Rhizosphere Enzyme Activities Research Articles

Effects of Biochar and Cladophora glomerata on Wheat (Triticum aestivum L.) Growth and Rhizosphere Enzyme Activities

The positive effects of biochar on both soil quality and plant growth and also on plant growth of macroalgae have been reported in studies. Studies on biochar and macroalgae interaction are quite limited. This study was carried out according to randomized plot design in greenhouse conditions to determine the effects of biochar and Cladophora glomerata applications and interaction on the growth of wheat (Triticum aestivum L.) and some enzyme activities in the rhizosphere. Biochar and C. glomerata interaction increased wheat root (90%) and shoot dry weight (84.2%), root length (43.1%) and plant height (84.2%) compared to control. Biochar application increased alkaline phosphatase activity by 66.3%, while C. glomerata increased β-glucosidase activity by 49%. The interaction of both applications increased catalase activity by 62.1% compared to control. These findings confirm the potential of biochar and C. glomerata to improve wheat production by inducing growth.

Intercropping wheat and appropriate nitrogen supply can alleviate faba bean wilt disease by reshaping soil microbial community structure

RationaleThe faba bean-wheat intercropping system is widely adopted to mitigate the incidence of faba bean wilt. The application of nitrogen fertilizers is imperative for promoting crop growth. Determining the optimal nitrogen dosage is crucial for enhancing the disease control efficacy of intercropping systems. So far, the impact of different nitrogen input management on soil microbial communities during the occurrence of faba bean diseases under intercropping conditions of faba bean and wheat has not been clear. ObjectiveTo explore the effect of different nitrogen application levels on the inter-root soil microbial community of faba bean in intercropping scenarios and its relationship with the incidence of faba bean wilt. Materials and methodsTwo planting modes, namely sole faba bean cultivation (M) and faba bean-wheat intercropping (I), were established in both field and pot experiments. Four nitrogen application levels (N0: 0 kg ha−1; N1: 45 kg ha−1; N2: 90 kg ha−1; and N3: 135 kg ha−1) were used to assess the incidence of wilt disease in faba bean. Furthermore, collect soil samples from the rhizosphere of faba bean plants for enzyme and microbial assays in the rhizosphere soil. ResultsThe application of nitrogen (N1, N2, and N3) reduced the incidence of faba bean wilt in the monocultures. Among the same N application levels, intercropping exhibited a significant decrease in wilt incidence compared with monocropping, with the lowest incidence observed at the N2 level. Additionally, the rhizosphere enzyme activity in faba bean was maximized under intercropping at the N2 level. Intercropping increased the richness and diversity of soil microorganisms, leading to an adjusted microbial community structure and the promotion of beneficial microorganism functions. Notably, nitrogen application played a pivotal role in changing the rhizosphere soil microbial community structure of faba bean. A reasonable nitrogen application rate (N2) can significantly improve the disease control effects of intercropping. ConclusionIntercropping with N2(90 kg ha−1) resulted in a significant increase in microbial diversity in faba bean soil. This led to an adaptable microbial structure, effectively mitigating the occurrence of faba bean wilt and ultimately promoting soil function and health.

Effects of drought on enzyme activities and hotspot distribution along plant roots

The frequency and severity of drought are projected to increase due to climate change, and Southeast Asia is no exception. Water scarcity hampers all biochemical processes in soil and induces stunted plant growth. While the rhizosphere harbors the most dynamic biochemical processes in the biosphere, the interaction mechanisms between residing microbes and plant roots under drought are poorly understood. In this research, soybean was planted in soil collected from the Red River Delta of Vietnam to test two hypotheses: (i) drought reduces rhizosphere enzyme activities and hampers the extent of the high enzyme activity along single root (from the root tips), and (ii) the turnover time of substrate by enzymes increases with decreasing soil moisture. The research aimed to characterize distributions of β-glucosidase and acid phosphatase enzymes in a distance from root tips. In addition, enzyme activities and plant root and shoot characteristics (length and weight) were investigated. The results demonstrated that shoot length was more impacted by drought than root length with the reduction of 25% for the former and 5% for the later. Meanwhile, the reduction in shoot weight was 61%, and root weight was 90% as the plant experienced drought conditions. The extent of a hotspot for enzymes along a single plant root, measured from the root tips, also decreased in response to drought. Furthermore, drought reduced both rhizosphere enzyme activities, resulting in a slower turnover time of β-D-glucopyranoside (MUF-G) and 4-methylumbelliferyl-phosphate(MUF-P) substrates. The research has shed light on the adverse impacts of drought on root-microbe interactions, which ultimately lead to poor crop growth.

