Soil Polyphenol Oxidase Activities Research Articles

Soil peroxidase and polyphenoloxidase activity under soil conservation practices on sloping terrains

Soil water erosion in Bulgaria has a significant negative impact on the arable inclined lands. Two experiments were conducted with wheat and maize with application of traditional and soil protection technologies, on Calcic Chernozem soil, on the slope of 5°. Calcic Chernozems are soils exposed to frequent water erosion processes due to significant structural deficiency and low aggregate stability. The first survey was carried out in the period 2018-2020, and in addition to conventional technologies, surface and vertical mulching (with manure as mulching material) were also tested. The second was carried out in 2020-2023 and included minimal treatments for growing wheat and maize and the inclusion of cover crop (barley) in the crop rotation. An increase in the amount of soil organic carbon was found, as well as an increase of the soil peroxidase and polyphenoloxidase activity. The ratio between two enzymes, is considered as humification factor, is higher in the variants under soil protection technologies. The application of soil conservation treatments such as surface mulching with manure, minimum tillage with vertical manure mulching, as well as minimum tillage combined with cover crop in a wheat-maize rotation on sloping farmlands lead to an improvement of soil organic carbon as well as an increase of soil polyphenoloxidase activity.

Combined addition of plant litter altered remediating effects on petroleum‐contaminated soil in Northern Shaanxi, China

AbstractIn the present study, we assessed whether the nonadditive effects of mixed litter decomposition on soil biological and chemical properties, which was usually recognized in clean soils, could be used to enhance the efficiency of petroleum‐contaminated soil necrophytoremediation. In particular, six common plant species from the petroleum production region of Northern Shaanxi, China were collected, forming nine mixture types. The single and mixed litters were used to treat petroleum‐contaminated soil with a proportion of 45 g kg−1 at 25°C and a constant humidity for 150 days. The possible nonadditive effects on the efficiency of removing contaminants and recovering the damaged soil traits caused by the mixed litter addition were then investigated. The results indicate that monospecific litter treatments significantly increased the degradation rates of petroleum contaminants, the available N and P contents, and the catalase and dehydrogenase activities by 36%–74%, 28%–455%, and 8%–102%, respectively (p < 0.05). The mixed addition of the litters from Lespedeza davurica and Artemisia scoparia or those from Agropyron cristatum and Bromus inermis caused significant synergistic effects, enhancing the overall petroleum component removal, replenishing nutrients (particularly nitrogen) or stimulating enzymatic activities (especially for sucrase, phosphatase, catalase, and urease). The observed values of the corresponding indicators following mixed litter treatment were observed to significantly increase by 12%–18%, 23%–58%, and 9%–24% (p < 0.05), relative to their predicted values, which were calculated based on the observed values from the monospecific litter treatments and the proportion of the litter in the mixture. However, other litter combinations may weaken the remediation effects of the litter addition. In general, a high content of nutrients, primary metabolites (e.g., soluble sugars and amino acids), and the potential bio‐surfactants and co‐metabolized substrates (including terpenoids and flavonoids) of mixed litters enhanced the remediation efficiency of mixed litters. Notably, an increase in the chemical diversity of mixed litter may weaken its synergistic effects on the degradation of petroleum components and the simulation of soil polyphenol oxidase activity. Our results demonstrate that appropriate litter mixing combinations can effectively enhance the efficiency of necrophytoremediation, thus providing new approaches for the more convenient and economical remediation of petroleum‐contaminated soil.

Rhizosphere soil affects pear fruit quality under rain-shelter cultivation

The use of rain shelters in pear cultivation has been shown to improve yields and the appearance and quality of fruit, as well as reduce diseases and pests; however, how rain shelters affect soil chemical properties, soil enzyme activity, and soil microbial diversity remains unknown. Here, we studied pear trees under rain-shelter cultivation and open-field cultivation in the same orchard and compared fruit quality, soil chemical characteristics, soil enzyme activity, and soil microbial diversity. Results showed that rain shelters can significantly (p < 0.05) increase the sugar content (sweetness) of pear fruits and decrease the content of acids. The levels of available phosphorus, available potassium, organic matter, and water in soils under rain shelters were significantly (p < 0.05) lower than in soils in open fields. Rain-shelter treatment increased soil polyphenol oxidase activity and decreased phosphomonoesterase, urease, and sucrase activity. Analysis of microbial carbon-source utilization rates and microbial diversity showed that open-field cultivation is beneficial for microbial carbon-source utilization and microbial diversity in rhizosphere soil. Our study found that rain-shelter cultivation is not beneficial to soil fertility, microbial carbon-source metabolism and utilization, matter cycling, or microbial diversity and that the use of rain shelters may require appropriate nutrient and organic matter supplementation to maintain long-term cultivation of crops; whereas, the effects of environmental factors on open-field cultivation are greater, and more refined water and fertilizer management is required to improve fruit quality.

