Thinning intensity affects microbial functional diversity and enzymatic activities associated with litter decomposition in a Chinese fir plantation

Microbial functional diversity and enzymatic activities are critical to maintaining material circulation during litter decomposition in forests.Thinning,an important and widely used silvicultural treatment,changes the microclimate and promotes forest renewal.However,how thinning affects microbial functional diversity and enzymatic activities during litter decomposition remains poorly understood.We conducted thinning treatments in a Chinese fir plantation in a subtropical region of China with four levels of tree stem removal（0,30,50,and 70%）,each with three replicates,and the effects of thinning on microbial functional diversity and enzymatic activities were studied 7 years after treatment by collecting litter samples four times over a 1-year period.Microbial functional diversity and enzymatic activities were analyzed using Biolog Ecoplates（Biolog Inc.,Hayward,CA,USA）based on the utilization of 31 carbon substrates.Total microbial abundance during litter decomposition was lower after the thinning treatments than without thinning.Microbial functional diversity did not differ significantly during litter decomposition,but the types of microbial carbon-source utilization did differ significantly with the thinning treatments.Microbial cellulase and invertase activities during litter decomposition were significantly higher under the thinning treatments due to changes in the litter carbon concentration and the ratios of carbon and lignin to nitrogen.The present study demonstrated the important influence of thinning on microbial activities during litter decomposition.Moderate-intensity thinning may maximize vegetation diversity and,in turn,increase the available substrate sources for microbial organisms in litter and promote nutrient cycling in forest ecosystems.

Soil enzymatic activities and microbial community structure with different application rates of Cd and Pb

This study focused on the changes of soil microbial diversity and potential inhibitory effects of heavy metals on soil enzymatic activities at different application rates of Cd and/or Pb. The soil used for experiments was collected from Beijing and classified as endoaquepts. Pots containing 500 g of the soil with different Cd and/or Pb application rates were incubated for a period of 0, 2, 9, 12 weeks in a glasshouse and the soil samples were analyzed for individual enzymes, including catalase, alkaline phosphatase and dehydrogenase, and the changes of microbial community structure. Results showed that heavy metals slightly inhibited the enzymatic activities in all the samples spiked with heavy metals. The extent of inhibition increased significantly with increasing level of heavy metals, and varied with the incubation periods. The soil bacterial community structure, as determined by polymerase chain reaction- denaturing gradient gel electrophoresis techniques, was different in the contaminated samples as compared to the control. The highest community change was observed in the samples amended with high level of Cd. Positive correlations were observed among the three enzymatic activities, but negative correlations were found between the amounts of the heavy metals and the enzymatic activities.

Insights into the changes of amino acids,microbial community,and enzymatic activities related with the nutrient quality of product during the composting of food waste

This study systematically investigated the changes of amino acids as the composting process of food waste proceeded.It is found that the addition of 0.3 g/g total solids of food waste achieved the highest seed germination index of the product(268%).The microbial community results indicated that the abundance of amino acid metabolism sequences remained at high levels during the whole composting process.Proline was identified as the key amino acid related with the nutrient quality of product during the composting of food waste.Further plant germination and hydroponic experiments found,that compared with those without the addition of proline,the addition of 50 mg/L proline increased seed germination rate by 20%,increased shoot length by 3%,increased root biomass of seedlings by 82%,and increased leaf biomass of seedlings by 76%,respectively.Firmicutes,γ-Pseudomonadota,Chloroflexi and Planctomycetes were the key identified bacteria related with the increase of proline during the composting of food waste.Meanwhile,the enzymatic tests of the activities of superoxide dismutase,peroxidase and malondialdehyde indicated that proline did not cause oxidative damage on the growth of plants.This study provided novel insights into the changes of amino acids,microbial community,and enzymatic activities related with the nutrient quality of product during the composting of food waste.

POLYPHENOLS, CYTOTOXICITY AND ENZYMATIC ACTIVITIES OF THREE ERIACEAE SPECIES FROM ALGERIA

In Algerian traditional medicine,Erica arborea(EA),Erica multiflora(EM)and Arbutus unedo(AU)are reported as antiseptic,diuretic,astringent,depurative,and to treat scalds and wounds.The methanolic extracts of their leaves and aerial parts were screened for enzyme inhibitory and cytotoxic activities.TLC and HPLC chromatographic profiles based on flavonoids allowed to easily distinguish between the three investigated species.Inhibitory

Irrigation regimes modulate non-structural carbohydrate remobilization and improve grain filling in rice(Oryza sativa L.)by regulating starch metabolism

