Accumulation In Shoots Research Articles

Direct determination of silicon overestimates the accumulation and translocation of SiO2 nanoparticles in rice seedlings

Silica nanoparticles (SiO2 NPs) have numerous applications in agriculture, but may also pose significant risks to plants. Nevertheless, their bioaccumulation, an important determinant of their risks, was often not accurately measured due to the lack of reliable methods. In this study, the accumulation in rice seedlings of SiO2 NPs of different sizes without and with a gold nanoparticle core (Au@SiO2 NPs) was examined. Potential interference from SiO2 NP dissolution was minimized by lowering the pH of the uptake medium, which did not result in any observable adverse bioeffects. Under this condition, the direct determination of Si showed the significant accumulation of SiO2 NPs in roots and shoots and a decrease in the accumulation of SiO2 NPs in shoots with increasing particle size. However, when accumulation was monitored using Au@SiO2 NPs, SiO2 NP accumulation was significantly higher when measured by direct Si determination than by Au determination, indicating that the former overestimates the accumulation of SiO2 NPs. Consequently, unlike direct Si determination, tracking the gold nanoparticle core revealed an increase in SiO2 NP accumulation in shoots with increasing particle size. Overall, accurate determination of SiO2 NP bioaccumulation is imperative for appropriate bioapplications and reliable biosafety assessments of these particles.

Immobilization of Pb, Cd, and Cr in contaminated soil around mining areas using Mg/Al LDH-zeolite and evaluation of maize growth

Abstract This study conducted simultaneous adsorption of Pb, Cd, and Cr ions using Mg/Al LDH-zeolite on contaminated soils from lead-zinc and tin mining areas. The optimal conditions were a 3% adsorbent-to-soil ratio, a 30-day incubation period, and 70% soil moisture. Characterization of the materials revealed that Mg/Al LDH-zeolite has superior physicochemical properties to natural zeolite, with a higher surface area and better adsorption capacity. Results indicated significant reductions in exchangeable heavy metal content: in lead-zinc mining area soil, exchangeable Pb decreased from 139.79 mg kg−1 to 10.95 mg kg−1, Cd−1 from 1.518 mg kg−1 to 0.533 mg kg−1, and Cr from 2.636 mg kg−1 to 0.461 mg/kg using Mg/Al LDH-zeolite. In tin mining area soil, exchangeable Pb decreased from 583.97 mg kg−1 to 48.22 mg kg−1, Cd−1 from 0.498 mg kg−1 to 0.122 mg kg−1, and Cr from 106.095 mg kg−1 to 38.038 mg/kg. Maize cultivation on post-adsorption soil showed improved growth performance, with plants exhibiting increased height and ear and reduced heavy metal accumulation in roots, shoots, and grains. Pb, Cd, and Cr concentrations in maize roots decreased significantly, with Pb reducing to 0.113 mg kg−1 in the lead-zinc area and 0.203 mg kg−1 in the tin area, Cd reducing to 0.061 mg kg−1 and 0.037 mg kg−1, respectively, and Cr reducing to 0.036 mg kg−1 and 0.243 mg kg−1 respectively. Mg/Al LDH-zeolite consistently demonstrated higher efficiency in reducing the bioavailability and translocation of heavy metals in maize tissues, confirming its potential as an effective adsorbent for soil remediation. Key mechanisms, including adsorption, surface complexation, ion exchange, precipitation, and structural incorporation, reduce metal mobility and bioavailability.

Zinc Enhances Cadmium Accumulation in Shoots of Hyperaccumulator Solanum nigrum by Improving ATP-Dependent Transport and Alleviating Toxicity.

