scholarly journals Photoprotective Role of Photosynthetic and Non-Photosynthetic Pigments in Phillyrea latifolia: Is Their “Antioxidant” Function Prominent in Leaves Exposed to Severe Summer Drought?

2021 ◽  
Vol 22 (15) ◽  
pp. 8303
Author(s):  
Antonella Gori ◽  
Cecilia Brunetti ◽  
Luana Beatriz dos Santos Nascimento ◽  
Giovanni Marino ◽  
Lucia Guidi ◽  
...  
Keyword(s):  
Photosynthetic Pigments ◽  
Light Stress ◽  
Climatic Conditions ◽  
Photochemical Quenching ◽  
Severe Drought ◽  
Summer Drought ◽  
Photooxidative Stress ◽  
Phillyrea Latifolia ◽  
Antioxidant Function

Carotenoids and phenylpropanoids play a dual role of limiting and countering photooxidative stress. We hypothesize that their “antioxidant” function is prominent in plants exposed to summer drought, when climatic conditions exacerbate the light stress. To test this, we conducted a field study on Phillyrea latifolia, a Mediterranean evergreen shrub, carrying out daily physiological and biochemical analyses in spring and summer. We also investigated the functional role of the major phenylpropanoids in different leaf tissues. Summer leaves underwent the most severe drought stress concomitantly with a reduction in radiation use efficiency upon being exposed to intense photooxidative stress, particularly during the central hours of the day. In parallel, a significant daily variation in both carotenoids and phenylpropanoids was observed. Our data suggest that the morning-to-midday increase in zeaxanthin derived from the hydroxylation of ß-carotene to sustain non-photochemical quenching and limit lipid peroxidation in thylakoid membranes. We observed substantial spring-to-summer and morning-to-midday increases in quercetin and luteolin derivatives, mostly in the leaf mesophyll. These findings highlight their importance as antioxidants, countering the drought-induced photooxidative stress. We concluded that seasonal and daily changes in photosynthetic and non-photosynthetic pigments may allow P. latifolia leaves to avoid irreversible photodamage and to cope successfully with the Mediterranean harsh climate.

scholarly journals Standardized Drought Indices for Pre-Summer Drought Assessment in Tropical Areas

Atmosphere ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 1209
Author(s):  
David Romero ◽  
Eric Alfaro ◽  
Roger Orellana ◽  
Maria-Engracia Hernandez Cerda
Keyword(s):  
Vegetation Index ◽  
Temporal Variations ◽  
Climatic Conditions ◽  
Drought Indices ◽  
Drought Severity ◽  
Severe Drought ◽  
Summer Drought ◽  
Tropical Zone ◽  
Drought Assessment ◽  
The Impact

The main climatic indices used for the determination of pre-summer drought severity were developed for temperate zones with very different climatic conditions from those found in the tropical climate zones, particularly with respect to seasonal rainfall variations. The temporal evolution of pre-summer drought leads the authors to compute the indices for each year over a defined period according to the climatic normals of each meteorological station and to consider the months inside the dry episode differently, according to the law of emptying the water reserves. As a function of this, standardized drought indices are proposed for the evaluation of the pre-summer drought in tropical zone. Two new indices were tested: one developed from precipitation and the other also considering temperature. These indices were validated by correlation with Advanced very-high-resolution radiometer (AVHRR) normalized difference vegetation index (NDVI) time series and used to identify the most severe drought conditions in the Yucatan Peninsula. The comparison between the indices and their temporal variations highlighted the importance of temperature in the most critical events and left indications of the impact of global warming on the phenomenon.

scholarly journals Light Quality-Dependent Regulation of Non-Photochemical Quenching in Tomato Plants

Biology ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 721
Author(s):  
Magdalena Trojak ◽  
Ernest Skowron
Keyword(s):  
Photosynthetic Pigments ◽  
Photosynthetic Apparatus ◽  
Photosynthetic Performance ◽  
Photochemical Quenching ◽  
Light Spectrum ◽  
Negative Effects ◽  
Tomato Plants ◽  
Lower Amplitude ◽  
Non Photochemical Quenching