Detoxification mechanism of herbicide in Polypogon fugax and its influence on rhizosphere enzyme activities

The excessive use of chemical herbicides has resulted in evolution of herbicide-resistant weeds. Cytochrome P450 monooxygenases (P450s) are vital detoxification enzymes for herbicide-resistant weeds. Herein, we confirmed a resistant (R) Polypogon fugax population showing resistance to quizalofop-p-ethyl, acetolactate synthase (ALS)-inhibiting herbicide pyroxsulam, and several other ACCase (acetyl-CoA carboxylase)-inhibiting herbicides. Molecular analysis revealed no target-site gene mutations in the R population. Foliar spraying with malathion clearly reversed the quizalofop-p-ethyl phytotoxicity. Higher level of quizalofop-p-ethyl degradation was confirmed in the R population using HPLC analysis. Subsequently, RNA-Seq transcriptome analysis indicated that the overexpression of CYP89A2 gene appeared to be responsible for reducing quizalofop-p-ethyl phytotoxicity. The molecular docking results supported a metabolic effect of CYP89A2 protein on most herbicides tested. Furthermore, we found that low doses of herbicides stimulated the rhizosphere enzyme activities in P. fugax and the increase of rhizosphere dehydrogenase of R population may be related to its resistance mechanism. In summary, our research has shown that metabolic herbicide resistance mediated by CYP89A2, contributes to quizalofop-p-ethyl resistance in P. fugax.

Effective utilization of weak alkaline soils with Cd-contamination by wheat and rape intercropping

Recently, there has been increasing concern about the health hazards of heavy metal-polluted farmlands. Recent findings suggest that intercropping could be effective remediation strategy for agricultural soils without affecting crop biomass yield. However, there are concerns on the heavy metal accumulation in plant organs in phytoremediation, emphasizing the need to develop an effective intercropping remediation model. In this study, we evaluated the effects of intercropping rape and wheat with different accumulation characteristics of cadmium (Cd), and crop growth and physiological characteristics. Intercropping significantly reduced the Cd content of rape shoot and root, with the rape–low Cd-accumulating wheat intercropping system yielding the best results. However, intercropping had no significant effect on Cd accumulation in wheat. Additionally, intercropping affected the root system configuration and structure, photosynthetic indicators, chlorophyll content, crop enzyme content, and rhizosphere enzyme activity of both species, but did not significantly affect the biomass of wheat and rape. Overall, our findings showed that intercropping rape with a low Cd-accumulating wheat variety could be an effective model for safe production of wheat and rape in weak alkaline soils without compromising biomass yield. The study demonstrates that similar innovative, effective, and judicious intercropping strategy can enrich the theory of contaminated soil remediation.

Phosphorus and water supply independently control productivity and soil enzyme activity responses to elevated CO2 in an understorey community from a Eucalyptus woodland

AimsWhile it is well-established that nitrogen (N) availability regulates elevated [CO2] (eCO2) effects on plant growth and soil carbon (C) storage in N-limited environments, there are fewer studies investigating the role of phosphorous (P) supply on such responses in P-limited environments. In this study, we explored whether P fertilization influences the response of plant growth, soil enzyme activity and C fluxes to eCO2, and determined how different levels of water availability regulate these processes.MethodsWe used soil collected from a temperate, P-limited Eucalyptus woodland containing the native soil seed bank to grow a potted replica of local understory communities. We exposed the emerging communities to eCO2 under two contrasting water levels and two levels of P fertilization. We assessed plant biomass allocation, the rhizosphere activity of extracellular enzymes related to C, N and P cycles, and pot-level CO2 fluxes.ResultsThe positive effects of eCO2 on plant production and ecosystem C dynamics were strongly constrained by low levels of P availability. Enhanced water supply increased rhizosphere enzyme activity with minor impacts on plant biomass responses to eCO2. Our data also suggest that plant and microbial mechanisms that increase nutrient release from SOM may not be able to overcome this P limitation.ConclusionsWhile current Earth System Models predict positive feedback responses of terrestrial ecosystems on C storage under eCO2, here we emphasize the importance of accounting for the widespread phenomenon of P-limitation in such responses.

