Reactive oxygen species

In addition to the often-cited advantages of using Arabidopsis thaliana as a model system in plant biological research (1), Arabidopsis has many additional characteristics that make it an attractive experimental organism for studying lea d (Pb) accumulation and tolerance in plants. These include its fortuitous familial relationship to many known metal hyperaccumulators (Brassicaceae), as well as similar Pbaccumulation patterns to most other plants. Using nutrient-agar plates, hydroponic culture, and Pb-contaminated soils as growth media, we found significant variation in Arabidopsis thaliana ecotypes in accumulation and tolerance of Pb. In addition, we have found that Pb accumulation is not obligatorily linked with Pb tolerance, suggesti ng that different genetic factors control these two processes. We also screened ethyl methanesulfonate-mutagenized M2 populations and identified several Pb-accumulating mutants. Current characterization of these mutants indicates that their phenotypes are likely due to alteration of general metal ion uptake or translocation processes since these mutants also accumulate many other metals in shoots. We expect that further characterization of the ecotypes and mutants will shed light on the basic genetic and physiological underpinnings of plant-based Pb remediation. 7. Aromatic nitroreduction of acifluorfen in soils, rhizospheres, and pure cultures of rhizobacteria. Zablotowicz, R. M., Locke, M. A., and Hoagland, R. E. Phytoremediation of soil and water contaminants. Washington, DC : American Chemical Society, 1997. p. 38-53. NAL Call #: QD1.A45-no.664 Abstract: Reduction of nitroaromatic compounds to their corresponding amino derivatives is one of several pathways in the degradation of nitroxenobiotics. Our studies with the nitrodiphenyl ether herbicide acifluorfen showed rapid metabolism to am inoacifluorfen followed by incorporation into unextractable soil components in both soil and rhizosphere suspensions. Aminoacifluorfen was formed more rapidly in rhizospheres compared to soil, which can be attributed to higher microbial populations, espec ially of Gram-negative bacteria. We identified several strains of Pseudomonas fluorescens that possess nitroreductase activity capable of converting acifluorfen to aminoacifluorfen. Factors affecting acifluorfen nitroreductase activity in pure cultures an d cell-free extracts, and other catabolic transformations of acifluorfen, ether bond cleavage, are discussed. Plant rhizospheres should be conducive for aromatic nitroreduction. Nitroreduction by rhizobacteria is an important catabolic pathway for the ini tial degradation of various nitroherbicides and other nitroaromatic compounds in soils under Reduction of nitroaromatic compounds to their corresponding amino derivatives is one of several pathways in the degradation of nitroxenobiotics. Our studies with the nitrodiphenyl ether herbicide acifluorfen showed rapid metabolism to am inoacifluorfen followed by incorporation into unextractable soil components in both soil and rhizosphere suspensions. Aminoacifluorfen was formed more rapidly in rhizospheres compared to soil, which can be attributed to higher microbial populations, espec ially of Gram-negative bacteria. We identified several strains of Pseudomonas fluorescens that possess nitroreductase activity capable of converting acifluorfen to aminoacifluorfen. Factors affecting acifluorfen nitroreductase activity in pure cultures an d cell-free extracts, and other catabolic transformations of acifluorfen, ether bond cleavage, are discussed. Plant rhizospheres should be conducive for aromatic nitroreduction. Nitroreduction by rhizobacteria is an important catabolic pathway for the ini tial degradation of various nitroherbicides and other nitroaromatic compounds in soils under phytoremediation management. 8. Ascorbate: a biomarker of herbicide stress in wetland plants. Lytle, T. F. and Lytle, J. S. Phytoremediation of soil and water contaminants. Washington, DC : American Chemical Society, 1997. p. 106-113. NAL Call #: QD1.A45-no.664 Abstract: In laboratory exposures of wetland plants to low herbicide levels (<0.1 micrograms/mL), some plants showed increased total ascorbic acid suggesting a stimulatory effect on ascorbic acid synthesis occurred; at higher herbicide conce ntrations (greater than or equal to 0.1 micrograms/mL) a notable decline in total ascorbic acid and increase in the oxidized form, dehydroascorbic acid occurred. Vigna luteola and Sesbania vesicaria were exposed for 7 and 21 days respectively to atrazine (0.05 to 1 microgram/mL); Spartina alterniflora 28 days at 0.1 micrograms/mL trifluralin; Hibiscus moscheutos 14 days at 0.1 and 1 microgram/mL metolachlor in fresh and brackish water. The greatest increase following low dosage occurred with S. alterniflo ra, increasing from <600 micrograms/g wet wt. total ascorbic acid to >1000 micrograms/g. Ascorbic acid may be a promising biomarker of estuarine plants exposed