Supplementation of Salicylic Acid and Citric Acid for Alleviation of Cadmium Toxicity to Brassica juncea

Journal of Plant Growth Regulation - The reported study investigated the interaction between salicylic acid (SA) and citric acid (CA) in cadmium (Cd)-stressed Brassica juncea plants. Seedling...     

Exogenous Abscisic Acid Alleviates Cadmium Toxicity by Restricting Cd2+ Influx in Populus euphratica Cells

Abscisic acid (ABA), a widely known phytohormone involved in the plant response to abiotic stress, plays a vital role in mitigating Cd²⁺ toxicity in herbaceous species. However, the role of ABA in ameliorating Cd²⁺ toxicity in woody species is largely unknown. In the present study, we investigated ABA restriction on Cd²⁺ uptake and the relevance to Cd²⁺ stress alleviation in Cd²⁺-hypersensitive Populus euphratica. ABA (5 μM) markedly improved cell viability and growth but reduced membrane permeability in CdCl₂ (100 μM)-stressed P. euphratica cells. Moreover, ABA significantly increased the activity of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX), contributing to the scavenging of Cd²⁺-elicited H₂O₂ within P. euphratica cells during the period of CdCl₂ exposure (100 μM, 24–72 h). ABA alleviation of Cd²⁺ toxicity was mainly the result of ABA restriction of Cd²⁺ uptake under Cd²⁺ stress. Steady-state and transient flux recordings showed that ABA inhibited Cd²⁺ entry into Cd²⁺-shocked (100 μM, 30 min) and short-term-stressed P. euphratica cells (100 μM, 24–72 h). Non-invasive micro-test technique data showed that H₂O₂ (3 mM) stimulated the Cd²⁺-elicited Cd²⁺ influx but that the plasma membrane (PM) Ca²⁺ channel inhibitor LaCl₃ blocked it, suggesting that the Cd²⁺ influx was through PM Ca²⁺-permeable channels. These results suggested that ABA up-regulated antioxidant enzyme activity in Cd²⁺-stressed P. euphratica and that these enzymes scavenged the Cd²⁺-elicited H₂O₂ within cells. The entry of Cd²⁺ through the H₂O₂-mediated Ca²⁺-permeable channels was subsequently restricted; thus, Cd²⁺ buildup and toxicity were reduced in the Cd²⁺-hypersensitive species, P. euphratica.

     

硫化氢通过抑制镉离子内流降低拟南芥体内的镉毒性

硫化氢（H₂S）作为一种新兴的气体信号分子,在植物体内主要由半胱氨酸脱巯基酶（CDes）降解半胱氨酸产生。已有报道表明,H₂S信号与植物激素共同作用增强植物的镉（Cd）耐受。然而,H₂S信号响应重金属Cd胁迫的作用机制尚缺乏系统研究。本文以拟南芥为实验材料,从不同水平探究H₂S分子对Cd胁迫诱导氧化应激的保护作用。结果表明,CDes基因表达量和H₂S的产率随CdCl₂浓度升高而逐渐增加。重金属Cd胁迫导致幼苗干重降低约33%、体内过氧化氢显著增加、丙二醛含量升高约110%、超氧化物歧化酶活性增加约100%、谷胱甘肽还原酶活性和过氧化氢酶活性分别下降27%和21%,还原性谷胱甘肽含量随之显著降低。生理浓度NaHS（H₂S供体）预处理显著缓解以上Cd胁迫产生的影响,使恢复到对照水平。同时,H₂S处理可显著下调质膜中Cd转运蛋白（HMA4和IRT1）的表达,同时上调液泡膜中MRP3和CAX2的表达。利用非损伤微测技术测定植物根系Cd²⁺的流动速度和流动方向。结果显示,生理浓度的H2S显著抑制Cd^{2 +}内流,最终表现为植物叶片和根中的Cd含量显著降低,分别下降了15%和38.4%。总之,在Cd胁迫条件下,H₂S信号可激活植物体内的抗氧化酶促和非酶促系统,以清除细胞内H₂O₂。H₂S对Cd²⁺转运和液泡区式化的调节,降低了体内Cd²⁺的浓度,减小Cd毒性对植物生长的影响。为理解农作物应对重金属胁迫的机制提供了新的思路。     