Solanum nigrum is a cadmium (Cd) and zinc (Zn) accumulator with potential for phytoextraction of soil contaminated with heavy metals. However, how Zn affects Cd accumulation in S. nigrum remains unclear. In this study, S. nigrum seedlings were treated with 100 μmol·L-1 Zn (Zn100), 100 μmol·L-1 Cd (Cd100), and the Zn and Cd combination (Zn100+Cd100) for 10 days under hydroponic culture. Compared with Cd100, the Cd content in stems, leaves, and xylem saps was 1.8, 1.6, and 1.3 times more than that in Zn100+Cd100, respectively. In addition, the production of reactive oxygen species in leaves was significantly upregulated in Cd100 compared with the control, and it was downregulated in Zn100. Comparative analyses of transcriptomes and proteomes were conducted with S. nigrum leaves. Differentially expressed genes (DEGs) were involved in Cd uptake, transport, and sequestration, and the upregulation of some transporter genes of Zn transporters (ZIPs), a natural resistance associated macrophage protein (Nramp1), a metal-nicotianamine transporter (YSL2), ATP-binding cassette transporters (ABCs), oligopeptide transporters (OPTs), and metallothionein (MTs) and glutathione S-transferase (GSTs) genes was higher in Zn100+Cd100 than in Cd100. In addition, differentially expressed proteins (DEPs) involved in electron transport chain, ATP, and chlorophyll biosynthesis, such as malate dehydrogenases (MDHs), ATPases, and chlorophyll a/b binding proteins, were mostly upregulated in Zn100. The results indicate that Zn supplement increases Cd accumulation and tolerance in S. nigrum by upregulating ATP-dependent Cd transport and sequestration pathways.

Modulation of Cd carriers by innovative nanocomposite (Ca+Mg) and Cd-resistance microbes (Bacillus pumilus): a mechanistic approach to enhance growth and yield of rice (Oryza sativa L.).

Cadmium (Cd) is a well-known pollutant in agricultural soil, affecting human health through the food chain. To combat this issue, Ca + Mg (25 mg L-1) nanocomposite and Bacillus pumilus, either alone or combined, were applied to rice plants under Cd (5 mg kg-1, 10 mg kg-1) contamination. In our study, growth and yield traits demonstrated the beneficial influence of Ca + Mg and B. pumilus application in improving rice defense mechanism by reducing Cd stress. Combined Ca + Mg and B. pumilus application increased SPAD (15), total chlorophyll (18), chlorophyll a (11), chlorophyll b (22), and carotenoids (21%) with Cd (10 mg kg-1), compared to the application alone. Combined Ca + Mg and B. pumilus application significantly regulated MDA (15), H2O2 (13), EL (10), and O2 •- (24%) in shoots under Cd (10 mg kg-1), compared to the application alone. Cd (10 mg kg-1) increased the POD (22), SOD (21), APX (12), and CAT (13%) in shoots with combined Ca + Mg and B. pumilus application, compared to the application alone. Combined Ca + Mg and B. pumilus application significantly reduced Cd accumulation in roots (22), shoots (13), and grains (20%) under Cd (10 mg kg-1), compared to the application alone. Consequently, the combined application of Ca + Mg and B. pumilus is a sustainable solution to enhance crop production under Cd stress.

Integrative approach to mitigate chromium toxicity in soil and enhance antioxidant activities in rice (Oryza sativa L.) using magnesium-iron nanocomposite and Staphylococcus aureus strains.

Pollutantsin soil, particularly chromium (Cr), posehigh environmental and health risks due to their persistence, bioavailability, and potential for causing toxicity. Cr impairment in plants act as a deleterious environmental pollutant that enters the food chain and eventually disturbs human health. Current study demonstrated the potential of integrative foliar application of magnesium-iron (Mg +Fe) nanocomposite with Staphylococcus aureus strains to alleviate Cr toxicity in rice (Oryza sativa) crops by improving yield and defense system. Growth and yield traits such as shoot length (15%), root length (17%), shoot fresh weight (14%), shoot dry weight (9%), root fresh weight (23%), root dry weight (7%), number of tillers (33%), number of grains (10%) and spike length (13%) improved by combined application of Mg + Fe (20mgL-1) nanocomposite and S. aureus strains with Cr (110mgkg-1), compared to when applied alone. Mutual Mg + Fe and S. aureus strains application augmented the SPAD value (9%), total chlorophyll (11%), a (12%), b (17%), and carotenoids (32%), with Cr (110mgkg-1), compared to alone. Malondialdehyde (13%), hydrogen peroxide (H2O2) (11%), and electrolyte leakage (7%) were significantly regulated in shoots with combined Mg + Fe and S. aureus strains application with Cr (110mgkg-1) contrasted to alone. Peroxidase (20%), superoxide dismutase (17%), ascorbate peroxidase (18%), and catalase (20%) were increased in shoots with combined Mg + Fe and S. aureus strains application with Cr (110mgkg-1) in comparison to alone. The combined application of Mg + Fe (20mgL-1) nanocomposite and S. aureus strains with Cr (110mgkg-1) enhanced the macro-micronutrients in shoots compared to alone. Cr accumulation in roots (21%), shoots (25%), and grains (47%) were significantly reduced under Cr (110mgkg-1) with combined Mg + Fe and S. aureus strains application, compared to alone. Subsequently, applying combined Mg + Fe and S. aureus strains is a sustainable solution to boost crop production under Cr toxicity.