Responses of polyphenoloxidase and catalase activities of rhizosphere and bulk soils to warming during the growing season in an alpine scrub ecosystem.

To understand the effects of climate warming on rhizosphere ecological processes in the alpine scrub ecosystem, the responses of polyphenoloxidase and catalase activities in the rhizosphere and bulk soils to experimental warming (1.3 ℃) were examined during the growing season in a Sibiraea angustata scrub ecosystem on the eastern Qinghai-Tibetan Plateau, China. The results showed that the activities of polyphenoloxidase in rhizosphere and bulk soils in the middle growing season were significantly higher than those in the early or late growing season. The activities of catalase in the bulk soil increased gradually during the growing season, while they showed no seasonal changes in the rhizosphere soil. In the bulk soil, warming significantly increased the activity of polyphenoloxidase by 17.5% in the late growing season and increased that of catalase by 2.2% in the middle growing season, whereas it did not affect soil enzyme activities in early or late growing seasons. In the rhizosphere soil, warming only significantly increased the activities of polyphenoloxidase and catalase by 6.5% and 1.3% in the early growing season. The rhizosphere effect of soil polyphenoloxidase activity was positive throughout the growing season, while there was no obvious rhizosphere effect for soil catalase activity. Furthermore, warming significantly decreased the rhizosphere effect of soil polyphenoloxidase activity by 15.2% during the late growing season. These results indicated that the activities of polyphenoloxidase and catalase activities differed between rhizosphere and bulk soils, with consequences on the rhizosphere soil ecological processes under climate warming in the alpine scrub ecosystem on the eastern Qinghai-Tibetan Plateau.

Differential mechanisms drive changes in soil C pools under N and P enrichment in a subalpine spruce plantation

Nitrogen (N) and phosphorus (P) availabilities can affect soil C cycling by altering both plants and microbial activity. It remains unclear how the changes in plant and microbial processes could regulate C dynamics of different soil fractions, thereby affecting soil C sequestration. Based on a field fertilization experiment in a subalpine spruce plantation, we examined the effects of N, P and combined N and P addition (NP) treatments on plant C inputs, soil C contents and enzyme activities of bulk soil and different aggregate fractions. We aimed to explore the mechanisms by which N and P addition affected soil C sequestration. After 4-year fertilization, the N treatment increased soil C content by 21%, accompanied by suppressed polyphenol oxidase activity (−43%). However, the P and NP treatments decreased soil C content by 14% and 7%, respectively, accompanied by reduction in fine root biomass (−51% and −50%, respectively). Fertilization also affected soil aggregate C pools, with decreased C content in the macroaggregates (5000–250 μm; MaA) under the P and NP treatments, and increased C content in the silt and clay fraction (<53 μm; S&C) under all fertilization treatments. The step-AIC analysis showed that the effects of fertilization on bulk soil C content were best explained by changes in soil polyphenol oxidase activity and fine root biomass. Overall, our results indicate that N-induced soil C accrual, mainly accumulating in the S&C, could be largely driven by the suppressed oxidase activity, and that decreases in soil C content under the P and NP treatments, mostly occurring in the MaA, was likely associated with the reduced C inputs by fine roots.

A Negative Feedback Regulation of Replanted Soil Microorganisms on Plant Growth and Soil Properties of Peach

Replant disease is one of the main growth limiting factors, interfering with plant growth and yield of stone fruit trees such as peach trees. The ecological feedback mechanisms by replanted soil microbes regulating peach growth and soil structure are rarely known. In our study, rhizosphere soils collected from 18-year-old peach trees were used to plant new peach seedlings, and all soil microbes (R) and soil microbes with the size of &lt; 100 μm (R&lt;100) and &lt; 40 μm (R&lt;40) were applied into peach rhizosphere. After 90 days of microbial inoculation, compared with no microbe treatment (R0), the treatments such as R, R&lt;40, and R&lt;100 reduced plant growth performance (biomass, leaf number, plant height, and stem diameter) and root morphology (total length, projected area, surface area, diameter, and volume), with treatment R being the most inhibition of all other treatments. Similar response of treatment R was observed on changes in concentrations of chlorophyll a, chlorophyll b, and carotenoid. Interestingly, compared with R0 treatment, R&lt;100 treatment produced a significant increase in glomalin-related soil protein (GRSP), percentage of water-stable aggregates in size of 0.25-0.5 mm, soil polyphenol oxidase activities and soil catalase activities. However, R treatment dramatically decreased the percentage of water-stable aggregates in size of 2-4 mm and soil peroxidase activities. Our results suggested that replanted soil microbes, especially with the size of &lt; 100 μm, played a strong negative role on plant growth and rhizosphere biology of peach.

