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1.
Int J Mol Sci ; 22(7)2021 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-33804852

RESUMO

Light is the primary regulator of various biological processes during the plant life cycle. Although plants utilize photosynthetically active radiation to generate chemical energy, they possess several photoreceptors that perceive light of specific wavelengths and then induce wavelength-specific responses. Light is also one of the key determinants of the initiation of leaf senescence, the last stage of leaf development. As the leaf photosynthetic activity decreases during the senescence phase, chloroplasts generate a variety of light-mediated retrograde signals to alter the expression of nuclear genes. On the other hand, phytochrome B (phyB)-mediated red-light signaling inhibits the initiation of leaf senescence by repressing the phytochrome interacting factor (PIF)-mediated transcriptional regulatory network involved in leaf senescence. In recent years, significant progress has been made in the field of leaf senescence to elucidate the role of light in the regulation of nuclear gene expression at the molecular level during the senescence phase. This review presents a summary of the current knowledge of the molecular mechanisms underlying light-mediated regulation of leaf senescence.


Assuntos
Folhas de Planta/crescimento & desenvolvimento , Luz Solar , Estiolamento , Fotossíntese , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais
2.
Int J Mol Sci ; 22(5)2021 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-33806362

RESUMO

Date palm (Phoenix dactylifera) is one of the most widespread fruit crop species and can tolerate drastic environmental conditions that may not be suitable for other fruit species. Excess UV-B stress is one of the greatest concerns for date palm trees and can cause genotoxic effects. Date palm responds to UV-B irradiation through increased DEG expression levels and elaborates upon regulatory metabolic mechanisms that assist the plants in adjusting to this exertion. Sixty-day-old Khalas date palm seedlings (first true-leaf stage) were treated with UV-B (wavelength, 253.7 nm; intensity, 75 µW cm-2 for 72 h (16 h of UV light and 8 h of darkness). Transcriptome analysis revealed 10,249 and 12,426 genes whose expressions were upregulated and downregulated, respectively, compared to the genes in the control. Furthermore, the differentially expressed genes included transcription factor-encoding genes and chloroplast- and photosystem-related genes. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to detect metabolite variations. Fifty metabolites, including amino acids and flavonoids, showed changes in levels after UV-B excess. Amino acid metabolism was changed by UV-B irradiation, and some amino acids interacted with precursors of different pathways that were used to synthesize secondary metabolites, i.e., flavonoids and phenylpropanoids. The metabolite content response to UV-B irradiation according to hierarchical clustering analysis showed changes in amino acids and flavonoids compared with those of the control. Amino acids might increase the function of scavengers of reactive oxygen species by synthesizing flavonoids that increase in response to UV-B treatment. This study enriches the annotated date palm unigene sequences and enhances the understanding of the mechanisms underlying UV-B stress through genetic manipulation. Moreover, this study provides a sequence resource for genetic, genomic and metabolic studies of date palm.


Assuntos
Phoeniceae/metabolismo , Phoeniceae/efeitos da radiação , Raios Ultravioleta/efeitos adversos , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Genes de Cloroplastos/efeitos da radiação , Genes de Plantas/efeitos da radiação , Redes e Vias Metabólicas/genética , Redes e Vias Metabólicas/efeitos da radiação , Anotação de Sequência Molecular , Fosforilação Oxidativa/efeitos da radiação , Phoeniceae/genética , Fotossíntese/efeitos da radiação , Folhas de Planta/genética , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Proteínas de Plantas/genética , RNA-Seq , Estresse Fisiológico/efeitos da radiação , Fatores de Transcrição/genética , Transcriptoma/efeitos da radiação
3.
Int J Mol Sci ; 22(3)2021 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-33530294

RESUMO

Light is an important cue that stimulates both plastid development and biosynthesis of carotenoids in plants. During photomorphogenesis or de-etiolation, photoreceptors are activated and molecular factors for carotenoid and chlorophyll biosynthesis are induced thereof. In fruits, light is absorbed by chloroplasts in the early stages of ripening, which allows a gradual synthesis of carotenoids in the peel and pulp with the onset of chromoplasts' development. In roots, only a fraction of light reaches this tissue, which is not required for carotenoid synthesis, but it is essential for root development. When exposed to light, roots start greening due to chloroplast development. However, the colored taproot of carrot grown underground presents a high carotenoid accumulation together with chromoplast development, similar to citrus fruits during ripening. Interestingly, total carotenoid levels decrease in carrots roots when illuminated and develop chloroplasts, similar to normal roots exposed to light. The recent findings of the effect of light quality upon the induction of molecular factors involved in carotenoid synthesis in leaves, fruit, and roots are discussed, aiming to propose consensus mechanisms in order to contribute to the understanding of carotenoid synthesis regulation by light in plants.