Transcriptome analysis of potassium-mediated cadmium accumulation in sweet sorghum

Cadmium (Cd) pollution in the soil is a serious environmental issue worldwide. Phytoextraction of Cd-polluted soil is a cost-effective, sustainable and environmentally-friendly strategy. Agricultural fertilizer management is beneficial for promoting the Cd phytoremediation efficiency. Potassium (K) is the nutrient required in the largest amount cation by plants. Sweet sorghum exhibits a substantial phytoremediation potential of Cd-polluted soil. Clarifying the mechanism of K-mediated Cd accumulation in sweet sorghum is imperative. Sweet sorghum plants were grown hydroponically with an extra K supply in the presence or absence of Cd treatment. An extra K application significantly increased plant growth under non-Cd addition, while K lost the profitable effect under Cd stress. K supplementation remarkably enhanced Cd concentrations and Cd accumulation in shoots and roots of sweet sorghum. Transcriptome analysis demonstrated that zinc ion transport, cysteine and methionine metabolism, flavonoid biosynthesis and phenylpropanoid biosynthesis pathways might contribute to the increased Cd accumulation as affected by an extra K supply. Furthermore, SbZIP9, SbSTP8, SbYS1, SbMAG and SbFOMT-like were targeted as they closely correlated with both plant growth and Cd stress in sweet sorghum. SbFOMT-like showed an independent pathway, while SbZIP9, SbSTP8, SbYS1 and SbMAG displayed positive correlations mutually. Notably, SbZIP9 and SbFOMT-like were highly expressed when compared with other target genes. Taken together, SbZIP9 and SbFOMT-like were upregulated and downregulated by an extra K supply under Cd stress, suggesting that SbZIP9 and SbFOMT-like enhances and declines Cd accumulation as regulated by K addition in sweet sorghum respectively.

Elevated CO2 and Nitrogen Supply Boost N Use Efficiency and Wheat (T. aestivum cv. Yunmai) Growth and Differentiate Soil Microbial Communities Related to Ammonia Oxidization.

Elevated CO2 levels (eCO2) pose challenges to wheat (Triticum aestivum L.) growth, potentially leading to a decline in quality and productivity. This study addresses the effects of two ambient CO2 concentrations (aCO2, daytime/nighttime = 410/450 ± 30 ppm and eCO2, 550/600 ± 30 ppm) and two nitrogen (N) supplements (without N supply-N0 and with 100 mg N supply as urea per kg soil-N100) on wheat (T. aestivum cv. Yunmai) growth, N accumulation, and soil microbial communities related to ammonia oxidization. The data showed that the N supply effectively mitigated the negative impacts of eCO2 on wheat growth by reducing intercellular CO2 concentrations while enhancing photosynthesis parameters. Notably, the N supply significantly increased N concentrations in wheat tissues and biomass production, thereby boosting N accumulation in seeds, shoots, and roots. eCO2 increased the agronomic efficiency of applied N (AEN) and the physiological efficiency of applied N (PEN) under N supply. Plant tissue N concentrations and accumulations are positively related to plant biomass production and soil NO3--N. Additionally, the N supply increased the richness and evenness of the soil microbial community, particularly Nitrososphaeraceae, Nitrosospira, and Nitrosomonas, which responded differently to N availability under both aCO2 and eCO2. These results underscore the importance and complexity of optimizing N supply and eCO2 for enhancing crop tissue N accumulation and yield production as well as activating nitrification-related microbial activities for soil inorganic N availability under future global environment change scenarios.

