Superoxide Dismutase, Catalase, and alpha-Tocopherol Content of Stored Potato Tubers

Variety-Driven Effect of Rhizosphere Microbial-Specific Recruitment on Drought Tolerance of Medicago ruthenica (L.)

As one of the environmental factors that seriously affect plant growth and crop production, drought requires an efficient but environmentally neutral approach to mitigate its harm to plants. Soil microbiomes can interact with plants and soil to improve the adverse effects of drought. Medicago ruthenica (L.) is an excellent legume forage with strong drought tolerance, but the key role of microbes in fighting drought stress remains unclear. What kind of flora plays a key role? Is the recruitment of such flora related to its genotype? Therefore, we selected three varieties of M. ruthenica (L.) for drought treatment, analyzed their growth and development as well as their physiological and biochemical characteristics, and performed 16S rRNA high-throughput sequencing analysis on their rhizosphere soils to clarify the variety-mediated response of rhizosphere bacteria to drought stress. It was found that among the three varieties of M. ruthenica (L.), Mengnong No.2, Mengnong No.1 and Zhilixing were subjected to drought stress and showed a reduction in plant height increment of 24.86%, 34.37%, and 31.97% and in fresh weight of 39.19%, 50.22%, and 41.12%, respectively, whereas dry weight was reduced by 23.26%, 26.10%, and 24.49%, respectively. At the same time, we found that the rhizosphere microbial community of Mengnong No. 2 was also less affected by drought, and it was able to maintain the diversity of rhizosphere soil microflora stable after drought stress, while Mennong No. 1 and Zhilixing were affected by drought stress, resulting in a decrease in rhizosphere soil bacterial community diversity indices to 92.92% and 82.27%, respectively. Moreover, the rhizosphere of Mengnon No. 2 was enriched with more nitrogen-fixing bacteria Rhizobium than the other two varieties of M. ruthenica (L.), which made it still have a good ability to accumulate aboveground biomass after drought stress. In conclusion, this study proves that the enrichment process of bacteria is closely related to plant genotype, and different varieties enrich different types of bacteria in the rhizosphere to help them adapt to drought stress, and the respective effects are quite different. Our results provide new evidence for the study of bacteria to improve the tolerance of plants to drought stress and lay a foundation for the screening and study mechanism of drought-tolerant bacteria in the future.

Strigolactones GR-24 and Nijmegen Applications Result in Reduced Susceptibility of Tobacco and Grapevine Plantlets to Botrytis cinerea Infection

Priming agents are plant defence-inducing compounds which can prompt a state of protection but may also aid in plant growth and interactions with beneficial microbes. The synthetic strigolactones (±)-GR24 and Nijmegen-1 were evaluated as potential priming agents for induced resistance against Botrytis cinerea in tobacco and grapevine plants. The growth and stress response profiles of B. cinerea to strigolactones were also investigated. Soil drench treatment with strigolactones induced resistance in greenhouse-grown tobacco plants and restricted lesion development. The mode of action appeared to function by priming redox-associated compounds to produce an anti-oxidant protective response for limiting the infection. The results obtained in the in vitro assays mirrored that of the greenhouse-grown plants. Exposure of B. cinerea to the strigolactones resulted in increased hyphal branching, with (±)-GR24 stimulating a stronger effect than Nijmegen-1 by affecting colony diameter and radial growth. An oxidative stress response was observed, with B. cinerea exhibiting increased ROS and SOD levels when grown with strigolactones. This study identified the application of strigolactones as potential priming agents to induce disease resistance in both tobacco and grapevine plants. In addition, strigolactones may alter the ROS homeostasis of B. cinerea, resulting in both morphological and physiological changes, thereby reducing virulence.

Investigating the Interplay between Tomato Leaf Curl New Delhi Virus Infection, Starch Metabolism and Antioxidant Defence System in Potato (Solanum tuberosum L.)

The potato apical leaf curl disease is caused by tomato leaf curl New Delhi virus-potato (ToLCNDV-potato), which severely alters a plant's starch metabolism, starch hydrolysing enzymes, and antioxidant mechanism. In this study, the result suggested that ToLCNDV-potato significantly (p < 0.01) affected the morphological parameters and photosynthetic pigment system in both the cultivars of potato, viz., Kufri Pukhraj (susceptible) and Kufri Bahar (tolerant). However, the impact of ToLCNDV-potato was lower in Kufri Bahar. Moreover, the viral infection in potato showed significant (p < 0.01) enhancement in the leakage of plant oxidative metabolites such as proline and malondialdehyde (MDA) which was further confirmed with higher electrolyte leakage. The viral infection imbalance of starch metabolism in the leaves ultimately affects the carbohydrate profile. ToLCNDV-potato significantly lowered starch synthesis, enhanced the accumulation of sucrose, glucose, fructose and-which was further validated by enzymatic estimation of β-amylase-α-amylase and phosphorylase activity in the leaves of both cultivars. The antioxidant enzymes, viz., catalase, ascorbate peroxidase, and superoxide dismutase, were reported to be enhanced in both the cultivars due to ToLCNDV-potato infection. The higher enhancement of antioxidant enzyme activity was observed in Kufri Bahar, which signifies its resistant attributes. These findings in the potato plant broaden our understanding of the regulatory mechanisms of starch metabolism and antioxidant activity and provide proof of concept for breeding potato for ToLCNDV-potato tolerance.

Effects of Exogenous Sodium Nitroprusside Spraying on Physiological Characteristics of Soybean Leaves at the Flowering Stage under Drought Stress

Nitric oxide (NO) plays a significant role in plant drought resistance. However, the effects of the exogenous application of NO to crops under drought stress vary within and among species. In this study, we explored the influence of exogenous sodium nitroprusside (SNP) on the drought resistance of soybean leaves in the full flowering stage using two varieties: drought-tolerant HN44 and non-drought-tolerant HN65. Spraying SNP on soybean leaves at the full flowering period under drought stress improved the NO content in soybean leaves. The activities of nitrite reductase (NiR) and nitrate reductase (NR) in leaves were affected by NO inhibition. The activity of antioxidant enzymes in leaves increased with the extension of SNP application time. Contents of osmomodulatory substances, including proline (Pro), soluble sugar (SS), and soluble protein (SP) increased gradually with the extension of SNP application time. The malondialdehyde (MDA) content decreased as the NO content increased, thus reducing membrane system damage. Overall, spraying SNP reduced damage and improved the ability of soybean to cope with drought. This study explored the physiological changes of SNP soybean under drought stress and provided theoretical basis for improving drought-resistant cultivation of soybean.

