2019 Vol. 34, No. 6
Display Method:
2019, 34(6): 621-629.
doi: 10.19303/j.issn.1008-0384.2019.06.001
Abstract:
Objective Conditions for simultaneous transformation of multiple genes in Indica rice, Minghui 86, were studied to facilitate the development of high yield and resistant breeds. Method Two multi-gene vectors designated as P5 and P8 that harbored the high-yield RRM2, drought-tolerant HS1, herbicide-resistant EPSPS, and insect-resistant Bt as well as the apoptosis-inhibiting iap and gene that promotes cell regeneration p35 were transformed to the receptor Minghui 86 using agrobacterium-based transformation methodology. The receptor, callus culture, agrobacterium concentration, infection time, co-culture, and screening concentrations of G418 and glyphosate were evaluated for the selection. Result Under same culture conditions, the recovery rate of Minghui 86 immature embryos was significantly higher with a better callus quality than that of the mature embryos. The optimal transformation conditions were determinated to be a bacterial concentration of OD600=0.4-0.6, an infection time of 15-20 m, co-culture for 2-3 d with the addition of sterile filter paper in medium, and the screening concentration of G418 at 150 mg·L-1 and of glyphosate at 800 mg·L-1. The PCR detection confirmed that GUS in the polygenic vector P5 was successfully transferred into Indica cv. Minghui 86. Conclusion The optimized culture conditions afforded significantly improved callus and resistance induction rates in Minghui 86.
2019, 34(6): 630-637.
doi: 10.19303/j.issn.1008-0384.2019.06.002
Abstract:
Objective Effect of various means to utilize straws after rice harvest on production and yield of Japonica rice in northern China was evaluated for optimal farm waste management. Method Seedlings of Shennong 265 were transplanted for the experimental cultivation using the conventional fertilization method, a direct straw reclamation in soil at a rate of 6 t·hm-2, the application of straw biochar at a rate of 2 t·hm-2, or the application of straw biochar at a rate of 40 t·hm-2. Rice production and grain yield at harvest were recorded for analysis. Result Adding the cut straws directly back to the field lowered the dry matter accumulation in the grains in the following season that significantly decreased the material output and contribution rates by the leaves by 41.19% and 34.69%, respectively. The grain count per panicle, 1 000-grain weight, panicle number, and grain yield of the rice plants were all negatively affected under the direct straw addition method. The biochar application at the higher rate also reduced dry matter accumulation in the grains with significantly decreased material output by the leaves (21.41% reduction) and stems/sheaths (17.43% reduction). The grain count per panicle was lower than the conventional method as well. On the other hand, when the biochar application was implemented at a lower rate, i.e., 2 t·hm-2 rather than 40 t·hm-2, the dry matters increased 11.68% on the material contribution rate by the leaves, along with the positive effects observed on the grain count per panicle, 1 000-grain weight, panicle number, and yield of the rice grown by using the method. Conclusion The waste utilization by adding straw biochar at 2 t·hm-2 to the soil appeared plausible for rice production in northern China.
2019, 34(6): 638-645.
doi: 10.19303/j.issn.1008-0384.2019.06.003
Abstract:
Objective To determine the sodium silicate concentration that could effectively mitigate the autotoxicity stress, which is one of the main factors causing difficulties on continuous cropping and seriously economic loss, on melon farming. Method Seedlings of Cucumis melo L. with two true leaves and one bud were used in this study. The 0.03 g·mL-1 water extract of the plant was used to simulate the autotoxicity stress. Sodium silicate solutions at different concentrations (0, 1, 2, 4, 8, 16 and 32 mmol·L-1) were added as treatments to determine the effectiveness in the stress alleviation through observations on the growth, plant height, root length, fresh weight, dry weight of shoot, stem diameter, and root surface area of the seedlings. Changes on chlorophyll fluorescence parameters of the seedlings were monitored as well for the analysis. Result The imposed autotoxicity significantly inhibited the increases on seedling height and leaf area. In varying degrees, the Fv'/Fm', Y (Ⅱ), qP, and Y (NPQ) of the plants decreased, while NPQ and Y (NO) increased. However, the presence of sodium silicate at 4mM effectively reduced the stress with the Fv'/Fm', Y (Ⅱ), NPQ, qP, Y (NPQ), and Y (NO) as they became closer to or better than those of control. Conclusion Appropriate exogenous silicon treatment appeared to enable the melon seedlings under autotoxicity stress to grow normally with a stable photosynthetic function.
