Ascorbate Peroxidase Activity Research Articles

Impact nano- and micro- form of CdO on barley growth and oxidative stress response

The objective was investigated the effects of CdO and nano-CdO as potential toxic pollutants on growth and redox response of barley. CdO and nano-CdO have been found to cause significant phytotoxicity in barley seedlings, with nano-CdO increasing plant tissue cadmium accumulation. This accumulation is linked to growth retardation and oxidative stress. Low molecular weight antioxidants like restored glutathione and ascorbate have been found to increase the activity of glutathione peroxidase (GPX), glutathione-S-transferase (GSTs), and ascorbate peroxidase (APX) in green tissues. Catalase (CAT) activity increased from 50 % with 100 mg/l CdO to 70 % with 1000 mg/l and nano-CdO. The observed disturbance in redox balance signals the upregulation of corresponding genes. Antioxidant enzyme isoform gene transcripts increased for SODB, CAT2, and APX. Cadmium buildup in root cells causes oxidative stress, leading to upregulation of SOD, CAT, GR, and GSTs isoform genes as well as protein carbonylation, sulfhydryl group degradation, and MDA accumulation. CdO and nano-CdO have similar phytotoxic effects, but bioavailability affects biochemical and molecular responses.

Responses of 'Flordaguard' and 'MP-29' Prunus spp. rootstocks to hypoxia and high root zone temperature.

Selecting the right rootstock is crucial for successful fruit production and managing both biotic and abiotic stresses in commercial fruit orchards. To enhance the resilience of peach orchards, this study evaluated the physiological and biochemical responses of Prunus spp. rootstocks , 'Flordaguard' and 'MP-29,' under normoxia (sufficient oxygen content) or short-term hypoxia (low-oxygen content) and ambient or high temperature (40°C) in the root zone. Physiological responses measured were net photosynthesis, stomatal conductance, transpiration, intercellular CO2 concentration, water use efficiency, the leaf chlorophyll index, and the maximum potential quantum efficiency of photosystem II. The leaf concentrations of nitrogen, phosphorus, potassium, magnesium, calcium, sulfur, boron, zinc, manganese, iron, and copper were also analyzed. Reactive oxygen species (ROS) and antioxidants analyzed were superoxide dismutase (SOD) activity, peroxidase (POD) activity, catalase (CAT) activity, ascorbate peroxidase (APX) activity, glutathione peroxidase (GPX) activity, proline content, glycine betaine content (GB), lipid peroxidation (LPO), superoxide (O2 -) concentration, and hydrogen peroxide (H2O2) concentration. When subjected to root zone hypoxia or high temperature individually, 'MP-29' performed better physiologically than 'Flordaguard'. However, when root zone hypoxia and high temperature were combined, 'MP-29' performed better biochemically with enhanced antioxidant activity, osmolyte content, and nutrient absorption. Nutrient analysis of leaves revealed that 'MP-29' had higher N, P, K, Ca, and B concentrations than 'Flordaguard'. Consequently, 'MP-29' demonstrated greater tolerance to short-term exposure to the combined effects of high root zone temperature and hypoxia. This research contributes to identifying a suitable rootstock within the Prunus genus able to withstand root zone conditions that often result from severe weather events commonly experienced in Florida and other parts of the world.

Ethylene and hydrogen sulfide regulate hexavalent chromium toxicity in two pulse crops: Implication on growth, photosynthetic activity, oxidative stress and ascorbate glutathione cycle

