Exogenous Application Of Ascorbic Acid Research Articles

Exogenous application of ascorbic acid improves physiological and productive traits of Nigella sativa

For thousands of years, plants have been utilized for medicinal purposes. For its naturally existing antibacterial properties, Nigella sativa is one of the most researched herbs. A study was conducted during rabi 2020-21 at The University of Haripur in order to evaluate the potential of ascorbic acid as plant growth enhancer. Two concentrations of ascorbic acid i-e 350 μm and 400 μm were sprayed along with control and water only spray on Nigella sativa crop. The study was arranged in RCBD two factor factorial arrangement. Factor A: ascorbic acid concentrations along with control and water spray, factor B: Growth stages (Stage1 = 40 days after sowing, Stage 2 = 80 DAS, Stage 3 = 120 DAS, Stage 4 = 40 + 80 DAS, Stage 5 = 40 + 120 DAS, Stage 6 = 80 + 120 DAS, Stage 7 = 40 + 80 + 120 DAS). Crop was sown in first week of November. Results reviled that chlorophyll b content, fixed oil content, 1000 seed weight, grain yield, Photosynthetic rate (μ mole m−2s−1), Transpiration rate (mmole m−2s−1), photosynthetic water use efficiency, Internal CO2 concentration (Ci) of leaf tissue and Stomatal conductance (mmole m−2s−1) were significantly affected by ascorbic acid concentrations and stage of application. Crop growth rate increased by 19.88% and 17.29%, chlorophyll b by 12.3% and 11.2%, fixed oil by 11.7% and 9%, grain yield by 10.29% and 9.8%, harvest index by 4% and 5.7% photosynthetic rate by 33%, 20% and stomatal conductance by 24.24% and 24.25 with application of ascorbic acid @ 350 μm, over control and water spray respectively. On the basis of these results it is concluded that application of ascorbic acid at the rate of 350 μm, followed by ascorbic acid at the rate of 400 μm significantly improves black cumin (Nigella sativa) yield and production. Hence it is recommended to apply ascorbic acid at the rate of 350 μm at 40 + 80+120 days after sowing of Nigella sativa crop for obtaining maximum results.

Physiological characterization, antioxidant potential, and bacterial survival of soybean sprouts subjected to pre- and post-harvest low intensity ultrasound and exogenous ascorbic acid application

The effects of individual ultrasound (US) and ascorbic acid (AsA), as well as their combination on the phytochemical composition and antioxidant activity of soybean sprouts, were studied. Present results showed that the application of US (100 W) improved the sprouting potential of sprouts, while combined treatment of US (100 W) and AsA (1%, w/v) gathered the highest biomass with the enhancement of AsA accumulation and sugar consumption in sprouts. Elicitation with both US and AsA markedly enhanced the content of proline and total phenolics, further resulting in the elevated antioxidant capacity in sprouts, as evidenced by the higher observation values of antioxidant enzyme (SOD, CAT, POD, and PAL) activities and radical scavenging capacities. Furthermore, simultaneous treatment of US and AsA exhibited excellent antibacterial activity against Escherichia coli and Salmonella enteritidis without the alteration of color in soybean sprouts. Thus, these results indicated that combined elicitation of US and AsA could serve as a sustainable strategy for improving the physicochemical characteristics, functional attributes, and microbial inactivation efficacy of soybean sprouts.

Exogenous Application of Ascorbic Acid to Induce Tolerance Against Salt Stress in Common Bean Plants