2019, 34(6): 646-651.
doi: 10.19303/j.issn.1008-0384.2019.06.004
Abstract:
Objective Bioinformatics and expression of NRAT1 gene of the ornamental Hydrangea macrophylla plants that tend to accumulate aluminum (Al), a growth-limiting heavy metal in acidic soil, were studied to understand the physiology of the plant on Al-tolerance. Method The RNA of H. medalensis cv. Laybla was extracted for RT-PCR to detect the real-time expression and cloned for bioinformatic analysis to determine the molecular structure of NRAT1. Result The cloned macrophage gene obtained in the lab revealed that the gene had a 1 881 bp open reading frame and encoded 548 amino acids. A multiple sequence analysis showed it to be highly conservative with 12 transmembrane structures located on the plasma or vacuole membrane. The secondary and tertiary structures of the hydrophobic protein were obtained. RT-PCR indicated that NRAT1 was expressed in the roots, stems and leaves of H. macrophylla, and the expressions increased initially to peak in 2h followed by a decline with time to a levered low level. After 12h under Al-stress, the expression was completely inhibited. Among the three issues, the roots had the highest expression and were affected the most by the stress. Conclusion The NRAT1 gene expression was up-regulated in Hydrangea macrophylla immediately upon the exposure to Al. The gene was positively confirmed to participate in the absorption and transport of Al ions playing an important role in the heavy metal accumulation in the plants.
2019, 34(6): 652-659.
doi: 10.19303/j.issn.1008-0384.2019.06.005
Abstract:
Objective Formulation of the medium for Carpesium macrocephalum culture to produce flavonoids was optimized from the one obtained by a previous study. Method Using NT+NAA 1.0 mg·L-1+0.2 mg·L-1 6-BA as the base, the medium optimizations were firstly carried out on the macro-elements, NH4+, NO3- and K+, then the micro-elements, MoO42-, Zn2+, BO33-, Co2+, Cu2+, I-, and Mn2+ and followed by the added 2, 4-D, KT and GA3. The cellular growth as well as the flavonoids yield in the culture suspension were monitored for evaluation. Result With the optimized addition of the macro- and micro-elements plus KT or GA3, the flavonoids produced by C. macrocephalum culture significantly increased (P < 0.05), but reduced by the presence of 2, 4-D. The finalized medium consisted of the base with added 15.46 NH4+ mmol·L-1, NO3- 14.10 mmol·L-1, K+ 19.10 mmol·L-1, MoO42- 3.0 μmol·L-1, Zn2+ 0.06 mmol·L-1, BO33- 0.4 mmol·L-1, Co2+ 0.2 μmol·L-1, Cu2+ 0.4 μmol·L-1, I- 10 μmol·L-1, Mn2+ 0.2 mmol·L-1, and KT 0.2 mg·L-1. The resulting flavonoids content in the culture suspension was 2.05%, which was 1.68-fold of control, and the flavonoids yield 517.87 mg·L-1, which was 1.80-fold of control. Conclusion By further modifying the previously obtained medium, the flavonoids produced from the C. macrocephalum culture significantly increased.
2019, 34(6): 660-667.
doi: 10.19303/j.issn.1008-0384.2019.06.006
Abstract:
Objective To determine the aromatic composition of loquat fruit and cyclohexanone concentration for the HS-SPME-GC/MS internal standard method. Methods The pulp of Xinbai 8 fruits was added with a cyclohexanone solution in the concentration of 947, 94.7, 9.47, 0.947 μg·μL-1 at a same volume as the internal standard for HS-SPME-GC/MS analysis. Results The analysis detected 10 classifications of chemicals including aldehydes, alkanes, dutrex, ketones and alcohols. Hexanal, (E)-2-hexenal, n-butyl cyclohexane, 2-heptanone, n-pentyl cyclohexane, (E)-2-hexene-1-alcohol, and styrene were the dominating volatiles among the 43 compounds identified.In the cyclohexanone-added samples, the decreasing concentration produced 31, 40, 42 and 33 aromatic substances with the effective peak area ratios of 38.20%, 28.49%, 42.70% and 39.52%, and the peak area ratios of 38.20%, 58.55%, 36.37% and 25.86%, respectively. A maximum number of aromatics was found in the sample that was added with 9.47 μg·μL-1 cyclohexanone which also had the highest effective peak area ratio and optimum peak area radio. Conclusion The aromatics in the fruits of Xinbai 8 were diverse, and the cyclohexanone concentration at 9.47 μg·μL-1 was the choice internal standard for the analytical.