硫化氢通过抑制镉离子内流降低拟南芥体内的镉毒性

硫化氢（H₂S）作为一种新兴的气体信号分子,在植物体内主要由半胱氨酸脱巯基酶（CDes）降解半胱氨酸产生。已有报道表明,H₂S信号与植物激素共同作用增强植物的镉（Cd）耐受。然而,H₂S信号响应重金属Cd胁迫的作用机制尚缺乏系统研究。本文以拟南芥为实验材料,从不同水平探究H₂S分子对Cd胁迫诱导氧化应激的保护作用。结果表明,CDes基因表达量和H₂S的产率随CdCl₂浓度升高而逐渐增加。重金属Cd胁迫导致幼苗干重降低约33%、体内过氧化氢显著增加、丙二醛含量升高约110%、超氧化物歧化酶活性增加约100%、谷胱甘肽还原酶活性和过氧化氢酶活性分别下降27%和21%,还原性谷胱甘肽含量随之显著降低。生理浓度NaHS（H₂S供体）预处理显著缓解以上Cd胁迫产生的影响,使恢复到对照水平。同时,H₂S处理可显著下调质膜中Cd转运蛋白（HMA4和IRT1）的表达,同时上调液泡膜中MRP3和CAX2的表达。利用非损伤微测技术测定植物根系Cd²⁺的流动速度和流动方向。结果显示,生理浓度的H2S显著抑制Cd^{2 +}内流,最终表现为植物叶片和根中的Cd含量显著降低,分别下降了15%和38.4%。总之,在Cd胁迫条件下,H₂S信号可激活植物体内的抗氧化酶促和非酶促系统,以清除细胞内H₂O₂。H₂S对Cd²⁺转运和液泡区式化的调节,降低了体内Cd²⁺的浓度,减小Cd毒性对植物生长的影响。为理解农作物应对重金属胁迫的机制提供了新的思路。     

Alleviation of Cadmium Toxicity in Brassica juncea L. (Czern. & Coss.) by Calcium Application Involves Various Physiological and Biochemical Strategies

Calcium (Ca) plays important role in plant development and response to various environmental stresses. However, its involvement in mitigation of heavy metal stress in plants remains elusive. In this study, we examined the effect of Ca (50 mM) in controlling cadmium (Cd) uptake in mustard (Brassica juncea L.) plants exposed to toxic levels of Cd (200 mg L⁻¹ and 300 mg L⁻¹). The Cd treatment showed substantial decrease in plant height, root length, dry weight, pigments and protein content. Application of Ca improved the growth and biomass yield of the Cd-stressed mustard seedlings. More importantly, the oil content of mustard seeds of Cd-stressed plants was also enhanced with Ca treatment. Proline was significantly increased in mustard plants under Cd stress, and exogenously sprayed Ca was found to have a positive impact on proline content in Cd-stressed plants. Different concentrations of Cd increased lipid peroxidation but the application of Ca minimized it to appreciable level in Cd-treated plants. Excessive Cd treatment enhanced the activities of antioxidant enzymes superoxide dismutase, ascorbate peroxidase and glutathione reductase, which were further enhanced by the addition of Ca. Additionally, Cd stress caused reduced uptake of essential elements and increased Cd accumulation in roots and shoots. However, application of Ca enhanced the concentration of essential elements and decreased Cd accumulation in Cd-stressed plants. Our results indicated that application of Ca enables mustard plant to withstand the deleterious effect of Cd, resulting in improved growth and seed quality of mustard plants.     

外源有机酸对小麦幼苗铝毒的缓解作用

用Al(50μmol／L)处理水培小麦(Triticum aestivum L．)幼苗24h,显著抑制Al敏感(Scout 66)和耐Al品种(Atlas 66)小麦幼苗根系伸长,明显增加根系的电解质渗漏率。在Al处理同时外加草酸或柠檬酸能缓解Al对小麦根系伸长的抑制作用,同时降低小麦根系的电解质渗漏率。铬花青R染色和碘化丙锭荧光染料染色实验结果显示,用Al(50μmol／L)处理Al敏感小麦Scout 66幼苗24h后,大量Al结合在根尖表面,并降低根尖表面细胞活力。而Al处理同时外加草酸,则减少Al与根尖表面的结合,缓解Al对细胞活力的抑制。分根结果表明,外源草酸有可能通过根系进入植物体内参与内部解Al毒机制。     

Phytoremediation of aspirin and tetracycline by Brassica juncea

With the increasing release of pharmaceutical drugs in the environment, research is in progress for investigating alternative methods for their remediation. Various studies have shown the phytoremediation potential of Brassica juncea for metals. The current study was aimed at evaluating the phytoremediation potential of B. juncea for two different pharmaceutical drugs i.e. aspirin and tetracycline in in-vitro conditions. The seeds of B. juncea were germinated and grown for a period of 28 and 24 days for aspirin and tetracycline, respectively. The study analyzed the remediation rate of B. juncea for the selected drugs in three different sets of varying concentration along with any phytotoxic effects exerted by the drugs on the seeds. Preliminary results showed that the average remediation rate of aspirin and tetracycline at the end of experiment was approximately 90% and 71%, respectively. As initial drug concentrations were increased in the media, the remediation rate also improved. However, at higher concentrations, the plants showed phytotoxicity as depicted by the decrease in shoot length of the germinated seeds. These preliminary results indicated that B. juncea could tolerate and remediate pharmaceutical drugs such as analgesics and antibiotics.     