Sustainable agriculture has become prime importance to feed growing population. To achieve this goal application of exogenous hormones and signaling molecules are gaining important. In this context, we have investigated potential of ethylene (25 μM ethephon; donor) and H2S (10 μM NaHS; donor) in mitigating hexavalent chromium [Cr (VI), 50 μM] toxicity in two pulse seedlings: black bean and mung bean. Cr(VI) declined growth and gas exchange parameters (photosynthetic rate, stomatal conductance, sub cellular CO2 concentration, and transpiration level) which was accompanied by intracellular accumulation of Cr in both pulse crops and the damaging effect was greater in mung bean seedlings. The suppression in the growth and related parameters was occurred due to higher buildup of oxidative stress markers; O2•‾, H2O2, lipid peroxidation (as malondialdehyde, MDA equivalents) and membrane injury in leaf and root of both pulse crops. Cr induced disturbance in AsA-GSH cycle (reduction in the activity of glutathione reductase, ascorbate peroxidase, monodehydroascorbate reductase and dehydroascorbate reductase, and the amount of ASA and GSH) could be one of the reasons for greater accumulation of H2O2. Further, exogenous application of ethylene and H2S significantly ameliorated Cr toxicity on growth and photosynthetic activity by significantly lowering the intracellular Cr accumulation and oxidative biomarkers, and also by strengthening the activity of AsA-GSH cycle. The exogenous application of biosynthesis inhibitors of ethylene (AVG) and H2S (PAG) caused greater damaging effect on these parameters due to more accumulation of Cr(VI), thereby suggesting that the endogenous levels of these regulators are critical for Cr(VI) tolerance. Interestingly, ET did not rescue adverse effects of Cr(VI) in absence of endogenous H2S, while H2S could do so even without endogenous ethylene, suggesting that H2S played downstream signaling to ethylene in regulating Cr(VI) toxicity. Hence, being cheap and easily available theses growth regulators may be considered for sustainable agriculture.

Optimizing Biochemical and Phytochemical Attributes in Peaches through Foliar Applications of Silicon and Zinc

Peach production faces significant pre-harvest challenges, including low moisture, nutrient deficiencies, flower drop, physical damage, and surface discoloration, which can limit yield and fruit quality. To mitigate these issues, the present study hypothesized that foliar applications of silicon and zinc could enhance peach growth, yield, and quality due to their known roles in improving stress tolerance, nutrient uptake, and antioxidant activity. Therefore, this research aimed to identify optimal concentrations of silicon and zinc for quality peach production. Ten-year-old peach trees of uniform size were sprayed with four levels of silicon (0%, 0.1%, 0.2%, and 0.3%) and zinc (0%, 0.25%, 0.50%, and 0.75%) for two consecutive growing seasons, at the berry and pit hardening stages, using a Randomized Complete Block Design (RCBD) with three replications. The averaged data from the two years showed that the pre-harvest foliar application of silicon significantly improved all yield and quality attributes of peaches. The foliar application of silicon at 0.3% notably enhanced fruit growth, yield, and biochemical attributes. Additionally, the highest fruit growth, yield, and quality of peach fruits were observed at the 0.75% zinc concentration. Maximum antioxidant activity, flavonoid content, proline content, and catalase activity were observed in fruits from plants treated with 0.3% silicon, which were statistically on par with 0.2% silicon. However, peroxidase activity was highest at 0.2% silicon. Regarding zinc levels, antioxidant activity, flavonoid content, proline content, and peroxidase activity were highest in fruits treated with 0.75% zinc, while catalase activity was superior when fruits were sprayed with 0.50% zinc. The interaction between silicon and zinc concentrations was found to be non-significant for most parameters, except for titratable acidity, TSS–acid ratio, ascorbic acid content, antioxidant activity, flavonoid content, and peroxidase activity. In conclusion, the foliar application of 0.3% silicon and 0.75% zinc independently enhanced all yield and quality characteristics of peaches. For the agro-climatic conditions of Peshawar, 0.2% silicon and 0.50% zinc are recommended for optimal peach production.

Bio-based coatings containing mycosporine-like amino acids (MAA) to control sunscald abiotic stress in orange fruit (Citrus sinensis L)

Oranges are susceptible to many abiotic stresses, and the fruit is particularly susceptible to sunscald, a physiological disorder caused by excessive solar radiation. Sunscald is commonly controlled by spraying the fruits with calcium hydroxide and/or kaolin, but this procedure is not always effective due to rain and the application of phytosanitary treatments. Since mycosporine-like amino acids (MAAs), produced by many marine organisms, protect them against ultraviolet radiation UV-A and UV-B, these compounds could be incorporated into bio-based emulsions to control sunscald in oranges. Therefore, increasing concentrations of the commercial product Helioguard™ 365 (0 %, 1 %, 2 %, and 4 % - v/v), a source of MAAs, were incorporated into lipid-based emulsions. The emulsions were applied during the final stage of development of ‘Hamlin’, ‘Pera-rio’, and ‘Valencia’ oranges at 21-day intervals. Spraying with 5 % (w/v) calcium hydroxide served as the positive control treatment, while untreated fruits served as the negative control. Incorporating MAA into the emulsion did not demonstrate effective control of sunburn compared to the positive control treatment with calcium hydroxide, as all fruits exhibited varying degrees of sunscald, ranging from low to high severity. Regarding physicochemical parameters, as well as oxidative metabolism, except for color parameters, soluble solids content, ascorbic acid, and overall biochemical parameters, there was no difference among treatments for any of the evaluated orange cultivars. The activities of ascorbate peroxidase (APX) and superoxide dismutase (SOD) did not show consistent with efficient antioxidant potential capable of significantly reducing the malondialdehyde (MDA) content. Despite using MAA at the evaluated concentrations and experiencing severe climatic interference in 2020, efficient control of sunscald in oranges was not achieved. Further research is needed to identify more effective alternatives and gain a better understanding of how climate affects oxidative aspects.