Effect of Co-Application of Chinese Milk Vetch and Iron-Modified Biochar on Rice in Antimony-Polluted Soil

Antimony (Sb) toxicity is a serious concern across the globe due to its hazardous impacts on plants and living organisms. The co-application of Chinese milk vetch (CMV) and biochar (BC) is a common agricultural practice, however, the effects of combined CMV and BC in mitigating Sb toxicity and bio-availability remain unclear. Therefore, this study investigated the impacts of CMV, rape straw biochar (RBC), and iron-modified biochar (FMB) and their combinations on rice productivity, physiological, and biochemical functioning of rice and Sb availability. Antimony toxicity caused a marked reduction in rice growth and productivity by decreasing chlorophyll, and anthocyanin synthesis, leaf water contents, osmolyte synthesis and antioxidant activities while, increasing hydrogen peroxide (H2O2), electrolyte leakage (EL), and malondialdehyde (MDA) production and Sb accumulation. Co-application of CMV and FMB increased biomass (29.50%) and grain yield (51.07%) of rice by increasing chlorophyll, and anthocyanin synthesis, leaf water contents, osmolyte synthesis, antioxidant activities, and decreasing production of H2O2, EL, and MDA and Sb accumulation in roots (90.41%) and shoots (96.38%). Furthermore, the combined addition of CMV and FMB also reduced the soil available Sb by 75.57% which resulted in less accumulation of Sb in plant parts and improved growth and yield. Given these facts, these findings indicate that co-application of CMV and FMB is a promising approach to remediate Sb-polluted soils and improve sustainable and safer rice productivity.

HKT1;1 modulated by vacuolar Na+ compartmentation functions in maintaining the salt-accumulating trait in a xerophyte

The xerophyte Zygophyllum xanthoxylum can accumulate large amounts of Na+ in leaves for osmotic adjustment. HKT I is crucial for withdrawing Na+ from root xylem in salt-excluding species, however, its function in maintaining the characteristics of salt accumulation in Z. xanthoxylum remains unclear. Here, we found that ZxHKT1;1, a HKT I homolog in Z. xanthoxylum, is localized to the plasma membrane and functions as a Na+-selective transporter based on the heterologous expression analyses conducted in yeast and Xenopus laevis oocytes. The results of in situ PCR showed that ZxHKT1;1 was specifically expressed in the root stele. The over-expression of ZxHKT1;1 under the control of AtHKT1;1 native promoter significantly enhanced the retrieval of Na+ from root xylem and loading of K+ into xylem, thereby reducing Na+ accumulation and increasing K+ accumulation in shoots, and consequently, improving the salt tolerance of wild-type Arabidopsis or athkt1;1 mutant. Interestingly, the expression of ZxHKT1;1 was significantly down-regulated in roots of Z. xanthoxylum while up-regulated in roots of the ZxNHX1-silenced line under 50 mM NaCl, a salt condition that stimulates growth of Z. xanthoxylum. These results demonstrated that ZxHKT1;1 functions in maintaining the characteristics of salt accumulation in Z. xanthoxylum by modulating the retrieval of Na+ from root xylem, and this regulation is determined by its distinct expression patterns relying on the capacity of vacuolar Na+ compartmentation mediated by ZxNHX1 in leaves. Meanwhile, ZxHKT1;1 is involved in regulating K+ transport from roots to shoots in Z. xanthoxylum.

Comparative assessment of pantothenic, aspartic, ascorbic and tartaric acids assisted Pb-phytoextraction by sunflower (Helianthus annuus L.).

