Size-dependent susceptibility of lake phytoplankton to light stress: An implication for succession of large green algae in a deep oligotrophic lake

Field observations of the population dynamics and measurements of photophysiology in Lake Biwa were conducted by size class (< vs. > 30 μm) from early summer to autumn to investigate the relationships between susceptibility to light stress and cell size. Also, a nutrient bioassay was conducted to clarify whether the growth rate and photosystem II (PSII) photochemistry of small and large phytoplankton are limited by nutrient availability. Large phytoplankton, which have lower intracellular Chl-a concentrations, had higher maximum PSII photochemical efficiency (Fv/Fm) but lower non-photochemical quenching (NPQNSV) than small phytoplankton under both dark and increased light conditions. The nutrient bioassay revealed that the PSII photochemistry of small phytoplankton was restricted by N and P deficiency at the pelagic site even at the end of the stratification period, while that of large phytoplankton was not. These results suggest that large phytoplankton have lower susceptibility to PSII photodamage than small phytoplankton due to lower intracellular Chl-a concentrations. The size dependency of susceptibility to PSII photoinactivation may play a key role in large algal blooms in oligotrophic water.

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Leaf Gas Exchange and Chlorophyll a Fluorescence Imaging of Rice Leaves Infected with Monographella albescens

Phytopathology ◽

10.1094/phyto-04-14-0097-r ◽

2015 ◽

Vol 105 (2) ◽

pp. 180-188 ◽

Cited By ~ 28

Author(s):

Sandro Dan Tatagiba ◽

Fábio Murilo DaMatta ◽

Fabrício Ávila Rodrigues

Keyword(s):

Gas Exchange ◽

Fluorescence Imaging ◽

Leaf Gas Exchange ◽

Photosynthetic Pigment ◽

Photochemical Efficiency ◽

Photosynthetic Apparatus ◽

Photochemical Quenching ◽

Chl A ◽

Chl A Fluorescence ◽

Rice Leaves

This study was intended to analyze the photosynthetic performance of rice leaf blades infected with Monographella albescens by combining chlorophyll (Chl) a fluorescence images with gas exchange and photosynthetic pigment pools. The net CO2 assimilation rate, stomatal conductance, transpiration rate, total Chl and carotenoid pools, and Chl a/b ratio all decreased but the internal CO2 concentration increased in the inoculated plants compared with their noninoculated counterparts. The first detectable changes in the images of Chl a fluorescence from the leaves of inoculated plants were already evident at 24 h after inoculation (hai) and increased dramatically as the leaf scald lesions expanded. However, these changes were negligible for the photosystem II photochemical efficiency (Fv/Fm) at 24 hai, in contrast to other Chl fluorescence traits such as the photochemical quenching coefficient, yield of photochemistry, and yield for dissipation by downregulation; which, therefore, were much more sensitive than the Fv/Fm ratio in assessing the early stages of fungal infection. It was also demonstrated that M. albescens was able to impair the photosynthetic process in both symptomatic and asymptomatic leaf areas. Overall, it was proven that Chl a fluorescence imaging is an excellent tool to describe the loss of functionality of the photosynthetic apparatus occurring in rice leaves upon infection by M. albescens.

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Substrate Application of 5-Aminolevulinic Acid Enhanced Low-temperature and Weak-light Stress Tolerance in Cucumber (Cucumis sativus L.)

Agronomy ◽

10.3390/agronomy10040472 ◽

2020 ◽

Vol 10 (4) ◽

pp. 472 ◽

Cited By ~ 2

Author(s):

Ali Anwar ◽

Jun Wang ◽

Xianchang Yu ◽

Chaoxing He ◽

Yansu Li

Keyword(s):