Melatonin Treatment Alleviates Chilling Injury of Loquat Fruit via Modulating ROS Metabolism.

Cold storage is one of the most effective methods to maintain postharvest fruit quality. However, loquat fruits are prone to chilling injury (CI) during cold storage, appearing as symptoms such as browning and pitting, which leads to quality deterioration and economic losses. In this study, the effects of melatonin on CI alleviation and the potential role of reactive oxygen species (ROS) metabolism in loquat fruit were investigated. The results showed that 50 μM melatonin was the optimal concentration to inhibit the increase in CI index and cell membrane permeability. Moreover, compared to control fruits, 50 μM melatonin inhibited the malonaldehyde (MDA) content, O2-. production rate and H2O2 content (ROS accumulation) by 17.8%, 7.2% and 11.8%, respectively, during cold storage. Compared to non-treated loquats, 50 μM melatonin maintained higher levels of 1-diphenyl-2-picrylhydrazyl radical-scavenging ability and reducing power, as well as the contents of ascorbic acid (AsA) and glutathione (GSH). Additionally, 50 μM melatonin enhanced the activities of antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) by increasing relevant gene expressions. The activities of SOD, CAT and APX were increased by up to 1.1-, 1.1- and 1.1-times (16 d) by melatonin, as compared with the control fruits. These findings indicate that melatonin mitigation of CI is involved in maintaining cellular redox apphomeostasis in loquat fruit during cold storage.

Exploring the impact of rice husk biochar on oxidative mechanisms and salt stress tolerance in lettuce plants

Salt stress, which impairs plant growth and induces oxidative stress, presents a major challenge in agriculture. In response, biochar has emerged as a promising soil amendment, capable of enhancing plants’ stress tolerance mechanisms. This study investigated the impact of rice husk biochar (RBC), derived from rice husks, on enhancing salt stress tolerance in lettuce plants grown under greenhouse conditions. Molecular and chemical characterization of the biochar samples was performed using Scanning Electron Microscopy (SEM) and Raman spectroscopy. Salinity reduced the fresh and dry weights of the plants from 25.0 g plant−1 and 1.83 g plant−1 to 20.4 g plant−1 and 1.42 g plant−1, respectively. The application of RBC recovered the growth decline caused by salinity, increasing the fresh and dry weights of the plants to 28.1 g plant−1 and 1.83 g plant−1, respectively. While the concentrations of sodium and chloride in plants decreased with RBC application, potassium and silicon concentrations significantly increased. As a result of salt stress, hydrogen peroxide levels (H2O2) increased in plant tissues, and a decrease in H2O2 levels was observed with an increase in superoxide dismutase, catalase, and ascorbate peroxidase activities. Consequently, RBC proved to be effective in enhancing salt tolerance in lettuce plants. In conclusion, while RBC demonstrates significant potential for enhancing salt tolerance, its successful application depends on several factors such as biochar dosage, application method, soil type, and plant species, underscoring the need for further research to elucidate the mechanisms at play and optimize its use for sustainable soil management in saline conditions.