Phytoextraction of lead (Pb) is a challenging task due to its extremely low mobility within soil and plant systems. In this study, we tested the influence of some novel chelating agents for Pb-phytoextraction using sunflower. The Pb was applied at control (0.0278mM) and 4.826mM Pb as Pb(NO3)2 through soil-spiking. After 10days of Pb addition, four different organic ligands (aspartic, ascorbic, tartaric, and pantothenic acids) were added to the soil at 1mM concentration each. respectively. In the absence of any chelate, sunflower plants grown at 4.826mM Pb level accumulated Pb concentrations up to 104µgg-1 DW in roots, whereas 64µgg-1 DW in shoot. By contrast, tartaric acid promoted significantly Pb accumulation in roots (191µgg-1 DW; + 45.5%) and shoot (131.6µgg-1 DW; + 51.3%). Pantothenic acid also resulted in a significant Pb-uptake in the sunflower shoots (123µgg-1 DW; + 47.9%) and in roots (177.3µgg-1 DW; + 41.3%). The least effective amongst the chelates tested was aspartic acid, but it still contributed to + 40.1% more Pb accumulation in the sunflower root and shoots. In addition, plant growth, biochemical, and ionomic parameters were positively regulated by the organic chelates used. Especially, an increase in leaf Ca, P, and S was evident in Pb-stressed plants in response to chelates. These results highlight that the use of biocompatible organic chelates positively alters plant physio-biochemical traits contributing to higher Pb-sequestration in sunflower plant parts.

Phytoremediation of metals in oil sands process affected water by native wetland species

Process affected water and other industrial wastewaters are a major environmental concern. During oil sands mining, large amounts of oil sands process affected water (OSPW) are generated and stored in ponds until reclaimed and ready for surface water discharge. While much research has focused on organics in process waters, trace metals at high concentrations may also pose environmental risks. Phytoremediation is a cost effective and sustainable approach that employs plants to extract and reduce contaminants in water. The research was undertaken in mesocosm scale constructed wetlands with plants exposed to OSPW for 60 days. The objective was to screen seven native emergent wetland species for their ability to tolerate high metal concentrations (arsenic, cadmium, copper, chromium, copper, nickel, selenium, zinc), and then to evaluate the best performing species for OSPW phytoremediation. All native plant species, except Glyceria grandis, tolerated and grew in OSPW. Carex aquatilis (water sedge), Juncus balticus (baltic rush), and Typha latifolia (cattail) had highest survival and growth, and had high metal removal efficiencies for arsenic (81–87 %), chromium (78–86 %), and cadmium (74–84 %), relative to other metals; and greater than 91 % of the dissolved portions were removed. The native plant species were efficient accumulators of all metals, as demonstrated by high root and shoot bioaccumulation factors; root accumulation was greater than shoot accumulation. Translocation factor values were greater than one for Juncus balticus (chromium, zinc) and Carex aquatilis (cadmium, chromium, cobalt, nickel). The results demonstrate the potential suitability of these species for phytoremediation of a number of metals of concern and could provide an effective and environmentally sound remediation approach for wastewaters.

Receptor-like cytoplasmic kinase 58 reduces tolerance of maize seedlings to low magnesium via promoting H2O2 over-accumulation.

ZmRLCK58, a negative growth regulator, reduces tolerance of maize seedlings to low Mg via enhancing H2O2 accumulation in the shoot. Magnesium (Mg) deficiency is one of critical limiting factors for crop production in widespread acidic soils worldwide. However, the molecular mechanism of crop response to Mg deficiency is still largely unclear. Here, we found higher concentrations of H2O2, soluble sugars, and starch (1.5-, 1.9-, and 1.4-fold, respectively) in the shoot of low-Mg-treated maize seedlings, compared with Mg sufficient plants under hydroponic culture. Consistent with over-accumulation of H2O2, transcriptome profiling revealed significant enrichment of 175 differentially expressed genes (DEGs) in "response to oxygen-containing compound" out of 641 DEGs in the shoot under low Mg. Among 175 DEGs, a down-regulated receptor-like cytoplasmic kinase ZmRLCK58 underwent a recent duplication event before Poaceae divergence and was highly expressed in the maize shoot. ZmRLCK58 overexpression enhanced H2O2 accumulation in shoots by 21.3% and 29.8% under control and low-Mg conditions, respectively, while reducing biomass accumulation compared with wild-type plants. Low Mg further led to 39.7% less starch accumulation in the ZmRLCK58 overexpression shoot and lower Mg utilization efficiency. Compared with wild-type plants, overall down-regulated expression of genes related to response to carbohydrate, photosynthesis, H2O2 metabolic, oxidation-reduction, and ROS metabolic processes in ZmRLCK58 overexpression lines preconditioned aforementioned physiological alterations. Together, ZmRLCK58, as a negative growth regulator, reduces tolerance of maize seedlings to low Mg via enhancing H2O2 accumulation.