Recently developed ‘super’ rice cultivars with greater yield potentials often suffer from the problem of poor grain filling, especially in inferior spikelets. Here, we studied the activities of enzymes related to starch metabolism in rice stems and grains, and the microstructures related to carbohydrate accumulation and transportation to investigate the effects of different water regimes on grain filling. Two ‘super’ rice cultivars were grown under two irrigation regimes of well-watered(WW) and alternate wetting and moderate soil drying(AWMD). Compared with the WW treatment,the activities of ADP glucose pyrophosphorylase(AGPase), starch synthase(StSase) and starch branching enzyme(SBE), and the accumulation of non-structural carbohydrates(NSCs) in the stems before heading were significantly improved, and more starch granules were stored in the stems in the AWMD treatment. After heading, the activities of α-amylase, β-amylase, sucrose phosphate synthase(SPS) and sucrose synthase in the synthetic direction(SSs)were increased in the stems to promote the remobilization of NSCs for grain filling under AWMD. During grain filling, the enzymatic activities of sucrose synthase in the cleavage direction(SSc), AGPase, StSase and SBE in the inferior spikelets were increased, which promoted grain filling, especially for the inferior spikelets under AWMD.However, there were no significant differences in vascular microstructures. The grain yield and grain weight could be improved by 13.1 and 7.5%, respectively, by optimizing of the irrigation regime. We concluded that the low activities of key enzymes in carbon metabolism is the key limitation for the poor grain filling, as opposed to the vascular microstructures, and AWMD can increase the amount of NSC accumulation in the stems before heading, improve the utilization rate of NSCs after heading, and increase the grain filling, especially in the inferior spikelets, by altering the activities of key enzymes in carbon metabolism.

Chitosan Nanoparticles as Biostimulant in Lettuce (Lactuca sativa L.) Plants

Biodegradable nanoparticles such as chitosan nanoparticles (CSNPs) are used in sustainable agriculture since theyavoid damage to the environment;CSNPs have positive effects such as the accumulation of bioactive compoundsand increased productivity in plants. This study aimed to investigate the impact of applying CSNPs on lettuce,specifically focusing on enzymatic activity, bioactive compounds, and yield. The trial was conducted using a completelyrandomized design, incorporating CSNPs: 0, 0.05, 0.1, 0.2, 0.4, and 0.8 mg mL−1. The doses of 0.4 mg mL−1improve yields up to 24.6% increases and 0.1 mg mL−1 of CSNPs increases total phenols by 31.2% and antioxidantcapacity by 34.6%. In addition, when low concentrations of CSNPs (0.05 and 0.1 mg L−1) were applied, anincrease in catalase was determined. The CSNPs represent a good alternative to be used as a biostimulant in sustainableagriculture because they improve the yield and quality of lettuce by increasing the bioactive compounds.

Film-mulched continuous ridge-furrow planting improves soil temperature,nutrient content and enzymatic activity in a winter oilseed rape field,Northwest China

Film mulching system is a widely employed agricultural practice worldwide. However, the effects of different planting and mulching patterns on soil nutrient content and enzymatic activity have not been well documented. In this study, we examined the impact of four planting and mulching patterns（including control, flat planting without mulching; M1, flat planting with film mulching; M2, ridge-furrow planting with film mulching on both ridges and furrows; and M3, ridge-furrow planting with film mulching on continuous ridges） on the seed yield of winter oilseed rape, soil moisture, soil temperature, soil organic carbon（SOC） content, soil nutrient content, and soil enzymatic activity over three growing seasons from 2012 to 2015 in a winter oilseed rape field in the semi-arid area of Northwest China. Seed yield of winter oilseed rape, soil moisture, soil temperature, enzymatic activities, and contents of nitrate-nitrogen, available phosphorus, and available potassium were all significantly higher in mulching treatments（M1, M2 and M3） than in control treatment over the three growing seasons, whereas SOC content was significantly lower in mulching treatments than in control treatment during 2013–2014 and 2014–2015. Among the three mulching treatments（M1, M2 and M3）, the M3 treatment showed consistently higher seed yield, SOC content, nutrient contents, and enzymatic activities than the other two treatments. Seed yield of winter oilseed rape was 41.1% and 15.0% higher in M3 than in M1 and M2, respectively. SOC content and soil enzymatic activities in the top 0–20 cm soil layers and nitrate-nitrogen content in the top 0–30 cm soil layers were all significantly higher in M3 than in M1 and M2. Therefore, we advise the ridge-furrow planting with film mulching on continuous ridges（i.e., M3） as an efficient planting and mulching pattern for sustainably improving the seed yield of winter oilseed rape and preserving soil fertility in the semi-arid area of Northwest China.

Single Nucleotide Polymorphism of CYP3A4 Intron 2 and Its Influence on CYP3A4 mRNA Expression and Liver Enzymatic Activity in Human Liver