Common beans have an important place in the world due to its high nutritional values in the human diet and with the largest cropping area among the legumes. Besides, they are named as quite sensitive to salt stress. Salinity is one of the utmost abiotic stress factors limiting agricultural production, which affects plant growth and development at different levels. Lately, exogenous applications of signalling and/or protective molecules to various parts of plants are used to combat salt stress before or at the time of stress. In this context, this research was conducted to assess the influence of foliar-applied ascorbic acid (AsA) on electrolyte leakage (EL), activity of antioxidative enzymes, total protein (TSP) content and protein profiles in the two common bean genotypes (salt-sensitive “Local Genotype” and salt-tolerant “Şeker Fasulye”) at early growth stage under salinity (0, 50, 100, 150 mM NaCl). The genotypes were exposed to salt stress from fully developed true leaf at the third nodes emerged stage for two weeks, meanwhile 3 mM AsA was foliar-applied every three days. Salt stress increased EL in both genotypes and exogenous AsA application decreased EL value especially in “Local Genotype”. Foliar-applied AsA generally reduced the adverse effects of NaCl on AsA content of both genotypes. Exogenous AsA application also increased the activities of catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) in the salt-stressed common bean plants and did not play a role in the TSP content. However, it has been determined that SDS-PAGE protein profiles represent adaptive mechanisms for dealing with excess salt in common bean genotypes. The results suggested that foliar-applied AsA was effective in reducing the adverse effects of salinity especially in relatively salt sensitive common bean genotype.

Germination and Growth Performance of Seedlings Of Ascorbic Acid, Silicon and Gibberellic Acid Treated Secondary Seed of Wheat Under Salt Stress

Considering the effect of salt stress on morph-physiological and biochemical changes of wheat (Triticum aestivum L. var. BARI Gom-26) as well as mitigation of the adverse effect through exogenous application of Ascorbic Acid (AsA), Silicon (Si) and Gibberellic Acid (GA3), the experiment was conducted at Department of Agronomy, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh. In the field experiment, four levels of salt stress (0, 50, 80, 120 mM NaCl) were applied at 20 days after sowing and grown up to harvest. AsA (2 mM ascorbic acid), Si (200 μM SiO2), GA3 (100 μM gibberellic acid) were applied as foliar spraying at 20 days interval. Seeds were collected from the field experiment which used as secondary seeds as planting materials for second experiment to evaluate the influence of AsA, Si and GA3 on growth performance and physiological attributes of seedlings under salt stress. Experiment revealed that AsA, Si and GA3 enhanced the germination and growth performance of seedling under salinity stress. Overall, GA3 significantly increased the seed germination (%) and seedling growth parameters, while silicon mostly improved the fresh weight and chlorophyll (a, b and a+b) and AsA showed better relative water contents with other parameters. Considering the results of experiments, GA3 performed better than the AsA and Si in mitigating salt stress.
 Bangladesh Agron. J. 2022, 25(1): 115-128

Impacts of Ascorbic Acid and Alpha-Tocopherol on Chickpea (Cicer arietinum L.) Grown in Water Deficit Regimes for Sustainable Production

Drought is a major abiotic stress forced by the changing climate that affects plant production and soil structure and functions. A study was conducted to explore the impacts of ascorbic acid (AsA) and α-tocopherol (α-toc) on the agro-physiological attributes and antioxidant enzymes of chickpea grown in water deficit regions. The results of the soil analysis showed that the electrical conductivity (EC) and pH were decreased from 521 mS/m and 7.08 to 151 mS/m and 6.6 in 20-day drought regimes, respectively. Agronomic outcomes showed that exogenous application of AsA and α-toc increased the germination rate index (GRI), mean germination time (MGT), germination energy (GE), water use efficiency (WUE), germination percentage (GP), and seed vigor index (SVI). However, all the above attributes experienced a decline under 10- and 20-day drought stress. Similarly, the Chl. a, Chl. b, carotenoids, proline, protein, sugar, glycine betaine, and hydrogen peroxide contents were significantly increased. Meanwhile, malondialdehyde, glutathione reductase, and enzymatic antioxidants (APOX, SOD, and POD) increased during 10- and 20-day drought, except CAT, which decreased during drought. The exogenous fertigation of these growth regulators improved the photosynthetic pigments and enzymatic and non-enzymatic antioxidants in stressed plants. The current research concludes that simultaneous dusting of AsA and α-toc could be an efficient technique to mitigate the antagonistic impacts of drought, which might be linked to the regulation of antioxidant defense systems.