Responses of crops for diverse soil phosphorus conditions and potential crops for phytoextraction of enriched soil phosphorus

Phytoextraction is an attractive method to extract excess soil phosphorus (P) builds up from the soils. The crops potential to extract an enriched P in soil is still lacking. Therefore, four crops were grown in three different soils with variable P levels (0 to 200 mg P/kg soil) and screened for P acquisition potentials. Total P accumulation in roots and shoot was high with enriched P levels in all soils, for example in soil A at 200 mg P/kg soil, the values were 0.44% for cucumber (Cucumis sativus), 0.40% for sunflower (Helianthus annus), and ∼0.30% for cabbage (Brassica oleracea) and 0.20% for Indian mustard (Brassica juncea). The cucumber and sunflower showed a greater biomass production (>6.0 g/pot) with enriched P levels and exhibited more prominent root characteristics, suggests more favorable for P acquisition from the P enriched soils. More prominent enhanced phosphomonoesterase and phytase activities in these crops possibly contributing to their P accumulation ability under high soil P conditions. This study shows that, cucumber and sunflower can generate high dry matter content and can accumulate greater quantity of P from the soils through different mechanisms and they can be potential candidates for phytoextraction of P from the soil P enriched areas.

Efficacy evaluation of biochar and activated carbon as carriers of bacterial inoculants in the remediation of multi-metal polluted soil

ABSTRACT Application of appropriate organic amendments as the carriers of bacterial consortium may improve the remediation efficiency of HMs-polluted soil. A greenhouse experiment was designed and carried out to investigate the capability of biochar, and activated carbon prepared from ostrich manure and almond husk as the carriers of bacterial inoculants in the phytoremediation of a calcareous soil polluted with Pb, Ni, Cd and Zn by maize. Results showed that the application of biochar and activated carbon prepared from ostrich manure increased root (78–129%) and shoot (72.3–272%) dry weight, as compared to the control. The values of metal accumulation in both maize root and shoot were in the order of Cd>Zn>Ni>Pb. While biochar and activated carbon prepared from ostrich manure significantly increased both root and shoot metals uptake, those prepared from almond husk drastically decreased the uptake of some metals. The foremost mechanism involved in the phytoremediation of Cd, Ni and Pb was phytostabilization while that of Zn was due to the phytoextraction. Results of the present study demonstrated the effectiveness of ostrich manure-derived biochar and activated carbon as an efficient treatment in the phytoremediation of multi-metal-polluted soils and the mitigation of HMs phytotoxicity.

Mitigation of uranium toxicity in rice by Sphingopyxis sp. YF1: Evidence from growth, ultrastructure, subcellular distribution, and physiological characteristics

Uranium (U) contamination of rice is an urgent ecological and agricultural problem whose effective alleviation is in great demand. Sphingopyxis genus has been shown to remediate heavy metal-contaminated soils. Rare research delves into the mitigation of uranium (U) toxicity to rice by Sphingopyxis genus. In this study, we exposed rice seedlings for 7 days at U concentrations of 0, 10, 20, 40, and 80 mg L−1 with or without the Sphingopyxis sp. YF1 in the rice nutrient solution. Here, we firstly found YF1 colonized on the root of rice seedlings, significantly mitigated the growth inhibition, and counteracted the chlorophyll content reduction in leaves induced by U. When treated with 1.1 × 107 CFU mL−1 YF1 with the amendment of 10 mg L−1 U, the decrease of U accumulation in rice seedling roots and shoots was the largest among all treatments; reduced by 39.3% and 32.1%, respectively. This was associated with the redistribution of the U proportions in different organelle parts, leading to the alleviation of the U damage to the morphology and structure of rice root. Interestingly, we found YF1 significantly weakens the expression of antioxidant enzymes genes (CuZnSOD,CATA,POD), promotes the up-regulation of metal-transporters genes (OsHMA3 and OsHMA2), and reduces the lipid peroxidation damage induced by U in rice seedlings. In summary, YF1 is a plant-probiotic with potential applications for U-contaminated rice, benefiting producers and consumers.

