found in the process of seeding pecan, providing ideal material for the study of the molecular mechanisms leading to the chlorina phenotype in plants. Both chlorophyll a and chlorophyll b contents in albino leaves (ALs) were significantly lower than those in green leaves (GLs). A total of 5171 differentially expression genes (DEGs) were identified in the comparison of ALs vs. GLs using high-throughput transcriptome sequencing; 2216 DEGs (42.85%) were upregulated and 2955 DEGs (57.15%) were downregulated. The expressions of genes related to chlorophyll biosynthesis (HEMA1, encoding glutamyl-tRNA reductase; ChlH, encoding Mg-protoporphyrin IX chelatase (Mg-chelatase) H subunit; CRD, encoding Mg-protoporphyrin IX monomethylester cyclase; POR, encoding protochlorophyllide reductase) in ALs were significantly lower than those in GLs. However, the expressions of genes related to chlorophyll degradation (PAO, encoding pheophorbide a oxygenase) in ALs were significantly higher than those in GLs, indicating that disturbance of chlorophyll a biosynthesis and intensification of chlorophyll degradation lead to the absence of chlorophyll in ALs of pecan. A total of 72 DEGs associated with photosynthesis pathway were identified in ALs compared to GLs, including photosystem I (15), photosystem II (19), cytochrome b6-f complex (3), photosynthetic electron transport (6), F-type ATPase (7), and photosynthesis-antenna proteins (22). Moreover, almost all the genes (68) mapped in the photosynthesis pathway showed decreased expression in ALs compared to GLs, declaring that the photosynthetic system embedded within the thylakoid membrane of chloroplast was disturbed in ALs of pecan. This study provides a theoretical basis for elucidating the molecular mechanism underlying the phenotype of chlorina seedlings of pecan.

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Glyphosate Does Not Inhibit Photosynthetic Electron Transport and Phosphorylation in Pea (Pisum sativum) Chloroplasts

Weed Science ◽

10.1017/s0043174500046142 ◽

1979 ◽

Vol 27 (6) ◽

pp. 684-688 ◽

Cited By ~ 6

Author(s):

E. P. Richard ◽

J. R. Goss ◽

C. J. Arntzen

Keyword(s):

Electron Transport ◽

Pisum Sativum ◽

Photosynthetic Electron Transport ◽

Photochemical Reactions ◽

Transport Processes ◽

Ps Ii ◽

Dark Incubation ◽

Fluorescence Studies ◽

Mixture Prior

The activity of glyphosate [N-(phosphonomethyl)glycine], formulated as the isopropylamine salt, on in vitro photosynthesis was investigated. When pH 4.7 glyphosate solutions were titrated to a pH equal to that of the reaction media (pH 7.8), glyphosate additions had no effect on whole chain electron transport between coupled photosystem II (PS II) and photosystem I (PS I) in stroma-free chloroplast thylakoids from peas (Pisum sativumL. ‘Morse's Progress No. 9′). Inhibition did not occur even after a 2-h dark incubation of lamellae in a 5-mM solution of glyphosate. Fluorescence studies failed to detect an effect of glyphosate on PS-II mediated electron transport processes or upon light harvesting properties of PS II even after a 2-h glyphosate/chloroplast preincubation. Glyphosate had no effect on cyclic and noncyclic photophosphorylation even after a 100-min dark incubation of chloroplast membranes in a 5-mM solution of glyphosate. Based on these assays it is concluded that glyphosate has no direct effect on the photochemical reactions of photosynthesis when the pH of the active compound is adjusted to that of the reaction mixture prior to addition to a chloroplast suspension.

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Photosynthesis Regulation in Response to Fluctuating Light in the Secondary Endosymbiont Alga Nannochloropsis gaditana

Plant and Cell Physiology ◽

10.1093/pcp/pcz174 ◽

2019 ◽

Vol 61 (1) ◽

pp. 41-52 ◽

Cited By ~ 3

Author(s):

Alessandra Bellan ◽

Francesca Bucci ◽

Giorgio Perin ◽

Alessandro Alboresi ◽

Tomas Morosinotto

Keyword(s):

Electron Transport ◽

Electron Flow ◽

Incident Light ◽

Photosynthetic Apparatus ◽

Photosynthetic Electron Transport ◽

Thermal Dissipation ◽

Photochemical Quenching ◽

Nannochloropsis Gaditana ◽

Fluctuating Light ◽

Light Fluctuations

Abstract In nature, photosynthetic organisms are exposed to highly dynamic environmental conditions where the excitation energy and electron flow in the photosynthetic apparatus need to be continuously modulated. Fluctuations in incident light are particularly challenging because they drive oversaturation of photosynthesis with consequent oxidative stress and photoinhibition. Plants and algae have evolved several mechanisms to modulate their photosynthetic machinery to cope with light dynamics, such as thermal dissipation of excited chlorophyll states (non-photochemical quenching, NPQ) and regulation of electron transport. The regulatory mechanisms involved in the response to light dynamics have adapted during evolution, and exploring biodiversity is a valuable strategy for expanding our understanding of their biological roles. In this work, we investigated the response to fluctuating light in Nannochloropsis gaditana, a eukaryotic microalga of the phylum Heterokonta originating from a secondary endosymbiotic event. Nannochloropsis gaditana is negatively affected by light fluctuations, leading to large reductions in growth and photosynthetic electron transport. Exposure to light fluctuations specifically damages photosystem I, likely because of the ineffective regulation of electron transport in this species. The role of NPQ, also assessed using a mutant strain specifically depleted of this response, was instead found to be minor, especially in responding to the fastest light fluctuations.