Ascorbic Acid Influences on Growth and Yield of Tomato

Reactive oxygen species (ROS) generated in various metabolic reactions in plants are mostly known for toxicity. Whereas ascorbic acid (AsA) involves in various physiological and biochemical processes; and acts as a ROS scavenger. Therefore, the experiment was conducted to investigate the effects of exogenous application of AsA on growth and yield of tomato plants. The ROS scavenger AsA was applied in the leaves of tomato plants in four treatment combinations (T1-Control; T2-0.5 mM; T3-2.0 mM and T4-4.0 mM) with three replications. Among the treatments, AsA at 4.0 mM (T4) efficiently increased leaf length (12%), inflorescence length (17%), and flower number (29%) than the untreated control plants. AsA at 0.5 and 2.0 mM also showed positive effects on the plant morphology to a lesser extent. Importantly, AsA at 4.0 mM increased yield by 18% than the control treatment. In physiochemical parameters, AsA at 4.0 mM (T4) was retained 64.07% higher chlorophyll content than the control plant even after 60 days of application. Exogenous application of AsA effectively reduced oxidative stress of the plant, which was attributed to the less accumulation of H2O2 and lipid peroxidation of membrane lipids. AsA at 4.0 mM decreased H2O2 and MDA accumulation by 39% and 45%, respectively, compared with the control plants. Therefore, exogenous application of AsA is a useful tool to enhance growth and yield of tomato under field conditions by lowering the accumulation of ROS and lipid peroxidation. Ann. Bangladesh Agric. (2021) 25 (1) : 55-65

Modulation of Antioxidant Activity Enhances Photoautotrophic Cell Growth of Rhodobacter sphaeroides in Microbial Electrosynthesis

Global warming is currently accelerating due to an increase in greenhouse gas emissions by industrialization. Microbial electrosynthesis (MES) using electroactive autotrophic microorganisms has recently been reported as a method to reduce carbon dioxide, the main culprit of greenhouse gas. However, there are still few cases of application of MES, and the molecular mechanisms are largely unknown. To investigate the growth characteristics in MES, we carried out growth tests according to reducing power sources in Rhodobacter sphaeroides. The growth rate was significantly lower when electrons were directly supplied to cells, compared to when hydrogen was supplied. Through a transcriptome analysis, we found that the expression of reactive oxygen species (ROS)-related genes was meaningfully higher in MES than in normal photoautotrophic conditions. Similarly, endogenous contents of H2O2 were higher and peroxidase activities were lower in MES. The exogenous application of ascorbic acid, a representative biological antioxidant, promotes cell growth by decreasing ROS levels, confirming the inhibitory effects of ROS on MES. Taken together, our observations suggest that reduction of ROS by increasing antioxidant activities is important for enhancing the cell growth and production of CO2-converting substances such as carotenoids in MES in R. sphaeroides

Exogenous ascorbic acid application alleviates cadmium toxicity in seedlings of two wheat (Triticum aestivum L.) varieties by reducing cadmium uptake and enhancing antioxidative capacity.

The aggravation of soil cadmium (Cd) pollution is a serious threat to human food health and safety. To reduce Cd uptake and alleviate Cd toxicity in staple food of wheat, a completely random experiment was performed to investigate the effect of exogenous ascorbic acid (AsA) on Cd toxicity in two wheat varieties (L979 and H27). In this study, the treatments with combinations of Cd (0, 5, and 10µmol L-1) and AsA (0, 50, and 200µmol L-1) were applied in a hydroponic system. Toxicity induced by Cd inhibited biomass accumulation; decreased wheat growth, photosynthesis, and chlorophyll content; increased lipid peroxidation; and reduced activity of superoxide dismutase (SOD), but stimulated catalase (CAT) and peroxidase (POD). The addition of AsA significantly improved the growth status by increasing the wheat biomass, chlorophyll content, photosynthetic rate, protein concentrations, and antioxidant enzyme activity. Besides, AsA significantly decreased Cd concentration of shoot and root by 14.1-53.9% and 20.8-59.5% in L979 and 23.7-58.8% and 22.1-58.1% in H27 under Cd5, and 23.7-53.6% and 16.6-57.1% in L979 and 21.5-51.6% and 15.3-54.0% in H27 under Cd10, respectively. Malondialdehyde (MDA) accumulation was decreased remarkably with the addition of AsA by 31.2-32.9% in L979 and 27.1-45.2% in H27 under Cd10, respectively. Overall, exogenous application of AsA alleviated the Cd toxicity in wheat plants by improving the wheat growth, soluble protein content, photosynthesis, and antioxidant defense systems, and decreasing MDA accumulation.

