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Chemosphere Jun 2024The modified biochars have positive effects in reducing heavy metal toxicity for plants. However, the mechanism and extent of these effects on mitigating arsenic...
Biochar-based nanoparticles mitigated arsenic toxicity and improved physiological performance of basil via enhancing cation exchange capacity and ferric chelate reductase activity.
The modified biochars have positive effects in reducing heavy metal toxicity for plants. However, the mechanism and extent of these effects on mitigating arsenic toxicity and plant performance are not clear. Thus, a pot experiment was conducted as factorial to evaluate the potential of fresh and enriched biochars with potassium and magnesium nano-sulfates [potassium-enriched biochar (K-BC), magnesium-enriched biochar (Mg-BC) in individual and combined forms] on reducing arsenic toxicity (non-contamination, 50, and 100 mg NaAsO kg soil) in basil plants. Biochar-related treatments reduced plant arsenic absorption rate (up to 24%), arsenic content of root (up to 38%) and shoot (up to 21%) and root tonoplast H-ATPase activity (up to 30%). The fresh and particularly enriched biochars improved soil properties (pH, CEC, and available iron content), ferric chelate reductase activity, iron, potassium and magnesium contents of plant tissues, chlorophyll content index, photochemical efficiency of photosystem II, relative electron transport rate, leaf area, and basil growth (shoot and root dry weight). These results revealed that enriched biochars are useful soil amendments for improving physiological performance of plants via reducing heavy metal toxicity and enhancing cation exchange capacity, nutrient availability and ferric chelate reductase activity. Therefore, soil amendment by enriched biochars could be a sustainable solution for enhancing plant productivity in contaminated soils via mitigating environmental impacts. This is an environmentally friendly method for using the natural wastes to overcome the adverse effects of soil pollutants on medicinal plants.
PubMed: 38897325
DOI: 10.1016/j.chemosphere.2024.142623 -
Planta Jun 2024By studying Cistus albidus shrubs in their natural habitat, we show that biological outliers can help us to understand the causes and consequences of maximum...
By studying Cistus albidus shrubs in their natural habitat, we show that biological outliers can help us to understand the causes and consequences of maximum photochemical efficiency decreases in plants, thus reinforcing the importance of integrating these often-neglected data into scientific practice. Outliers are individuals with exceptional traits that are often excluded of data analysis. However, this may result in very important mistakes not accurately capturing the true trajectory of the population, thereby limiting our understanding of a given biological process. Here, we studied the role of biological outliers in understanding the causes and consequences of maximum photochemical efficiency decreases in plants, using the semi-deciduous shrub C. albidus growing in a Mediterranean-type ecosystem. We assessed interindividual variability in winter, spring and summer maximum PSII photochemical efficiency in a population of C. albidus growing under Mediterranean conditions. A strong correlation was observed between maximum PSII photochemical efficiency (F/F ratio) and leaf water desiccation. While decreases in maximum PSII photochemical efficiency did not result in any damage at the organ level during winter, reductions in the F/F ratio were associated to leaf mortality during summer. However, all plants could recover after rainfalls, thus maximum PSII photochemical efficiency decreases did not result in an increased mortality at the organism level, despite extreme water deficit and temperatures exceeding 40ºC during the summer. We conclude that, once methodological outliers are excluded, not only biological outliers must not be excluded from data analysis, but focusing on them is crucial to understand the causes and consequences of maximum PSII photochemical efficiency decreases in plants.
Topics: Photosystem II Protein Complex; Seasons; Plant Leaves; Cistus; Photosynthesis; Ecosystem; Water; Temperature; Chlorophyll
PubMed: 38896307
DOI: 10.1007/s00425-024-04466-3 -
Plant Cell Reports Jun 2024Saline-alkali stress induces oxidative damage and photosynthesis inhibition in H. citrina, with a significant downregulation of the expression of photosynthesis- and...