Silicon Alleviates Cadmium Toxicity in Two Cypress Varieties by Strengthening the Exodermis Tissues and Stimulating Phenolic Exudation of Roots

The aim of this work was to investigate the effect of silicon (Si) on phenolic exudation of plant roots and cadmium (Cd) bioavailability in rhizospheres. For this purpose, pot experiments with two cypress varieties, Juniperus chinensis and Platycladus orientalis, each subjected to 100 mg kg^?1 Cd and/or 400 mg kg^?1 Si for 220 days, were conducted using a rhizobag technique. The results showed that P. orientalis accumulated a higher amount of Cd, hence caused higher growth inhibition on the leaves compared with J. chinensis. Si alleviated the growth inhibition induced by Cd toxicity on both varieties, but the mechanisms involved were species specific. For J. chinensis, Si did not affect the root exudation but enhanced the Cd retention of the roots by strengthening the exodermis tissues, restraining Cd translocation from the roots to the shoots. For P. orientalis, Si exposure significantly elevated the phenolic exudation (for example, ferulic acid, catechin, and gallic acid) of the roots, which caused greater Cd mobility in the rhizosphere and enhancement of Cd accumulation in the shoots compared with Cd treatment alone. These results suggest that Cd-chelating with the Si-induced phenolics in the rhizosphere is involved in the Cd detoxification in P. orientalis.     

Simultaneous Removal of Lindane,Lead and Cadmium from Soils by Rhamnolipids Combined with Citric Acid

This study investigated the performance of rhamnolipids-citric acid mixed agents in simultaneous desorption of lindane and heavy metals from soils. The capacity of the mixed agents to solubilize lindane, lead and cadmium in aqueous solution was also explored. The results showed that the presence of citric acid greatly enhanced the solubilization of lindane and cadmium by rhamnolipids. A combined effect of the mixed agents on lindane and heavy metals removal from soils was observed. The maximum desorption ratios for lindane, cadmium and lead were 85.4%, 76.4% and 28.1%, respectively, for the mixed agents containing 1% rhamnolipidsand 0.1 mol/L citric acid. The results also suggest that the removal efficiencies of lead and cadmium were strongly related to their speciations in soils, and metals in the exchangeable and carbonate forms were easier to be removed. Our study suggests that the combining use of rhamnolipids and citric acid is a promising alternative to simultaneously remove organochlorine pesticides and heavy metals from soils.     

Impact of Lead and Cadmium on Enzyme of Citric Acid Cycle in Germinating Pea Seeds

The present investigations were conducted to ascertain the influence of Pb₂₊ and Cd₂₊ both individually and in combination on selected enzymes of tricarboxylic acid (TCA) cycle. All the enzymes of TCA cycle examined (-ketoglutarate dehydrogenase, isocitrate dehydrogenase, succinate dehydrogenase, malate dehydrogenase) were affected deleteriously by Pb₂₊ as well as Cd₂₊ and these metals in combination gave more or less an additive effect.     

Phosphate-assisted phytoremediation of arsenic by Brassica napus and Brassica juncea: Morphological and physiological response

In this study, we examined the potential role of phosphate (P; 0, 50, 100 mg kg^?1) on growth, gas exchange attributes, and photosynthetic pigments of Brassica napus and Brassica juncea under arsenic (As) stress (0, 25, 50, 75 mg kg^?1) in a pot experiment. Results revealed that phosphate supplementation (P100) to As-stressed plants significantly increased shoot As concentration, dry biomass yield, and As uptake, in addition to the improved morphological and gas exchange attributes and photosynthetic pigments over P0. However, phosphate-assisted increase in As uptake was substantially (up to two times) greater for B. napus, notably due to higher shoot As concentration and dry biomass yield, compared to B. juncea at the P100 level. While phosphate addition in soil (P100) led to enhanced shoot As concentration in B. juncea, it reduced shoot dry biomass, primarily after 50 and 75 mg kg^?1 As treatments. The translocation factor and bioconcentration factor values of B. napus were higher than B. juncea for all As levels in the presence of phosphate. This study demonstrates that phosphate supplementation has a potential to improve As phytoextraction efficiency, predominantly for B. napus, by minimizing As-induced damage to plant growth, as well as by improving the physiological and photosynthetic attributes.     