Comparative physiological and transcriptomic analyses reveal ascorbate and glutathione coregulation of cadmium toxicity resistance in wheat genotypes

BackgroundCadmium (Cd) is a heavy metal with high toxicity that severely inhibits wheat growth and development. Cd easily accumulates in wheat kernels and enters the human food chain. Genetic variation in the resistance to Cd toxicity found in wheat genotypes emphasizes the complex response architecture. Understanding the Cd resistance mechanisms is crucial for combating Cd phytotoxicity and meeting the increasing daily food demand.ResultsUsing two wheat genotypes (Cd resistant and sensitive genotypes T207 and S276, respectively) with differing root growth responses to Cd, we conducted comparative physiological and transcriptomic analyses and exogenous application tests to evaluate Cd detoxification mechanisms. S276 accumulated more H2O2, O2−, and MDA than T207 under Cd toxicity. Catalase activity and levels of ascorbic acid (AsA) and glutathione (GSH) were greater, whereas superoxide dismutase (SOD) and peroxidase (POD) activities were lower in T207 than in S276. Transcriptomic analysis showed that the expression of RBOHA, RBOHC, and RBOHE was significantly increased under Cd toxicity, and two-thirds (22 genes) of the differentially expressed RBOH genes had higher expression levels in S276 than inT207. Cd toxicity reshaped the transcriptional profiling of the genes involving the AsA-GSH cycle, and a larger proportion (74.25%) of the corresponding differentially expressed genes showed higher expression in T207 than S276. The combined exogenous application of AsA and GSH alleviated Cd toxicity by scavenging excess ROS and coordinately promoting root length and branching, especially in S276.ConclusionsThe results indicated that the ROS homeostasis plays a key role in differential Cd resistance in wheat genotypes, and the AsA-GSH cycle fundamentally and vigorously influences wheat defense against Cd toxicity, providing insight into the physiological and transcriptional mechanisms underlying Cd detoxification.

Wheat Cultivar Growth, Biochemical, Physiological and Yield Attributes Response to Combined Exposure to Tropospheric Ozone, Particulate Matter Deposition and Ascorbic Acid Application.

In the present study wheat (Triticum aestivum) cultivar HD 2967 was exposed to ambient and elevated levels of O3 and PM deposition, with and without exogenous application of ascorbic acid (AA). Cultivar HD 2967 exposed to eight treatments in free air O3 enrichment facility and the assessed results showed that wheat cultivar, growth, biochemical, physiological and yield attributes were variably but adversely affected by combined exposure to O3 and PM deposition. PM deposition clogged stomata and enhanced leaf temperature. However, plants exposed to O3 and PM deposition and treated with AA exhibited less reduction in yield as compared to plants exposed to O3 and PM deposition without AA treatment. The decline in grain yield of HD 2967 due to combined exposure of O3 and PM deposition were in the range of 4%-17%. AA spray partially mitigated ozone and PM deposition adverse impact and enhanced wheat yield by 16%.