Physiological mechanism of exogenous brassinolide alleviating salt stress injury in rice seedlings

Brassinolide (BR) is a sterol compound, which can regulate plant seed germination, flowering, senescence, tropism, photosynthesis, stress resistance, and is closely related to other signaling molecules. This study aimed to evaluate the ability of soaking with BR to regulate growth quality at rice seedling stage under salt stress. Results demonstrated that salt stress increases the contents of ROS, MDA, Na⁺ and ABA, reduces the the SPAD value, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), maximum fluorescence (Fm), variable fluorescence (Fv), the effective photochemical efficiency of PSII (Fv/Fo) and the maximum photochemical efficiency of PSII (Fv/Fm), reduces the biomass production and inhabits plant growth. All of these responses were effectively alleviated by BR soaking treatment. Soaking with BR could increase the activities of superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, and the contents of ascorbic acid, glutathione as well as soluble protein and proline, while BR soaking treatment inhibited the accumulation of ROS and reduced the content of MDA. BR soaking significantly reduced the contents of Na⁺ and increased the contents of K⁺ and Ca²⁺, indicating that soaking with BR is beneficial to the excretion of Na⁺, the absorption of K⁺ and Ca²⁺ and the maintenance of ion balance in rice seedlings under salt stress. BR also maintained endogenous hormone balance by increasing the contents of indoleacetic acid (IAA), zeatin (ZT), salicylic acid (SA), and decreasing the ABA content. Soaking with BR significantly increased the SPAD value, Pn and Tr and enhanced the Fm, Fv/Fm and Fv/Fo of rice seedlings under NaCl stress, protected the photosythetic system of plants, and improved their biomass. It is suggested that BR was beneficial to protect membrane lipid peroxidation, the modulation of antioxidant defense systems, ion balance and endogenous hormonal balance with imposition to salt stress.

Physiological mechanisms of ABA-induced salinity tolerance in leaves and roots of rice

Abscisic acid (ABA) plays a crucial role in response to abiotic stress as important small molecules in regulating metabolism. This study aimed to evaluate the ability of foliar spraying ABA to regulate growth quality at rice seedling stage under salt stress. Results demonstrated that salt stress strongly reduced all the growth parameters of two rice seedlings ('Chaoyouqianhao' and 'Huanghuazhan'), caused prominent decrease in the levels of photosynthetic pigments (mainly in Huanghuazhan), photosynthesis and fluorescence parameters. Salinity treatment increased the concentration of malondialdehyde (MDA) and hydrogen peroxide (H2O2) in roots, whereas significant decreased H2O2 was found in leaves of Huanghuazhan. Additionally, salinity triggered high Na+ content particularly in leaves and enhanced catalase (CAT) activities, ascorbate peroxidase (APX) and peroxidase (POD) activities of the two rice seedlings. Nevertheless, salinity-induced increased root ascorbic acid (AsA) and glutathione (GSH) levels while decreased in leaves, which depended on treatment time. Conversely, ABA application partially or completely mitigated salinity toxicity on the seedlings. ABA could reverse most of the changed physiological parameters triggered by salt stress. Specially, ABA treatment improved antioxidant enzyme levels and significantly reduced the Na+ content of two varieties as well as increased the K+, Mg2+ and Ca2+ content in leaves and roots. ABA treatment increased the hormone contents of 1-aminocclopropane carboxylic acid (ACC), trans-zeatin (TZ), N6-isopentyladenosine (IPA), Indole-3-acetic acid (IAA), and ABA in leaves of two rice varieties under salt stress. It is suggested that ABA was beneficial to protect membrane lipid peroxidation, the modulation of antioxidant defense systems and endogenous hormonal balance with imposition to salt stress.

Foliar Application of Salicylic Acid Improves Salt Tolerance of Sorghum (Sorghum bicolor (L.) Moench)

It has been reported that around the world, approximately 19.5% of all irrigated land and 2.1% of dry land is affected by salt stress, and these percentages continue to increase. Sorghum is the fifth most important cereal in the world and therefore research on its salt tolerance is of global importance. In our research, we focused on foliar application of salicylic acid (SA) on salt-stressed sorghum. We performed a pot experiment with two salt levels (0 and 100 mM sodium chloride NaCl) and five SA concentrations (0, 50, 100, 150 and 200 mg/L). Our results suggest that in saline conditions foliar application of SA induced an adaptive response to salinity by inducing proline accumulation as well as antioxidant enzymes activities and enhanced the protection of the photosynthetic machinery, maintained photosynthesis activities, and improved the growth of sorghum plants. These alleviation effects were depended on applied SA concentration. Under saline condition 150 mg/L, SA was the most effective for relieving the adverse effect of salt stress. Under non-saline conditions 100 mg/L SA was the best for improving sorghum growth and dry matter production. Our results demonstrated that foliar SA application is effective in improving sorghum growth under salinity.

Activation of defense response in common bean against stem rot disease triggered by Trichoderma erinaceum and Trichoderma viride

White mold and stem rot is a common disease of Phaseolus vulgaris caused by Sclerotinia sclerotiorum. Biological control is a promising alternative for the control of this disease. In the present study, two Trichoderma spp., T. erinaceum and T. viride, and the consortium of both were evaluated as biocontrol agents against sclerotinia stem rot disease. The results revealed that T. erinaceum (NAIMCC-F-02171) and T. viride (NAIMCC-F-02500) when applied alone, significantly suppressed the infection rate of S. sclerotiorum and increased the rate of survival of plants by 74.5%. On the contrary, the combination of both the Trichoderma spp. was found to be more effective in reducing stem rot by 57.2% and increasing the survival of plants by 87.5% when compared to the individual Trichoderma applications. Further, the exogenous supplementation of Trichoderma activated antioxidative machineries, such as peroxidase, polyphenol oxidase, superoxide dismutase, catalase, and ascorbic acid in the plant. Besides, hydrogen peroxide and superoxide-free radical accumulation were also found to be reduced when T. erinaceum and T. viride were used either individually or in combination under the pathogen-challenged condition. Additionally, the photopigments in the bioprimed plants were markedly increased. Moreover, the combined inoculation of the two isolates yielded the highest records of growth parameters (root weight, shoot length, and leaf weight) compared with individual inoculation. Therefore, based on the above results, it was concluded that the combination of T. erinaceum and T. viride can be effectively used as an alternative to control white mold and stem rot caused by S. sclerotiorum.

Abscisic acid modulates differential physiological and biochemical responses of roots, stems, and leaves in mung bean seedlings to cadmium stress

Experiments were conducted to determine how exogenous abscisic acid (ABA) mediates the tolerance of plants to cadmium (Cd) exposure. Cd stress strongly reduced all the growth parameters of mung bean seedlings. Cd significantly increased ascorbate peroxidase (APX) and catalase (CAT) activities in roots and stems, and peroxidase (POD) activities in roots, stems, and leaves of mung bean seedlings. Cd caused remarkable increases in the levels of leaf chlorophyll and carotenoid, root polyphenols, and malondialdehyde (MDA) and proline in the three organs. However, Cd greatly decreased leaf CAT activity, root and leaf ascorbic acid (AsA) levels, and stem and leaf polyphenol levels. Foliar application of ABA partially alleviated Cd toxicity on the seedlings. ABA could restore most of the changed biochemical parameters caused by Cd, suggesting that ABA played roles in the protection of membrane lipid peroxidation and the modulation of antioxidative defense systems in response to Cd stress. Our results also implied the differential physiological and biochemical responsive patterns of roots, stems, and leaves to Cd and ABA in mung bean seedlings. The great changes in many biochemical parameters in roots suggested that roots were the first to be affected by Cd and play pivotal roles in response to Cd, especially in chelating Cd and reducing Cd absorption.