2019, 34(6): 668-677.
doi: 10.19303/j.issn.1008-0384.2019.06.007
Abstract:
Objective Effects of diet composition on growth performance, serum biochemistry and carcass trait-related gene expression of Sujiang pigs at final stage prior to slaughtering were investigated. Method Randomly selected 162 Sujiang pigs with a body weight of (50.49±4.78)kg were divided in 9 groups with 3 replicates per group and 6 pigs per replicate (half male and half female) for the study. The diets used in the L9(34) orthogonal experiment were varied with 3 levels of digestible energy (DE) at 11.64, 12.24, and 12.84 MJ·kg-1, 3 levels of crude protein (CP) at 12%, 13%, and 14%, and 3 levels of crude fiber (CF) at 5%, 8%, and 11%. A pre-feeding period lasted 7 d followed by 42-d-feeding before sampling for serum analysis on the pigs. Result (1) The TP content in the 12.84 MJ·kg-1 DE group was significantly higher than that in the 11.64 MJ·kg-1 DE group (P < 0.05), and GLB in the 12.84 MJ·kg-1 DE groups were significantly higher than those in the 11.64 and 12.24 MJ·kg-1 DE groups (P < 0.01). UN in the 8% CF and the 11% CF groups were extremely significantly (P < 0.01) and significantly (P < 0.05) higher than that in the 5% CF group. TC in the 14% CP groups were significantly lower than that in the 12% CP group (P < 0.01), and TG in the 14% CP group was significantly lower than that in the 12% CP group (P < 0.01). Glu in the 11% CF group was significantly lower than that in the 5% CF group (P < 0.01), and CREA in the 12.84 MJ·kg-1 DE group was significantly lower than that in the 11.64 MJ·kg-1 DE group (P < 0.05). (2) The serum insulin in the 12.84 MJ·kg-1 DE group was significantly higher than that in the 11.64 MJ·kg-1 DE group (P < 0.05). Serum T3 in the 11% CF group was significantly lower than that in the 5% CF group (P < 0.05). However, the dietary nutrition showed no significant effect on serum enzyme activities in the pigs (P>0.05). (3) The expressions of H-FABP and PRAKG3 genes in the longissimus dorsi muscle of the 11.64 MJ·kg-1 DE group were significantly higher than those in the muscle of the 12.24 and 12.84 MJ·kg-1 DE groups (P < 0.05), while that of HSL gene was significantly higher than those of 12.24 and 12.84 MJ·kg-1 DE groups (P < 0.01). The dietary CP or CF induced no significant effect on the expression of the genes in the pigs (P>0.05). Conclusion Dietary DE, CP and CF affected the growth and development of Sujiang pigs at the final fattening stage through regulating the serum biochemistry and carcass trait-related gene expression of the animals. It appeared that a provision of DE at 12.84 MJ·kg-1, CP at 12%, and CF at 11% in the forage was appropriate for the pigs in that stage.
2019, 34(6): 678-683.
doi: 10.19303/j.issn.1008-0384.2019.06.008
Abstract:
Objective The N and P in the excretion of pigs at final growth stage fed under two different feeding programs were compared for forage utilization and ecological effect on the environment. Method A total of 72 growing Duroc×Landrace×Yorkshire pigs weighing 19.5±1.6 kg were randomly divided into two groups with 6 replicates of 6 pigs each. The groups were fed under two different programs:a 3-phase-feeding at 20-50 kg, 50-80 kg, and 80-120 kg pig weight stages or a 5-phase-feeding at 20-35 kg, 35-55 kg, 55-75 kg, 75-95 kg, and 95-120 kg pig weight stages. The fecal N and P of the pigs were determined for the analysis. Result The variation on feeding program did not cause significant difference on the apparent N and P digestibility of the pigs. On the other hand, comparing to the 3-phase-feeding, the pigs under the 5-phase-feeding program showed significant reductions of 5.17% on total dietary N intake (P < 0.05) and of 8.79% on P (P < 0.05), as well as of 6.10% on fecal N (P < 0.05) and of 8.64% on fecal P (P < 0.05). Conclusion Feeding the pigs at final growth stage on the 5-phase program reduced the forage consumption and also the N and P in excretion of the animals resulting in financial as well as ecological benefits.