芥菜(Brassica juncea)花粉胚状体与离体种胚脂肪酸的变化

在油菜改良品质育种中,利用单个花粉胚状体筛选低或无芥酸株系,需要了解花粉胚状体在发育过程中芥酸含量的变化及与其他脂肪酸变化的关系。Gurr(1972),Dasgupta等(1973)和黄尚琼(1980)研究了不同种、不同品种种子发育过程中脂肪酸组成的变化,但均未曾对离体花粉胚状体和离体种胚进行研究。本文在于探索离     

Biochemical Changes Associated With Brassica juncea Seed Development. IV. Acid and Alkaline Phosphatases

Changes in acid and alkaline phosphatase activities in cytoplasmic and wall-bound fractions of developing mustard (Brassica juncea) seed were studied. Growth was measured by seed dry weight and water content. Seed dry weight data were fitted to a cubic polynomial equation. Seed water content and dry matter accumulation was significantly correlated. Cytoplasmic acid and alkaline phosphatase activities were substantially less in the cytoplasmic fraction than the wall-bound fraction. Wall-bound acid phosphatase activity was low initially, but high levels were maintained after day 25, indicating a relationship with dry matter accumulation. The results suggest that acid phosphatase plays an important role during mustard seed development. Received February 19, 1998; accepted May 6, 1999     

Somatic hybridization between Brassica juncea and Moricandia arvensis by protoplast fusion

Intergeneric somatic hybrids have been produced between Brassica juncea (2n=36, AABB) cv. RLM-198 and Moricandia arvensis (2n=28, MM) by protoplast fusion. Hypocotyl protoplasts of B. juncea were fused with mesophyll protoplasts of M. arvensis using polyethylene glycol. Fusion frequency, estimated on the basis of differential morphological characterstics of parental protoplasts was about 5%. Of the 156 calli obtained, four calli produced shoots intermediate in morphology between the parents. Hybrid nature of the plants was confirmed using wheat nuclear rDNA probe. Hybridization of total DNA with a mitochondrial DNA probe carrying 5s–18s rRNA genes of maize showed that the mitochondria of the somatic hybrids were derived from the wild species M. arvensis. Meiosis in the only hybrid that produced normal flowers revealed the occurrence of 64 chromosomes, the sum of chromosomes of parental species. Inspite of complete pollen sterility, siliquas were produced in this hybrid by back-crossing with B. juncea. These siliquas on in vitro culture produced 12 seeds.     

Nitric Oxide Alleviates Photochemical Damage Induced by Cadmium Stress in Pea Seedlings

Cadmium (Cd), a life threatening hazardous heavy metal is abundant in nature. Cd amounts are greater in leaves than other plant parts, and it shows considerable effects on photosynthesis. Nitric oxide (NO), a free radical present in living organisms, is now known as an important signaling molecule playing various physiological processes in plants. In this study, the possible ameliorative effect of NO on photosynthesis was examined on pea seedlings grown under Cd stress. Results showed that chlorophyll, net photosynthetic rate, transpiration rate, stomatal conductance, photochemical efficiency of Photosystem II and Photosystem I decreased, and Fo and non-photochemical parameters for PSII and PSI significantly increased due to Cd stress. This suggests that Cd affects the photochemistry efficiency at both the PSII and PSI levels. Nitric oxide supplementation through SNP ameliorated Cd stress by enhancing all the above mentioned parameters but causing a reduction in the Fo, and non-photochemical parameters of PSII and PSI in pea plants. These data indicate that the exogenous application of NO was useful in mitigating Cd-induced damage to photosynthesis in pea seedling.     

Histone H3 methylation patterns in Brassica nigra, Brassica juncea, and Brassica carinata species

Core histones are subjected to various post-translational modifications, and one of them, most intensively studied in plants, is the methylation of histone H3. In the majority of analyzed plant species, dimethylation of H3 at lysine 9 (H3K9me2) is detected in heterochromatin domains, whereas methylation of H3 at lysine 4 (H3K4me2) is detected in euchromatin domains. The distribution of H3K9me2 in the interphase nucleus seems to be correlated with genome size, chromatin organization, but also with tissue specificity. In this paper, we present the analysis of the pattern and level of histone H3 methylation for two allotetraploid and one diploid Brassica species. We have found that the pattern of H3K9me2 in interphase nuclei from root meristematic tissue is comparable within the analyzed species and includes both heterochromatin and euchromatin, but the level of modification differs not only among species but even among nuclei in the same phase of the cell cycle within one species. Moreover, the differences in the level of H3K9me2 are not directly coupled with DNA content in the nuclei and are probably tissue specific.