Biochar Additions Alter the Abundance of P-Cycling-Related Bacteria in the Rhizosphere Soil of Portulaca oleracea L. under Salt Stress

Numerous reports confirm a positive impact of biochar amendments on soil enzyme activities, nutrient cycles, and, finally, plant growth and development. However, reports explaining the process behind such diverse observations are scarce. The aim of the present study was (1) to evaluate the effect of biochar on the growth of purslane (Portulaca oleracea L.) and nutrients; (2) to determine the response of rhizosphere enzyme activities linked to soil phosphorus cycling after bio-char amendment under non–saline and saline soil conditions. Furthermore, we investigate whether adding biochar to soil alters the abundance of P-cycling-related bacteria. Two rates of biochar (2% and 4%) were applied in pot experiments. Biochar addition of 2% significantly increased plant growth under non-saline and saline soil conditions by 21% and 40%, respectively. Moreover, applying biochar increased soil microbial activity as observed by fluorescein diacetate (FDA) hydrolase activity, as well as phosphomonoesterase activities, and the numbers of colony-forming units (CFU) of P-mobilizing bacteria. Soil amended with 2% biochar concentration increased total soil nitrogen (Nt), phosphorus (P), and total carbon (Ct) concentrations by 18%, 15%, and 90% under non-saline soil conditions and by 29%, 16%, and 90% in saline soil compared the control, respectively. The soil FDA hydrolytic activity and phosphatase strongly correlate with soil Ct, Nt, and P contents. The rhizosphere soil collected after biochar amendment showed a higher abundance of tricalcium phosphate-solubilizing bacteria than the control soil without biochar. Overall, this study demonstrated that 2% maize-derived biochar positively affects halophyte plant growth and thus could be considered for potential use in the reclamation of degraded saline soil.

Long-term compost amendment modulates wheat genotype differences in belowground carbon allocation, microbial rhizosphere recruitment and nitrogen acquisition

The implementation of soil health-promoting practices, such as cover cropping and compost application, has important implications for nutrient cycling and management in agroecosystems. At the same time, plant belowground carbon (C) allocation patterns can influence nutrient cycling and availability in soil through changes to the microbial community, but the effects may depend on the crop genotype and management practices in place. We evaluated belowground C allocation patterns using 13C labeling and root architecture in two genotypes of winter wheat (Triticum aestivum) with different levels of exudation and belowground allocation strategies in soils with contrasting compost amendment legacy (108.7 Mg ha−1 every 2 years over 10 years vs. no compost). We also measured microbial community structure and function in the rhizosphere and quantified uptake of residue-derived N from 15N-labelled cover crop residues. We found an interactive effect between soil management and genotype, where in the no-compost soil, the high-exudation genotype (Snowmass) increased exudation by over 4-fold, while the low-exudate genotype (Byrd) increased only 2-fold. While we did not observe genotype differences in rhizosphere enzyme activity or dissolved N pools, residue N uptake was 1.8 times greater for Snowmass in the compost-amended soil. There were more rhizosphere microbial taxa associated with the high-exudate genotype (Snowmass); nine bacterial and seven fungal families were indicative of Snowmass, versus one bacterial and four fungal families for Byrd. Our results suggest that the high-exudation strategy can influence the rhizosphere microbial community, and lead to greater short-term residue N uptake in high SOM soil. By directly linking root architecture, exudation, microbial communities, and N mineralization and uptake dynamics, this work demonstrates that plasticity in root C allocation is genotype-specific and influences microbial communities and nutrient cycling depending on the soil health context.