Assuntos
Vias Biossintéticas , Carotenoides/metabolismo , Desenvolvimento Vegetal , Fenômenos Fisiológicos Vegetais , Plastídeos/genética , Cloroplastos , Frutas/genética , Frutas/metabolismo , Luz , Fotossíntese , Folhas de Planta/genética , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Raízes de Plantas/efeitos da radiação
4.
Food Chem ; 347: 129005, 2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-33482487

RESUMO

Jujube leaf is well known for its high nutritional value and medicinal benefits. However, a thorough and dynamic assessment of the metabolites present in jujube leaves is lacking. Here, the primary and secondary metabolites from purple leaf buds and green mature leaves were investigated using ultra-high-performance liquid chromatography/tandem mass spectrometry. A total of 778 metabolites were characterized and more than 700 compounds were reported for the first time. Analysis of differentially accumulated metabolites showed that the flavonoids were the major differential metabolites and determined the leaf coloration. The transcriptome data indicated that 20 flavonoid structural genes and three main types of flavonoid regulatory genes were significantly differentially expressed. Moreover, light had a significant influence on flavonoid accumulation. These results improve our understanding of metabolite accumulation and the molecular mechanisms of flavonoid biosynthesis in jujube leaf.


Assuntos
Metaboloma , Transcriptoma , Ziziphus/metabolismo , Cromatografia Líquida de Alta Pressão , Cor , Análise Discriminante , Flavonoides/análise , Análise dos Mínimos Quadrados , Luz , Folhas de Planta/química , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Análise de Componente Principal , RNA de Plantas/metabolismo , Espectrometria de Massas em Tandem , Ziziphus/química , Ziziphus/genética
5.
Planta ; 253(2): 35, 2021 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-33459906

RESUMO

MAIN CONCLUSION: Growth temperature and light intensity are major drivers of phenolic accumulation in Lotus corniculatus resulting in major changes in carbon partitioning which significantly affects tissue digestibility and forage quality. The response of plant growth, phenolic accumulation and tissue digestibility to light and temperature was determined in clonal plants of three genotypes of Lotus corniculatus (birdsfoot trefoil) cv Leo, with low, intermediate or high levels of proanthocyanidins (condensed tannins). Plants were grown from 10 °C to 30 °C, or at light intensities from 20 to 500 µm m-2 s-1. Plants grown at 25 °C had the highest growth rate and highest digestibility, whereas the maximum tannin concentration was found in plants grown at 15 °C. Approximately linear increases in leaf flavonol glycoside levels were found with increasing growth temperature in the low tannin genotype. Tannin hydroxylation increased with increasing growth temperature but decreased with increasing light intensity. The major leaf flavonols were kaempferol glycosides of which kaempferol-3-glucoside and kaempferol-3,7-dirhamnoside were the major components. Increases in both tannin and total flavonol concentrations in leaves were linearly related to light intensity and were preceded by a specific increase in the transcript level of a non-legume type chalcone isomerase. Changes in growth temperature and light intensity, therefore, result in major changes in the partitioning of carbon into phenolics, which significantly affects tissue digestibility and nutritional quality with a high correlation between tannin concentration and leaf digestibility.


Assuntos
Luz , Lotus , Taninos , Temperatura , Lotus/genética , Lotus/metabolismo , Lotus/efeitos da radiação , Fenômenos Fisiológicos da Nutrição , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Taninos/metabolismo
6.
PLoS One ; 16(1): e0244758, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33471831