to herbicide runoff; stimulation of ascorbic acid synthesis may enable some wetland plant s used in phytoremediation to cope with low levels of these compounds. In laboratory exposures of wetland plants to low herbicide levels (<0.1 micrograms/mL), some plants showed increased total ascorbic acid suggesting a stimulatory effect on ascorbic acid synthesis occurred; at higher herbicide conce ntrations (greater than or equal to 0.1 micrograms/mL) a notable decline in total ascorbic acid and increase in the oxidized form, dehydroascorbic acid occurred. Vigna luteola and Sesbania vesicaria were exposed for 7 and 21 days respectively to atrazine (0.05 to 1 microgram/mL); Spartina alterniflora 28 days at 0.1 micrograms/mL trifluralin; Hibiscus moscheutos 14 days at 0.1 and 1 microgram/mL metolachlor in fresh and brackish water. The greatest increase following low dosage occurred with S. alterniflo ra, increasing from <600 micrograms/g wet wt. total ascorbic acid to >1000 micrograms/g. Ascorbic acid may be a promising biomarker of estuarine plants exposed to herbicide runoff; stimulation of ascorbic acid synthesis may enable some wetland plant s used in phytoremediation to cope with low levels of these compounds. 9. Atmospheric nitrogenous compounds and ozone--is NO(x) fixation by plants a possible solution. Wellburn, A. R. New phytol. 139: 1 pp. 5-9. (May 1998). NAL Call #: 450-N42 Descriptors: ozoneair-pollution nitrogen-dioxide nitric-oxide air-quality tolerancebioremediationacclimatizationnutrient-sources nutrient-uptake plantscultivarsgenetic-variation literature-reviews 10. Atrazine degradation in pesticide-contaminated soils: phytoremediation potential. Kruger, E. L., Anhalt, J. C., Sorenson, D., Nelson, B., Chouhy, A. L., Anderson, T. A., and Coats, J. R. Phytoremediation of soil and water contaminants. Washington, DC : American Chemical Society, 1997. p. 54-64. NAL Call #: QD1.A45-no. 664 Abstract: Studies were conducted in the laboratory to determine the fate of atrazine in pesticide-contaminated soils from agrochemical dealer sites. No significant differences in atrazine concentrations occurred in soils treated with atrazine i ndividually or combinations with metolachlor and trifluralin. In a screening study carried out in soils from four agrochemical dealer sites, rapid mineralization of atrazine occurred in three out of eight soils tested, with the greatest amount occurring i n Bravo rhizosphere soil (35% of the applied atrazine after 9 weeks). Suppression of atrazine mineralization in the Bravo rhizosphere soil did not occur with the addition of high concentrations of herbicide mixtures, but instead was increased. Plants had a positive impact on dissipation of aged Studies were conducted in the laboratory to determine the fate of atrazine in pesticide-contaminated soils from agrochemical dealer sites. No significant differences in atrazine concentrations occurred in soils treated with atrazine i ndividually or combinations with metolachlor and trifluralin. In a screening study carried out in soils from four agrochemical dealer sites, rapid mineralization of atrazine occurred in three out of eight soils tested, with the greatest amount occurring i n Bravo rhizosphere soil (35% of the applied atrazine after 9 weeks). Suppression of atrazine mineralization in the Bravo rhizosphere soil did not occur with the addition of high concentrations of herbicide mixtures, but instead was increased. Plants had a positive impact on dissipation of aged atrazine in soil, with significantly less atrazine extractable from Kochia-vegetated soils than from nonvegetated soils. 11. Bacterial inoculants of forage grasses that enhance degradation of 2-chlorobenzoic acid in soil. Siciliano, S. D. and Germida, J. J. Environ toxicol chem. 16: 6 pp. 1098-1104. (June 1997). NAL Call #: QH545.A1E58 Descriptors: polluted-soils bioremediationAbstract: Biological remediation of contaminated soil is an effective method of reducing risk to human and ecosystem health. Bacteria and plants might be used to enhance remediation of soil pollutants in situ. This study assessed the potential of bacteria (12 isolates), plants (16 forage grasses), and plant-bacteria associations (selected pairings) to remediate 2-chlorobenzoic acid (2CBA)-contaminated soil. Initially, grass viability was assessed in 2CBA-contaminated soil. Soil was contaminated wi th 2CBA, forage grasses were grown under growth chamber conditions for 42 or 60 d, and the 2CBA concentration in soil was determined by gas chromatography. Only five of 16 forage grasses grew in 2CBA-treated (816 mg/kg) soil. Growth of Bromus inermis had no effect on 2CBA concentration, whereas Agropyron intermedium, B. biebersteinii, A. riparum, and Elymus dauricus decreased 2CBA relative to nonplanted control soil by 32 to 42%. The 12 bacteria isolates were screened for their ability to promote the germ ination of the five grasses in 2CBA-contaminated soil. Inoculation of A. riparum with Pseudomonas aeruginos