Low Temperature ◽

Stress Tolerance ◽

Antioxidant Enzyme ◽

Aminolevulinic Acid ◽

Light Stress ◽

Photochemical Quenching ◽

Antioxidant Enzyme Activities ◽

Cucumber Seedlings ◽

Chl A ◽

Weak Light

5-Aminolevulinic acid (ALA) is a type of nonprotein amino acid that promotes plant stress tolerance. However, the underlying physiological and biochemical mechanisms are not fully understood. We investigated the role of ALA in low-temperature and weak-light stress tolerance in cucumber seedlings. Seedlings grown in different ALA treatments (0, 10, 20, or 30 mg ALA·kg−1 added to substrate) were exposed to low temperature (16/8 ˚C light/dark) and weak light (180 μmol·m−2·s−1 photosynthetically active radiation) for two weeks. Treatment with ALA significantly alleviated the inhibition of plant growth, and enhanced leaf area, and fresh and dry weight of the seedlings under low-temperature and weak-light stress. Moreover, ALA increased chlorophyll (Chl) a, Chl b, and Chl a+b contents. Net photosynthesis rate, stomatal conductance, transpiration rate, photochemical quenching, non-photochemical quenching, actual photochemical efficiency of photosystem II, and electron transport rate were significantly increased in ALA-treated seedlings. In addition, ALA increased root activity and antioxidant enzyme (superoxide dismutase, peroxidase, and catalase) activities, and reduced reactive oxygen species (hydrogen peroxide and superoxide radical) and malondialdehyde accumulation in the root and leaf of cucumber seedlings. These findings suggested that ALA incorporation in the substrate alleviated the adverse effects of low-temperature and weak-light stress, and improved Chl contents, photosynthetic capacity, and antioxidant enzyme activities, and thus enhanced cucumber seedling growth.

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Overexpression of a zeaxanthin epoxidase gene from Medicago sativa enhances the tolerance to low light in transgenic tobacco

Acta Biochimica Polonica ◽

10.18388/abp.2018_2551 ◽

2018 ◽

Vol 65 (3) ◽

Cited By ~ 3

Author(s):

Yuman Cao ◽

Zhiqiang Zhang ◽

Tong Zhang ◽

Zhang You ◽

Jincai Geng ◽

...

Keyword(s):

Medicago Sativa ◽

Light Stress ◽

Photochemical Efficiency ◽

Light Condition ◽

Photochemical Quenching ◽

Low Light ◽

Zeaxanthin Epoxidase ◽

Significant Difference ◽

Non Photochemical Quenching ◽

Low Light Stress

Zeaxanthin epoxidase (ZEP) plays an important role in xanthophyll cycle which is a process closely related to photosynthesis. However, an impact of ZEP on low light stress has not been reported. In this study, the functions of an alfalfa (Medicago sativa) zeaxanthin epoxidase gene, MsZEP, in response to low light stress were investigated by heterologous expression in tobacco (Nicotiana tabacum). Under normal light condition, parameters measured were not significantly different between transgenic and wild-type (WT) plants except for non-photochemical quenching value and chlorophyll a content, while difference existed in low light stress. We found that MsZEP-overexpression tobacco grew faster than WT (p≤0.05). The leaf fresh weight and leaf area of transgenic plants were significantly higher, and the number of stoma was greater in MsZEP-overexpression tobacco. As for photosynthetic characteristics, quantum yield of PSII (ΦPSII) and maximal photochemical efficiency of PSII (Fv/Fm) were not significantly different, wherase non-photochemical quenching (NPQ), net photosynthetic rate (Pn), stomata conductance (Gs) and transpiration rate (Tr) of MsZEP-overexpression tobacco were significantly higher than WT plants. However, no significant difference was existed between the two types of tobacco in chlorophyll and carotenoids content. In conclusion, MsZEP can improve the ability of tobacco to withstand low light stress, which might be due to its stronger photosynthetic activity and the improvement of stomata density under low light.

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Boosting photosynthetic machinery and defense priming with chitosan application on tomato plants infected with Fusarium oxysporum f. sp. lycopersici

10.1101/2020.08.18.256628 ◽

2020 ◽

Author(s):

Sandra L. Carmona ◽

Andrea del Pilar Villarreal-Navarrete ◽

Diana Burbano-David ◽

Magda Gómez-Marroquín ◽

Esperanza Torres-Rojas ◽

...