Saline-alkali stress induces oxidative damage and photosynthesis inhibition in H. citrina, with a significant downregulation of the expression of photosynthesis- and antioxidant-related genes at high concentration. Soil salinization is a severe abiotic stress that impacts the growth and development of plants. In this study, Hemerocallis citrina Baroni was used to investigate its responsive mechanism to complex saline-alkali stress (NaCl:NaSO:NaHCO:NaCO = 1:9:9:1) for the first time. The growth phenotype, photoprotective mechanism, and antioxidant system of H. citrina were studied combining physiological and transcriptomic techniques. KEGG enrichment and GO analyses revealed significant enrichments of genes related to photosynthesis, chlorophyll degradation and antioxidant enzyme activities, respectively. Moreover, weighted gene co-expression network analysis (WGCNA) found that saline-alkali stress remarkably affected the photosynthetic characteristics and antioxidant system. A total of 29 key genes related to photosynthesis and 29 key genes related to antioxidant enzymes were discovered. High-concentration (250 mmol L) stress notably inhibited the expression levels of genes related to light-harvesting complex proteins, photosystem reaction center activity, electron transfer, chlorophyll synthesis, and Calvin cycle in H. citrina leaves. However, most of them were insignificantly changed under low-concentration (100 mmol L) stress. In addition, H. citrina leaves under saline-alkali stress exhibited yellow-brown necrotic spots, increased cell membrane permeability and accumulation of reactive oxygen species (ROS) as well as osmolytes. Under 100 mmol L stress, ROS was eliminate by enhancing the activities of antioxidant enzymes. Nevertheless, 250 mmol L stress down-regulated the expression levels of genes encoding antioxidant enzymes, and key enzymes in ascorbate-glutathione (AsA-GSH) cycle as well as thioredoxin-peroxiredoxin (Trx-Prx) pathway, thus inhibiting the activities of these enzymes. In conclusion, 250 mmol L saline-alkali stress caused severe damage to H. citrina mainly by inhibiting photosynthesis and ROS scavenging capacity.
Topics: Photosynthesis; Antioxidants; Gene Expression Regulation, Plant; Stress, Physiological; Chlorophyll; Alkalies; Plant Leaves; Salt Stress; Oxidative Stress
PubMed: 38896259
DOI: 10.1007/s00299-024-03261-4 -
International Journal of Molecular... May 2024Photosystem II (PSII) functions were investigated in basil ( L.) plants sprayed with 1 mM salicylic acid (SA) under non-stress (NS) or mild drought-stress (MiDS)...
Photosystem II (PSII) functions were investigated in basil ( L.) plants sprayed with 1 mM salicylic acid (SA) under non-stress (NS) or mild drought-stress (MiDS) conditions. Under MiDS, SA-sprayed leaves retained significantly higher (+36%) chlorophyll content compared to NS, SA-sprayed leaves. PSII efficiency in SA-sprayed leaves under NS conditions, evaluated at both low light (LL, 200 μmol photons m s) and high light (HL, 900 μmol photons m s), increased significantly with a parallel significant decrease in the excitation pressure at PSII (1-) and the excess excitation energy (EXC). This enhancement of PSII efficiency under NS conditions was induced by the mechanism of non-photochemical quenching (NPQ) that reduced singlet oxygen (O) production, as indicated by the reduced quantum yield of non-regulated energy loss in PSII (Φ). Under MiDS, the thylakoid structure of water-sprayed leaves appeared slightly dilated, and the efficiency of PSII declined, compared to NS conditions. In contrast, the thylakoid structure of SA-sprayed leaves did not change under MiDS, while PSII functionality was retained, similar to NS plants at HL. This was due to the photoprotective heat dissipation by NPQ, which was sufficient to retain the same percentage of open PSII reaction centers (q), as in NS conditions and HL. We suggest that the redox status of the plastoquinone pool (q) under MiDS and HL initiated the acclimation response to MiDS in SA-sprayed leaves, which retained the same electron transport rate (ETR) with control plants. Foliar spray of SA could be considered as a method to improve PSII efficiency in basil plants under NS conditions, at both LL and HL, while under MiDS and HL conditions, basil plants could retain PSII efficiency similar to control plants.