Rhizosphere enzyme activities and microorganisms drive the transformation of organic and inorganic carbon in saline\u2013alkali soil region

Western Jilin Province is one of the world's three major saline–alkali land distribution areas, and is also an important area of global climate change and carbon cycle research. Rhizosphere soil microorganisms and enzymes are the most active components in soil, which are closely related to soil carbon cycle and can reflect soil organic carbon (SOC) dynamics sensitively. Soil inorganic carbon (SIC) is the main existing form of soil carbon pool in arid saline–alkali land, and its quantity distribution affects the pattern of soil carbon accumulation and storage. Previous studies mostly focus on SOC, and pay little attention to SIC. Illumina Miseq high-throughput sequencing technology was used to reveal the changes of community structure in three maize fields (M1, M2 and M3) and three rice fields (R1, R2 and R3), which were affected by different levels of salinization during soil development. It is a new research topic of soil carbon cycle in saline–alkali soil region to investigate the effects of soil microorganisms and soil enzymes on the transformation of SOC and SIC in the rhizosphere. The results showed that the root—soil—microorganism interaction was changed by saline–alkali stress. The activities of catalase, invertase, amylase and β-glucosidase decreased with increasing salinity. At the phylum level, most bacterial abundance decreases with increasing salinity. However, the relative abundance of Proteobacteria and Firmicutes in maize field and Firmicutes, Proteobacteria and Nitrospirae in rice field increased sharply under saline–alkali stress. The results of redundancy analysis showed that the differences of rhizosphere soil between the three maize and three rice fields were mainly affected by ESP, pH and soil salt content. In saline–alkali soil region, β-glucosidase activity and amylase were significantly positively correlated with SOC content in maize fields, while catalase and β-glucosidase were significantly positively correlated with SOC content in rice fields. Actinobacteria, Bacteroidetes and Verrucomicrobia had significant positive effects on SOC content of maize and rice fields. Proteobacteria, Gemmatimonadetes and Nitrospirae were positively correlated with SIC content. These enzymes and microorganisms are beneficial to soil carbon sequestration in saline–alkali soils.

No CO2 fertilization effect on plant growth despite enhanced rhizosphere enzyme activity in a low phosphorus soil

No CO2 fertilization effect on plant growth despite enhanced rhizosphere enzyme activity in a low phosphorus soil

The Effect of Microbial Fertilizer on the Growth, Rhizospheric Environment and Medicinal Quality of Fritillaria taipaiensis

Fritillaria taipaiensis is a valuable traditional Chinese medicinal plant affected by germplasm degradation during cultivation. To find a suitable solution for this problem, F. taipaiensis was inoculated with exogenous arbuscular mycorrhiza (AM) fungi, potassium-solubilizing bacteria, and phosphorus-solubilizing bacteria in pot experiments. The effects of inoculation on the AM colonization, photosynthetic pigment, and superoxide dismutase contents, rhizospheric enzyme activities, alkaloid, and nucleotide content of F. taipaiensis were studied. The results showed that the inoculation increased mycorrhizal infection intensity of F. taipaiensis. Compared to the control group, the photosynthetic pigment contents in the leaf of the inoculation groups were increased; the content of soluble protein, the activities of the superoxide dismutase, catalase, and peroxidase in leaves were all significantly increased, and the content of malondialdehyde was decreased. The microbial inoculum also increased the content of active ingredients in F. taipaiensis bulbs and increased the enzyme activities, total microorganism number, bacteria/fungi, and actinomycetes/fungi ratios in the rhizosphere. To sum up, microbial fertilizer can significantly improve the rhizospheric environment and medicinal quality of F. taipaiensis. This research provides a theoretical basis and experimental evidence for the sustainable development of an F. taipaiensis industry.