Induction of Salt Tolerance in Arabidopsis thaliana by Volatiles From Bacillus amyloliquefaciens FZB42 via the Jasmonic Acid Signaling Pathway

Previously, we showed that Bacillus amyloliquefaciens FZB42 can confer salt tolerance in plants by root inoculation under salt stress condition, and the FZB42 volatile organic compounds (VOCs) promoted plant growth and development under non-salt stress condition. In the present study, we investigated the mechanism that allows FZB42 VOCs to confer salt tolerance in Arabidopsis without colonization of plant roots. We found that FZB42 VOCs significantly increased the biomass of Arabidopsis and also maintained the leaf chlorophyll content under salt stress condition. Physiological tests showed that the plant anti-oxidation system was activated by FZB42 VOCs, where higher peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) activities were detected in plants exposed to FZB42 VOCs compared with non-exposed plants. In addition, FZB42 VOCs increased the leaf total soluble sugars (TSS) content but decreased the proline content compared with the non-exposed plants. Moreover, FZB42 VOCs significantly decreased the Na⁺ contents of the whole plants and induced the expression of genes (NHX1; Na⁺/H⁺ exchanger 1 and HKT1; high-affinity K⁺ transporter 1) that function to alleviate Na⁺ toxicity. Furthermore, analysis of mutants with defects in specific hormone pathways showed that FZB42 VOCs induced salt tolerance in plants by modulating jasmonic acid (JA) signaling, which was confirmed by the up-regulation of JA synthesis, defense-related genes, and JA biosynthesis inhibitor tests. The results of this study provide new insights into the molecular mechanism related to the interactions between plant growth-promoting rhizobacteria and plants under salt stress condition.

Assessment of physiological age and antioxidant status of new somatic hybrid potato seeds during extended cold storage

Yield components of potato are largely affected by the physiology age of the tuber seeds at planting. The current study focuses on monitoring seed tuber aging in two CN1 and CN2 somatic hybrid lines and Spunta (Sp) variety during 270 days of storage at 4 °C. Aging rate was monitored based on sprouting, emergence and tissue oxidation rates. Investigation of sprouting parameters such as physiological age index (PAI) considering physiological and chronological age and the incubation period (IP) indicated lower physiological age in hybrids than in Sp during the storage. Moreover, these analyses showed that off-seasonal growing conditions increased the aging, more clearly, in Sp tubers than in hybrid ones. However, dormancy periods (endodormancy and after storage dormancy) were equivalent in the different tuber lots. PAI and IP data when combined with those from emergence parameters (duration until emergence and stem number) seem more efficient for the characterization of the different potato lines. However, emergence indicators, when considered separately, were not able to distinguish clearly between seasonal and off-seasonal tubers. Data suggest that hybrid seeds exhibited high performances since they produced higher stem number per plant than Sp. The high aging rate in Sp tubers seems to be associated with the few developed stems. Biochemical analyses supported in part morphophysiological differences between hybrids and Sp seeds although these indicators seem more sensitive to aging. Indeed data showed that the dormancy break, and then, the development were associated with some level of tissue oxidation. Antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and carotenoids seem more enhanced after the release of dormancy. However, induction of these activities started earlier in off-seasonal tubers than in seasonal ones, this was consistent with their advanced aging level revealed by PAI and IP data. Activation of these antioxidants appears to respond effectively to the increase of ROS suggesting a better control of postharvest development and tissue deterioration especially in CN2 off-seasonal tubers. This study suggests that CN2 followed by CN1 exhibited the best performance compared to Sp variety.

Increased Precipitation Shapes Relationship between Biochemical and Functional Traits of Stipa glareosa in Grass-Dominated Rather than Shrub-Dominated Community in a Desert Steppe

Understanding the effects of precipitation variations on plant biochemical and functional traits is crucial to predict plant adaptation to future climate changes. The dominant species, Stipa glareosa, plays an important role in maintaining the structure and function of plant communities in the desert steppe, Inner Mongolia. However, little is known about how altered precipitation affects biochemical and functional traits of S. glareosa in different communities in the desert steppe. Here, we examined the responses of biochemical and functional traits of S. glareosa in shrub- and grass-dominated communities to experimentally increased precipitation (control, +20%, +40%, and +60%). We found that +40% and +60% increased plant height and leaf dry matter content (LDMC) and decreased specific leaf area (SLA) of S. glareosa in grass community. For biochemical traits in grass community, +60% decreased the contents of protein and chlorophyll b (Cb), while +40% increased the relative electrical conductivity and superoxide dismutase. Additionally, +20% increased LDMC and malondialaenyde, and decreased SLA and protein in shrub community. Chlorophyll a, Cb, carotenoids, protein and superoxide dismutase in the grass community differed with shrub community, while +60% caused differences in SLA, LDMC, leaf carbon content, malondialaenyde and peroxidase between two communities. The positive or negative linear patterns were observed between different functional and biochemical traits in grass- rather than shrub-community. Soil water content explained changes in some biochemical traits in the grass community, but not for functional traits. These results suggest that increased precipitation can affect functional traits of S. glareosa in the grass community by altering biochemical traits caused by soil water content. The biochemical and functional traits of S. glareosa were more sensitive to extreme precipitation in grass- than shrub-community in the desert steppe. Our study highlights the important differences in adaptive strategies of S. glareosa in different plant communities at the same site to precipitation changes.

Postharvest application of antibrowning chemicals modulates oxidative stress and delays pericarp browning of controlled atmosphere stored litchi fruit

Litchi fruit were treated with methionine [(0.25%) MN] and cysteine [(025%) CN] alone or in combination, and kept under 1% O₂ + 5% CO₂ controlled atmosphere (CA) at 5 ± 1ºC for 28 days. Among different treatments, CN was most effective to inhibit browning, than MN and CN + MN under CA conditions. Application of 0.25% CN significantly delayed browning index, reduced disease incidence, weight loss, malondialdehyde (MDA) contents, electrolyte leakage, hydrogen peroxide (H₂ O₂ ), superoxide anion (O₂ ^-• ) and polyphenol oxidase (PPO) and peroxidase (POD) activities with higher contents of total anthocyanins under CA-storage. In addition, 0.25% CN treatment showed higher contents of ascorbic acid, total phenolics (TPC), and 2,2-diphenyl-1-picrylhydrazyl-radical scavenging capacity and activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) enzymes having maintained quality attributes. Therefore, 0.25% CN pre-treatment could be considered a promising way for managing browning, and conserving litchi fruit quality under CA-storage. PRACTICAL APPLICATIONS: Litchi fruit are highly perishable due to rapid pericarp browning having limited postharvest market potential. The browning takes place due to enzymatic reactions and phenolic oxidation. However, it can be delayed by exogenous antibrowning treatments and suitable storage environment. The delayed incidence of pericarp browning may help to maintain its quality with extended storage potential suitable for domestic and international markets. So, the outcomes of the current work may help to maintain overall quality and to extend its storage potential that would be helpful in extending its market life with maintained visual quality at domestic and international destinations.

Physiological characterization, transcriptomic profiling, and microsatellite marker mining of Lycium ruthenicum

Lycium ruthenicum is a perennial shrub species that has attracted considerable interest in recent years owing to its nutritional value and ability to thrive in a harsh environment. However, only extremely limited transcriptomic and genomic data related to this species can be found in public databases, thereby limiting breeding research and molecular function analysis. In this study, we characterized the physiological and biochemical responses to saline-alkaline mixed stress by measuring photochemical efficiency, chlorophyll content, and protective enzyme activity. We performed global transcriptomic profiling analysis using the Illumina platform. After optimizing the assembly, a total of 68 063 unique transcript sequences with an average length of 877 bp were obtained. Among these sequences, 4096 unigenes were upregulated and 4381 unigenes were down-regulated after saline-alkaline mixed treatment. The most abundant transcripts and over-represented items were assigned to gene ontology (GO) terms or Kyoto Encyclopedia of Genes and the Genomes (KEGG) categories for overall unigenes, and differentially expressed unigenes were analyzed in detail. Based on this set of RNA-sequencing data, a total of 9216 perfect potential simple sequence repeats (SSRs) were identified within 7940 unigenes with a frequency of 1/6.48 kb. A total of 77 primer pairs were synthesized and examined in wet-laboratory experiments, of which 68 loci (88.3%) were successfully amplified with specific products. Eleven pairs of polymorphic primers were verified in 225 individuals from nine populations. The inbreeding coefficient and the polymorphism information content value ranged from 0.011 to 0.179 and from 0.1112 to 0.6750, respectively. The observed and expected heterozygosities ranged from 0.064 to 0.840 and from 0.115 to 0.726, respectively. Nine populations were clustered into three groups based on a genetic diversity study using these novel markers. Our data will be useful for functional genomic investigations of L. ruthenicum and could be used as a basis for further research on the genetic diversity, genetic differentiation, and gene flow of L. ruthenicum and other closely related species.