RESUMO

Pecan bacterial leaf scorch caused by Xylella fastidiosa is an emerging disease for the U.S. and international pecan industries and can be transmitted from scion to rootstock via grafting. With the expanse of global transportation and trade networks, phytosanitation is critical for reducing the spread of economically significant pathogens, such as X. fastidiosa. We developed and evaluated thermal treatments using microwave irradiation and microwave absorbers [sterile deionized water (dH2O) and carbon nanotubes (CNTs)] as novel disinfectant methods for remediating X. fastidiosa in pecan scions. Partial submergence of scions in dH2O or CNT dispersions resulted in the transport of microwave absorbers in the xylem tissue via transpiration but did not compromise plant health. The microwave absorbers effectively transferred heat to the scion wood to reach an average temperature range of 55-65°C. Microwave radiation exposure for 6 sec (3 sec for two iterations) of CNT- or dH2O-treated scions reduced the frequency of X. fastidiosa-positive in pecan scions without negatively affecting plant viability when compared to the control group (dH2O-treated with no microwave). The efficacy of the new thermal treatments based on microwave irradiation was comparable to the conventional hot-water treatment (HWT) method, in which scions were submerged in 46°C water for 30 min. Microwave irradiation can be employed to treat X. fastidiosa-infected scions where the conventional HWT treatment is not feasible. This study is the first report to demonstrate novel thermal treatment methods based on the microwave irradiation and microwave absorbers of dH2O and CNT as an application for the phytosanitation of xylem-inhabiting bacteria in graftwood.


Assuntos
Carya/microbiologia , Micro-Ondas , Saneamento/métodos , Xylella/efeitos da radiação , Carya/crescimento & desenvolvimento , Carya/efeitos da radiação , Nanotubos de Carbono/química , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/microbiologia , Folhas de Planta/efeitos da radiação , Temperatura , Água/química , Xilema/química , Xilema/metabolismo
7.
Plant Physiol Biochem ; 160: 166-174, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33497847

RESUMO

Aralia elata (Miq.) Seem is widely used as a medicinal plant and functional food in China. In this study, A. elata plants were exposed to full sunlight (CK), 40% shading (LS), 60% shading (MS), and >80% shading (ES) condition to investigate the effects of shading treatments on growth, stress levels, antioxidant enzymes activity, araloside content and related gene expression. The greatest growth and leaf biomass were achieved in 40% shading, and leaf biomass per plant increased by 16.09% compared to the non-shading treatment. Furthermore, the lowest reactive oxide species (ROS) production and lipid peroxidation resulting from increasing antioxidant enzyme activity were also observed in LS treatment. Overall, shading percentage negatively regulated the expression of key enzymes (squalene synthase, SS; squalene epoxidase, SE and ß-amyrin synthase, bAS) involved in the saponin biosynthesis, resulting in the greatest yields of total and four selected aralosides in A. elata leaves were achieved in sunlight group. However, the greatest yield of total saponin in the leaves was observed in the 40% shading group due to higher leaf biomass. The results suggest that optimizing the field growing conditions would be important for obtaining the greatest yield of bioactive components. Total saponin and selected aralosides also have a significant correlation with ROS production and antioxidant enzyme activity, these indicated the increased yield of these saponins may be part of a defense response. The study concludes that the production of saponin was the interaction of oxidative stress and photosynthesis.


Assuntos
Aralia , Escuridão , Folhas de Planta/efeitos da radiação , Saponinas/metabolismo , Triterpenos/metabolismo , Aralia/genética , Aralia/efeitos da radiação , Regulação da Expressão Gênica de Plantas
8.
J Sci Food Agric ; 101(1): 240-252, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33460178

RESUMO

BACKGROUND: Light-emitting diodes (LEDs) are widely used in closed-type plant production systems to improve biomass and accumulate bioactive compounds in plants. Perilla has been commonly used as herbal medicine because of its health-promoting effects. This study aimed to investigate the physiological and biochemical responses of green and red perilla under various visible-light spectra. RESULTS: Results showed that red (R) LEDs improved fresh weights of shoots and roots, plant height, internode length, node number and leaf area, as well as photosynthetic rate of green and red perilla plants compared to blue (B) LEDs and RB combined LEDs. Meanwhile, B resulted in higher stomatal conductance, transpiration rate and Fv/Fm compared to R. Supplementation of green (G) and far-red (FR) did not enhance perilla growth. Reduction or absence of B decreased leaf thickness, adaxial and abaxial epidermis, and palisade and spongy mesophyll. Total phenolic content, antioxidant capacity, rosmarinic acid content and caffeic acid content of green perilla were higher under R, R8B2 and RGB + FR, while greater values were obtained in red perilla under R. Accumulation of perillaldehyde, luteolin and apigenin presented different trends from those of rosmarinic and caffeic acids in both cultivars. CONCLUSIONS: Growth and accumulation of bioactive compounds in green perilla were greater than in red perilla under similar light quality, and R LEDs or a higher R ratio in combination treatments were suitable for cultivating high-quality green and red perilla plants in closed-type plant factories. © 2020 Society of Chemical Industry.