2019, 34(6): 684-689.
doi: 10.19303/j.issn.1008-0384.2019.06.009
Abstract:
Objective The sensitivity of Phomopsis asparagi to difenoconazole, and the disease control efficacies of 3 fungicide products in the field were studied. Method Pathogen samples of the stem blight disease on asparagus were collected from Fujian, Henan, Hunan, Shanxi, and Shandong provinces and isolated to determine their mycelial growth on a medium laden with difenoconazole. The disease control efficacies of 3 fungicide products, i.e., (a) 10% difenoconazole WG, (b) 35% fluopyram+tebuconazole SC, and (c) 325 g·L-1 difenoconazole+azoxystrobin SC, were assessed in the field. Result The EC50 of the 132 isolates to difenoconazole ranged between 0.010 8 μg·L-1 and 2.654 8 μg·mL-1 averaging (0.693 4±0.044 1)μg·mL-1. The data did not exhibit a normal distribution pattern. A significant difference in difenoconazole sensitivity was found between the isolates from Fujian and Shandong or Hunan (P < 0.05). Even the pathogen samples from a same province varied in their sensitivity toward the fungicide. The field test demonstrated that when (a) was applied at 135.00 g·hm-2 the disease severity was reduced by 75.60% in 2017 and 75.91% in 2018; when (b) was employed at 118.13+118.13 g·hm-2 the severity was lessened by 82.08% in 2017 and 82.32% in 2018; and, when (c) was used at 84.38+135.00 g·hm-2 the severity was decreased by 82.74% in 2017 and 83.23% in 2018. It indicated that the latter two applications were significantly more effective than the first one for the disease control (P < 0.05). Conclusion The non-normal distribution of the sensitivities to difenoconazole of the pathogen isolates from various localities suggested the existence of resistant subpopulations of P. asparagi in the field. Being safe to Asparagus officinalis, the application of either 35% fluopyram+tebuconazole SC or 325 g·L-1difenoconazole+azoxystrobin SC was recommended for the control of stem blight disease on asparagus.
Microbial Diversity and Community Structure in Soil under Tea Bushes-Ganoderma lucidum Intercropping
2019, 34(6): 690-696.
doi: 10.19303/j.issn.1008-0384.2019.06.010
Abstract:
Objective Effects of intercropping Ganoderma lucidum among tea bushes on the microbial diversity and community structure in the soil were investigated. Method The microbial communities in the monoculture (CK) and tea bush-G. lucidum intercropping soils were compared using the high-throughput sequencing technology. Result Compared with CK, the intercropping significantly increased the organic matters, total nitrogen, alkali-hydrolyzed nitrogen, and available phosphorus and significantly reduced the available potassium and pH with no significant effect on the total phosphorus and total potassium in the soil. No significant differences were observed on the richness and diversity indices between them. Furthermore, the relative abundance of Proteobacteria in the intercropping soil significantly increased by 21.18% over CK, while that of Acidobacteria declined by 15.09% and that of Gemmatimonadetes by 53.52%, as none found on those of other bacterial phyla. On genus level, the intercropping significantly increased the relative abundance of beneficial microorganisms, such as, Burkholderia, Sphingomonas and Dyella, in the soil. A correlation analysis showed that the pH, total nitrogen, total phosphorus, and available potassium in soil exerted a greater effect on the dominant than the minor bacterial communities. Conclusion By intercropping G. lucidum among tea bushes, the structure of microbial community in the soil was altered with an increased abundance of beneficial microbial species without significant changes on diversity.
2019, 34(6): 697-704.
doi: 10.19303/j.issn.1008-0384.2019.06.011
Abstract:
Objective To construct a kinetic model for the optimized fermentation of Bacillus amyloliquefaciens FJAT-8754, which was capable of effectively producing cellulase and amylase. Method A 50 L fermenter experiment was conducted to study the cellular growth, pH value, enzyme production and carbohydrate consumption of the fermentation and for subsequent process optimization. A kinetic model was established using the logistic and Luedeking-Piret equations, and experimental data calculated and analyzed with SPSS 16.0 software. Result The optimal fermentation conditions fitted well in the non-linear model as shown by Origin 9.0 software. Conclusion The kinetic model obtained accurately reflected the performance of the fermentation. The cellulase and amylase were products of FJAT-8754 metabolism in the culture.