How can salicylic acid and jasmonic acid mitigate salt toxicity in soybean plants?

This research was undertaken to assess the impact of 1mM salicylic acid (SA) and 0.5mM jasmonic acid (JA) on alleviation of oxidative, ionic and osmotic stresses of different levels of salinity (0, 4, 7, 10 dS m-1 NaCl, respectively). Salinity increased the contents of glycine betaine, proline, soluble sugars, proteins and the activities of peroxidase, catalase, superoxide dismutase, ascorbate peroxidase, and the amount of malondialdehyde and sodium ion of soybean leaves, but decreased the leaf water content, membrane stability index, potassium and calcium ions, chlorophylls content, chlorophyll stability index, plant biomass and seed yield. Foliar spray of JA reduced Na+ entry to the cells, while enhancing the glycine betaine and soluble proteins content, antioxidant enzymes activity, membrane stability index and leaf water content. This treatment had no effect on potassium and the calcium ions content, chlorophyll contents, chlorophyll stability index, soluble sugars, plant biomass and seed yield. In contrast, SA enriched the leaf cells with potassium and calcium ions under different levels of salt stress and increased glycine betaine, soluble sugars, proteins, antioxidant enzymes, leaf water content, membrane stability index, chlorophyll content and chlorophyll stability index, but reduced proline content. These superiorities of SA treatment led to considerable improvement in plant biomass (10%) and seed yield (17%) of soybean.

Salt stress-induced changes in antioxidative defense system and proteome profiles of salt-tolerant and sensitive Frankia strains

An appreciation of comparative microbial survival is most easily done while evaluating their adaptive strategies during stress. In the present experiment, antioxidative and whole cell proteome variations based on spectrophotometric analysis and SDS-PAGE and 2-dimensional gel electrophoresis have been analysed among salt-tolerant and salt-sensitive Frankia strains. This is the first report of proteomic basis underlying salt tolerance in these newly isolated Frankia strains from Hippophae salicifolia D. Don. Salt-tolerant strain HsIi10 shows higher increment in the contents of superoxide dismutase, catalase and ascorbate peroxidase as compared to salt-sensitive strain HsIi8. Differential 2-DGE profile has revealed differential profiles for salt-tolerant and salt-sensitive strains. Proteomic confirmation of salt tolerance in the strains with inbuilt efficiency of thriving in nitrogen-deficient locales is a definite advantage for these microbes. This would be equally beneficial for improvement of soil nitrogen status. Efficient protein regulation in HsIi10 suggests further exploration for its potential use as biofertilizer in saline soils.

Antioxidant enzyme and osmotic adjustment changes in bean seedlings as affected by biochar under salt stress

Salinity damaged cellular membranes through overproduction of reactive oxygen species (ROS), while osmolytes and antioxidant capacities play a vital role in protecting plants from salinity caused oxidative damages. Biochar also could alleviate the negative impacts of salt stress in crops. The pot experiment was conducted to investigate the effects of biochar on some antioxidant enzyme activities and osmolyte adjustments of common bean (Phaseolus vulgaris L. cv. Derakhshan) under salinity stress. Bean plants were subjected to three salinity levels (non-saline, 6 and 12 dSm^-1 of NaCl) and biochar treatments (non-biochar, 10% and 20% total pot mass). Shoot and root dry weights of bean were decreased at two salt stress treatments. Salinity increased the activity of catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), polyphenol oxidase (PPO) and superoxide dismutase (SOD), and the content of malondialdehyde (MDA), oxygen radicals (O^2•-), and hydrogen peroxide (H₂O₂) in leaf and root compared to control. Additionally, increased magnitudes of proline, glycine betaine, soluble sugar and soluble protein contents were more pronounced under 12 dSm^-1 NaCl than those under 6 dSm^-1 NaCl. In contrast, biochar applied to soil enhanced the shoot and root dry weight in comparison with the non-biochar treatment. Furthermore, all of the antioxidant activities of seedlings in soil treated with biochar, particularly at 20% biochar, declined. With the addition of biochar, the contents of MDA, O^2•- and H₂O₂ displayed remarkable decrease, and the osmotic substances accumulation in leaves and roots also reduced. The presented results supported the view that biochar can contribute to protect common bean seedlings against NaCl stress by alleviating the oxidative stress.

Biocontrol potential of Trichoderma harzianum isolate T-aloe against Sclerotinia sclerotiorum in soybean

Sclerotinia stem rot, caused by Sclerotinia sclerotiorum (Lib.) de Bary is a major disease of soybean (Glycine max (L.) Merr.). At present, we revealed the three-way interaction between Trichoderma harzianum T-aloe, pathogen S. sclerotiorum and soybean plants in order to demonstrate biocontrol mechanism and evaluate biocontrol potential of T-aloe against S. sclerotiorum in soybean. In our experiments, T-aloe inhibited the growth of S. sclerotiorum with an efficiency of 56.3% in dual culture tests. T-aloe hyphae grew in parallel or intertwined with S. sclerotiorum hyphae and produced hooked contact branches, indicating mycoparasitism. Plate tests showed that T-aloe culture filtrate inhibited S. sclerotiorum growth with an inhibition efficiency of 51.2% and sclerotia production. T-aloe pretreatment showed growth-promoting effect on soybean plants. The activities of peroxidase, superoxide dismutase, and catalase increased, and the hydrogen peroxide (H2O2) as well as the superoxide radical (O2(-)) content in soybean leaves decreased after T-aloe pretreatment in response to S. sclerotiorum pathogen challenge. T-aloe treatment diminished damage caused by pathogen stress on soybean leaf cell membrane, and increased chlorophyll as well as total phenol contents. The defense-related genes PR1, PR2, and PR3 were expressed in the leaves of T-aloe-treated plants. In summary, T-aloe displayed biocontrol potential against S. sclerotiorum. This is the first report of unraveling biocontrol potential of Trichoderma Spp. to soybean sclerotinia stem rot from the three-way interaction between the biocontrol agent, pathogen S. sclerotiorum and soybean plants.