Effects of Various Levels of Water Stress on Morpho-Physiological Traits and Spectral Reflectance of Maize at Seedling Growth Stage

Water stress (drought and waterlogging) is one highly important factor affecting food security in China. Investigating the effects of soil moisture stress on the morphological and physiological characteristics of maize seedlings is crucial for ensuring food production. The use of spectral monitoring to observe crop phenotypic traits and assess crop health has become a focal point in field crop research. However, studies exploring the contribution of crop phenotypic and physiological data to the Normalized Difference Vegetation Index (NDVI) are still limited. In this study, a 35-day pot experiment was conducted with seven soil moisture gradients: 50%, 60%, 70%, 80% (control group, CK), 90%, 100%, and 110% treatment. In order to investigate the effects of soil moisture stress on seedling phenotypes, antioxidant enzyme activities, and NDVI, an ASD FieldSpec 4 Hi-Res NG portable spectrometer was used to collect spectral data from maize (Zea mays L. B73) leaves. The contributions of maize phenotypic and physiological traits to NDVI were also examined. The results indicated that (1) the 50% and 110% treatments significantly affected maize seedling phenotypes compared to the CK group; (2) the activities of superoxide dismutase (SOD) and peroxidase (POD) in the leaves increased under water stress, while the activities of glutathione peroxidase (GSH-PX) and ascorbate peroxidase (APX) decreased; (3) soil moisture stress (drought and waterlogging) reduced photosynthetic pigments, chlorophyll content (SPAD), and NDVI, with inhibitory effects intensifying as the stress level increased; (4) Redundancy analysis showed that antioxidant enzymes explained 69.87% of the variation in seedling height, leaf area, and NDVI. Soil moisture stress, chlorophyll, and SPAD explained 58.14% of the variation in these parameters. The results demonstrated that maize seedlings were highly sensitive to soil moisture changes, and the SPAD value contributed significantly to NDVI (p < 0.01). This study provides valuable insights for future research in precision agriculture management

Effect of chlorine dioxide (ClO2) combined with different oxygen permeability package treatments on postharvest antioxidant activity and storage life of ‘Liaofeng’ grapes

To enhance the storage quality of ‘Liaofeng’ grapes, this research employed chlorine dioxide in collaboration with different package of preservative bags to explore its preservative effect on ‘Liaofeng’ grapes. After fumigating the grapes with 300 mg L−1 ClO2 solution, the control group was packaged in unpacked and PE bags, while the treatment group was packaged in three kinds of bags with different oxygen permeability, and stored in 4 °C and relative humidity controlled at 90%–95% for 90 days. The results showed that ClO2-GB package treatment significantly delayed the decline of grape hardness (P < 0.05), and decreased the weight loss, threshing, decay and peduncle browning index after storage for 90 days. ClO2-GB package treatment not only diminishes the levels of soluble solids content, titrable acidity, ascorbic acid and glutathione but also effectively suppresses the respiration rate in fruits. The contents of total phenols, flavonoids, anthocyanins and reduced glutathione after ClO2-GB treatment were significantly higher than those in unpackaged group (P < 0.05), and curbed the increase in relative electrical conductivity and malondialdehyde concentration. In comparison to ClO2-YTB and ClO2-YB treatments, ClO2-GB treatment demonstrated superior efficacy in modulating the antioxidant metabolism of grapes. It notably elevated the enzymatic activities of catalase, superoxide dismutase, ascorbate peroxidase, and glutathione reductase, while inhibiting the activities of peroxidase and polyphenol oxidase. The quality assessment of ‘Liaofeng’ grapes after 90 d storage period, conducted through principal component analysis (PCA), yielded the following ranking: ClO2-GB > ClO2-YB > ClO2-YTB > ClO2-PE > ClO2. This suggests that 300 mg L−1 ClO2 fumigation combined with different package treatments was more beneficial to the storage of ‘Liaofeng’ grape. ClO2-GB package treatment emerged as the most advantageous.

Exogenous Melatonin Alleviates NaCl Injury by Influencing Stomatal Morphology, Photosynthetic Performance, and Antioxidant Balance in Maize.