2019, 34(6): 705-710.
doi: 10.19303/j.issn.1008-0384.2019.06.012
Abstract:
Objective Relationship between carbon (C), nitrogen (N) and pH in meadow soil at the forests of Cryptomeria japonica(L. f.)D. Don after afforested 34 years previously in Mt. Wugong was studied to extract crucial information on the restoration and construction of the fragile ecosystem. Method Samples from 0-20 cm soil layer and litter on the meadow ground were collected by 5-point sampling method at representative plots at the forests for the determinations of C- and N-indices and soil pH. Result Planting of C. japonica significantly increased the total N, ammonium N, nitrate N, available N, soluble organic N, soluble organic C, and microbial biomass C in soil, as well as the organic C and total N in litter (P < 0.05), but significantly reduced soil pH (P < 0.05). Soil pH inversely correlated with the organic C, total N, ammonium N, nitrate N, available N, soluble organic N, soluble organic C, and microbial biomass C in soil, and the organic C in litter. Conclusion C. japonica planting positively impacted the microbial activity as well as the quality and N mineralization capacity of the soil, and decreased the svil pH, which was closely related with the organic matter decomposition.
2019, 34(6): 711-718.
doi: 10.19303/j.issn.1008-0384.2019.06.013
Abstract:
Objective Bioavailability of chromium (Cr), zinc (Zn) and nickel (Ni) as well as factors affecting it in plantation soil were studied as they closely relate to the growth of tea plants. Method Contents and forms of Cr, Zn and Ni in the soil and the leaves on plants at rock tea plantations in Mt. Wuyi, Fujian were determined. Factors affecting the bioavailability of these elements were analyzed. Result Majority of the elements in the sampled soils was residues from the native land, rather than accumulated from external sources. Both bioavailability and enrichment coefficients of Zn were the greatest followed by Ni, then Cr. The bioavailability of Ni inversely correlated to the pH and organic matters of the soil, and the enrichment coefficient of Zn to the pH only. Whereas, the Ni enrichment coefficient correlated inversely to the organic matters, altitude of plantation or age of plant. Conclusion Cr, Zn and Ni in the soil basically existed from the origin of the land. Their bioavailability directly governed the mineral absorption of the tea plants and could be affected to varying degrees by the pH and organic matters in soil, the elevation of plantation, and/or the age of tea bushes.
2019, 34(6): 730-738.
doi: 10.19303/j.issn.1008-0384.2019.06.015
Abstract:
Objective Extraction process of flavonoids from the flowers of Dendrobium chrysotoxum Lindl. was optimized, and the antioxidative activity of the extract determined in vitro. Method Flowers of D. chrysotoxum was subjected to an ethanol extraction for flavonoids. The resulting yield was weighed against the processing conditions based on the single-factor tests and Box-Benhnken center composite experiment with four factors including ethanol volume fraction, solvent-to-substrate ratio, temperature, and time of ultrasonic treatment. The antioxidant capacity was estimated by the ability of the extract to scavenge 1, 1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl free radicals. Result The optimized processing conditions were determined to include ethanol volume fraction at 83%, solvent-to-substrate ratio at 31 mL·g-1, temperature at 59℃ and ultrasound application for 44m to obtain up to 9.71 mg·g-1 of total flavonoids in the extract. The yield exceeded the theoretically expected 9.60 mg·g-1 with a relative deviation of 1.15%. The in vitro tests showed an IC50 for DPPH to be 11.30 μg·mL-1, a scavenging ability 0.51-time of L-ascorbic acid or 1.42-time of BHT, while that for hydroxyl radicals, 137.26 μg·mL-1, a scavenging ability 0.70-time of L-ascorbic acid or 1.95-time of BHT. Conclusion The optimized flavonoid extraction paved the way for scale-up utilization of D. chrysotoxum flowers.
2019, 34(6): 719-729.