Keyword(s):

Fusarium Oxysporum ◽

Stomatal Closure ◽

Photochemical Efficiency ◽

Defense Responses ◽

Dry Mass ◽

Systemic Resistance ◽

Photochemical Quenching ◽

Molecular Responses ◽

Tomato Plants ◽

Psii Photochemistry

AbstractPhysiological processes of plants infected by vascular pathogens are mainly affected by vascular bundle obstruction, decreasing the absorption of water and nutrients and gas exchange by stomatal closure, and inducing oxidative cascades and PSII alterations. Chitosan, a derivative of chitin present in the cell wall of some organisms including fungi, induces plant defense responses, activating systemic resistance. In this study, the effect of chitosan on the physiological and molecular responses of tomato plants infected with Fusarium oxysporum f. sp. lycopersici (Fol) was studied, evaluating the maximum potential quantum efficiency of PSII photochemistry (Fv/Fm), photochemical efficiency of PSII (Y(II)), photochemical quenching (qP), stomatal conductance (gs), relative water content (RWC), proline content, photosynthetic pigments, dry mass, and differential gene expression (PAL, LOXA, ERF1, and PR1) of defense markers. A reduction of 70% in the incidence and 91% in the severity of the disease was achieved in plants treated with chitosan, mitigating the damage caused by Fol on Fv/Fm, Y(II), and chlorophyll contents by 23%, 36%, and 47%, respectively. Less impact was observed on qP, gs, RWC, and dry mass (16%, 11%, and 26%, respectively). Chitosan-treated and Fol-infected plants over-expressed PR1a gene suggesting a priming-associated response. These results demonstrate the high potential of chitosan to protect tomato plants against Fol by regulating physiological and molecular responses in tomato plants.

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Praseodymium enhanced the tolerance of maize seedlings subjected to cadmium stress by up-regulating the enzymes in the regeneration and biosynthetic pathways of ascorbate and glutathione

Plant Soil and Environment ◽

10.17221/217/2021-pse ◽

2021 ◽

Author(s):

Qidi Zhu ◽

Yanyan Li ◽

Shang Gao ◽

Changjuan Shan

Keyword(s):

Plant Height ◽

Photochemical Efficiency ◽

Enzymatic Activities ◽

Monodehydroascorbate Reductase ◽

Photochemical Quenching ◽

Biosynthetic Pathways ◽

Cd Stress ◽

Maize Seedlings ◽

Cd Tolerance ◽

Psii Photochemistry

To test whether praseodymium (Pr) regulates cadmium (Cd) tolerance, we explored the effects of Pr on enzymatic activities in the regeneration and biosynthetic pathways of ascorbate and glutathione in maize seedlings under Cd stress. The findings demonstrated that Cd stress increased enzymatic activities in the regeneration pathway (ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR)) and in the biosynthetic pathway of ascorbate and glutathione (γ-ECS and GalLDH), as well as ascorbate (AsA) and glutathione (GSH) contents. However, Cd stress significantly decreased AsA/dehydroascorbic acid (DHA) ratio and GSH/oxidised glutathione (GSSG) ratio, net photosynthetic rate (Pn), chlorophylls (Chl) and carotenoids (Car) contents, maximum photochemical efficiency of PSII (Fv/Fm), photochemical quenching (qP) and quantum efficiency of PSII photochemistry (ΦPSII), as well as plant height and biomass. Application of Pr to Cd-stressed seedlings enhanced above enzymatic activities, AsA and GSH contents, AsA/DHA and GSH/GSSG ratios, Pn, Chl and Car contents, Fv/Fm, qP and ΦPSII, as well as plant height and biomass. Meanwhile, the application of Pr to Cd-stressed seedlings reduced malondialdehyde (MDA) content and electrolyte leakage. The above results indicated that Pr enhanced Cd tolerance of maize by up-regulating enzymatic activities in regeneration and biosynthetic pathways of ascorbate and glutathione.