Maize (Zea mays L.) is sensitive to salt stress, especially during seed germination and seedling morphogenesis, which limits maize growth and productivity formation. As a novel recognized plant hormone, melatonin (MT) participates in multiple growth and developmental processes and mediates biotic/abiotic stress responses, yet the effects of salt stress on maize seedlings remain unclear. Herein, we investigated the effects of 150 μM exogenous MT on multiple phenotypes and physiologic metabolisms in three-leaf seedlings across eight maize inbred lines under 180 mM NaCl salt stress, including growth parameters, stomatal morphology, photosynthetic metabolisms, antioxidant enzyme activities, and reactive oxygen species (ROS). Meanwhile, the six gene expression levels controlling antioxidant enzyme activities and photosynthetic pigment biosynthesis in two materials with contrasting salt resistance were examined for all treatments to explore the possible molecular mechanism of exogenous MT alleviating salt injury in maize. The results showed that 150 μM exogenous MT application protected membrane integrity and reduced ROS accumulation by activating the antioxidant system in leaves of maize seedlings under salt stress, their relative conductivity and H2O2 level average reduced by 20.91% and 17.22%, while the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) averaged increased by 13.90%, 17.02%, 22.00%, and 14.24% relative to salt stress alone. The improvement of stomatal size and the deposition of photosynthetic pigments were more favorable to enhancing photosynthesis in leaves when these seedlings treated with MT application under salt stress, their stomatal size, chlorophyll content, and net photosynthetic rate averaged increased by 11.60%, 19.64%, and 27.62%. Additionally, Gene expression analysis showed that MT stimulation significantly increased the expression of antioxidant enzyme genes (Zm00001d009990, Zm00001d047479, Zm00001d014848, and Zm00001d007234) and photosynthetic pigment biosynthesis genes (Zm00001d011819 and Zm00001d017766) under salt stress. At the same time, 150 μM MT significantly promoted seedling growth and biomass accumulation. In conclusion, our study may unravel crucial evidence of the role of MT in maize seedlings against salt stress, which can provide a novel strategy for improving maize salt stress resistance.

Hormetic responses to cadmium exposure in wheat seedlings: insights into morphological, physiological, and biochemical adaptations.

Cadmium is commonly recognized as toxic to plant growth, low-level Cd has promoting effects on growth performance, which is so-called hormesis. Although Cd toxicity in wheat has been widely investigated, knowledge of growth response to a broad range of Cd concentrations, especially extremely low concentrations, is still unknown. In this study, the morphological, physiological, and biochemical performance of wheat seedlings to a wide range of Cd concentrations (0-100 µΜ) were explored. Low Cd treatment (0.1-0.5µM) improved wheat biomass and root development by enhancing the photosynthetic system and antioxidant system ability. Photosynthetic rate (Pn) was improved by 5.72% under lower Cd treatment (1 µΜ), but inhibited by 6.05-49.85% from 5 to 100 µΜ. Excessive Cd accumulation induced oxidative injury manifesting higher MDA content, resulting in lower photosynthetic efficiency, stunted growth, and reduction of biomass. Further, the contents of ascorbate, glutathione, non-protein thiols, and phytochelatins were improved under 5-100 µΜ Cd treatment. The ascorbate peroxidase activity in the leaf showed a hormetic dose-response characteristic. Correlation analysis and partial least squares (PLS) results indicated that antioxidant enzymes and metabolites were closely correlated with Cd tolerance and accumulation. The results of the element network, correlation analysis, and PLS showed a crucial role for exogenous Cd levels in K, Fe, Cu, and Mn uptake and accumulation. These results provided a deeper understanding of the hormetic effect of Cd in wheat, which would be beneficial for improving the quality of hazard and risk assessments.

Be prepared: how does discontinuous hydration in Tabebuia heterophylla seeds induce stress tolerance in seedlings?

Discontinuous hydration and dehydration (HD) cycles refer to controlled imbibition followed by dehydration before seed germination. Here, we investigated whether the level of imbibition before HD cycles affects the physiology of Tabebuia heterophylla seeds and seedlings. Seeds were imbibed for 10 h (T1; phase I of imbibition) or 35 h (T2; phase II), dehydrated, and progressively rehydrated one to four times (HD cycles). Germination and biochemical parameters (membrane integrity; total soluble, reducing, and nonreducing (NRS) sugars; proteins, amino acids, proline, H2O2, catalase, ascorbate peroxidase, and glutathione reductase activity) were quantified at the last rehydration step of each cycle. Biometric and biochemical parameters (including pigments) were analysed in seedlings 60 days after germination. HD cycles at T1 led to reduced seed germination and greater plasma membrane damage, higher enzyme activity (catalase and glutathione reductase) and accumulation of NRS, total amino acids, and proline compared to the controls and T2 treatment. Cellular damage became more severe with more HD cycles. HD cycles at T2 synchronized germination regardless of the number of cycles and also had a priming effect. T2 seeds had less NRS, total amino acids, and proline content than T1. HD cycles at T1 produced seedlings with higher carotenoid and total chlorophyll content than controls and T2, while seedlings from HD cycles at T2 had higher amounts of osmoprotectants. HD cycles at T2 benefited seeds and seedlings more than at T1. This suggests that the physiological and biochemical effects of HD cycles in seeds modulate seedling plasticity, depending on water availability, potentially promoting increased tolerance to recurrent droughts that will be intensified with ongoing climate changes.