doi: 10.19303/j.issn.1008-0384.2019.06.014
Abstract:
Objective To improve the development and application value of resourcos of Auricularia auricula (L. ex Hook) Underw, extraction process of uronic acid from Auricularia auricula (L. ex Hook) Underw was optimized. Method By comparing the uronic acid yield, applications of ultrasound, microwave, light, neutral protease, cellulase, and/or pectinase were incorporated in the extraction to maximize the production. Critical processing conditions including substrate particle size, pectinase dosage, solvent to substrate ratio, temperature, time, pH, ultrasonic power, and ultrasound application time were evaluated in a single factor test. The ultrasound-assisted process with added pectinase was selected for the process optimization using the response surface method with 4 factors and 3 levels. Result The optium method for extracting uronic acid from A.auricula were ultrasound and pectinase. The optimum extraction conditions were determined to include the substrate particle size of 58 μm, pectinase addition at 0.25%, solvent to substrate ratio at 100 mL·g-1, temperature at 50℃, 2 h process duration, pH at 5.50, and 540 W ultrasonic treatment for 30 min. The response surface experiment indicated that a solvent to substrate ratio of 110 mL·g-1, pH at 5.60, ultrasonic power of 540 W, and temperature at 49℃ would maximize the uronic acid yield at 7.95‰, which was 201% of what a traditional hot water method delivered. Conclusion The newly established highly efficient process to extract uronic acid from ultra-fine A. auricula powder applied 540 W ultrasound, added pectinase, used 110 mL per gram of substrate, adjusted pH to 5.60, and maintained a temperature at 49℃ throughout the process, which optimized the extration process of uronic acid of A.auricula, improved the economic value and provided reference for exploiting resources of A.auricula.
2019, 34(6): 739-747.
doi: 10.19303/j.issn.1008-0384.2019.06.016
Abstract:
Rare earth oxide nanoparticles (REO NPs) have caught the attention by scientists worldwide as they can potentially harm the environment due to the toxicity associated with the particle size as well as the chemical property. With the advancement of nanotechnology, NPs inevitably enter the environment through various channels causing detrimental effects on the environment and human health. Therefore, studying the translocation and transformation of REO NPs in media and the response mechanism of plants toward the toxicity carries important theoretical and practical significance for the material applications and ecological security. This article summarizes the mechanism and affecting factors associated with the toxicity of REO NPs on the crops cultivated on soil or hydroponics and discusses the prospects of future research and utilization of the NPs. Currently, the toxic effects induced by REO NPs on plants were believed to include (1) the inhibition of root growth and development and (2) the retardation of chlorophyll synthesis reducing the photosynthetic efficiency and biomass accumulation. The toxicity mechanisms focused by various studies were mainly on (1) the functions directly caused by the dissolved REO NPs ions or their competing with other mineral ions on nutrient absorption, (2) the obstruction of selective cellular permeability, the production of oxygen free radicals, and the lipid peroxidation of cell membrane, and (3) the adherence of particles on surface of the plant tissues interfering normal water and nutrients transportation and ion exchange. Major factors that affect the toxicity might encompass the properties of REO NPs (such as, solubility, electrification, particle size, and shape), the sensitivity or tolerance of a plant to REO NPs, and the environmental conditions (such as, acidity, alkalinity, electrification, etc.).The study on toxic effects of REO NPs has fewer types of selected pollutants, mainly for plants in seedling stage, and fewer study on molecular biology, soil culture methods, and all environmental conditions. In the later stage, we can conduct in-depth research from the above aspects.
Rare earth oxide nanoparticles (REO NPs) have caught the attention by scientists worldwide as they can potentially harm the environment due to the toxicity associated with the particle size as well as the chemical property. With the advancement of nanotechnology, NPs inevitably enter the environment through various channels causing detrimental effects on the environment and human health. Therefore, studying the translocation and transformation of REO NPs in media and the response mechanism of plants toward the toxicity carries important theoretical and practical significance for the material applications and ecological security. This article summarizes the mechanism and affecting factors associated with the toxicity of REO NPs on the crops cultivated on soil or hydroponics and discusses the prospects of future research and utilization of the NPs. Currently, the toxic effects induced by REO NPs on plants were believed to include (1) the inhibition of root growth and development and (2) the retardation of chlorophyll synthesis reducing the photosynthetic efficiency and biomass accumulation. The toxicity mechanisms focused by various studies were mainly on (1) the functions directly caused by the dissolved REO NPs ions or their competing with other mineral ions on nutrient absorption, (2) the obstruction of selective cellular permeability, the production of oxygen free radicals, and the lipid peroxidation of cell membrane, and (3) the adherence of particles on surface of the plant tissues interfering normal water and nutrients transportation and ion exchange. Major factors that affect the toxicity might encompass the properties of REO NPs (such as, solubility, electrification, particle size, and shape), the sensitivity or tolerance of a plant to REO NPs, and the environmental conditions (such as, acidity, alkalinity, electrification, etc.).The study on toxic effects of REO NPs has fewer types of selected pollutants, mainly for plants in seedling stage, and fewer study on molecular biology, soil culture methods, and all environmental conditions. In the later stage, we can conduct in-depth research from the above aspects.