Effects of Kinetin and Gibberellic Acid on Growth and Ion Transport of Rice Under Cadmium Stress

An experiment was conducted to analyze the effects of kinetin and gibberellic acid on growth, and ion transport of rice (Oryza sativa var. BRRI-80) under cadmium stress. Exogenous application of both kinetin (2 µM) and gibberellic acid (1 µM) alleviated the negative effects of cadmium (Cd) on growth parameters by enhancing the length of both root and shoot, and biomass of Cd stressed rice plants grown on sand culture. Kinetin and GA3 caused decrease in Na+ accumulation while increasing K+ accumulation in both root and shoot. Accumulation of NO3- and PO43- were improved under cadmium stress by kinetin and GA3 in cadmium stressed rice plants. In addition to this, kinetin and GA3 reduced Cd accumulation in the root and shoot of cadmium stressed rice plants. Both kinetin and gibberellic acid were found effective in improving relative water contents in shoots of cadmium stressed rice plants. Bangladesh J. Bot. 53(2): 209-216, 2024 (June)

Morphological and physiological features of genotypes of Zea mays towards salt tolerance influenced by mycorrhizal fungi

Soil salinity poses a significant constraint on plant growth and productivity of maize. Salinity causes reduction in water content in plant tissues, ultimately reducing the photosynthetic capacity and resulting in decreased productivity. Normally in saline soils, chloride ions (Cl−) are particularly considered toxic to certain crops, but in case of maize, sodium ion (Na+) is the main ion responsible for toxicity due to its competition with K+ for binding sites at the plasma membrane. Mycorrhizoremediation which is an enhanced form of phytoremediation is one of the key players in remediation saline soils. Inoculation of these beneficial arbuscular mycorrhizae fungi can alleviate growth inhibition and the adverse effects of salinity in both halophytes and glycophytes by establishing symbiotic relationships with plants. AM fungi colonize the roots of maize plants, perform a crucial role in nutrient cycles in terrestrial ecosystems and own highly efficient and various mitigation mechanisms. Under saline conditions, AM fungi restrict the absorption and translocation of Na+ to shoot tissues and enhance the uptake of K+ in plants. An experiment aiming to enhance salt tolerance in maize through AMF symbiosis was conducted. In this experiment three AMF were evaluated at two salinity levels 66 mM and 100 mM. analysis of data revealed that AMF Ri collect showed showed highest percentage of root colonization at all salinity levels. While plants inoculated with AMF Ce CdG showed highest shoot and root biomass. Furthermore, plants inoculated with Sc CdG and Ce CdG showed a significant reduction in Na+ accumulation and enhance K+ accumulation in shoot and root tissues as compared to non-mycorrhizal plants.

Polystyrene microplastics enhanced the toxicity of cadmium to rice seedlings: Evidence from rice growth, physiology, and element metabolism

Microplastics (MPs) and cadmium (Cd) are toxic to rice; however, the effects and mechanisms of their combined exposure are unclear. The combined exposure effects of polystyrene microplastics (PS-MPs) with different particle sizes (1–10 μm, 50–150 μm) and concentrations (50, 500 mg·L−1) and Cd on rice were explored. PS-MPs combined with Cd amplifies the inhibition of each individual exposure on the height and biomass of rice seedlings, and they showed antagonistic effects. PS-MPs reduced the content of chlorophyll and increased the content of carotenoid rice seedlings significantly. High concentrations of PS-MPs enhanced the inhibition of Cd on chlorophyll content. Cd, PS-MPs single and combined exposures significantly altered the antioxidant enzyme (POD, CAT, SOD) activities in rice seedlings. Under PS-MPs exposure, overall, the MDA content in shoots and roots exhibited opposite trends, with a decrease in the former and an increase in the latter. In comparison with Cd treatment, the combined exposures' shoot and root MDA content was reduced. Cd and PS-MPs showed “low concentration antagonism, high concentration synergism” on the composite physiological indexes of rice seedlings. PS-MPs significantly increased the Cd accumulation in shoots. PS-MPs promoted the root absorption of Cd at 50 mg·L−1 while inhibited at 500 mg·L−1. Cd and PS-MPs treatments interfered with the balance of microelements (Mn, Zn, Fe, Cu, B, Mo) and macroelements (S, P, K, Mg, Ca) in rice seedlings; Mn was significantly inhibited. PS-MPs can enhance of Cd's toxicity to rice seedlings. The combined toxic effects of the two contaminants appear to be antagonistic or synergistic, relying on the particle size and concentration of the PS-MPs. Our findings offer information to help people understanding the combined toxicity of Cd and MPs on crops.