GO promotes detoxification of nicosulfuron in sweet corn by enhancing photosynthesis, chlorophyll fluorescence parameters, and antioxidant enzyme activity

Although graphene oxide (GO) has extensive recognized application prospects in slow-release fertilizer, plant pest control, and plant growth regulation, the incorporation of GO into nano herbicides is still in its early stages of development. This study selected a pair of sweet corn sister lines, nicosulfuron (NIF)-resistant HK301 and NIF-sensitive HK320, and sprayed them both with 80 mg kg–1 of GO-NIF, with clean water as a control, to study the effect of GO-NIF on sweet corn seedling growth, photosynthesis, chlorophyll fluorescence, and antioxidant system enzyme activity. Compared to spraying water and GO alone, spraying GO-NIF was able to effectively reduce the toxic effect of NIF on sweet corn seedlings. Compared with NIF treatment, 10 days after of spraying GO-NIF, the net photosynthetic rate (A), stomatal conductance (Gs), transpiration rate (E), photosystem II photochemical maximum quantum yield (Fv/Fm), photochemical quenching coefficient (qP), and photosynthetic electron transfer rate (ETR) of GO-NIF treatment were significantly increased by 328.31%, 132.44%, 574.39%, 73.53%, 152.41%, and 140.72%, respectively, compared to HK320. Compared to the imbalance of redox reactions continuously induced by NIF in HK320, GO-NIF effectively alleviated the observed oxidative pressure. Furthermore, compared to NIF treatment alone, GO-NIF treatment effectively increased the activities of superoxide dismutase (SOD), guaiacol peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in both lines, indicating GO induced resistance to the damage caused by NIF to sweet corn seedlings. This study will provides an empirical basis for understanding the detoxification promoting effect of GO in NIF and analyzing the mechanism of GO induced allogeneic detoxification in cells.

A Hydroponic System to Study the Effects of Root and Meristem Night Temperature on Growth, Photosynthesis Carbon Balance, and Antioxidant Enzymes in Rice

Nocturnal root and meristem temperature (RMT) can have a strong effect on rice growth and yield. However, underlying mechanisms are not well understood. To investigate the effects of night-time RMT on photosynthesis biomass allocation and activities of antioxidant enzymes, we designed a hydroponic system that maintained the following daily patterns of day/night temperature: 18/28 °C (HNT) or 28/18 °C (LNT). Rice plants cv. IR64 were grown in the greenhouse and subjected to either HNT or LNT. HNT stimulated growth and tillering but did not affect biomass allocation. HNT plants increased total biomass by 16 and 35%, depending on time of exposure. HNT increased rates of photosynthesis (Pn) compared to LNT plants in leaves of different ages. Overnight carbohydrate remobilisation was larger in HNT than in LNT plants, particularly at 16 days after treatment (dat), when Pn and relative growth rates were highest. Leaf soluble protein concentrations and specific leaf area were not affected by RMT, indicating higher photosynthetic nitrogen use efficiency in HNT plants. Super Oxide Dismutase, Ascorbate Peroxidase, and Glutathione Reductase activities did not respond to RMT, indicating no change in the production of reactive oxygen species in LNT plants despite lower photosynthesis rates. HNT increased sink demand by stimulating tillering, the increased sink demand upregulated the source activity through a larger leaf area per plant and a higher Pn throughout the canopy. The hydroponic system described here was able to control the temperature of the nutrient solution effectively, the installation of a second pump directly circulating the nutrient solution from and back to the reservoir through the cooling system allowed reaching the target temperature within 1 h. This system opens new opportunities to characterise plant responses to RMT alone or in combination with other environmental drivers.

Salicylic Acid Treatment Ameliorates Postharvest Quality Deterioration in 'France' Prune (Prunus domestica L. 'Ximei') Fruit by Modulating the Antioxidant System.