Assuntos
Perilla/efeitos da radiação , Folhas de Planta/química , Apigenina/análise , Apigenina/metabolismo , Luz , Luteolina/análise , Luteolina/metabolismo , Monoterpenos/análise , Monoterpenos/metabolismo , Perilla/química , Perilla/crescimento & desenvolvimento , Perilla/metabolismo , Extratos Vegetais/química , Extratos Vegetais/metabolismo , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação
9.
Plant Physiol Biochem ; 159: 43-52, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33338819

RESUMO

An experiment was set up to investigate physiological responses of soybeans to silicon (Si) under normal light and shade conditions. Two soybean varieties, Nandou 12 (shade resistant), and Nan 032-4 (shade susceptible), were tested. Our results revealed that under shading, the net assimilation rate and the plant growth were significantly reduced. However, foliar application of Si under normal light and shading significantly improved the net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and decreased intercellular carbon dioxide concentration (Ci). The net photosynthetic rate of Nandou 12 under normal light and shading increased by 46.4% and 33.3% respectively with Si treatment (200 mg/kg) compared to controls. Si application also enhanced chlorophyll content, soluble sugars, fresh weight, root length, root surface area, root volume, root-shoot ratio, and root dry weight under both conditions. Si application significantly increased the accumulation of some carbohydrates such as soluble sugar and sucrose in stems and leaves ensuring better stem strength under both conditions. Si application significantly increased the yield by increasing the number of effective pods per plant, the number of beans per plant and the weight of beans per plant. After Si treatment, the yield increased 24.5% under mono-cropping, and 17.41% under intercropping. Thus, Si is very effective in alleviating the stress effects of shading in intercropped soybeans by increasing the photosynthetic efficiency and lodging resistance.


Assuntos
Carbono , Luz , Folhas de Planta , Silício , Soja , Carbono/metabolismo , Clorofila/metabolismo , Fotossíntese/efeitos dos fármacos , Fotossíntese/efeitos da radiação , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Silício/farmacologia , Soja/efeitos dos fármacos , Soja/efeitos da radiação
10.
J Sci Food Agric ; 101(2): 424-432, 2021 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-32648588

RESUMO

BACKGROUND: Pesticides have been widely used to control pests on agricultural products in China, and large amounts of pesticide residues have caused a serious threat to human health. Thus, developing a high-efficiency pesticide degradation method for fresh vegetables represents a great challenge. The present study investigated the effects of dielectric barrier discharge (DBD) plasma on the degradation of malathion and chlorpyrifos in aqueous solutions and on lettuces. RESULTS: DBD treatment significantly degraded malathion and chlorpyrifos in water and on lettuce. After cold plasma treatment at 80 kV for 180 s, the degradation efficiency of malathion (0.5 µg mL-1 ) and chlorpyrifos (1.0 µg mL-1 ) in aqueous solutions reached 64.6% and 62.7%, respectively. The degradation intermediates were explored by HPLC-mass spectrometry and the DBD plasma degradation pathways of malathion and chlorpyrifos were proposed. There was no significant damage to the quality of lettuces, including color and chlorophyll content, after plasma treatment. Ascorbic acid decreased significantly during long-term treatment with DBD plasma. To ensure the quality of lettuces during processing, the treatment time was shortened to 120 s. Under this condition, the degradation efficiency of malathion (0.5 mg kg-1 ) and chlorpyrifos (1.0 mg kg-1 ) on lettuces was found to be 53.1% and 51.4%. More importantly, we noted that cold plasma treatment significantly inactivated the microorganisms on lettuces. CONCLUSION: The results of the present study show that cold plasma is an effective and safe method for the degradation of organic pesticide residues on fresh vegetables at the same time as retaining the original quality. © 2020 Society of Chemical Industry.


Assuntos
Clorpirifos/química , Contaminação de Alimentos/prevenção & controle , Manipulação de Alimentos/métodos , Alface/efeitos dos fármacos , Malation/química , Resíduos de Praguicidas/química , Folhas de Planta/química , Gases em Plasma/farmacologia , Contaminação de Alimentos/análise , Manipulação de Alimentos/instrumentação , Cinética , Alface/química , Folhas de Planta/efeitos da radiação , Poluentes Químicos da Água/química
11.
Plant Physiol Biochem ; 154: 353-359, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32912481