Exogenous application of ascorbic acid and putrescine: A natural eco-friendly potential for alleviating NaCl stress in barley (Hordeum vulgare)

A pot experiment was performed in the green house of Agricultural Botany Department, Faculty of Agriculture, Cairo University, Giza, Egypt during the winter seasons of 2019 and 2020 to investigate the effect of exogenous application of ascorbic acid (AsA) and putrescine (Put) in ameliorating the growth parameters of barley (Hordeum vulgare L.) plant under saline conditions (9.3 and 14 dS m-1). Two concentrations of either AsA (100 and 300 ppm) or Put (100 and 200 ppm) were foliar-sprayed individually or in combination with both salt concentrations. Vegetative, yield, and anatomical characters, leaf photosynthetic pigments, and grain crude protein declined in response to stress, while electrolyte leakage (EL), proline, glycine betaine (GB), total carbohydrates and antioxidant enzymes increased under same conditions. The maximum increments in vegetative characters were notable at concentrations of either AsA at 300 ppm or Put at 100 ppm. Yield characters were enhanced at 300 ppm AsA and both concentrations of Put. Improvement in anatomical features of leaf and stem was achieved with the combination of either AsA at 300 ppm or Put at 100 ppm with salinity at 14 dS m-1. AsA was more effective in enhancing photosynthetic pigments and crude protein individually or in combination with salinity. Combinations of either AsA or Put with salinity induced decrements in EL, GB and antioxidant enzymes and increments in proline and total carbohydrates. In conclusion, foliar application of AsA and Put could be considered an eco-friendly approach to alleviate the adverse effects of salinity on morphological and physiological characters of barley.

Foliar application of ascorbic acid enhances salinity stress tolerance in barley (Hordeum vulgare L.) through modulation of morpho-physio-biochemical attributes, ions uptake, osmo-protectants and stress response genes expression.

Barley (Hordeum vulgare L.) is a major cereal grain and is known as a halophyte (a halophyte is a salt-tolerant plant that grows in soil or waters of high salinity). We therefore conducted a pot experiment to explore plant growth and biomass, photosynthetic pigments, gas exchange attributes, stomatal properties, oxidative stress and antioxidant response and their associated gene expression and absorption of ions in H. Vulgare. The soil used for this analysis was artificially spiked at different salinity concentrations (0, 50, 100 and 150 mM) and different levels of ascorbic acid (AsA) were supplied to plants (0, 30 and 60 mM) shortly after germination of the seed. The results of the present study showed that plant growth and biomass, photosynthetic pigments, gas exchange parameters, stomatal properties and ion uptake were significantly (p < 0.05) reduced by salinity stress, whereas oxidative stress was induced in plants by generating the concentration of reactive oxygen species (ROS) in plant cells/tissues compared to plants grown in the control treatment. Initially, the activity of antioxidant enzymes and relative gene expression increased to a saline level of 100 mM, and then decreased significantly (P < 0.05) by increasing the saline level (150 mM) in the soil compared to plants grown at 0 mM of salinity. We also elucidated that negative impact of salt stress in H. vulgare plants can overcome by the exogenous application of AsA, which not only increased morpho-physiological traits but decreased oxidative stress in the plants by increasing activities of enzymatic antioxidants. We have also explained the negative effect of salt stress on H. vulgare can decrease by exogenous application of AsA, which not only improved morpho-physiological characteristics, ions accumulation in the roots and shoots of the plants, but decreased oxidative stress in plants by increasing antioxidant compounds (enzymatic and non-enzymatic). Taken together, recognizing AsA's role in nutrient uptake introduces new possibilities for agricultural use of this compound and provides a valuable basis for improving plant tolerance and adaptability to potential salinity stress adjustment.

Ascorbic Acid (Asa) improves Salinity Tolerance in Wheat (Triticum Aestivum L.) by Modulating Growth and Physiological Attributes.

Wheat (Triticum aestivum L.) is one of the most important staple foods. High concentration of sodium chloride severely affects plants in general and wheat in specific. In this study the ameliorative effects of ascorbic acid (AsA) against sodium chloride stress were investigated in two commercial wheat cultivars (Galaxy 2013 and Akbar 2019). Experiments were conducted in three replicates. Two levels of salt (0, 150 mM) along with exogenous application of ascorbic acid (0, 30 mM, 60 mM) were applied at three leaves seedling stage. At the establishment of treatments, data regarding physiological, biochemical and yield attributes were recorded and subjected to statistical analysis. The application of AsA significantly (p≤0.05) improved growth, yield and key physiological attributes in tested wheat varieties under salinity stress. Overall wheat genotype Akbar 2019 showed better growth under salt stress. It is concluded from this study that AsA may be used to mitigate salinity effects in wheat.