Exogenous IAA treatment enhances phytoremediation of soil contaminated with phenanthrene by promoting soil enzyme activity and increasing microbial biomass.

In this study, we aimed to confirm that indole-3-acetic acid promotes plant uptake of phenanthrene (PHE), stimulates the activity of soil enzymes or microflora, and thereby accelerates the dissipation of PHE in soil. Four treatments were evaluated: PHE-contaminated soil planted with (1) ryegrass (T0), (2) ryegrass and supplemented with 1mgkg(-1) indole-3-acetic acid (IAA) (T1), (3) ryegrass and supplemented with 5mgkg(-1) IAA (T5), and (4) ryegrass and supplemented with 10mgkg(-1) IAA (T10). After 30days, PHE concentrations were lower for all treatments and the removal rate was 70.19, 89.17, 91.26, and 97.07% for T0, T1, T5, and T10, respectively. PHE was only detected in the roots and not in the shoots. IAA facilitated the accumulation of PHE in the roots, and plants subjected to the T10 treatment had the highest levels. Exogenous IAA stimulated soil peroxidase activity in a dose-dependent manner, whereas soil polyphenoloxidase activity was not significantly increased, except in T10. Soil microbial biomass also increased in response to IAA treatment, particularly in T10. Furthermore, phospholipid fatty acid analysis showed that IAA treatment increased microbial biomass and alleviated environmental stress. Gram-positive bacteria are largely responsible for polycyclic aromatic hydrocarbon degradation, and we found that the ratio of gram-positive to gram-negative bacteria in the soil significantly increased as the IAA concentrations increased (P < 0.05). Correlation analysis indicated that the increase in soil microbial biomass, enzyme activity, and plant uptake of PHE promotes removal of PHE from the soil.

Isolation and Characterization of Chlorothalonil-Degrading Bacterial Strain H4 and Its Potential for Remediation of Contaminated Soil

A chlorothalonil (CTN)-degrading bacterial strain H4 was isolated in this study from a contaminated soil by continuous enrichment culture to identify its characteristics and to investigate its potential for remediation of CTN in contaminated soil. Based on the morphological, physiological and biochemical tests and 16S rDNA sequence analysis, the strain was identified as Stenotrophomonas sp. After liquid culture for 7 d, 82.2% of CTN was removed by strain H4. The isolate could degrade CTN over a broad range of temperatures and pH values, and the optimum conditions for H4 degradation were pH 7.0 and 30 °C. Reintroduction of the bacteria into artificially contaminated soil resulted in substantial removal of CTN (> 50%) after incubation for 14 d. Soil samples treated by H4 showed significant increases (P < 0.05) in soil dehydrogenase activity, soil polyphenol oxidase activity, average well-color development obtained by the Biolog Eco plateTM assay and Shannon-Weaver index, compared with the control. Strain H4 might be a promising candidate for application in the bioremediation of CTN-contaminated soils.

Analysis of the phenolic compounds in root exudates produced by a subalpine coniferous species as responses to experimental warming and nitrogen fertilisation

In terrestrial ecosystems, plant root exudates clearly play a crucial role in the belowground ecosystem. However, there have been few reports on root exudates from field-grown plants or mature trees in situ, especially when exposed to experimental warming. In this study, we adopted and modified a culture-based cuvette system developed especially for root exudation collection in the field to collect soluble root exudates of a subalpine coniferous species, Abies faxoniana, under experimental warming and nitrogen fertilisation treatments. We then analysed the chemical composition and relative abundance of root exudates using gas chromatography-mass spectrometry (GC-MS). The major chemical constituents of root exudates were phenols and their derivatives of all the different treatments, such as 2,6-di-tert-butyl-4-methylphenol. Experimental warming had significant effects on the relative contents of major compounds and an increase effect on the total phenolic acid compounds. By contrast, there were small significant effects of N fertilisation on root exudation and no significant effects of the warming×N fertilisation interaction. Meanwhile, warming also markedly increased soil polyphenol oxidase activity and it may be soil ecological adjustment response to changes of root exudation under global climate warming.