Positive intercropping effects on biomass production are species-specific and involve rhizosphere enzyme activities: Evidence from a field study

Less attention has been given to soil enzymes that contribute to beneficial rhizosphere interactions in intercropping systems. Therefore, we performed a field experiment by growing faba bean, lupine, and maize in mono and mixed cultures in a moderately fertile soil. We measured shoot biomass and the kinetic parameters (maximal velocity (Vmax) and Michaelis-constant (Km)) of three key enzymes in the rhizosphere: Leucine-aminopeptidase (LAP), β-1,4-N-acetylglucosaminidase (NAG), and phosphomonoesterase (PHO). Faba bean benefitted in mixed cultures by greater shoot biomass production with both maize and lupine compared to its expected biomass in monoculture. Next, LAP and NAG kinetic parameters were less responsive to mono and mixed cultures across the crop species. In contrast, both the Vmax and Km values of PHO increased in the faba bean rhizosphere when grown in mixed cultures with maize and lupine. A positive relative interaction index for shoot P and N uptake for faba bean showed its net facilitative interactions in the mixed cultures. Overall, these results suggest that over-productivity in intercropping is crop-specific and the positive intercropping effects could be modulated by P availability. We argue that the enzyme activities involved in nutrient cycling should be incorporated in further research.

English

Experiments were conducted with arsenic-hyperaccumulator, Pteris vittata, and non-hyperaccumulator, Pteris ensiformis, subjected to various arsenic toxicity levels (0 to 1500 mg As kg-1) in peat-moss or soil for up to 14 weeks, to evaluate phenotypic responses and total lipid with fatty acid profiles, and P. vittata influence on rhizosphere enzyme activities. P. ensiformis exhibited significant phenotypic toxicity response compared to P. vittata. P. vittata sequestered significantly (p<0.5) higher arsenic (5,160.6 mg As kg-1) than P. ensiformis (313.4 mg As kg-1). Cellular damage and physiological death occurred in P. ensiformis with alteration in fatty acids and lipid compositions but no significant changes in P. vittata. Both showed no detectable C16:3 but a decrease in C18:3, which was more pronounced in P. ensiformis (51.2%); hence, are reported as C18:3 plants for the first time. Acid phosphatase, β-glucosidase, alrysulphatase, and N-acetyl-β-D-glucosaminidase activities were inhibited by As and significantly (p<0.5) negatively correlated to As concentration. Enzyme inhibition range from 6% in β-glucosidase to 67% in N-acetyl-β-D-glucosaminidase. These results revealed P. vittata phenotypic tolerance to As stress was mediated through metabolic-readjustment, especially its fatty acid and lipid compositions. Additionally, P. vittata rhizospheric events modulate soil enzyme activities in the As-contaminated soil. Key words: Fern, heavy metal, phenotypic response, fatty acids, acid phosphatase, β-glucosidase, alrysulphatase, N-acetyl-β-D-glucosaminidase, rhizosphere.

Optimization of EDTA and citric acid for risk assessment in the remediation of lead contaminated soil

So far, more attention has been mostly paid to the effects of the chelates application to improve phytoextraction efficiency, but less information is available about their effects on the rhizosphere enzyme activities. A greenhouse study was conducted to investigate the effect of EDTA and citric acid (CA) (3 and 5 mmol/kg) on the Pb accumulation in plant organs, the dehydrogenase, urease and alkaline phosphomonoesterase activities, geometric mean of enzyme activities (GMea), total enzyme activity (TEA), and Shannon's diversity index. The application of EDTA harmed plant growth, whereas CA treatments improved plant growth. The 3 and 5 mmol/kg EDTA enhanced Pb accumulation in shoots by 2.6–6 and 1.7–3 times, respectively, in comparison with the control. Pb accumulation in roots after the CA application was significantly higher than control and EDTA treatments. The high dose of EDTA reduced the dehydrogenase and urease activities, GMea, TEA, and diversity of enzyme activities. In contrast, the low dose of EDTA increased the dehydrogenase and alkaline phosphomonoesterase activities, and enzyme-based indices compared with control treatment. In both high and low concentrations, CA significantly stimulated enzyme activities of the rhizosphere, as well as the enzyme-based indices, compared with control and EDTA treatments. CA increased Pb accumulation in the root while did not elevate Pb translocation to the shoot, and also improved the rhizosphere enzyme activities. Thus, we conclude that: i) the effect of EDTA on the Pb phytoextraction and rhizosphere enzyme activities depended on the dosage of EDTA used; ii) CA can be a more suitable choice to increase Pb phytostabilization due to enhancement of the rhizosphere microbial activities.