Heterologous expression of ACC deaminase from Trichoderma asperellum improves the growth performance of Arabidopsis thaliana under normal and salt stress conditions

Transgenic Arabidopsis thaliana plants expressing the 1-aminocyclopropane-1-carboxylate deaminase gene (ACCD) of Trichoderma asperellum ACCC30536 (TaACCD) were created and their growth performance was assessed under normal and salt stress conditions. In order to characterize their growth, root length, root number, fresh weight (FW), relative water content (RWC), seed production, and seed number were measured. Under normal growing condition, all growth parameters except for dry weight (DW) of the transgenic plants increased significantly compared to WT plants. Furthermore, the transgenic line also exhibited higher tolerance and faster growth than WT plants in the presence of 150 mM NaCl. The increased salt stress tolerance of the transgenic plants is attributed to a greater RWC, root weight, root length, root number and FW under salt stress, and to reduced reactive oxygen species (ROS) level, cell death and electrolyte leakage compared to WT plants. The reduction in ROS levels could be explained by increased activity of several antioxidant enzymes, including peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT). Thus, we propose that heterologous expression of TaACCD could be used to improve salt stress tolerance in plants.

Combined Effects of Lanthanum (III) and Acid Rain on Antioxidant Enzyme System in Soybean Roots

Rare earth element pollution (REEs) and acid rain (AR) pollution simultaneously occur in many regions, which resulted in a new environmental issue, the combined pollution of REEs and AR. The effects of the combined pollution on the antioxidant enzyme system of plant roots have not been reported. Here, the combined effects of lanthanum ion (La3+), one type of REE, and AR on the antioxidant enzyme system of soybean roots were investigated. In the combined treatment of La3+ (0.08 mM) and AR, the cell membrane permeability and the peroxidation of cell membrane lipid of soybean roots increased, and the superoxide dismutase, catalase, peroxidase and reduced ascorbic acid served as scavengers of reactive oxygen species. In other combined treatments of La3+ (0.40 mM, 1.20 mM) and AR, the membrane permeability, malonyldialdehyde content, superoxide dismutase activity, peroxidase activity and reduced ascorbic acid content increased, while the catalase activity decreased. The increased superoxide dismutase activity, peroxidase activity and reduced ascorbic acid content were inadequate to scavenge the excess hydrogen peroxide and superoxide, leading to the damage of the cell membrane, which was aggravated with the increase in the concentration of La3+ and the level of AR. The deleterious effects of the combined treatment of La3+ and AR were stronger than those of the single treatment of La3+ or AR. Moreover, the activity of antioxidant enzyme system in the combined treatment group was affected directly and indirectly by mineral element content in soybean plants.

Chlorogenic Acid Biosynthesis Appears Linked with Suberin Production in Potato Tuber (Solanum tuberosum)

Potato (Solanum tuberosum L.) is a good source of dietary antioxidants. Chlorogenic acid (CGA) and caffeic acid (CA) are the most abundant phenolic acid antioxidants in potato and are formed by the phenylpropanoid pathway. A number of CGA biosynthetic routes that involve hydroxycinnamoyl-CoA quinate hydroxycinnamoyl transferase (HQT) and/or hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyl transferase (HCT) have been proposed, but little is known about their path in potato. CA production requires a caffeoyl shikimate esterase (CSE), and CA serves as a substrate of lignin precursor ferulic acid via the action of caffeic/5-hydroxyferulic acid O-methyltransferase (COMT I). CGA is precursor of caffeoyl-CoA and, via caffeoyl-CoA O-methyltransferase (CCoAOMT), of feruloyl-CoA. Feruloyl-CoA is required for lignin and suberin biosynthesis, crucial for tuber development. Here, metabolite and transcript levels of the mentioned and related enzymes, such as cinnamate 4-hydroxylase (C4H), were determined in the flesh and skin of fresh and stored tubers. Metabolite and transcript levels were higher in skin than in flesh, irrespective of storage. CGA and CA production appear to occur via p-coumaroyl-CoA, using HQT and CSE, respectively. HCT is likely involved in CGA remobilization toward suberin. The strong correlation between CGA and CA, the correspondence with C4H, HQT, CCoAOMT2, and CSE, and the negative correlation of HCT and COMT I in potato tubers suggest a major flux toward suberin.

Effects of bisphenol A on antioxidant system in soybean seedling roots

Bisphenol A (BPA), an emerging pollutant in the environment, has potential toxic effects on plants. The toxicity mechanism, however, remains largely unknown. The antioxidant system plays an important role in protecting plants against the damage of stress. The present study investigated the effects of BPA on the antioxidant system (superoxide dismutase [SOD], peroxidase [POD], catalase [CAT], ascorbic acid [AsA], proline, reduced glutathione [GSH]), reactive oxygen species (ROS; hydrogen peroxide [H2 O2 ], superoxide anion [O2 (-) ]) accumulation, and membrane lipid peroxidation (malondialdehyde [MDA], cell membrane permeability) in soybean seedling roots. The 1.5 mg L(-1) BPA exposure did not affect test indices in the roots. Exposure to 3.0 mg L(-1) , 6.0 mg L(-1) , 12.0 mg L(-1) , or 24.0 mg L(-1) BPA caused increases in SOD (except for 3.0 mg L(-1) BPA) and CAT activities, as well as in AsA, proline, and GSH (except for 3.0 mg L(-1) BPA) content, leading to increases in the H2 O2 and O2 (-) content and to membrane lipid peroxidation. Exposure to 48.0 mg L(-1) or 96.0 mg L(-1) BPA caused decreases in the CAT activity and AsA/GSH content, as well as increases in the SOD and POD activities and the proline content, leading to excess ROS accumulation (i.e., H2 O2 and O2 (-) ) and cell membrane damage. After withdrawal of BPA exposure, ROS accumulation and membrane lipid peroxidation were alleviated by regulating a special antioxidant enzyme or substance.

Wounding induces changes in tuber polyamine content, polyamine metabolic gene expression, and enzyme activity during closing layer formation and initiation of wound periderm formation

Tuber wound-healing processes are complex, and the associated regulation and modulation of these processes are poorly understood. Polyamines (PA) are involved in modulating a variety of responses to biotic and abiotic plant stresses and have been suggested to be involved in tuber wound responses. However, the time course of wound-induced changes in tuber PA content, activity of key biosynthetic enzymes and associated gene expression has not been determined and coordinated with major wound-healing processes. The objective of this study was to determine these wound-induced changes and their coordination with wound-healing processes. Wounding induced increases in putrescine (Put) and spermidine (Spd), but had only minor effects on spermine (Spm) content during the 168 h time course which encompassed the initiation and completion of the closing layer formation, and the initiation of cell division and wound periderm formation. As determinants of the first committed step in PA biosynthesis, arginine and ornithine decarboxylase (ADC and ODC, respectively) activities were below levels of detectability in resting tubers and expression of genes encoding these two enzymes was low. Within 6h of wounding, increases in the in vitro activities of ADC and ODC and expression of their cognate genes were observed. Expression of a gene encoding S-adenosylmethionine decarboxylase, required for Spd and Spm biosynthesis, was also increased 6h after wounding and remained elevated throughout the time course. Expression of a polyamine catabolic gene, encoding polyamine oxidase, was down-regulated after wounding. Results indicated a rapid wound-induced increase in PA biosynthesis during closing layer formation and the time of nuclei entry and exit from S-phase. PA content remained elevated as wound-induced cells became meristematic and initiated formation of the wound periderm suggesting sustained involvement in wound-healing.