Topics: Photosystem II Protein Complex; Salicylic Acid; Ocimum basilicum; Droughts; Plant Leaves; Stress, Physiological; Chlorophyll; Photosynthesis; Thylakoids; Light
PubMed: 38891916
DOI: 10.3390/ijms25115728 -
Plants (Basel, Switzerland) Jun 2024Drought affects several plant physiological characteristics such as photosynthesis, carbon metabolism, and chlorophyll content, causing hormonal and nutritional...
Design of Microbial Consortia Based on Arbuscular Mycorrhizal Fungi, Yeasts, and Bacteria to Improve the Biochemical, Nutritional, and Physiological Status of Strawberry Plants Growing under Water Deficits.
Drought affects several plant physiological characteristics such as photosynthesis, carbon metabolism, and chlorophyll content, causing hormonal and nutritional imbalances and reducing nutrient uptake and transport, which inhibit growth and development. The use of bioinoculants based on plant growth-promoting microorganisms such as plant growth-promoting rhizobacteria (PGPR), yeasts, and arbuscular mycorrhizal fungi (AMF) has been proposed as an alternative to help plants tolerate drought. However, most studies have been based on the use of a single type of microorganism, while consortia studies have been scarcely performed. Therefore, the aim of this study was to evaluate different combinations of three PGPR, three AMF, and three yeasts with plant growth-promoting attributes to improve the biochemical, nutritional, and physiological behavior of strawberry plants growing under severe drought. The results showed that the growth and physiological attributes of the non-inoculated plants were significantly reduced by drought. In contrast, plants inoculated with the association of the fungus , the yeast , and the rhizobacterium showed a stronger improvement in tolerance to drought. High biomass, relative water content, fruit number, photosynthetic rate, transpiration, stomatal conductance, quantum yield of photosystem II, N concentration, P concentration, K concentration, antioxidant activities, and chlorophyll contents were significantly improved in inoculated plants by up to 16.6%, 12.4%, 81.2%, 80%, 79.4%, 71.0%, 17.8%, 8.3%, 6.6%, 57.3%, 41%, and 22.5%, respectively, compared to stressed non-inoculated plants. Moreover, decreased malondialdehyde levels by up to 32% were registered. Our results demonstrate the feasibility of maximizing the effects of inoculation with beneficial rhizosphere microorganisms based on the prospect of more efficient combinations among different microbial groups, which is of interest to develop bioinoculants oriented to increase the growth of specific plant species in a global scenario of increasing drought stress.
PubMed: 38891364
DOI: 10.3390/plants13111556 -
Plants (Basel, Switzerland) May 2024Salt stress severely reduces photosynthetic efficiency, resulting in adverse effects on crop growth and yield production. Two key thylakoid membrane lipid components,...
Salt stress severely reduces photosynthetic efficiency, resulting in adverse effects on crop growth and yield production. Two key thylakoid membrane lipid components, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), were perturbed under salt stress. MGDG synthase 1 (MGD1) is one of the key enzymes for the synthesis of these galactolipids. To investigate the function of in response to salt stress, the overexpression (OE) and RNA interference (Ri) rice lines, and a wild type (WT), were used. Compared with WT, the OE lines showed higher chlorophyll content and biomass under salt stress. Besides this, the OE plants showed improved photosynthetic performance, including light absorption, energy transfer, and carbon fixation. Notably, the net photosynthetic rate and effective quantum yield of photosystem II in the OE lines increased by 27.5% and 25.8%, respectively, compared to the WT. Further analysis showed that the overexpression of alleviated the negative effects of salt stress on photosynthetic membranes and oxidative defense by adjusting membrane lipid composition and fatty acid levels. In summary, OsMGD1-mediated membrane lipid remodeling enhanced salt tolerance in rice by maintaining membrane stability and optimizing photosynthetic efficiency.