Phytoremediation : 植物による環境/土壌浄化

Mineral Nutrition of Higher Plants, 2nd edition, H. Marschner. Academic Press, London (1995), 889, (ISBN 0-12-473543-6). Price: 29.95 Pound Sterling

Salinity is a major problem affecting crop production all over the world: 20% of cultivated land in the world, and 33% of irrigated land, are salt-affected and degraded. This process can be accentuated by climate change, excessive use of groundwater (mainly if close to the sea), increasing use of low-quality water in irrigation, and massive introduction of irrigation associated with intensive farming. Excessive soil salinity reduces the productivity of many agricultural crops, including most vegetables, which are particularly sensitive throughout the ontogeny of the plant. The salinity threshold (ECt) of the majority of vegetable crops is low (ranging from 1 to 2.5 dS m−1 in saturated soil extracts) and vegetable salt tolerance decreases when saline water is used for irrigation. The objective of this review is to discuss the effects of salinity on vegetable growth and how management practices (irrigation, drainage, and fertilization) can prevent soil and water salinization and mitigate the adverse effects of salinity.

Soil Salinity: Effect on Vegetable Crop Growth. Management Practices to Prevent and Mitigate Soil Salinization

Reactive oxygen species (ROS) generation is a usual phenomenon in a plant both under a normal and stressed condition. However, under unfavorable or adverse conditions, ROS production exceeds the capacity of the antioxidant defense system. Both non-enzymatic and enzymatic components of the antioxidant defense system either detoxify or scavenge ROS and mitigate their deleterious effects. The Ascorbate-Glutathione (AsA-GSH) pathway, also known as Asada–Halliwell pathway comprises of AsA, GSH, and four enzymes viz. ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase, play a vital role in detoxifying ROS. Apart from ROS detoxification, they also interact with other defense systems in plants and protect the plants from various abiotic stress-induced damages. Several plant studies revealed that the upregulation or overexpression of AsA-GSH pathway enzymes and the enhancement of the AsA and GSH levels conferred plants better tolerance to abiotic stresses by reducing the ROS. In this review, we summarize the recent progress of the research on AsA-GSH pathway in terms of oxidative stress tolerance in plants. We also focus on the defense mechanisms as well as molecular interactions.

https://www.mdpi.com/2076-3921/8/9/384/pdf

Regulation of Ascorbate-Glutathione Pathway in Mitigating Oxidative Damage in Plants under Abiotic Stress

We investigated the effects of light quality during night interruption (NI) on morphogenesis, flowering, and the transcription of photoreceptor genes in the geranium Pelargonium × hortorum L.H. Bailey ‘Ringo 2000 Violet’ (day neutral plant, DNP). Plants were grown in an environment-controlled chamber under a constant light intensity of 180 μmol·m-2·s-1 PPF. The light was supplied by white (W) light emitting diodes (LEDs) to create long day (LD, 16 h light/8 h dark), short day (SD, 10 h light/14 h dark), or SD with a 4 h night interruption (NI) conditions. The NI was provided by green (NI-G), blue (NI-B), red (NI-R), far-red (NI-Fr), or white (NI-W) LEDs at a significantly reduced intensity of 10 μmol·m-2 ·s-1 PPF (only 5.5% of the intensity of the main light source). Plant height was greatest under NI-Fr. The percent flowering was not affected by light quality during NI, and all plants flowered under all treatments. Among NI treatments, days to visible flower buds (DVB) increased under NI-Fr. All photoreceptor genes except phyB and FTL were highly expressed under normal LD conditions. Under the NI treatment with different qualities of light, these photoreceptor genes were expressed at even higher levels, except under NI-B, as compared to SD. These results suggest that morphogenesis, flowering, and the expression of transcription factor genes are affected by light quality during NI. Light quality during NI in the DNP geranium has more pronounced effects on morphogenesis than on flowering.