Accumulation of Hydrocarbons by Maize (Zea mays L.) in Remediation of Soils Contaminated with Crude Oil

This study has investigated the use of screened maize for remediation of soil contaminated with crude oil. Pots experiment was carried out for 60 days by transplanting maize seedlings into spiked soils. The results showed that certain amount of crude oil in soil (≤2 147 mg·kg(-1)) could enhance the production of shoot biomass of maize. Higher concentration (6 373 mg·kg(-1)) did not significantly inhibit the growth of plant maize (including shoot and root). Analysis of plant shoot by GC-MS showed that low molecular weight polycyclic aromatic hydrocarbons (PAHs) were detected in maize tissues, but PAHs concentration in the plant did not increase with higher concentration of crude oil in soil. The reduction of total petroleum hydrocarbon in planted soil was up to 52.21-72.84%, while that of the corresponding controls was only 25.85-34.22% in two months. In addition, data from physiological and biochemical indexes demonstrated a favorable adaptability of maize to crude oil pollution stress. This study suggested that the use of maize (Zea mays L.) was a good choice for remediation of soil contaminated with petroleum within a certain range of concentrations.

Hexanoyl-lysine as a deterioration marker for rice during storage

N(ε)-(hexanoyl)lysine (HEL) is known to be an oxidative lipid-decomposition product, and a powerful marker indicating oxidative stress in animal tissue. We investigated whether HEL could be useful as a marker in rice seeds damaged by oxidative stress during storage, as well as animals. We could show an accumulation of HEL in rice stored at high temperature (40 °C). This result significantly corresponded with an accumulation of TBARS. Rice germination deteriorated with non-enzymatic lipid peroxidation during storage at high temperature for a few months. These results suggested that a deterioration of rice germination ability resulted from oxidative damage caused by lipid peroxidation during storage. Moreover, HEL could become a useful marker for oxidative stress induced by lipid peroxidation. In addition, the activities of antioxidant enzymes, catalase and superoxide dismutase, significantly decreased in the rice seeds during storage at 40 °C. The relationship between accumulation of HEL and increases in antioxidant enzymes activities must be further studied. But, these results suggest that HEL might be a useful marker of oxidative stress in rice as well as in animals.

Involvement of abscisic acid in regulating antioxidative defense systems and IAA-oxidase activity and improving adventitious rooting in mung bean [Vigna radiata (L.) Wilczek] seedlings under cadmium stress

In vitro experiments were conducted to investigate the effects of abscisic acid (ABA) and Cd on antioxidative defense systems and indole-3-acetic acid (IAA) oxidase during adventitious rooting in mung bean [Vigna radiata (L.) Wilczek] seedlings. The exogenous ABA significantly enhanced the number and fresh weight of the adventitious roots. CdCl2 strongly inhibited adventitious rooting. Pretreatment with 10 μM ABA clearly alleviated the inhibitory effect of Cd on rooting. ABA significantly reduced superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD), and catalase (CAT) activities, as well as the levels of glutathione (GSH) and ascorbic acid (ASA) during adventitious rooting. ABA strongly increased IAA-oxidase activity during the induction (0-12 h) and expression (after 48 h) phases and increased the phenols levels. Cd treatment significantly reduced the activities of SOD, APX, POD, and IAA oxidase, as well as GSH level. Cd strongly increased ASA levels. ABA pretreatment counteracted Cd-induced alterations of certain antioxidants and antioxidative enzymes, e.g., remarkably rescued APX and POD activities, reduced the elevated SOD and CAT activities and ASA levels, and recovered the reduced GSH levels, caused by Cd stress. Thus, the physiological effects of the combination of ABA and Cd treatments were opposite of those obtained with Cd treatment alone, suggesting that ABA involved in the regulation of antioxidative defense systems and the alleviation of wounding- and Cd-induced oxidative stress.

Translucent tissue defect in potato (Solanum tuberosum L.) tubers is associated with oxidative stress accompanying an accelerated aging phenotype

Translucent tissue defect (TTD) is an undesirable postharvest disorder of potato tubers characterized by the development of random pockets of semi-transparent tissue containing high concentrations of reducing sugars. Translucent areas turn dark during frying due to the Maillard reaction. The newly released cultivar, Premier Russet, is highly resistant to low temperature sweetening, but susceptible to TTD. Symptoms appeared as early as 170 days after harvest and worsened with time in storage (4-9 °C, 95 % RH). In addition to higher concentrations of glucose, fructose and sucrose, TTD resulted in lower dry matter, higher specific activities of starch phosphorylase and glc-6-phosphate dehydrogenase, higher protease activity, loss of protein, and increased concentrations of free amino acids (esp. asparagine and glutamine). The mechanism of TTD is unknown; however, the disorder has similarities with the irreversible senescent sweetening that occurs in tubers during long-term storage, where much of the decline in quality is a consequence of progressive increases in oxidative stress with advancing age. The respiration rate of non-TTD 'Premier Russet' tubers was inherently higher (ca. 40 %) than that of 'Russet Burbank' tubers (a non-TTD cultivar). Moreover, translucent tissue from 'Premier Russet' tubers had a 1.9-fold higher respiration rate than the average of non-translucent tissue and tissue from non-TTD tubers. Peroxidation of membrane lipids during TTD development resulted in increased levels of malondialdehyde and likely contributed to a measurable increase in membrane permeability. Superoxide dismutase and catalase activities and the ratio of oxidized to total glutathione were substantially higher in translucent tissue. TTD tubers also contained twofold less ascorbate than non-TTD tubers. TTD appears to be a consequence of oxidative stress associated with accelerated aging of 'Premier Russet' tubers.

Effect of bleaching with two different concentrations of hydrogen peroxide containing sweet potato extract as an additive on human enamel: An in vitro spectrophotometric and scanning electron microscopy analysis

Objectives:

To evaluate the color change in teeth bleached with two different concentrations of hydrogen peroxide, containing sweet potato extract as an additive, using a spectrophotometer, and to evaluate the surface changes in enamel using a scanning electron microscope (SEM).

Materials and Methods:

Baseline color values of 24 artificially stained incisors were obtained using a spectrophotometer. The specimens were divided into two groups of 12 teeth, each based on the concentration of hydrogen peroxide (H₂O₂) as follows: Group I — 35% H₂O₂ and Group II — 10% H₂O₂. One-half of the tooth was bleached with H₂O₂ alone (Subgroup A) and the other half was bleached with a combination of H₂O₂ and sweet potato extract (Subgroup B). Post bleaching the Commission Internationale de l’ Eclairage L^*, a^*, b^* (CIEL^*a^*b^*) values were obtained and ΔE was calculated. The surfaces of the samples were examined using SEM.

Results:

The mean ΔE values of groups IB (72.52 ± 2.03) and IIB (71.50 ± 1.81) were significantly higher than those of groups IA (65.24 ± 1.02) and IIA (64.19 ± 1.88), respectively, (P < 0.05). The SEM images of groups IB and IIB showed lesser surface irregularities and morphological alterations in enamel.

Conclusion:

The addition of sweet potato extract to hydrogen peroxide not only resulted in the restoration of the natural tooth color, but also decreased the effects of bleaching on the enamel morphology, compared to the use of hydrogen peroxide alone.

Aspects of plant behaviour under anoxia and post-anoxia

All plants are able to survive anoxic periods, but the degree of tolerance shows large variation. The main injuries related to anoxia are eventually due to changes in energy metabolism. Low energy charge values indicate a cessation of many ATP consuming processes. Sugar starvation, lactic acid fermentation and proton release from leaky vacuoles are responsible for cell death. Long-term anoxia tolerance is dependent on storage products in the vicinity of sinks, on an adequate control of glycolysis, synthesis of essential proteins, and stability of membranes and organelles. However, no fundamental differences between the metabolic pathways of tolerant and non-tolerant tissues are known. It is rather a question of minor changes and the regulation of anaerobic metabolism.