Potential determinants of salinity tolerance in rice (Oryza sativa L.) and modulation of tolerance by exogenous ascorbic acid application

Rice is a relatively salt-sensitive crop with the reproductive and seedling stages being the most sensitive. Two separate experiments were conducted to isolate potential determinants of salinity tolerance and to investigate the possibility of modulating salt tolerance by exogenous ascorbic acid (AsA) application. Rice plants were imposed to salinity (EC= 10.0 dS m-1) both at the seedling and reproductive phases of growth. Salinity at the seedling stage resulted a sharp decline in shoot and root growth related traits including leaf chlorophyll content, while hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels increased. Plants experienced with salinity at the reproductive phases of growth showed a significant reduction in yield attributing traits while the tissue levels of H2O2 increased. Exogenous AsA application reversed the negative impact of salt stress, modulating the root and shoots growth and yield related traits and lowering H2O2 and MDA levels. FL-478 was identified as the most tolerant genotype at the seedling stage, with Binadhan-10 being the most tolerant at the reproductive stage. Grain yield panicle-1 significantly and positively corrected with number of filled grains panicle-1, panicle length, plant height, and spikelet fertility, and negatively correlated with H2O2 levels. Stress tolerance indices clearly separated the tolerant and susceptible genotypes. A principal component analysis revealed that the first two components explained 87% of the total variation among the genotypes. Breeding efforts could therefore to undertake for developing salinity tolerance by manipulating endogenous AsA content in rice.

Influence of Ascorbic Acid, Gibberellic Acid and Moringa oleifera Extract for Alleviating Salinity Stress by Enhancing Antioxidant Enzymatic Activity and Some Physiological Studies on Two Tomato Cultivars

This study aimed to explain the influence of Ascorbic acid (ASA), Gibberellic Acid (GA3) and Moringa oleifera Leaf Extract (MLE) for alleviating salinity stress by enhancing antioxidant enzymatic activity as follow: Super Oxide Dismutase (SOD), Catalase (CAT), Ascorbate Peroxidase (APX), and Glutathione Reductase (GR); nitrogenous components (proline and total amino acids) and some inorganic mineral nutrient elements in two tomato cultivars, cv. Cobra (resistant) and cv. Newton (sensitive) under salinity stress. Germination tomato seeds after soaking in ASA (0.75 mM); GA3 (0.05 mM) and MLE (5%), transplanted to plastic containers containing a mixture of sand/peat-moss (1:2). The tomato seeds for both cultivars watering using distilled water until the true leaf appearance then irrigated with NaCl salinity concentrations (0.0, 50, 100, 150, 200 mM) alternative with Hoagland nutrient solution. The experiment was carried out under greenhouse conditions with temperature 18oC±1oC (night) &amp; 22oC±2°C (day) and relative humidity varied between 60 - 70%. Overall, the results indicated that the organic and inorganic components in tomato plants for both cultivars increased significantly in the present of ASA, GA3 and MLE under salinity stress respectively compared with control, there by reduces the harmful effects of salinity and increases resistance to salinity stress more than in the absent of ASA, GA3 and MLE. The data provide strong support to the hypothesis that exogenous application of ASA, GA3 and MLE reduced the harmful effects of NaCl concentrations and increases resistance to salinity in cv. Cobra and cv. Newton respectively. The evident recorded a significantly increased the antioxidant enzymes activity, proline, total amino acids and inorganic macro-mineral nutrient elements (N+3, P+3, K+, Ca+2 &amp; Mg+2) and micro-nutrient mineral elements (Mn+2, Fe+3 &amp; B+2) but after soaked the seeds in ASA, GA3 and MLE, these components tended to increase more compared with the control. Whereas, the tomato seeds soaked before planting in ASA, GA3 and MLE which leads to remarkably increasing more for all antioxidant enzymatic activity, nitrogenous components and inorganic mineral nutrient elements contents respectively. The relationship between compatible solutes (osmolytes) here are the strategies that plants have developed to tolerate salt stress and produced new strains adapted to salinity stress.