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Gradual Response of Cyanobacterial Thylakoids to Acute High-Light Stress—Importance of Carotenoid Accumulation

Cells ◽

10.3390/cells10081916 ◽

2021 ◽

Vol 10 (8) ◽

pp. 1916

Author(s):

Myriam Canonico ◽

Grzegorz Konert ◽

Aurélie Crepin ◽

Barbora Šedivá ◽

Radek Kaňa

Keyword(s):

Single Cell ◽

Thylakoid Membrane ◽

Intermediate Phase ◽

Light Stress ◽

Fast Response ◽

High Light ◽

Photochemical Quenching ◽

Second Phase ◽

Ros Scavenging ◽

Non Photochemical Quenching

Light plays an essential role in photosynthesis; however, its excess can cause damage to cellular components. Photosynthetic organisms thus developed a set of photoprotective mechanisms (e.g., non-photochemical quenching, photoinhibition) that can be studied by a classic biochemical and biophysical methods in cell suspension. Here, we combined these bulk methods with single-cell identification of microdomains in thylakoid membrane during high-light (HL) stress. We used Synechocystis sp. PCC 6803 cells with YFP tagged photosystem I. The single-cell data pointed to a three-phase response of cells to acute HL stress. We defined: (1) fast response phase (0–30 min), (2) intermediate phase (30–120 min), and (3) slow acclimation phase (120–360 min). During the first phase, cyanobacterial cells activated photoprotective mechanisms such as photoinhibition and non-photochemical quenching. Later on (during the second phase), we temporarily observed functional decoupling of phycobilisomes and sustained monomerization of photosystem II dimer. Simultaneously, cells also initiated accumulation of carotenoids, especially ɣ–carotene, the main precursor of all carotenoids. In the last phase, in addition to ɣ-carotene, we also observed accumulation of myxoxanthophyll and more even spatial distribution of photosystems and phycobilisomes between microdomains. We suggest that the overall carotenoid increase during HL stress could be involved either in the direct photoprotection (e.g., in ROS scavenging) and/or could play an additional role in maintaining optimal distribution of photosystems in thylakoid membrane to attain efficient photoprotection.

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Exogenous melatonin improves the salt tolerance of cotton by removing active oxygen and protecting photosynthetic organs

BMC Plant Biology ◽

10.1186/s12870-021-03082-7 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Dan Jiang ◽

Bin Lu ◽

Liantao Liu ◽

Wenjing Duan ◽

Yanjun Meng ◽

...

Keyword(s):

Salt Stress ◽

Salt Tolerance ◽

Oxidative Damage ◽

Photosynthetic Capacity ◽

Photochemical Efficiency ◽

Photochemical Quenching ◽

Plant Tolerance ◽

Signal Molecule ◽

Ion Balance ◽

Photosynthetic System

Abstract Background As damage to the ecological environment continues to increase amid unreasonable amounts of irrigation, soil salinization has become a major challenge to agricultural development. Melatonin (MT) is a pleiotropic signal molecule and indole hormone, which alleviates the damage of abiotic stress to plants. MT has been confirmed to eliminate reactive oxygen species (ROS) by improving the antioxidant system and reducing oxidative damage under adversity. However, the mechanism by which exogenous MT mediates salt tolerance by regulating the photosynthetic capacity and ion balance of cotton seedlings still remains unknown. In this study, the regulatory effects of MT on the photosynthetic system, osmotic modulators, chloroplast, and anatomical structure of cotton seedlings were determined under 0–500 μM MT treatments with salt stress induced by treatment with 150 mM NaCl. Results Salt stress reduces the chlorophyll content, net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, PSII photochemical efficiency, PSII actual photochemical quantum yield, the apparent electron transfer efficiency, stomata opening, and biomass. In addition, it increases non-photochemical quenching. All of these responses were effectively alleviated by exogenous treatment with MT. Exogenous MT reduces oxidative damage and lipid peroxidation by reducing salt-induced ROS and protects the plasma membrane from oxidative toxicity. MT also reduces the osmotic pressure by reducing the salt-induced accumulation of Na+ and increasing the contents of K+ and proline. Exogenous MT can facilitate stomatal opening and protect the integrity of cotton chloroplast grana lamella structure and mitochondria under salt stress, protect the photosynthetic system of plants, and improve their biomass. An anatomical analysis of leaves and stems showed that MT can improve xylem and phloem and other properties and aides in the transportation of water, inorganic salts, and organic substances. Therefore, the application of MT attenuates salt-induced stress damage to plants. Treatment with exogenous MT positively increased the salt tolerance of cotton seedlings by improving their photosynthetic capacity, stomatal characteristics, ion balance, osmotic substance biosynthetic pathways, and chloroplast and anatomical structures (xylem vessels and phloem vessels). Conclusions Our study attributes help to protect the structural stability of photosynthetic organs and increase the amount of material accumulation, thereby reducing salt-induced secondary stress. The mechanisms of MT-induced plant tolerance to salt stress provide a theoretical basis for the use of MT to alleviate salt stress caused by unreasonable irrigation, fertilization, and climate change.