PubMed: 38891283
DOI: 10.3390/plants13111474 -
Plants (Basel, Switzerland) May 2024Rare earth elements (REEs) have been intentionally used in Chinese agriculture since the 1980s to improve crop yields. Around the world, REEs are also involuntarily...
Rare earth elements (REEs) have been intentionally used in Chinese agriculture since the 1980s to improve crop yields. Around the world, REEs are also involuntarily applied to soils through phosphate fertilizers. These elements are known to alleviate damage in plants under abiotic stresses, yet there is no information on how these elements act in the physiology of plants. The REE mode of action falls within the scope of the hormesis effect, with low-dose stimulation and high-dose adverse reactions. This study aimed to verify how REEs affect rice plants' physiology to test the threshold dose at which REEs could act as biostimulants in these plants. In experiment 1, 0.411 kg ha (foliar application) of a mixture of REE (containing 41.38% Ce, 23.95% La, 13.58% Pr, and 4.32% Nd) was applied, as well as two products containing 41.38% Ce and 23.95% La separately. The characteristics of chlorophyll fluorescence, gas exchanges, SPAD index, and biomass (pot conditions) were evaluated. For experiment 2, increasing rates of the REE mix (0, 0.1, 0.225, 0.5, and 1 kg ha) (field conditions) were used to study their effect on rice grain yield and nutrient concentration of rice leaves. Adding REEs to plants increased biomass production (23% with Ce, 31% with La, and 63% with REE Mix application) due to improved photosynthetic rate (8% with Ce, 15% with La, and 27% with REE mix), favored by the higher electronic flow (photosynthetic electron transport chain) (increase of 17%) and by the higher F/F (increase of 14%) and quantum yield of photosystem II (increase of 20% with Ce and La, and 29% with REE Mix), as well as by increased stomatal conductance (increase of 36%) and SPAD index (increase of 10% with Ce, 12% with La, and 15% with REE mix). Moreover, adding REEs potentiated the photosynthetic process by increasing rice leaves' N, Mg, K, and Mn concentrations (24-46%). The dose for the higher rice grain yield (an increase of 113%) was estimated for the REE mix at 0.72 kg ha.
PubMed: 38891244
DOI: 10.3390/plants13111435 -
BMC Plant Biology Jun 2024Tropospheric ozone is an air pollutant that causes negative effects on vegetation, leading to significant losses in crop productivity. It is generated by chemical...
BACKGROUND
Tropospheric ozone is an air pollutant that causes negative effects on vegetation, leading to significant losses in crop productivity. It is generated by chemical reactions in the presence of sunlight between primary pollutants resulting from human activity, such as nitrogen oxides and volatile organic compounds. Due to the constantly increasing emission of ozone precursors, together with the influence of a warming climate on ozone levels, crop losses may be aggravated in the future. Therefore, the search for solutions to mitigate these losses becomes a priority. Ozone-induced abiotic stress is mainly due to reactive oxygen species generated by the spontaneous decomposition of ozone once it reaches the apoplast. In this regard, compounds with antioxidant activity offer a viable option to alleviate ozone-induced damage. Using enzymatic technology, we have developed a process that enables the production of an extract with biostimulant properties from okara, an industrial soybean byproduct. The biostimulant, named as OEE (Okara Enzymatic Extract), is water-soluble and is enriched in bioactive compounds present in okara, such as isoflavones. Additionally, it contains a significant fraction of protein hydrolysates contributing to its functional effect. Given its antioxidant capacity, we aimed to investigate whether OEE could alleviate ozone-induced damage in plants. For that, pepper plants (Capsicum annuum) exposed to ozone were treated with a foliar application of OEE.