The OsABCI7 Transporter Interacts with OsHCF222 to Stabilize the Thylakoid Membrane in Rice.

The thylakoid membrane is a highly complex membrane system in plants and plays crucial roles in the biogenesis of the photosynthetic apparatus and plant development. However, the genetic factors involved in chloroplast development and its relationship with intracellular metabolites are largely unknown. Here, a rice (Oryza sativa) chlorotic and necrotic leaf1 (cnl1) mutant was identified and map-based cloning revealed that a single base substitution followed by a 6-bp deletion in the ATP-binding cassette transporter I family member7 (OsABCI7) resulted in chlorotic and necrotic leaves with thylakoid membrane degradation, chlorophyll breakdown, photosynthesis impairment, and cell death in cnl1 Furthermore, the expression of OsABCI7 was inducible under lower temperatures, which severely affected cnl1 chloroplast development, and etiolated cnl1 seedlings were unable to recover to a normal green state under light conditions. Functional complementation and overexpression showed that OsABCI7 could rescue the cnl1 chlorotic and necrotic phenotype. OsABCI7 interacted with HIGH CHLOROPHYLL FLUORESCENCE222 (OsHCF222) to regulate cellular reactive oxygen species (ROS) homeostasis for thylakoid membrane stability. OsABCI7 localized to thylakoid membranes, while OsHCF222 targeted to endoplasmic reticulum and chloroplasts. Exogenous application of ascorbic acid eased the yellowish leaf phenotype by increasing chlorophyll content and alleviating ROS stress in cnl1 Unlike cnl1, the CRISPR/Cas9-mediated OsHCF222 knockout lines showed chlorotic leaves but were seedling lethal. Our results provide insight into the functions of ABC transporters in rice, especially within the relationship between ROS homeostasis and stability of thylakoid membranes.

A metabolomics study of ascorbic acid-induced in situ freezing tolerance in spinach (Spinacia oleracea L.).

Freeze–thaw stress is one of the major environmental constraints that limit plant growth and reduce productivity and quality. Plants exhibit a variety of cellular dysfunctions following freeze–thaw stress, including accumulation of reactive oxygen species (ROS). This means that enhancement of antioxidant capacity by exogenous application of antioxidants could potentially be one of the strategies for improving freezing tolerance (FT) of plants. Exogenous application of ascorbic acid (AsA), as an antioxidant, has been shown to improve plant tolerance against abiotic stresses but its effect on FT has not been investigated. We evaluated the effect of AsA‐feeding on FT of spinach (Spinacia oleracea L.) at whole plant and excised‐leaf level, and conducted metabolite profiling of leaves before and after AsA treatment to explore metabolic explanation for change in FT. AsA application did not impede leaf growth, instead slightly promoted it. Temperature‐controlled freeze–thaw tests revealed AsA‐fed plants were more freezing tolerant as indicated by: (a) less visual damage/mortality; (b) lower ion leakage; and (c) less oxidative injury, lower abundance of free radicals (O2·- and H2O2). Comparative leaf metabolite profiling revealed clear separation of metabolic phenotypes for control versus AsA‐fed leaves. Specifically, AsA‐fed leaves had greater abundance of antioxidants (AsA, glutathione, alpha‐ & gamma‐tocopherol) and compatible solutes (proline, galactinol, and myo‐inositol). AsA‐fed leaves also had higher activity of antioxidant enzymes (superoxide dismutase, ascorbate peroxidase, and catalase). These changes, together, may improve FT via alleviating freeze‐induced oxidative stress as well as protecting membranes from freeze desiccation. Additionally, improved FT by AsA‐feeding may potentially include enhanced cell wall/lignin augmentation and bolstered secondary metabolism as indicated by diminished level of phenylalanine and increased abundance of branched amino acids, respectively.