Re-exposure of anoxic tissues to air may even be more detrimental than anoxia itself. These injuries are mainly due to enhanced radical generation. Lipid peroxidation processes lead to membrane damage, disintegration, and leakage of solutes. Under natural conditions plants are equipped with radical-detoxifying systems (SOD, peroxidases and antioxidants). Natural detoxifying systems can be reduced in non-adapted plants under anoxia and they become more sensitive to post-anoxic damage. In addition, the rapid conversion of ethanol to extremely toxic acetaldehyde seems to be a cause of tissue injury and death.

Storage elevates phenolic content and antioxidant activity but suppresses antiproliferative and pro-apoptotic properties of colored-flesh potatoes against human colon cancer cell lines

Colored-flesh potatoes are an excellent source of health-benefiting dietary polyphenols, but are stored for up to 3-6 months before consumption. This study investigated the effect of simulated commercial storage conditions on antioxidant activity (DPPH, ABTS), phenolic content (FCR) and composition (UPLC-MS), and anticancer properties (early, HCT-116 and advanced stage, HT-29 human colon cancer cell lines) of potato bioactive compounds. Extracts from seven potato clones of differing flesh colors (white, yellow, and purple) before and after 90 days of storage were used in this study. The antioxidant activity of all clones increased with storage; however, an increase in total phenolic content was observed only in purple-fleshed clones. Advanced purple-fleshed selection CO97227-2P/PW had greater levels of total phenolics, monomeric anthocyanins, antioxidant activity and a diverse anthocyanin composition as compared with Purple Majesty. Purple-fleshed potatoes were more potent in suppressing proliferation and elevating apoptosis of colon cancer cells compared with white- and yellow-fleshed potatoes. The extracts from both fresh and stored potatoes (10-30 μg/mL) suppressed cancer cell proliferation and elevated apoptosis compared with the solvent control, but these anticancer effects were more pronounced with the fresh potatoes. Storage duration had a strong positive correlation with antioxidant activity and percentage of viable cancer cells and a negative correlation with apoptosis induction. These results suggest that although the antioxidant activity and phenolic content of potatoes were increased with storage, the antiproliferative and pro-apoptotic activities were suppressed. Thus, in the assessment of the effects of farm to fork operations on the health-benefiting properties of plant foods, it is critical to use quantitative analytical techniques in conjunction with in vitro and/or in vivo biological assays.

Arbuscular mycorrhizal fungi in alleviation of salt stress: a review

BACKGROUND

Salt stress has become a major threat to plant growth and productivity. Arbuscular mycorrhizal fungi colonize plant root systems and modulate plant growth in various ways.

SCOPE

This review addresses the significance of arbuscular mycorrhiza in alleviation of salt stress and their beneficial effects on plant growth and productivity. It also focuses on recent progress in unravelling biochemical, physiological and molecular mechanisms in mycorrhizal plants to alleviate salt stress.

CONCLUSIONS

The role of arbuscular mycorrhizal fungi in alleviating salt stress is well documented. This paper reviews the mechanisms arbuscular mycorrhizal fungi employ to enhance the salt tolerance of host plants such as enhanced nutrient acquisition (P, N, Mg and Ca), maintenance of the K(+) : Na(+) ratio, biochemical changes (accumulation of proline, betaines, polyamines, carbohydrates and antioxidants), physiological changes (photosynthetic efficiency, relative permeability, water status, abscissic acid accumulation, nodulation and nitrogen fixation), molecular changes (the expression of genes: PIP, Na(+)/H(+) antiporters, Lsnced, Lslea and LsP5CS) and ultra-structural changes. Theis review identifies certain lesser explored areas such as molecular and ultra-structural changes where further research is needed for better understanding of symbiosis with reference to salt stress for optimum usage of this technology in the field on a large scale. This review paper gives useful benchmark information for the development and prioritization of future research programmes.

Improved health-relevant functionality in dark germinated Mucuna pruriens sprouts by elicitation with peptide and phytochemical elicitors

The health-relevant functionality of Mucuna pruriens was improved by priming the seeds with elicitors of the pentose phosphate pathway (PPP) such as fish protein hydrolysates (FPHs), lactoferrin (LF) and oregano extract (OE) followed by dark germination. FPH elicited the highest phenolic content of 19 mg/g FW on day 1, which was 38% higher than control sprouts. OE enhanced Parkinson's disease-relevant L-DOPA content by 33% on day 1 compared to control sprouts. Anti-diabetes-relevant alpha-amylase inhibition percent (AIP) and alpha-glucosidase inhibition percent (GIP) were high in the cotyledons and decreased following elicitation and sprouting. For potential anti-diabetic applications, low AIP and high GIP with moderate L-DOPA content on day 4 of dark germination could be optimal. Improved L-DOPA concentrations in a soluble phenolic and antioxidant-rich M. pruriens background on day 1 sprouts have potential for Parkinson's disease management.

Protective effect of rare earth against oxidative stress under ultraviolet-B radiation

The effects of lanthanum (III) (La(III)) in protecting soybean leaves against oxidative stress induced by ultraviolet-B (UV-B) radiation were investigated. The increase in contents of hydrogen peroxide (H(2)O(2)) and superoxide (O2*-) due to UV-B radiation suggested oxidative stress. The increase in the content of malondialdehyde (MDA) and the decrease in the index of unsaturated fatty acid (IUFA) indicated oxidative damage on cell membrane induced by UV-B radiation. La(III) partially reversed UV-B-radiation-induced damage of plant growth. The reduction in the contents of H(2)O(2), O2*-, and MDA and increase in the content of IUFA, compared with UV-B treatment, also indicated that La(III) alleviated the oxidative damage induced by UV-B radiation. The increase in the activities of superoxide dismutase and peroxidase and the contents of ascorbate, carotenoids, and flavonoids were observed in soybean leaves with La(III) + UV-B treatment, compared with UV-B treatment. Our data suggested that La(III) could protect soybean plants from UV-B-radiation-induced oxidative stress by reacting with reactive oxygen species directly or by improving the defense system of plants.

Modification of the health-promoting value of potato tubers field grown under drought stress: emphasis on dietary antioxidant and glycoalkaloid contents in five native andean cultivars (Solanum tuberosum L.)

The effects of drought stress on dietary antioxidant and glycoalkaloid contents in potato tubers were investigated using a selection of five native Andean cultivars. Both freshly harvested and 4 month-stored tubers were analyzed. Responses to drought stress were highly cultivar-specific. The antioxidant contents of the yellow tuber-bearing cultivars (Sipancachi and SS-2613) were weakly affected by the drought treatment, whereas the pigmented cultivars demonstrated highly cultivar-dependent variations. A drastic reduction of anthocyanins and other polyphenols was revealed in the red- (Sullu) and purple-fleshed (Guincho Negra) cultivars, whereas an increase was shown in the purple-skinned and yellow-fleshed cultivar (Huata Colorada). The hydrophilic antioxidant capacity (evaluated by Folin-Ciocalteu and H-oxygen radical absorbance capacity assays) was highly correlated with the polyphenol content and followed, therefore, the same behavior upon drought. Carotenoid contents, including beta-carotene, as well as vitamin E, tended to increase or remain stable following drought exposure, except for the cultivar Sullu, in which the level of these lipophilic antioxidants was decreased. Vitamin C contents were not affected by drought with the exception of Guincho Negra, in which the level was increased. These variations of health-promoting compounds were associated with increased or stable levels of the toxic glycoalkaloids, alpha-solanine and alpha-chaconine. Storage at 10 degrees C for 4 months tended to decrease the concentrations of all dietary antioxidants, except those of vitamin E. This storage also reduced the drought-induced variations observed in freshly harvested tubers. These results were discussed in terms of their implications for human diet and health as well as in plant stress defense mechanisms.