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Resistance to chlortoluron in a downy brome (Bromus tectorum) biotype

Weed Science ◽

10.1614/ws-05-073r.1 ◽

2006 ◽

Vol 54 (02) ◽

pp. 237-245 ◽

Cited By ~ 12

Author(s):

Julio Menendez ◽

Fernando Bastida ◽

Rafael de Prado

Keyword(s):

Electron Transport ◽

Photosynthetic Electron Transport ◽

Fold Increase ◽

Downy Brome ◽

Fresh Weight ◽

Wheat Field ◽

P450 Monooxygenases ◽

Fluorescence Measurements ◽

Higher Ed ◽

Herbicide Metabolism

A downy brome population in a winter wheat field at Córdoba, Spain, survived use rates of chlortoluron (2.5 to 3.5 kg ai ha−1) over 2 consecutive yr, where wheat monoculture and multiple annual chlortoluron applications had been carried out. The resistant (CR) biotype showed a higher ED50value (7.4 kg ai ha−1; the concentration required for 50% reduction of fresh weight) than the susceptible (S) control (2.2 kg ai ha−1), with a 3.4-fold increase in chlortoluron tolerance. Chlortoluron resistance in the CR downy brome biotype was not caused by altered absorption, translocation, or modification of the herbicide target site but by enhanced detoxification. The inhibition of both the recovery of photosynthetic electron transport and chlortoluron metabolism in the CR biotype due to the presence of the Cyt P450 inhibitor 1-aminobenzotriazole (ABT) indicates that herbicide metabolism catalyzed by Cyt P450 monooxygenases is related to chlortoluron resistance in CR plants. Although both biotypes degraded chlortoluron byN-dealkylation and ring-methyl hydroxylation and seem to share the same ability to form polar conjugates, degradation in the resistant biotype is more efficacious as this biotype metabolizes the parent herbicide faster and to a greater extent than its susceptible counterpart. The ability of the susceptible biotype to ring-hydroxylate chlortoluron, albeit at much slower rate, probably explains its moderate tolerance to chlortoluron observed in the growth assays and its minor photosynthetic electron transport recovery observed in fluorescence measurements.

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Role of oxidative stress and thiol antioxidant enzymes in nickel toxicity and resistance in strains of the green alga Scenedesmus acutus f. alternans

Canadian Journal of Microbiology ◽

10.1139/cjm-47-11-987 ◽

2001 ◽

Vol 47 (11) ◽

pp. 987-993 ◽

Cited By ~ 1

Author(s):

Varinder K. Randhawa ◽

Fengzhen Zhou ◽

Xiaolei Jin ◽

Czesia Nalewajko ◽

Donn J. Kushner

Keyword(s):

Oxidative Stress ◽

Antioxidant Enzymes ◽

Green Alga ◽

Nickel Toxicity ◽

Scenedesmus Acutus ◽

Thiol Antioxidant

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Anthracene phytotoxicity in the freshwater flagellate alga Euglena agilis Carter

Scientific Reports ◽

10.1038/s41598-019-51451-y ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 2

Author(s):

Sreejith Kottuparambil ◽

Jihae Park

Keyword(s):

Growth Rate ◽

Environmental Protection Agency ◽

Photosynthetic Pigment ◽

Photosynthetic Electron Transport ◽

Photosynthetic Parameters ◽

Energy Regulation ◽

Total Carotenoids ◽

Ecological Processes ◽

Polycyclic Aromatic ◽

Median Effective Concentration

Abstract The freshwater flagellate alga Euglena agilis Carter was exposed to the polycyclic aromatic hydrocarbon (PAH) anthracene for 96 h under optimal photosynthetically active radiation (PAR), and responses of growth, photosynthetic pigment production, and photosynthetic efficiency were assessed. Anthracene reduced the growth rate (μ) and levels of chlorophyll a (Chl a), chlorophyll b (Chl b), and total carotenoids. The growth rate was more sensitive than photosynthetic parameters, with a median effective concentration (EC50) of 4.28 mg L−1. Between 5 and 15 mg L−1, anthracene inhibited the maximum quantum yield (Fv/Fm) of photosystem II (PSII) and the maximum photosynthetic electron transport rate through PSII (rETRmax) with EC50 values of 14.88 and 11.8 mg L−1, respectively. At all anthracene concentrations, intracellular reactive oxygen species (ROS) were elevated, indicating increased oxidative stress. Anthracene presumably reduced the PSII efficiency of photochemical energy regulation and altered the photochemistry through intracellular ROS formation. Acute exposure to PAHs may induce severe physiological changes in phytoplankton cells, which may influence vital ecological processes within the aquatic environments. Additionally, growth and Chl a content may serve as sensitive risk assessment parameters of anthracene toxicity in water management since EC50 values for both overlap with anthracene levels (8.3 mg L−1) permitted by the US Environmental Protection Agency (USEPA).

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