Light quality during night interruption affects morphogenesis and flowering in geranium

Functional vascular connections and light quality effects on tomato grafted unions

We investigated the effects of light quality during night interruption (NI) on morphogenesis, flowering, and the transcription of photoreceptor genes in Petunia hybrida Hort. ‘Easy Wave Pink’ (a qualitative long-day plant, LDP). Plants were grown in a closed-type plant factory under a constant light intensity of 180 μmol·m-2·s-1 PPF provided by white (W) light emitting diodes (LEDs) under long day (LD, 16 h light/8 h dark), short day (SD, 10 h light/14 h dark), or SD conditions with a 4 h NI using green (NI-G), blue (NI-B), red (NI-R), far-red (NI-Fr), or white (NI-W) LEDs at an intensity of 10 μmol·m-2·s-1 PPF. Shoot length was greatest under NI-Fr. Flowering was observed under LD, NI-G, NI-Fr, and NI-W. The expression of photoreceptor genes was induced by NI. Specifically, phyA, phyB, and cry1 were more highly expressed under NI-G, NI-B, and NI-R compared to LD and SD. These results suggest that morphogenesis, flowering, and transcriptional factors are strongly affected by light quality during NI.

Light quality during night interruption affects morphogenesis and flowering in Petunia hybrida, a qualitative long-day plant

The rose is one the most commercially grown and costly ornamental plants because of its aesthetic beauty and aroma. A large number of pests attack its buds, flowers, leaves, and stem at every growing stage due to its high sugar content. The most common pest on roses are aphids which are considered to be the major cause for product loss. Aphid infestations lead to major changes in rose plants, such as large and irregular holes in petals, intact leaves and devouring tissues. It is hypothesized that different cut rose cultivars would have different levels of sensitivity or resistance to aphids, since different levels of infestation are observed in commercially cut rose production greenhouses. The present work compared four cut rose cultivars which were bred in Korea and were either resistant or sensitive to aphid infestation at different flower developmental stages. An integrative study was conducted using comprehensive proteome analyses. Proteins related to ubiquitin metabolism and the stress response were differentially expressed due to aphid infestation. The regulations and possible functions of identified proteins are presented in detail. The differential expressions of the identified proteins were validated by immunoblotting and blue native page. In addition, total sugar and carbohydrate content were also observed.

https://www.mdpi.com/2227-7382/6/2/25/pdf

Proteomic Analysis of Aphid-Resistant and -Sensitive Rose (Rosa Hybrida) Cultivars at Two Developmental Stages.

We investigated transcriptional and physiological changes in relation to Fe transport and uptake under various conditions of iron (Fe)-deficiency and cadmium (Cd) toxicity. Responses to four such Fe/Cd conditions were evaluated, revealing that oxidative stress was generated in the presence of Cd, followed by a decrease in Fe and an increase in Cd concentrations in green gram (Vigna radiata) material, whereas supplementation with Fe had a protective effect against Cd toxicity. The involvement of enzymes in Fe-uptake for the formation of root-nodules was largely reduced in the presence of Cd toxicity, a condition recovered by Fe-supplementation. Insufficient ferric chelate reducing activity in Fe-deprived roots in the presence of Cd was also largely improved by Fe supplementation. The expression of Fe2+ transporters (IRT1, IRT2, and IRT3), Fe(III) chelate reductase (FRO1–FRO8) and phytochelatin synthase (PCS1, PCS2 and PCS3) genes was up regulated for the first 5 days and decreased after 10 days in roots in the presence of Cd toxicity, but was sustained with Fe-supplementation. Additionally, root biomass was fully recovered in plants in the presence of Fe during Cd toxicity. Our results suggest that Fe-status plays a significant role in ameliorating the damage in Fe transport for chelation and its uptake caused by Cd toxicity. This supports the hypothesis that leguminous plants, particularly those that are sensitive to Fe such as green gram, can cope to some extent with Cd toxicity by improving the uptake and transport of Fe.

Sowbiya Muneer

Papers

Light quality during night interruption affects morphogenesis and flowering in geranium

Functional vascular connections and light quality effects on tomato grafted unions

Light quality during night interruption affects morphogenesis and flowering in Petunia hybrida, a qualitative long-day plant

Proteomic Analysis of Aphid-Resistant and -Sensitive Rose (Rosa Hybrida) Cultivars at Two Developmental Stages.

Transcriptional and physiological changes in relation to Fe uptake under conditions of Fe-deficiency and Cd-toxicity in roots of Vigna radiata L.