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Non-photochemical quenching of chlorophyll a fluorescence: early history and characterization of two xanthophyll-cycle mutants of Chlamydomonas reinhardtii

Functional Plant Biology ◽

10.1071/fp02061 ◽

2002 ◽

Vol 29 (10) ◽

pp. 1141 ◽

Cited By ~ 28

Author(s):

Govindjee ◽

Manfredo J. Seufferheld

Keyword(s):

Chlamydomonas Reinhardtii ◽

Oxygen Evolution ◽

Xanthophyll Cycle ◽

Photochemical Quenching ◽

Chl A ◽

Fluorescence Transient ◽

Chl A Fluorescence ◽

Non Photochemical Quenching

This paper deals first with the early, although incomplete, history of photoinhibition, of 'non-QA-related chlorophyll (Chl) a fluorescence changes', and the xanthophyll cycle that preceded the discovery of the correlation between non-photochemical quenching of Chl a fluorescence (NPQ) and conversion of violaxanthin to zeaxanthin. It includes the crucial observation that the fluorescence intensity quenching, when plants are exposed to excess light, is indeed due to a change in the quantum yield of fluorescence. The history ends with a novel turn in the direction of research — isolation and characterization of NPQ xanthophyll-cycle mutants of Chlamydomonas reinhardtii Dangeard and Arabidopsis thaliana (L.) Heynh., blocked in conversion of violaxanthin to zeaxanthin, and zeaxanthin to violaxanthin, respectively. In the second part of the paper, we extend the characterization of two of these mutants (npq1, which accumulates violaxanthin, and npq2, which accumulates zeaxanthin) through parallel measurements on growth, and several assays of PSII function: oxygen evolution, Chl a fluorescence transient (the Kautsky effect), the two-electron gate function of PSII, the back reactions around PSII, and measurements of NPQ by pulse-amplitude modulation (PAM 2000) fluorimeter. We show that, in the npq2 mutant, Chl a fluorescence is quenched both in the absence and presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). However, no differences are observed in functioning of the electron-acceptor side of PSII — both the two-electron gate and the back reactions are unchanged. In addition, the role of protons in fluorescence quenching during the 'P-to-S' fluorescence transient was confirmed by the effect of nigericin in decreasing this quenching effect. Also, the absence of zeaxanthin in the npq1 mutant leads to reduced oxygen evolution at high light intensity, suggesting another protective role of this carotenoid. The available data not only support the current model of NPQ that includes roles for both pH and the xanthophylls, but also are consistent with additional protective roles of zeaxanthin. However, this paper emphasizes that we still lack sufficient understanding of the different parts of NPQ, and that the precise mechanisms of photoprotection in the alga Chlamydomonas may not be the same as those in higher plants.

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Interaction between simulated dense Scenedesmus dimorphus (Chlorophyta) bloom and freshwater meta-zooplankton community

Journal of Limnology ◽

10.4081/jlimnol.2018.1742 ◽

2018 ◽

Vol 77 (2) ◽

Cited By ~ 2

Author(s):

Zengling Ma ◽

Hengguo Yu ◽

Ronald Thring ◽

Chuanjun Dai ◽

Anglv Shen ◽

...