RESULTS
OEE mitigated ozone-induced damage, as evidenced by the net photosynthetic rate, electron transport rate, effective quantum yield of PSII, and delayed fluorescence. This protection was confirmed by the level of expression of genes associated with photosystem II. The beneficial effect was primarily due to its antioxidant activity, as evidenced by the lipid peroxidation rate measured through malondialdehyde content. Additionally, OEE triggered a mild oxidative response, indicated by increased activities of antioxidant enzymes in leaves (catalase, superoxide dismutase, and guaiacol peroxidase) and the oxidative stress index, providing further protection against ozone-induced stress.
CONCLUSIONS
The present results support that OEE protects plants from ozone exposure. Taking into consideration that the promotion of plant resistance against abiotic damage is an important goal of biostimulants, we assume that its use as a new biostimulant could be considered.
Topics: Ozone; Glycine max; Stress, Physiological; Antioxidants; Capsicum; Photosynthesis; Plant Extracts
PubMed: 38890606
DOI: 10.1186/s12870-024-05290-3 -
Structural basis for an early stage of the photosystem II repair cycle in Chlamydomonas reinhardtii.Nature Communications Jun 2024Photosystem II (PSII) catalyzes water oxidation and plastoquinone reduction by utilizing light energy. It is highly susceptible to photodamage under high-light...
Photosystem II (PSII) catalyzes water oxidation and plastoquinone reduction by utilizing light energy. It is highly susceptible to photodamage under high-light conditions and the damaged PSII needs to be restored through a process known as the PSII repair cycle. The detailed molecular mechanism underlying the PSII repair process remains mostly elusive. Here, we report biochemical and structural features of a PSII-repair intermediate complex, likely arrested at an early stage of the PSII repair process in the green alga Chlamydomonas reinhardtii. The complex contains three protein factors associated with a damaged PSII core, namely Thylakoid Enriched Factor 14 (TEF14), Photosystem II Repair Factor 1 (PRF1), and Photosystem II Repair Factor 2 (PRF2). TEF14, PRF1 and PRF2 may facilitate the release of the manganese-stabilizing protein PsbO, disassembly of peripheral light-harvesting complexes from PSII and blockage of the Q site, respectively. Moreover, an α-tocopherol quinone molecule is located adjacent to the heme group of cytochrome b, potentially fulfilling a photoprotective role by preventing the generation of reactive oxygen species.
Topics: Photosystem II Protein Complex; Chlamydomonas reinhardtii; Thylakoids; Light-Harvesting Protein Complexes; Plant Proteins; Cytochrome b Group; Oxidation-Reduction; Reactive Oxygen Species; Light
PubMed: 38890314
DOI: 10.1038/s41467-024-49532-2 -
Scientific Reports Jun 2024Non-photochemical quenching (NPQ) is a protective mechanism for dissipating excess energy generated during photosynthesis in the form of heat. The accelerated relaxation...
Non-photochemical quenching (NPQ) is a protective mechanism for dissipating excess energy generated during photosynthesis in the form of heat. The accelerated relaxation of the NPQ in fluctuating light can lead to an increase in the yield and dry matter productivity of crops. Since the measurement of NPQ is time-consuming and requires specific light conditions, theoretical NPQ (NPQ) was introduced for rapid estimation, which could be suitable for High-throughput Phenotyping. We investigated the potential of NPQ to be used for testing plant genetic resources of chickpea under drought stress with non-invasive High-throughput Phenotyping complemented with yield traits. Besides a high correlation between the hundred-seed-weight and the Estimated Biovolume, significant differences were observed between the two types of chickpea desi and kabuli for Estimated Biovolume and NPQ. Desi was able to maintain the Estimated Biovolume significantly better under drought stress. One reason could be the effective dissipation of excess excitation energy in photosystem II, which can be efficiently measured as NPQ. Screening of plant genetic resources for photosynthetic performance could take pre-breeding to a higher level and can be implemented in a variety of studies, such as here with drought stress or under fluctuating light in a High-throughput Phenotyping manner using NPQ.
Topics: Cicer; Droughts; Phenotype; Stress, Physiological; Photosynthesis; Photosystem II Protein Complex
PubMed: 38886488
DOI: 10.1038/s41598-024-63372-6