Feldspar Mine Spoil Rehabilitation: Use of Legumes and Bio Inoculants to Establish Soil Fertility on Agro–Silviculture Basis

In recent researches, legumes have been used to revegetate the mining areas with nitrogen-fixing species. The current study also used legumes to revive the fertility of feldspar mine spoil along with Azotobacter chrococcum, Azospirillum brasilense and Glomus mosseae (AMF) in various combinations with organic and inorganic nutrient supplements. All legumes Acacia nilotica, Acacia senegal, Prosopis cineraria, Cyamopsis tetragonoloba and Cassia angustifolia have shown significant enhancement in rhizosphere enzyme activities up to 65%, metabolites up to 51% and nutrient uptake up to 52% whereas, physical growth showed the increment in the range of 10–59% over the uninoculated control. Treatment of Azotobacter+ organic manure+ NPK 50% has been found to enhance maximum growth in most of the parameters significantly, followed by AMF+ organic manure+ NPK50% treatment, while Azospirillum showed its highest impact in enhancing enzyme activities and nitrogen uptake in comparison to Azotobacter and AMF. Legume tree and crop species showed significant response towards the nitrogen fixation thus helped in improving the nutritional value of the mine spoil. Hence, the integrated approach of agro-silviculture practices using legumes and bioinoculants can play a key role in the rehabilitation of feldspar mine spoil.

Ecoenzymatic stoichiometry and microbial nutrient limitations in rhizosphere soil along the Hailuogou Glacier forefield chronosequence

Mountain glaciers retreat at an increased rate under global warming, resulting in exposed barren surfaces for primary succession. Soil microbes are an important driver of ecosystem processes. Although variations in soil microbes after deglaciation have been studied extensively, the roles of rhizosphere soil microbes in the biogeochemistry cycle during primary succession are less understood. In this study, Populus purdomii was present throughout the 123-year chronosequence as a representative tree species. We therefore investigated variations in the rhizosphere enzyme activity, microbial community structure, and ecoenzymatic stoichiometry of P. purdomii along Hailuogou Glacier chronosequences. The objective was to determinechanges in rhizosphere enzyme activities and microbial communities, as well as the effects of nutrient limitation on rhizosphere microbes. According to the results, the enzyme activities and microbial group biomass in rhizosphere soil all showed a bimodal trend and were highest at the 43rd or 123rd year, and enzyme activity varied with succession time but not microbial community structure. The rhizosphere soil bacterial community was the dominant community during the 123-year chronosequence. Ecoenzymatic stoichiometry indicated nitrogen restrictions on microbial activity throughout primary succession, with early succession stages (5–15 years) showing greater carbon restriction than late succession stages. Moreover, redundancy and correlation analyses demonstrated that soil microbial phospholipid fatty acid biomass was an important factor for increases in enzyme activities and that enzyme activities in turn played important roles in carbon, nitrogen and phosphorus cycling in rhizosphere soil. Additionally, rhizosphere soil microbial development significantly affected soil organic carbon, total nitrogen and dissolved organic carbon accumulation. Overall, our study links the rhizosphere microbial community and activity to successional chronosequences, providing a deeper understanding of the dynamics of ecosystem succession.

Effect of Bio-Organic Amendments on Growth, Yield, Nodulation Status, and Microbial Activity in the Rhizosphere Soil of Peanut Plants under Sandy Soil Conditions