Differential reduction in cadmium accumulation in barley under cadmium-salt co-exposure involves specific HMA genes and antioxidative responses

Salinity and heavy metal accumulation adversely affect agricultural productivity and environmental sustainability. Little information exists about the combinatory effect of various stresses on plants, but it is assumed that stress interaction may trigger a specific response. Here, we assessed the combinatory effect of salinity and cadmium on various physiological and molecular traits in two cultivated barley genotypes with contrasting salinity tolerance; Rihane (RH, salt tolerant) and Lemsi (LM, salt sensitive). Studied genotypes were hydroponically exposed to CdCl2 (30 µM), NaCl (300 mM) or the combined Cd-NaCl stresses for 15 days. Salinity and to a lesser degree Cd-NaCl stress significantly reduced growth, leaf water content, chlorophyll pigments, and K uptake, and increased Na and Cl contents for both genotypes, with LM being more affected than RH. Cd content in roots was higher than in shoots for both genotypes either under Cd alone or when combined with NaCl. Interestingly, NaCl addition reduced Cd accumulation in both roots and shoots of the two barley genotypes, suggesting that the interaction of NaCl and Cd on their uptake and accumulation is antagonistic. The tolerant genotype (RH) accumulated lower Cd levels in shoots and roots than the salt-sensitive one (LM). Cd-NaCl stress significantly lowered H2O2 and MDA contents relative to NaCl treatment alone. The activity of several antioxidant enzymes was essentially higher in RH than in LM, under the different stresses. These responses were in concomitant with an enhanced expression of specific Heavy Metal ATPases (HvHMA) genes, mainly in RH, which can partially, explain the reduced Cd accumulation in this genotype. Overall, these findings suggest the possibility of cultivating salt-tolerant barley genotypes in saline soils slightly contaminated with Cd, whereas barley sensitive genotypes could be assessed for phytoremediation purposes.

Environmental microplastic interact with heavy metal in polluted soil from mine site in the North of Tunisia: Effects on heavy metal accumulation, growth, photosynthetic activities, and biochemical responses of alfalfa plants (Medicago saliva L.)

As emerging persistent pollutants, microplastic (MPs) pollution attracted increasing attention worldwide since it is posing several environmental concerns. MPs interact with heavy metals in soil and may provoke damages on soil properties and ultimately impaired plants and human health. The present study aims to evaluate alfalfa plants (Medicago sativa) response after exposure to heavy metal polluted soils from mine site in the North of Tunisia in presence of environmental microplastic. For that, soils were sampled from two sites of Jebel Ressass mine in addition to a control soil. Plants were exposed to the three soils in presence of two increasing rates of microplastics D1 (1 mg/kg of soil) and D2 (100 mg/kg of soil) for 60 days. After harvest, agronomic parameters, chlorophyll content as well as heavy metal accumulation in plants were analyzed. Furthermore, oxidative status was evaluated in terms of malondialdehyde accumulation (MDA), catalase (CAT) activities and glutathion-S-transferase (GST). Overall, our finding highlights that MPs disrupted agronomic parameters and the photosynthetic activities of alfalfa plants. Additionally, our results revealed that the presence of MPs in polluted soils cause an increase on heavy metal accumulation in alfalfa shoots. Biochemical analyses demonstrated that the combined exposure to MPs and heavy metal induced oxidative stress in alfalfa plants by increasing CAT activity and MDA accumulation. The present investigation highlights the ecological risks of microplastics in terrestrial environment.