Photosynthetic pigments of plants capture light as a source of energy for photosynthesis. However, the amount of energy absorbed often exceeds its utilization, thus causing damage to the photosynthetic apparatus. Plants possess several mechanisms to minimize such risks, including non-photochemical quenching (NPQ), which allows them to dissipate excess excitation energy in the form of harmless heat. However, under non-stressful conditions in indoor farming, it would be favorable to restrict the NPQ activity and increase plant photosynthetic performance by optimizing the light spectrum. Towards this goal, we investigated the dynamics of NPQ, photosynthetic properties, and antioxidant activity in the leaves of tomato plants grown under different light qualities: monochromatic red (R), green (G), or blue (B) light (L) at 80 µmol m−2 s−1 and R:G:B = 1:1:1 (referred to as the white light (WL)) at 120 µmol m−2 s−1. The results confirm that monochromatic BL increased the quantum efficiency of PSII and photosynthetic pigments accumulation. The RL and BL treatments enhanced the NPQ amplitude and showed negative effects on antioxidant enzyme activity. In contrast, plants grown solely under GL or WL presented a lower amplitude of NPQ due to the reduced accumulation of NPQ-related proteins, photosystem II (PSII) subunit S (PsbS), PROTON GRADIENT REGULATION-LIKE1 (PGRL1), cytochrome b6f subunit f (cytf) and violaxanthin de-epoxidase (VDE). Additionally, we noticed that plants grown under GL or RL presented an increased rate of lipid peroxidation. Overall, our results indicate the potential role of GL in lowering the NPQ amplitude, while the role of BL in the RGB spectrum is to ensure photosynthetic performance and photoprotective properties.

Role of Acacia Spp. In Nutrient Balance and Cycling in Regenerating Eucalyptus regnans F. Muell. Forests. II. Field Studies of Acetylene Reduction

1984 ◽  
Vol 32 (2) ◽  
pp. 217 ◽  
Author(s):  
MA Adams ◽  
PM Attiwill
Keyword(s):  
N2 Fixation ◽  
Nutrient Balance ◽  
Sampling Period ◽  
Climatic Conditions ◽  
Severe Drought ◽  
Fresh Weight ◽  
Eucalyptus Regnans ◽  
Acacia Dealbata ◽  
C2h2 Reduction

Rates of C2H2 reduction by nodules of Acacia dealbata growing in 2-year-old Eucalyptus regnans regeneration were determined at monthly intervals for 1 year under field conditions. Intact soil cores containing roots and nodules showed maximum values of 7.1 μmol h-1 g-1 fresh weight of nodules with a mean value of 4.4 μmol h-1 g-1 fresh weight. Nodule mass was clearly related to climatic conditions, being greatest when both temperature and moisture levels were favourable, and was probably depressed during the sampling period by the prevailing severe drought. From the measured rates of C2H2 reduction, estimated N2 fixation was 12-32 kg ha-1 year-1. Rates of N2 fixation as high as this confirm the role of acacias as fast-growing pioneer species important in maintaining the nitrogen pool of the forest ecosystem.

scholarly journals Monodehydroascorbate Reductase Plays a Role in the Tolerance of Chlamydomonas reinhardtii to Photooxidative Stress

2019 ◽  
Vol 60 (10) ◽  
pp. 2167-2179 ◽  
Author(s):  
Hui-Ling Yeh ◽  
Tsen-Hung Lin ◽  
Chi-Chih Chen ◽  
Tian-Xing Cheng ◽  
Hsin-Yang Chang ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Enzyme Activity ◽  
Chlamydomonas Reinhardtii ◽  
Light Stress ◽  
Light Condition ◽  
Transcript Level ◽  
Transcript Abundance ◽  
Monodehydroascorbate Reductase ◽  
Photooxidative Stress

Abstract Monodehydroascorbate reductase (MDAR; EC 1.6.5.4) is one of the key enzymes in the conversion of oxidized ascorbate (AsA) back to reduced AsA in plants. This study investigated the role of MDAR in the tolerance of Chlamydomonas reinhardtii P.A. Dangeard to photooxidative stress by overexpression and downregulation of the CrMDAR1 gene. For overexpression of CrMDAR1 driven by a HSP70A:RBCS2 fusion promoter, the cells survived under very high-intensity light stress (VHL, 1,800 μmol�m−2�s−1), while the survival of CC-400 and vector only control (vector without insert) cells decreased for 1.5 h under VHL stress. VHL increased lipid peroxidation of CC-400 but did not alter lipid peroxidation in CrMDAR1 overexpression lines. Additionally, overexpression of CrMDAR1 showed an increase in viability, CrMDAR1 transcript abundance, enzyme activity and the AsA: dehydroascorbate (DHA) ratio. Next, MDAR was downregulated to examine the essential role of MDAR under high light condition (HL, 1,400 μmol�m−2�s−1). The CrMDAR1 knockdown amiRNA line exhibited a low MDAR transcript abundance and enzyme activity and the survival decreased under HL conditions. Additionally, HL illumination decreased CrMDAR1 transcript abundance, enzyme activity and AsA:DHA ratio of CrMDAR1-downregulation amiRNA lines. Methyl viologen (an O2�− generator), H2O2 and NaCl treatment could induce an increase in CrMDAR1 transcript level. It represents reactive oxygen species are one of the factor inducing CrMDAR1 gene expression. In conclusion, MDAR plays a role in the tolerance of Chlamydomonas cells to photooxidative stress.