RESUMO

Our aim was to understand how moderately increased light intensities influenced the response of chickpea to high temperature. Three chickpea genotypes (Acc#3, Acc#7 and Acc#8) were treated at control (26 °C and 300 µmol m-2 s-1 photosynthetic photon flux density/PPFD), high temperature (38 °C and 300 µmol m-2 s-1 PPFD), increased light intensity (26 °C and 600 µmol m-2 s-1 PPFD) and combination of increased light and temperature (38 °C and 600 µmol m-2 s-1 PPFD). The net photosynthetic rate (PN) of Acc#3 and Acc#8 significantly decreased at high temperature regardless of light intensity. The PN of all three genotypes at increased light intensity was significantly higher than that at high temperature. The intracellular CO2 concentration (Ci), stomatal conductance (gs) and transpiration rate (E) of Acc#3 and Acc#8 at increased light intensity with or without high temperature significantly decreased in comparison with control and individually high temperature treatment. The relative water content of Acc#3 at high temperature and the combination treatment decreased as compared with control. The relative water content of Acc#7 at control was higher than the other three treatments. The Fv/Fm (Maximum quantum efficiency of photosystem II) of leaves from the three genotypes at 38 °C were lower than at 26 °C regardless of light intensity. The high temperature decreased chlorophyll content in the lower bottom leaf of Acc#7 and Acc#8 than control. In conclusion, chickpeas showed a higher net photosynthetic rate at increased light intensity to withstand heat stress, which was genotype-dependent. Physiological responses of different chickpea genotypes to increased temperature and light intensity indicated that distinct responsive mechanism of photosynthesis. This study provides information on how chickpea respond to high temperature and increased light intensity, which will help us to improve chickpea to deal with future climate changes.


Assuntos
Cicer/fisiologia , Genótipo , Temperatura Alta , Luz , Fotossíntese , Clorofila , Cicer/genética , Cicer/efeitos da radiação , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação
12.
Plant Physiol Biochem ; 154: 429-438, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32912483

RESUMO

Hyperspectral analysis represents a powerful technique for diagnostics of morphological and chemical information from aboveground parts of the plants, but the real potential of the method in pre-screening of phenolics in leaves is still insufficiently explored. In this study, assessment of the sensitivity and reliability of non-invasive methods of various phenolic compounds, also analyzed by HPLC in chicory plants (Cichorium intybus L.) exposed to various color light pretreatments was done. The hyperspectral records in visible and near infrared (VNIR) spectra were recorded using a handheld spectrometer and relationships between the specific hyperspectral parameters and the contents of tested phenolic compounds in chicory leaves were analyzed. Moreover, the correlations between the hyperspectral parameters and related parameters derived from the multispectral fluorescence records were assessed to compare the sensitivity of both techniques. The results indicated a relatively high correlation of anthocyanin-related parameters (ARI, mARI, mACI indices) with the content of some of tested phenolic compounds (quercetin-3-gluconuride, isorhamnetine-3-gluconuride, etc.), as well as with fluorescence ANTH index. Similar trends were observed in flavonoid parameter based on the near infra-red spectral bands (700, 760 nm), which expressed a high correlation with chlorogenic acid. On the other hand, the most frequently used flavonoid (FLAVI) indices based on UV-to-blue band reflectance showed very weak correlations with phenolic compounds, as well as with fluorescence FLAV index. The detailed analysis of the correlation between reflectance and fluorescence flavonoid parameters has shown that the parameters based on spectral reflectance are sensitive to increase of UV-absorbing compounds from low to moderate values, but, unlike the fluorescence parameter, they are not useful to recognize a further increase from middle to high or very high contents. Thus, our results outlined the possibilities, but also the limits of the use of hyperspectral analysis for rapid screening phenolic content, providing a practical evidence towards more efficient production of bioactive compounds for pharmaceutical or nutraceutical use.


Assuntos
Chicória/química , Luz , Fenóis/análise , Chicória/efeitos da radiação , Flavonoides/análise , Folhas de Planta/química , Folhas de Planta/efeitos da radiação , Reprodutibilidade dos Testes
13.
PLoS One ; 15(7): e0235918, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32645090

RESUMO

Leaves of lettuce, pepper, tomato and grapevine plants grown in greenhouse conditions were exposed to UV-C light for either 60 s or 1 s, using a specific LEDs-based device, and wavelengths and energy were the same among different light treatments. Doses of UV-C light that both effectively stimulated plant defences and were innocuous were determined beforehand. Tomato plants and lettuce plants were inoculated with Botrytis cinerea, pepper plants with Phytophthora capsici, and grapevine with Plasmopara viticola. In some experiments we investigated the effect of a repetition of treatments over periods of several days. All plants were inoculated 48 h after exposure to the last UV-C treatment. Lesions on surfaces were measured up to 12 days after inoculation, depending on the experiment and the pathogen. The results confirmed that UV-C light stimulates plant resistance; they show that irradiation for one second is more effective than irradiation for 60 s, and that repetition of treatments is more effective than single light treatments. Moreover a systemic effect was observed in unexposed leaves that were close to exposed leaves. The mechanisms of perception and of the signalling and metabolic pathways triggered by flashes of UV-C light vs. 60 s irradiation exposures are briefly discussed, as well as the prospects for field use of UV-C flashes in viticulture and horticulture.