Saline soil enzyme activities of four plant communities in Sangong River basin of Xinjiang, China

Soil enzyme activity plays an important role in the conversion of soil organic carbon into inorganic carbon, which is significant for the global carbon cycle. In this study, we investigated the soil enzyme activities of two ligninolytic enzymes (peroxidase and polyphenol oxidase) and five non-ligninolytic enzymes (α-1,4-glucosidase (AG); β-1,4-glucosidase (BG); N-acetyl-β-glucosaminidase (NAG); β-D-cellobiosidase (CBH); and β-xylosidase (BXYL)) in four plant communities of the Sangong River basin in Fukang, North Xinjiang, China. The four typical plant communities were dominated by Haloxylon ammodendron, Reaumuria soongonica, Salsola passerina, and Tamarix rarmosissima, respectively, with saline soils of varied alkalinity. The results showed that the soil peroxidase activity decreased seasonally. The activities of the five non-ligninolytic enzymes decreased with increasing soil depths, while those of the two ligninolytic enzymes did not show such a trend. In the four plant communities, BG had the highest activity among the five non-ligninolytic enzymes, and the activities of the two ligninolytic enzymes were higher than those of the four non-ligninolytic ones (AG, NAG, CBH, and BXYL). The community of H. ammodendron displayed the highest activity with respect to the two ligninolytic enzymes in most cases, but no significant differences were found among the four plant communities. The geometric mean of soil enzyme activities of the four plant communities was validated through an independently performed principal component analysis (PCA), which indicated that different plant communities had different soil enzyme activities. The correlation analysis showed that soil polyphenol oxidase activity was significantly positively correlated with the activities of the five non-ligninolytic enzymes. The soil pH value was positively correlated with the activities of all soil enzymes except peroxidase. Soil microbial carbon content also showed a significant positive correlation (P<0.01) with the activities of all soil enzymes except polyphenol oxidase. The results suggested that the H. ammodendron community has the highest ability to utilize soil organic carbon, and glucoside could be the most extensively utilized non-ligninolytic carbon source in the saline soil of arid areas in Xinjiang.

Effects of Different Cropping Patterns of Soybean and Maize Seedlings on Soil Enzyme Activities and MBC and MBN

Through the pot experiment, the effects of different cropping patterns of soybean and maize seedlings on rhizosphere soil urease, catalase, polyphenol oxidase and invertase activities and microbial biomass carbon (MBC) and nitrogen (MBN) were studied. Six treatments of soybean-soybean, soybean-maize, soybean-mixed, maize-soybean, maize-maize and maize-mixed were conducted in pots. Results showed that catalase activity and invertase activity of maize-maize were the highest and significantly different from those of the other treatments except maize-soybean; soil polyphenol oxidase activity of soybean-maize was the highest, and reached significant level among the other treatments, but there was no significant difference of urease activity among treatment soils; MBC of maize-maize soil and MBN of maize-mixed soil reached the highest and significant levels compared with other treatments; MBC and C/N ratio had positive and very significant correlations with soil catalase activity and invertase activity, respectively. Therefore, different cropping patterns could affect rhizosphere soil enzyme activities and soil MBC and MBN, which influenced soil carbon and nitrogen mineralization.

Methyl-β-cyclodextrin enhanced biodegradation of polycyclic aromatic hydrocarbons and associated microbial activity in contaminated soil

The contamination of soils by polycyclic aromatic hydrocarbons (PAHs) is a widespread environmental problem and the remediation of PAHs from these areas has been a major concern. The effectiveness of many in situ bioremediation systems may be constrained by low contaminant bioavailability due to limited aqueous solubility or a large magnitude of sorption. The objective of this research was to evaluate the effect of methyl-β-cyclodextrin (MCD) on bioaugmentation by Paracoccus sp. strain HPD-2 of an aged PAH-contaminated soil. When 10% (W/W) MCD amendment was combined with bioaugmentation by the PAH-degrading bacterium Paracoccus sp. strain HPD-2, the percentage degradation of total PAHs was significantly enhanced up to 34.8%. Higher counts of culturable PAH-degrading bacteria and higher soil dehydrogenase and soil polyphenol oxidase activities were observed in 10% (W/W) MCD-assisted bioaugmentation soil. This MCD-assisted bioaugmentation strategy showed significant increases (p < 0.05) in the average well color development (AWCD) obtained by the BIOLOG Eco plate assay, Shannon-Weaver index (H) and Simpson index (γ) compared with the controls, implying that this strategy at least partially restored the microbiological functioning of the PAH-contaminated soil. The results suggest that MCD-aided bioaugmentation by Paracoccus sp. strain HPD-2 may be a promising practical bioremediation strategy for aged PAH-contaminated soils.