scholarly journals Characteristics of Phomopsis juglandina (Sacc.) Hohn. Associated with Dieback of Walnut in the Climatic Conditions of Southern Romania

Agronomy ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 46
Author(s):  
Cristina Mihaescu ◽  
Daniel Dunea ◽  
Adrian Gheorghe Bășa ◽  
Loredana Neagu Frasin
Keyword(s):  
Growth Temperature ◽  
Potential Evapotranspiration ◽  
Optimal Growth ◽  
Climatic Conditions ◽  
Cultural Characteristics ◽  
Optimal Growth Temperature ◽  
Conidial State ◽  
Optimal Ph

Phomopsis juglandina (Sacc.) Höhn., which is the conidial state of Diaporthe juglandina (Fuckel) Nitschke, and the main pathogen causing the dieback of branches and twigs of walnut was recently detected in many orchards from Romania. The symptomatological, morphological, ultrastructural, and cultural characteristics, as well as the pathogenicity of an isolate of this lignicolous fungus, were described and illustrated. The optimum periods for infection, under the conditions prevailing in Southern Romania, mainly occur in the spring (April) and autumn months (late September-beginning of October). Strong inverse correlations (p < 0.001) were found between potential evapotranspiration and lesion lengths on walnut branches in 2019. The pathogen forms two types of phialospores: alpha and beta; the role of beta phialospores is not well known in pathogenesis. In Vitro, the optimal growth temperature of mycelial hyphae was in the range of 22–26 °C, and the optimal pH is 4.4–7. This pathogen should be monitored continuously due to its potential for damaging infestations of intensive plantations.

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

Cells ◽  
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.

scholarly journals The Role of Acidic Residues in the C Terminal Tail of the LHCSR3 Protein of Chlamydomonas reinhardtii in Non-Photochemical Quenching

2021 ◽  
pp. 6895-6900
Author(s):  
Franco V. A. Camargo ◽  
Federico Perozeni ◽  
Gabriel de la Cruz Valbuena ◽  
Luca Zuliani ◽  
Samim Sardar ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Photochemical Quenching ◽  
Acidic Residues ◽  
Non Photochemical Quenching

scholarly journals Spermine: Its Emerging Role in Regulating Drought Stress Responses in Plants

Cells ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 261
Author(s):  
Md. Mahadi Hasan ◽  
Milan Skalicky ◽  
Mohammad Shah Jahan ◽  
Md. Nazmul Hossain ◽  
Zunaira Anwar ◽  
...  
Keyword(s):  
Drought Stress ◽  
Drought Tolerance ◽  
Stress Responses ◽  
Abiotic Stresses ◽  
Defense Mechanisms ◽  
Antioxidant Defense ◽  
Severe Drought ◽  
New Information ◽  
Effects Of Drought

In recent years, research on spermine (Spm) has turned up a lot of new information about this essential polyamine, especially as it is able to counteract damage from abiotic stresses. Spm has been shown to protect plants from a variety of environmental insults, but whether it can prevent the adverse effects of drought has not yet been reported. Drought stress increases endogenous Spm in plants and exogenous application of Spm improves the plants’ ability to tolerate drought stress. Spm’s role in enhancing antioxidant defense mechanisms, glyoxalase systems, methylglyoxal (MG) detoxification, and creating tolerance for drought-induced oxidative stress is well documented in plants. However, the influences of enzyme activity and osmoregulation on Spm biosynthesis and metabolism are variable. Spm interacts with other molecules like nitric oxide (NO) and phytohormones such as abscisic acid, salicylic acid, brassinosteroids, and ethylene, to coordinate the reactions necessary for developing drought tolerance. This review focuses on the role of Spm in plants under severe drought stress. We have proposed models to explain how Spm interacts with existing defense mechanisms in plants to improve drought tolerance.

Role of a Fasciclin domain protein in photooxidative stress and flocculation in Azospirillum brasilense Sp7

2021 ◽  
pp. 103875
Author(s):  
Ashutosh Prakash Dubey ◽  
Parul Pandey ◽  
Shivangi Mishra ◽  
Parikshit Gupta ◽  
Anil Kumar Tripathi
Keyword(s):  
Azospirillum Brasilense ◽  
Photooxidative Stress ◽  
Azospirillum Brasilense Sp7 ◽  
Domain Protein
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