Potato (Solanum tuberosum L.) tuber ageing induces changes in the proteome and antioxidants associated with the sprouting pattern

During post-harvest storage, potato tubers age as they undergo an evolution of their physiological state influencing their sprouting pattern. In the present study, physiological and biochemical approaches were combined to provide new insights on potato (Solanum tuberosum L. cv. Désirée) tuber ageing. An increase in the physiological age index (PAI) value from 0.14 to 0.83 occurred during storage at 4 degrees C over 270 d. Using this reference frame, a proteomic approach was followed based on two-dimensional electrophoresis. In the experimental conditions of this study, a marked proteolysis of patatin occurred after the PAI reached a value of 0.6. In parallel, several glycolytic enzymes were up-regulated and cellular components influencing protein conformation and the response to stress were altered. The equilibrium between the 20S and 26S forms of the proteasome was modified, the 20S form that recycles oxidized proteins being up-regulated. Two proteins belonging to the cytoskeleton were also differentially expressed during ageing. As most of these changes are also observed in an oxidative stress context, an approach focused on antioxidant compounds and enzymes as well as oxidative damage on polyunsaturated fatty acids and proteins was conducted. All the changes observed during ageing seemed to allow the potato tubers to maintain their radical scavenging activity until the end of the storage period as no accumulation of oxidative damage was observed. These data are interpreted considering the impact of reactive oxygen species on the development and the behaviour of other plant systems undergoing ageing or senescence processes.

Oxylipin profile and antioxidant status of potato tubers during extended storage at room temperature

Potato tubers (cv. Bintje) (Solanum tuberosum L.) were stored under extreme conditions at 20 degrees C for 350 days without sprout inhibitors in order to assess whether aging- and/or senescence-related processes occurred. Under these extreme storage conditions, multiple sprouting followed by the formation of daughter tubers occurs. At the same time, an increase in respiration intensity, as evidenced by cytochrome c oxidase activity (E.C. 1.9.3.1), is observed, leading to a potential increase in reactive oxygen species (ROS) production. As polyunsaturated fatty acids are priority targets of oxidative attacks, the damage to lipids was assessed by oxylipin profiling in both free and esterified forms. Oxylipin profiling showed a predominance of linoleic acid-derived oxylipins and of 9-hydroxy and 9-hydroperoxy fatty acids in both free and esterified forms. No significant accumulation of individual oxylipin was observed 350 days after harvest. To further understand the absence of lipid breakdown products accumulation, the main enzymatic and non-enzymatic antioxidants were assessed. Antioxidant enzyme activities [superoxide dismutase (E.C. 1.15.1.1), catalase (E.C. 1.11.1.6.), ascorbate peroxidase (E.C. 1.11.1.11)] were enhanced during the advanced phase of aging. The main non-enzymatic antioxidant compound, ascorbate, decreased markedly in the early stages of storage, followed by a slower decline. Total radical scavenging activity was also maintained at the end of the storage period. Our results indicate that the enhanced aging process occurring during storage at room temperature does not seem to be associated with the changes classically encountered during leaf senescence or seed aging and that the observed degenerative processes do not surpass the protective potential of the tubers.

Biotechnological approach of improving plant salt tolerance using antioxidants as markers

Salt stress causes multifarious adverse effects in plants. Of them, production of reactive oxygen species (ROS) is a common phenomenon. These ROS are highly reactive because they can interact with a number of cellular molecules and metabolites thereby leading to a number of destructive processes causing cellular damage. Plants possess to a variable extent antioxidant metabolites, enzymes and non-enzymes, that have the ability to detoxify ROS. In the present review, the emphasis of discussion has been on understanding the role of different antioxidants in plants defense against oxidative stress caused by salt stress. The role of different antioxidants as potential selection criteria for improving plant salt tolerance has been critically discussed. With the advances in molecular biology and availability of advanced genetic tools considerable progress has been made in the past two decades in improving salt-induced oxidative stress tolerance in plants by developing transgenic lines with altered levels of antioxidants of different crops. The potential of this approach in counteracting stress-induced oxidative stress has been discussed at length in this review.

Antioxidant profiling of native Andean potato tubers (Solanum tuberosum L.) reveals cultivars with high levels of beta-carotene, alpha-tocopherol, chlorogenic acid, and petanin

The antioxidant profile of 23 native Andean potato cultivars has been investigated from a human nutrition perspective. The main carotenoid and tocopherol compounds were studied using high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD) and a fluorescence detector, respectively, whereas polyphenols (including anthocyanins in colored tubers) were identified by means of both HPLC-mass spectrometry and HPLC-DAD. Antioxidant profiling revealed significant genotypic variations as well as cultivars of particular interest from a nutritional point of view. Concentrations of the health-promoting carotenoids, lutein and zeaxanthin, ranged from 1.12 to 17.69 microg g(-1) of dry weight (DW) and from 0 to 17.7 microg g(-1) of DW, with cultivars 704353 and 702472 showing the highest levels in lutein and zeaxanthin, respectively. Whereas beta-carotene is rarely reported in potato tubers, remarkable levels of this dietary provitamin A carotenoid were detected in 16 native varieties, ranging from 0.42 to 2.19 microg g(-1) of DW. The amounts of alpha-tocopherol found in Andean potato tubers, extending from 2.73 to 20.80 microg g(-1) of DW, were clearly above the quantities generally reported for commercial varieties. Chlorogenic acid and its isomers dominated the polyphenolic profile of each cultivar. Dark purple-fleshed tubers from the cultivar 704429 contained exceptionally high levels of total anthocyanins (16.33 mg g(-1) of DW). The main anthocyanin was identified as petanin (petunidin-3-p-coumaroyl-rutinoside-5-glucoside). The results suggest that Andean potato cultivars should be exploited in screening and breeding programs for the development of potato varieties with enhanced health and nutritional benefits.

Protective effect of nitric oxide on iron deficiency-induced oxidative stress in maize (Zea mays)

The effects of nitric oxide (NO) in protecting maize (Zea mays) leaves against iron deficiency-induced oxidative stress were investigated. The increased contents of hydrogen peroxide (H(2)O(2)) and superoxide (O(2)(-)*) due to iron deficiency suggested oxidative stress. The increased contents of thiobarbituric acid-reacting substances (TBARS) and the decreased contents of protein-bound thiol (PT) and non-protein-bound thiol (NPT) indicated iron deficiency-induced oxidative damage on proteins and lipids. Sodium nitroprusside (SNP), a nitric oxide (NO) donor, partially reversed iron deficiency-induced retardation of plant growth as well as chlorosis. Reduced contents of H(2)O(2), O(2)(-)*, TBARS and increased contents of PT and NPT also indicated that NO alleviated iron deficiency-induced oxidative damage. The activities of SOD and GR decreased sharply while the activities of CAT, POD and APX increased under SNP treatment. Our data suggest that NO can protect maize plants from iron deficiency-induced oxidative stress by reacting with ROS directly or by changing activities of ROS-scavenging enzymes.