Assuntos
Alface/efeitos da radiação , Lycopersicon esculentum/efeitos da radiação , Piper/efeitos da radiação , Raios Ultravioleta , Botrytis/patogenicidade , Clorofila/química , Alface/microbiologia , Lycopersicon esculentum/microbiologia , Redes e Vias Metabólicas/efeitos dos fármacos , Phytophthora/patogenicidade , Piper/parasitologia , Doenças das Plantas/microbiologia , Doenças das Plantas/parasitologia , Doenças das Plantas/prevenção & controle , Folhas de Planta/microbiologia , Folhas de Planta/parasitologia , Folhas de Planta/efeitos da radiação , Transdução de Sinais/efeitos dos fármacos
14.
PLoS One ; 15(6): e0231611, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32555603

RESUMO

Plants respond to changes in ultraviolet (UV) radiation both morphologically and physiologically. Among the variety of plant UV-responses, the synthesis of UV-absorbing flavonoids constitutes an effective non-enzymatic mechanism to mitigate photoinhibitory and photooxidative damage caused by UV stress, either reducing the penetration of incident UV radiation or acting as quenchers of reactive oxygen species (ROS). In this study, we designed a UV-exclusion experiment to investigate the effects of UV radiation in Silene littorea. We spectrophotometrically quantified concentrations of both anthocyanins and UV-absorbing phenolic compounds in petals, calyces, leaves and stems. Furthermore, we analyzed the UV effect on the photosynthetic activity in hours of maximum solar radiation and we tested the impact of UV radiation on male and female reproductive performance. We found that anthocyanin concentrations showed a significant decrease of about 20% with UV-exclusion in petals and stems, and a 30% decrease in calyces. The concentrations of UV-absorbing compounds under UV-exclusion decreased by approximately 25% in calyces and stems, and 12% in leaves. Photochemical efficiency of plants grown under UV decreased at maximum light stress, reaching an inhibition of 58% of photosynthetic activity, but their ability to recover after light-stress was not affected. In addition, exposure to UV radiation did not affect ovule production or seed set per flower, but decreased pollen production and total seed production per plant by 31% and 69%, respectively. Our results demonstrate that UV exposure produced opposing effects on the accumulation of plant phenolic compounds and reproduction. UV radiation increased the concentration of phenolic compounds, suggesting a photoprotective role of plant phenolics against UV light, yet overall reproduction was compromised.


Assuntos
Fenóis/análise , Silene/química , Raios Ultravioleta , Antocianinas/análise , Antocianinas/metabolismo , Fenóis/metabolismo , Fotossíntese/efeitos da radiação , Folhas de Planta/química , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Caules de Planta/química , Caules de Planta/metabolismo , Caules de Planta/efeitos da radiação , Estações do Ano , Sementes/química , Sementes/metabolismo , Silene/crescimento & desenvolvimento , Silene/efeitos da radiação
15.
Biochim Biophys Acta Bioenerg ; 1861(9): 148235, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32485160

RESUMO

Photosynthetic electron flux from water via photosystem II (PSII) and PSI to oxygen (water-water cycle) may act as an alternative electron sink under fluctuating light in angiosperms. We measured the P700 redox kinetics and electrochromic shift signal under fluctuating light in 11 Camellia species and tobacco leaves. Upon dark-to-light transition, these Camellia species showed rapid re-oxidation of P700. However, this rapid re-oxidation of P700 was not observed when measured under anaerobic conditions, as was in experiment with tobacco performed under aerobic conditions. Therefore, photo-reduction of O2 mediated by water-water cycle was functional in these Camellia species but not in tobacco. Within the first 10 s after transition from low to high light, PSI was highly oxidized in these Camellia species but was over-reduced in tobacco leaves. Furthermore, such rapid oxidation of PSI in these Camellia species was independent of the formation of trans-thylakoid proton gradient (ΔpH). These results indicated that in addition to ΔpH-dependent photosynthetic control, the water-water cycle can protect PSI against photoinhibition under fluctuating light in these Camellia species. We here propose that the water-water cycle is an overlooked strategy for photosynthetic regulation under fluctuating light in angiosperms.