Exogenous ascorbic acid delayed leaf senescence of early flowering rice mutant FTL10

FTL10 is an early flowering mutant of OsFTL10-suppressed transgenic rice (Oryza sativa L.) with premature senescence phenotype. Early leaf senescence can cause negative effects on rice yield, therefore delaying leaf senescence and prolonging the leaf functional stage is one of the important approaches to increase the rice yield. It is well known that ascorbic acid (AsA) is involved in regulating plant growth. To explore the effect of AsA on leaf senescence of FTL10, we treated rice leaves with 0.28 mM AsA. Results showed that total antioxidant capacity was higher and reactive oxygen species were lower in the AsA-treated group. The expression of senescence-associated genes was higher in the control group. Exogenous AsA can stabilize chlorophyll and Rubisco protein contents, delay leaf senescence, and maintain net photosynthetic rate (PN) of rice leaves. Our results suggest that exogenous application of AsA can delay leaf senescence, increase PN, and then increase the rice yield.

Exogenous ascorbic acid induces systemic heat stress tolerance in tomato seedlings: transcriptional regulation mechanism.

The current study was devoted to assessing the impact of exogenous ascorbic acid (AsA) in inducing systemic thermotolerance against acute heat stress in tomato (Solanum lycopersicum) seedlings. There were four treatment groups including untreated control (CK), heat-stressed tomato (HS: exposure to 40 °C for 8 h), and treated with ascorbic acid (0.5 mM AsA), and the last group includes both the exogenous application of ascorbic acid and heat stress (AsA + HS). The HS led to leaf curling and mild wilting while plants treated with AsA displayed similar phenotype with control plants, approving that AsA eliminated the injurious effects of the heat stress. The oxidative damage to cell components was confirmed by higher levels of hydrogen peroxide, lipid peroxidation, electrolyte leakage, total oxidant status, and oxidative stress index. Moreover, acute heat stress significantly reduced the photosynthetic pigment contents, and nutrient contents in tomato seedling leaves. In contrast, ascorbic acid postulated a priming effect on tomato roots and, substantially, alleviated heat stress effects on seedlings through reducing the oxidative damage and increasing the contents of ascorbic acid, proline, photosynthetic pigments, and upregulation of heat shock proteins in leaves. Ascorbic acid seems to be a key signaling molecule which enhanced the thermotolerance of tomato plants.

Exogenous application of ascorbic acid mitigates cadmium toxicity and uptake in Maize (Zea mays L.).

Cadmium (Cd) contamination in agricultural soils is a prevalent environmental issue and poses potential threats to food security. Foliar ascorbic acid might prove a potent tool to alleviate toxicity of Cd toxicity in maize. An experiment was conducted with objectives to study exogenous ascorbic acid-modulated improvements in physiochemical attributes of maize under Cd toxicity. The experiment was conducted under completely randomized design. Treatments were comprised of varying concentrations of foliar ascorbic acid viz. 0.0, 0.1, 0.3, and 0.5 mM of AsA. Toxicity of Cd decreased the maize growth, increased lipid peroxidation, disturbed protein metabolism, and reduced the antioxidant defense capabilities compared with the control. However, foliar AsA significantly improved maize growth and development, photosynthetic capabilities, and protein concentrations in Cd-stressed maize plants. Meanwhile, the malondialdehyde contents and hydrogen peroxide accumulation levels in Cd-stressed maize plants decreased remarkably with increasing AsA concentrations. Furthermore, the combined treatments conspicuously boosted activities of superoxide dismutase, peroxidase, catalase, and glutathione reductase under the Cd stress alone. In addition, the application of AsA reduced the Cd uptake by 10.3-12.3% in grains. Conclusively, foliar ascorbic acid alleviated the negative effects of Cd stress in maize and improved photosynthetic processes, osmolytes, and antioxidant defense systems.