Keyword(s):

Community Structure ◽

Green Algae ◽

Aquatic Ecosystems ◽

Algal Blooms ◽

Algal Bloom ◽

Photochemical Efficiency ◽

Zooplankton Community ◽

Post Inoculation ◽

Zooplankton Community Structure ◽

Scenedesmus Dimorphus

Algal bloom has been a subject of much research, especially the occurrence of blue-green algae (cyanobacteria) blooms and their effects on aquatic ecosystems. However, the interaction between green algae blooms and zooplankton community was rarely investigated. In the present study, the effects exerted by Scenedesmus dimorphus (green alga) bloom on the community structure of zooplankton and the top-down control of the bloom process mediated by the zooplankton were evaluated using a series of laboratory cultures. The results showed that a dense S. dimorphus bloom could change the zooplankton community structure by decreasing its diversity indices, leading to the enrichment of a particular zooplankton species, Brachionus calyciflorus. In the presence of mixed species of zooplankton, the density of S. dimorphus in the culture was decreased as determined by a change in total chlorophyll a (Chl a) concentration, which was about 200 μg L-1 lower than that of the zooplankton-free culture. Furthermore, the number of species belonging to Cladocera, Copepoda and Rotifera all decreased, with all the cladocerans disappeared in the co-culture within 2 weeks of culturing, while the density of rotifers increased from 818 (±243) ind L-1 at the time of inoculation to 40733 (±2173) ind L-1 on the 14th day post-inoculation. Grazing of S. dimorphus by the rotifer B. calyciflorus neutralized its growth, and the gradual increase in B. calyciflorus density eventually led to the collapse of the bloom. Furthermore, grazing by B. calyciflorus also led to a decrease in the maximal photochemical efficiency (Fv/Fm) of photosystem II (PSII). The combined changes occurring in the zooplankton community structure during the process of S. dimorphus bloom and the negative effects of grazing on algal growth, morphology and photosynthetic activities confirmed the key role of zooplankton in the control of algal bloom. The results of the study therefore indicated that dense algal blooms caused by non-toxic algae could still remain a threat to aquatic ecosystems.

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Biomass accumulation, photochemical efficiency of photosystem II, nutrient contents and nitrate reductase activity in young rosewood plants (Aniba rosaeodora Ducke) submitted to different NO3-:NH4+ ratios

Acta Amazonica ◽

10.1590/s0044-59672007000400008 ◽

2007 ◽

Vol 37 (4) ◽

pp. 533-541 ◽

Cited By ~ 2

Author(s):

Denize Caranhas de Sousa Barreto ◽

José Francisco de Carvalho Gonçalves ◽

Ulysses Moreira dos Santos Júnior ◽

Andreia Varmes Fernandes ◽

Adriana Bariani ◽

...

Keyword(s):

Photosystem Ii ◽

Nitrate Reductase ◽

Growth Performance ◽

Nitrate Reductase Activity ◽

Reductase Activity ◽

Photochemical Efficiency ◽

Biomass Accumulation ◽

Nitrate Content ◽

Chl A ◽

Culture Substrate

The rosewood (Aniba rosaeodora Ducke) is a native tree species of Amazon rainforest growing naturally in acidic forest soils with reduced redox potential. However, this species can also been found growing in forest gaps containing oxide soils. Variations in the forms of mineral nitrogen (NO3- or NH4+) may be predicted in these different edaphic conditions. Considering that possibility, an experiment was carried out to analyze the effects of different NO3-:NH4+ ratios on the growth performance, mineral composition, chloroplastid pigment contents, photochemical efficiency photosystem II (PSII), and nitrate redutase activity (RN, E.C.1.6.6.1) on A. rosaeodora seedlings. Nine-month-old seedlings were grown in pots with a washed sand capacity of 7.5 kg and submitted to different NO3-:NH4+ ratios (T1 = 0:100%, T2 = 25:75%, T3 = 50:50%, T4 = 75:25%, and T5 = 100:0%). The lowest relative growth rate was observed when the NO3-:NH4+ ratio was equal to 0:100%. In general, high concentrations of NO3- rather than NH4+ favored a greater nutrient accumulation in different parts of the plant. For the chloroplastid pigment, the highest Chl a, Chl b, Chl tot, Chl a/b and Chl tot/Cx+c contents were found in the treatment with 75:25% of NO3-:NH4+, and for Chl b and Cx+c it was observed no difference. In addition, there was a higher photochemical efficiency of PSII (Fv/Fm) when high NO3- concentrations were used. A linear and positive response for the nitrate reductase activity was recorded when the nitrate content increased on the culture substrate. Our results suggest that A. rosaeodora seedlings have a better growth performance when the NO3- concentrations in the culture substrate were higher than the NH4+ concentrations.

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