Assuntos
Camellia/metabolismo , Camellia/efeitos da radiação , Luz , Complexo de Proteína do Fotossistema I/metabolismo , Água/metabolismo , Transporte de Elétrons/efeitos da radiação , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação
16.
Plant Physiol Biochem ; 152: 232-242, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32449682

RESUMO

Growing conditions at different tree canopy positions may significantly vary and lead to foliar changes even within the same tree. An assessment of foliar anatomy, including also epidermal features, can help us understand how plants respond to environmental factors. Working with two model tree species (i.e., Quercus petraea and Fagus sylvatica) grown at their southernmost European distribution area in Central Spain, the influence of irradiation and canopy height was examined by sampling lower canopy leaves and comparing them with fully irradiated, top canopy leaves and shaded top canopy leaves grown for months within a bag made of shade netting fabric before they sprouted. At the end of the summer, samples were collected, and several parameters were analysed. The results indicate that SLA (specific leaf area) differences are significant both between species and groups. Leaf and cuticle thickness differed significantly between groups while stomatal densities only between species. Regarding mineral concentrations, differences between species were significant for K, Mn, N and N: P ratios. It is concluded that leaf responses to environmental conditions may be variable both within the same tree and between species.


Assuntos
Fagus , Folhas de Planta/anatomia & histologia , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação , Quercus , Escuridão , Fotossíntese , Estômatos de Plantas , Espanha , Luz Solar , Árvores
17.
Biochim Biophys Acta Bioenerg ; 1861(8): 148211, 2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32315624

RESUMO

Flavodoxins are electron carrier flavoproteins present in bacteria and photosynthetic microorganisms which duplicate the functional properties of iron-sulphur containing ferredoxins and replace them under adverse environmental situations that lead to ferredoxin decline. When expressed in plant chloroplasts, flavodoxin complemented ferredoxin deficiency and improved tolerance to multiple sources of biotic, abiotic and xenobiotic stress. Analysis of flavodoxin-expressing plants grown under normal conditions, in which the two carriers are present, revealed phenotypic effects unrelated to ferredoxin replacement. Flavodoxin thus provided a tool to alter the chloroplast redox poise in a customized way and to investigate its consequences on plant physiology and development. We describe herein the effects exerted by the flavoprotein on the function of the photosynthetic machinery. Pigment analysis revealed significant increases in chlorophyll a, carotenoids and chlorophyll a/b ratio in flavodoxin-expressing tobacco lines. Results suggest smaller antenna size in these plants, supported by lower relative contents of light-harvesting complex proteins. Chlorophyll a fluorescence and P700 spectroscopy measurements indicated that transgenic plants displayed higher quantum yields for both photosystems, a more oxidized plastoquinone pool under steady-state conditions and faster plastoquinone dark oxidation after a pulse of saturating light. Many of these effects resemble the phenotypes exhibited by leaves adapted to high irradiation, a most common environmental hardship faced by plants growing in the field. The results suggest that flavodoxin-expressing plants would be better prepared to cope with this adverse situation, and concur with earlier observations reporting that hundreds of stress-responsive genes were induced in the absence of stress in these lines.


Assuntos
Aclimatação/efeitos da radiação , Flavodoxina/genética , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Luz , Fotossíntese/efeitos da radiação , Folhas de Planta/genética , Tabaco/metabolismo , Relação Dose-Resposta à Radiação , Fenótipo , Folhas de Planta/efeitos da radiação , Tabaco/genética , Tabaco/fisiologia , Tabaco/efeitos da radiação
18.
Int J Mol Sci ; 21(5)2020 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-32131496

RESUMO

Leaf senescence is the final stage of plant development. Many internal and external factors affect the senescence process in rice (Oryza sativa L.). In this study, we identified qCC2, a major quantitative trait locus (QTL) for chlorophyll content using a population derived from an interspecific cross between O. sativa (cv. Hwaseong) and Oryza grandiglumis. The O. grandiglumis allele at qCC2 increased chlorophyll content and delayed senescence. GW2 encoding E3 ubiquitin ligase in the qCC2 region was selected as a candidate for qCC2. To determine if GW2 is allelic to qCC2, a gw2-knockout mutant (gw2-ko) was examined using a dark-induced senescence assay. gw2-ko showed delayed leaf senescence in the dark with down-regulated expression of senescence-associated genes (SAGs) and chlorophyll degradation genes (CDGs). The association of the GW2 genotype with the delayed senescence phenotype was confirmed in an F2 population. RNA-seq analysis was conducted to investigate 30-day-old leaf transcriptome dynamics in Hwaseong and a backcross inbred line-CR2002-under dark treatment. This resulted in the identification of genes involved in phytohormone signaling and associated with senescence. These results suggested that transcriptional regulation was associated with delayed senescence in CR2002, and RING-type E3 ubiquitin ligase GW2 was a positive regulator of leaf senescence in rice.