The potential of salicylic acid (SA) in delaying postharvest fruit senescence has been extensively documented; nevertheless, its effect on antioxidant activity and quality of 'France' prune fruit is largely unknown. The study investigated the effects of SA (0.5 mM) on postharvest quality deterioration of 'France' prune fruit. Results indicated that SA impeded the increase in respiration rate and weight loss, and mitigated the decrease of soluble solids content (SSC), titratable acidity (TA) content, firmness, and hue angle. SA sustained the ascorbate-glutathione cycle by inducing the production of ascorbic acid (AsA) and glutathione (GSH) and attenuates flavonoids, total phenols, and anthocyanins degradation by inhibiting polyphenol oxidase (PPO) activity and PdPPO. Moreover, SA significantly improved superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), and glutathione reductase (GR) activities and gene expression levels, sustained higher 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging capacity, ferric reducing antioxidant power (FRAP), and hydroxyl radical (·OH) inhibition capacity, and impeded the production of hydrogen peroxide (H2O2) and superoxide anion (O2•-). Overall, SA improved the antioxidant capacity by inducing the synthesis of defense response-related substances and promoting antioxidant enzyme activities to sustain the storage quality of 'France' prune fruit.

Unravelling the role of proline in glyphosate-mediated toxicity - tolerance mechanism or stress signal?

Glyphosate (GLY), the most widely used herbicide, has been regarded as an emergent environmental contaminant due to its constant and cumulative use, with potential harm to non-target organisms, such as crops, disrupting cells' redox balance. Therefore, plants need to fine-tune their antioxidant (AOX) mechanisms to thrive under GLY-contaminated environments. Proline overaccumulation is a common response in plants exposed to GLY, yet its role in GLY-induced toxicity remains unclear. Thus, this study explores whether Pro overaccumulation in response to GLY is perceived as a downstream tolerance mechanism or an early-warning stress signal. To investigate this, Arabidopsis thaliana T-DNA mutant lines for Pro biosynthetic (P5CS1) and catabolic genes (ProDH) were used and screened for their GLY susceptibility. Upon seedlings' exposure to GLY (0.75 mg L-1) for 14 days, the herbicide led to reduced biomass in all genotypes, accompanied by Pro overaccumulation. Mutants with heightened Pro levels (prodh) exhibited the greatest biomass reduction, increased lipid peroxidation (LP), and hydrogen peroxide (H2O2) levels, accompanied by a compromised performance of the AOX system. Conversely, p5cs1-4, mutants with lower Pro levels, demonstrated an enhanced AOX system activation, not only with increased levels of glutathione (GSH) and ascorbate (AsA), but also with increased activity of both ascorbate peroxidase (APX) and catalase (CAT). These findings suggest that Pro overaccumulation under GLY exposure is associated with stress sensitivity rather than tolerance, highlighting its potential as an early-warning signal for GLY toxicity in non-target plants and for detecting weed resistance.

Effector CLas0185 targets methionine sulphoxide reductase B1 of Citrus sinensis to promote multiplication of 'Candidatus Liberibacter asiaticus' via enhancing enzymatic activity of ascorbate peroxidase 1.

Citrus huanglongbing (HLB) has been causing enormous damage to the global citrus industry. As the main causal agent, 'Candidatus Liberibacter asiaticus' (CLas) delivers a set of effectors to modulate host responses, while the modes of action adopted remain largely unclear. Here, we demonstrated that CLIBASIA_00185 (CLas0185) could attenuate reactive oxygen species (ROS)-mediated cell death in Nicotiana benthamiana. Transgenic expression of CLas0185 in Citrus sinensis 'Wanjincheng' enhanced plant susceptibility to CLas. We found that methionine sulphoxide reductase B1 (CsMsrB1) was targeted by the effector, and its abundance was elevated in CLas0185-transgenic citrus plants. Their interaction promoted CLas proliferation. We then determined that CsMsrB1 sustained redox state and enzymatic activity of ascorbate peroxidase 1 (CsAPX1) under oxidative stress. The latter reduced H2O2 accumulation and was associated with host susceptibility to CLas infection. Consistently, citrus plants expressing CLas0185 and CsMsrB1 conferred enhanced APX activity and decreased H2O2 content. Taken together, these findings revealed how CLas0185 benefits CLas colonization by targeting CsMsrB1, which facilitated the antioxidant activity and depressed ROS during pathogen infection.