In a field experiment, plant growth, nodulation status, yield, mineral content, and the rhizosphere enzyme activities of peanut (Arachis hypogaea L), cultivated in sandy loam soil were studied under the effect of the amendment with humic acid and the inoculation with plant growth promoting rhizobacteria (PGPR) that applied as foliar andor as seed coating. Bradyrhizobium was used as a single inoculum andor accompanied with PGPR (Azospirillum sp.+ Paeniacillus polymyxa+ Serratia marcescens) with or without humic acid. Results revealed that inoculation with Bradyrhizobium as a single inoculum or accompanied with PGPR, increased significantly shoot dry weight, and yield of peanut under coating and foliar applications. Incorporation of humic acid at two rates of 3L/fed and 5L/fed as foliar and seed coating gave the highest significant values for all tested parameters. inoculation with Bradyrhizobium as single inoculum or accompanied with PGPR enhanced the nodulation status and nitrogenase activity. Also, the values of nodules and nitrogenase activity achieved by coating application method were higher than those recorded by foliar application. In addition, the combined application of coinoculation Bradyrhizobium and PGPR accompanied with humic acid led to significant increases in the content of N, P, and K in shoot plant and in soil. Likewise, humic acid amendment can stimulate the microbial activities in the rhizosphere soil. Higher values of dehydrogenase activity in the rhizosphere soil and carbon dioxide were found with coinoculation and foliar application of humic acid.

Soil extract from an alfalfa (Medicago sativa L.) field improves potato rhizosphere enzyme activity and microbial quantity in a pot experiment

Soil extract from an alfalfa (Medicago sativa L.) field improves potato rhizosphere enzyme activity and microbial quantity in a pot experiment

Expansion of rice enzymatic rhizosphere: temporal dynamics in response to phosphorus and cellulose application

The rhizosphere has ecological importance as a microbial hotspot to understand the ‘real’ processing rates of element cycles without being misled by inactive bulk soil. It is thus essential to estimate the rhizosphere size and its response to anthropogenic distribution during crop growth. In situ β-glucosidase, cellobiohydrolase (C-acquiring), and acid and alkaline phosphatase (P-acquiring) activity was examined using soil zymography in rice rhizosphere. Temporal dynamics of enzymatic rhizosphere size under phosphate and cellulose fertilization were calculated based on the expansion of enzyme activity hotspot. After 35 days of root development, radial expansion of cellobiohydrolase and acid phosphatase from the root centre to bulk soil was further than that of β-glucosidase and alkaline phosphatase, respectively. Root development expanded β-glucosidase hotspot in rhizosphere, but inhibited rhizosphere expansion of phosphatase activities. P fertilization caused strong N competition between plants and microorganisms, reducing rhizosphere expansion of all tested enzyme activities. Cellulose had no significant effects on C-acquiring enzyme activity expansion, but led to extended acid and alkaline phosphatase hotspots in the rice rhizosphere under P fertilization. i) Plant growth stage affects the rice enzymatic rhizosphere size; ii) P fertilization in P-limited soil enhances rhizosphere enzyme activities but reduces the radial expansion; iii) non-labile C application affects enzymatic rhizosphere expansion in an enzyme-specific manner interactively with P fertilization.

Rhizospheric soil enzyme activities and phytominimg potential of Aeluropus lagopoides and Cyperus conglomeratus growing in contaminated soils at the banks of artificial lake of reclaimed wastewater

ABSTRACTThis work investigates the phytoremediation potential of Aeluropus lagopoides and Cyperus conglomeratus, growing indigenously in the vicinity of an artificial lake of reclaimed water in Tabuk, Saudi Arabia . The sampling sites were located at different distances from the wastewater treatment plants. Trace metal contents were higher in roots than shoots in both these plants. Soil urease activity in rhizophere increased linearly along the sampling sites, however, soil alkaline phosphatase and β-glucosidase activities were higher at site 2 but at site 3, the activities of both these soil enzymes reduced. Significant correlations were observed between soil urease activity and the bioconcentration factor (BCF) of Cd, Cu, Pb, and As in A. lagopoides and translocation factor (TF) for all metals in both these plants. Soil β-glucosidase activity was negatively correlated with the TF of Cd, Cu, Pb, and As in A. lagopoides and positively in C. conglomeratus, respectively. Higher BCF of Cd, Cu and Pb than C. conglomeratus and suitable for phytostabilization, however at site 3, C. conglomeratus showed better phytostabilization efficiency for As, as the BCF of As was higher than the A. lagopoides. On the basis of metal accumulation efficiency and rhizospheric soil urease and β-glucosidase activities, A. lagopoides species proved to be a better option for application in phytostabilization strategy than C. conglomeratus plants in the area surrounding the artificial lake of reclaimed water in Tabuk, Saudi Arabia.