Assuntos
Clorofila/metabolismo , Oryza/genética , Folhas de Planta/genética , Proteínas de Plantas/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Clorofila/genética , Oryza/crescimento & desenvolvimento , Oryza/metabolismo , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Proteínas de Plantas/genética , Locos de Características Quantitativas , Luz Solar , Transcriptoma , Ubiquitina-Proteína Ligases/genética
19.
Plant Physiol Biochem ; 151: 1-9, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32179467

RESUMO

Light and temperature are two primary environmental factors for plant growth and development. The response of plants to multiple stresses of high light intensity and heat stress are complex. The priming effects of high light and heat stress on improving heat tolerance of plants need to be further illuminated. This study aimed to explain the effect of high light intensity, high temperature and their combination on tomato and clarify the response of tomato to heat stress after priming. Tomato plants were treated under control, high light, heat stress and the combination for the first-round treatments, followed by recurring heat stress as the second-round treatments. For the first-round treatments, the net photosynthetic rate (PN) of the plants at individual high light and individual high temperature on day four significantly increased and decreased, respectively, as compared with control. Combined stress caused significant reduction in Fv/Fm (maximum quantum efficiency of photosystem II) and chlorophyll content as well as increase in carotenoids and carbohydrates content. No significant difference in the PN was observed in tomato with and without priming; however, heat priming did improve the heat avoidance ability by increasing evaporation and decreasing leaf temperature. Overall, the high light affected the physiological response of tomatoes at heat stress. The tomato plants developed their defense systems including chlorophyll loss and synthesis of carotenoids to protect themselves from multiple stresses. Our work provided new insights into the understanding of plants response to high light and heat stress.


Assuntos
Resposta ao Choque Térmico , Temperatura Alta , Luz , Lycopersicon esculentum/fisiologia , Folhas de Planta/fisiologia , Clorofila , Lycopersicon esculentum/efeitos da radiação , Fotossíntese , Folhas de Planta/efeitos da radiação
20.
Plant Physiol Biochem ; 151: 10-20, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32179468

RESUMO

Soldanella alpina differing in leaf epidermal UV-A absorbance (DEA375), as measured with the Dualex, was investigated as a model alpine plant for the flavonoid (Flav) composition and concentration and for anatomical and pigment characteristics. In sun leaves, twenty-three flavones were characterised by their mass formula, their maximum absorption, their glycosylation, their methylation and dehydroxylation pattern. The flavones belonged to four subfamilies (tetra-hydroxy-flavones, penta-hydroxy-flavones, penta-hydroxy-methyl-flavones and tri-hydroxy-di-methoxy-flavones), abundant in sun and shade leaves. Their concentration was estimated by their absorption at 350 nm after HPLC separation. Sun leaves contained relatively higher contents of penta-hydroxy-methyl-flavones and shade leaves higher contents of tetra-hydroxy-flavones. The flavones were present mainly in vacuoles, all over the leaf. After shade-sun transfer, the content of most flavones increased, irrespective of the presence or absence of UV radiation. Highly significant correlations with the log-transformed DEA375 suggest that DEA375 can be readily applied to predict the flavone content of S. alpina leaves. Shade-sun transfer of leaves decreased the hydroxycinnamic acid (HCA) content, the mass-based chlorophyll (Chl) a+b content and the Chl/Carotenoid (Car) ratio but increased DEA375, and the Car content. Together with previously reported anatomical characteristics all these parameters correlated significantly with the DEA375. The Flav content is therefore correlated to most of the structural characteristics of leaf acclimation to light and this can be probed in situ by DEA375.


Assuntos
Aclimatação , Folhas de Planta/fisiologia , Primulaceae/fisiologia , Raios Ultravioleta , Carotenoides/análise , Clorofila/análise , Flavonoides/análise , Fotossíntese , Folhas de Planta/efeitos da radiação , Primulaceae/efeitos da radiação , Luz Solar
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