Screening and Physiological Responses of Maize Inbred Lines to Drought Stress in South China

The frequent occurrence of localized and seasonal droughts has caused severe economic losses in maize production in South China. To promote sustainable maize production, selecting and breeding drought-tolerant varieties is vital for addressing water scarcity. Drought stress affects all aspects of crop morphological performance. In this study, the morphological performance of 285 maize inbred lines under drought stress was investigated using D-value analysis, correlation analysis, principal component analysis, cluster analysis and stepwise regression analysis. All indicators were significantly different in the regular treatment compared to the drought treatment. Specifically, survival rate, root fresh weight, root dry weight, plant dry weight, root/crown ratio, and plant fresh weight were used as indicators for drought-tolerance evaluation. Furthermore, the drought-tolerant inbred line CML323 and the drought-sensitive inbred line CB2-49-1 were screened by comprehensively evaluating D values. The drought-tolerant inbred line CML323 exhibits higher leaf relative water content, chlorophyll content, proline content, and ascorbate peroxidase and peroxidase activity while having lower malondialdehyde content, consequently demonstrating excellent drought tolerance. This study provides valuable insights into drought-tolerance indicators and reference materials for breeding maize varieties.

Glycine betaine enhances chilling tolerance in peach fruit by modulating PpbHLH130-mediated antioxidant metabolism

Peaches are vulnerable to chilling injury (CI) after long-term refrigeration. Glycine betaine (GB) treatment was found to substantially mitigate CI in peach fruit, but its molecular mechanism is still unclear. In this study, 288 uniformly sized fruit for three repetitions were immersed in 10 mmol L−1 GB for 10 min and then stored at 5 ± 0.5 °C for 49 d. GB-treated peaches retained lower levels of internal browning index, relative conductivity and malondialdehyde content compared to control during cold storage. Meanwhile, GB treatment increased the gene expression and activities of catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX) and peroxidase (POD), accompanied by decreased reactive oxygen species (ROS) content in cold stored peaches. Moreover, PpbHLH130 transcription factor was cloned by a one-step cloning method from peaches, which was located in the nucleus with transcriptional activation ability. PpbHLH130 expression was induced by chilling stress and GB treatment. Further investigation revealed that PpbHLH130 up-regulated the expression of PpPOD and PpAPX by directly interacting with E-box elements in their promoters. Therefore, these results indicated that GB treatment activated the PpbHLH130-mediated transcriptional activation of PpPOD and PpAPX genes, improved the gene expression and activities of antioxidant-related enzymes and suppressed the accumulation of ROS, contributing to the maintenance of cell membrane integrity and the improvement of chilling tolerance in refrigerated peach fruit.

Anti-browning action of melatonin is dependent on the type of tissue in minimally processed sweet potatoes

This study explored the impact of exogenous melatonin on oxidative damage, protective mechanisms against oxidation, and reactions leading to browning, as well as the accumulation of antioxidants in minimally processed white-fleshed and orange sweet potato roots. Sweet potato roots with white and orange pulp were subjected to minimal processing and immersion in melatonin solutions at concentrations of 0, 10, 100, and 1000 µmol L−1. Following packaging, these were stored at 5 ± 2 °C for 20 days. Results indicate that increasing melatonin concentrations significantly reduced browning symptoms in both white and orange sweet potato slices. This reduction was associated with decreased levels of hydrogen peroxide (H2O2), thiobarbituric acid-reactive substances (TBARs), and electrolyte leakage, indicating reduced cell membrane damage. Enhanced protection was observed through increased activity of antioxidant enzymes superoxide dismutase, catalase, and ascorbate peroxidase and higher levels of antioxidant metabolites, including vitamin C and phenolic compounds, as confirmed by in vitro assays for antioxidant capacity (FRAP and DPPH), however, the levels of total carotenoids, anthocyanins, and yellow flavonoids did not show a significant difference between the melatonin treatments. Notably, sweet potato slices treated with higher melatonin doses of 100 and 1000 µmol L−1 exhibited reduced phenylalanine ammonia-lyase activity and phenolic compound accumulation. This effect, coupled with lower polyphenol oxidase (PPO) and peroxidase (POD) activities, likely contributed to prolonged preservation quality by maintaining cellular redox homeostasis.