Effects of intercropping cucumber with onion or garlic on soil enzyme activities, microbial communities and cucumber yield

Soil enzyme activities, soil bacterial and fungal community structures and cucumber yield as affected by different cropping systems were evaluated in a three-successive-growing-season experiment under greenhouse conditions. Intercropping systems, in which onion or garlic were planted on the side of cucumber in the first growing season, were compared to cucumber monoculture. Only cucumber was planted in the second and third growing seasons in order to see if the impacts of intercropping in the first growing season still exist in later growing seasons. Results showed that cucumber yield increased under both intercropping systems in these three growing seasons, compared with monoculture. Increases of soil urease activities under intercropping systems were detected in these three growing seasons. Soil polyphenol oxidase activities under intercropping systems also increased in the first two growing seasons. Soil catalase activity was higher under garlic–cucumber intercropping systems than under monoculture in the last two growing seasons. PCR-DGGE analysis showed that soil bacterial community band numbers and diversity indices decreased with growing seasons under monoculture. These indices were relatively stable under intercropping systems throughout these three growing seasons, and were higher than under monoculture. Garlic–cucumber system had a more obvious effect on soil fungal community structure than onion–cucumber system. This study demonstrated that intercropping cucumber with onion or garlic increased cucumber productivity and improved soil environment at different levels. These impacts of intercropping still existed in the second and third growing seasons.

Increased degradation of phenanthrene in soil by Pseudomonas sp. GF3 in the presence of wheat

A phenanthrene-degrading bacterial strain Pseudomonas sp. GF3 was examined for plant-growth promoting effects and phenanthrene removal in soil artificially contaminated with low and high levels of phenanthrene (0, 100 and 200 mg kg −1) in pot experiments. Low and high phenanthrene treatments significantly decreased the growth of wheat. Inoculation with bacterial strain Pseudomonas sp. GF3 was found to increase root and shoot growth of wheat. Strain GF3 was able to degrade phenanthrene effectively in the unplanted and planted soils. Over a period of 80 days the concentration of phenanthrene in soil in which wheat was grown was significantly lower than in unplanted soil ( p < 0.05 ). At the end of the 80-d experiments, 62.2% and 42.3% of phenanthrene had disappeared from planted soils without Pseudomonas sp. GF3 when the phenanthrene was added at 100 and 200 mg kg −1 soil, respectively, but 84.8% and 70.2% of phenanthrene had disappeared from planted soils with the bacterial inoculation. The presence of vegetation significantly enhances the dissipation of phenanthrene in the soil. There was no significant difference in soil polyphenol oxidase activities among the applications of 0, 100 and 200 mg kg −1 of phenanthrene. However, the enzyme activities in planted and unplanted soils inoculated with the strain Pseudomonas sp. GF3 were significantly higher than those of non-inoculation controls. The bacterial isolate was also able to colonize and develop in the rhizosphere soil of wheat after inoculation.

Effects of Single Chinese Fir and Mixed Leaf Litters on Soil Chemical, Microbial Properties and Soil Enzyme Activities

The quality of leaf litter can control decomposition processes and affect the nutrient availability for plant uptake. In this study, we investigated the effect of single leaf litter (Chinese fir – Cunninghamia lamcealata (Lamb.) Hook) and mixed leaf litters (C. lamcealata, Liquidamba formosana Hance and Alnus cremastogyne Burk) on soil chemical properties, soil microbial properties and soil enzyme activities during 2 years decomposition. The results showed that soil microbial biomass C, the ratio of soil microbial biomass C to total soil organic C (soil microbial quotient, Cmic/Corg) and soil enzymes (urease, invertase, dehydrogenase) activities increased significantly in mixed leaf litters treatments whereas soil chemical properties remained unchanged. However, soil microbial metabolic quotient (qCO2) values and soil polyphenol oxidase activity were higher in the single Chinese fir leaf litter treatment that had a higher C:N (carbon:nitrogen) ratio (79.53) compared with the mixed leaf litter (C:N ratios of 76.32, 56.90, 61.20, respectively). Our results demonstrated that the mixed leaf litter can improve forest soil quality, and that soil microbial properties and soil enzyme activities are more sensitive in response to litter quality change than soil chemical properties.