Summary： In adult liver, CYP3A4 plays an important role in the metabolism of a wide range of en- dogenous and exogenous compounds. To investigate whether there is a single nucleotide polymorphism （SNP） of CYP3A4 intron 2 in the liver and its effects on the mRNA expression and enzymatic activity of CYP3A4, genomic DNA was extracted from 96 liver tissue samples obtained from patients who had undergone liver surgery. An SNP of CYP3A4 intron 2 was identified by polymerase chain reaction （PCR）-single-strand confirmation polymorphism and DNA sequencing. The mRNA expression of CYP3A4 was determined by the fluorescence quantitative PCR technique. The enzymatic activity of CYP3A4 was measured using erythromycin and testosterone as probe substrates. Twelve patients were found to have the SNP/T4127G CYP3A4 within intron 2. The mRNA levels of CYP3A4 in wild-type and SNP/T4127G samples were 2.62±1.09 and 2.79±1.63, respectively （P〉0.05）. Erythromycin N-demethylase activity in wild-type and SNP/T4127G samples were 121.2±32.8 and 124.7±61.6 nmol·mg^-1min^-1, respectively （P〉0.05）. The activity of testosterone 613-hydroxylase was significantly different between wild-type （648±173 pmol·mg^-1·min^-1） and SNP/T4127G samples （540-4-196 pmol.mg-l-minl; P〈0.05）. In conclusion, the SNP/T4127G of CYP3A4 intron 2 exists in the liver. This SNP does not affect the mRNA expression of CYP3A4 but significantly decreases the hepatic micro- somal testosterone 613-hydroxylase activity of CYP3A4. Furthermore, this study indicates that the ap- propriate selection of probe substrates is very important in studying the relationship between the geno- type and phenotype of CYP3A4.

Morphological characteristics of rock fissure networks and the main factors affecting their soil nutrients and enzyme activities in Guizhou Province,China

Rock fissures constitute the main habitat type in the karst rocky desertification(KRD)area,but the effects of their network morphology on soil properties remain unknown.To address this,we investigated 46 rock vertical profile plots in Guizhou Province of China and classified their habitats using the morphological characteristics of their fissure networks.The response characteristics of soil nutrients and enzyme activities to the rock fissure morphologies in different rock habitats were discussed,and the main factors affecting soil nutrients and enzyme activities were comprehensively analyzed.Rock fissure networks were divided into three types:Type 1,a random type,with a low dip angle,long trace length,multiple turns,multiple connections,and high density;Type 2,a uniform type,with a moderate dip angle,moderate trace length,fewer turns,fewer connections,and moderate density;and Type 3,an aggregation type,with a high dip angle,short trace length,fewer turns,moderate connections,and low density.Soil nutrient levels and enzyme activities were the highest in Type 1,followed by Types 2 and 3.There were no significant differences between the total phosphorus and available phosphorus content in Types 1-3.The dip angle,fractal dimension,and average trace length were identified as the main factors affecting soil nutrients and enzyme activities,and Type 1 was the most conducive for soil nutrient and enzyme accumulation.The restoration of Type 2 and 3 areas should be emphasized in future research,as these results will help guide vegetation restoration in KRD areas.

Effects of soil metal(loid)s pollution on microbial activities and environmental risks in an abandoned chemical smelting site

Abandoned chemical smelting sites containing toxic substances can seriously threaten and pose a risk to the surrounding ecological environment.Soil samples were collected from different depths(0 to 13 m)and analyzed for metal(loid)s content and fractionation,as well as microbial activities.The potential ecological risk indices for the different soil depths(ordered from high to low)were:1 m(D-1)>surface(S-0)>5 m(D-5)>13 m(D-13)>9 m(D-9),ranging between 1840.65-13,089.62,and representing extremely high environmental risks,of which Cd(and probably not arsenic)contributed to the highest environmental risk.A modified combined pollution risk index(MCR)combining total content and mobile proportion of metal(loid)s,and relative toxicities,was used to evaluate the degree of contamination and potential environmental risks.For the near-surface samples(S-0 and D-1 layers),the MCR considered that As,Cd,Pb,Sb,and Zn achieved high and alarming degrees of contamination,whereas Fe,Mn,and Ti were negligible or low to moderate pollution degrees.Combined microcalorimetry and enzymatic activity measurements of contaminated soil samples were used to assess the microbial metabolic activity characteristics.Correlation analysis elucidated the relationship between metal(loid)s exchangeable fraction or content and microbial activity characteristics(p<0.05).The microbial metabolic activity in the D-1 layer was low presumably due to heavy metal stress.Enzyme activity indicators and microcalorimetric growth rate(k)measurements were considered sensitive indicators to reflect the soil microbial activities in abandoned chemical smelting sites.

Improvement of Selected Morphological, Physiological, and Biochemical Parameters of Banana (Musa acuminata L.) Using Potassium Silicate under Drought Stress Condition Grown in vitro

Drought stress has become more common in recent years as a result of climate change impacts on the production of banana crops and other fruit trees.The growth and productivity of Musa spp are severely impacted by the gradual degradation of water resources and the erratic distribution pattern of annual precipitation amount.The aim of the work includes increased drought tolerance in light of water scarcity in the world as a result of the bananas’being gluttonous for water needs.This investigation was carried out from 2019 to 2020 to study the effect of potassium silicate on morphological growth and biochemical parameters of Musa acuminata L under drought stress by PEG.As a result,drought stress reduced the morphological characteristics such as shoots number,shoot length,roots number,and survival percentage and biochemical characteristics such as chlorophyll a,b,carotenoids,stomatal status,and RWC.While proline content increased in the leaf of M.acuminata L.Media complemented with K2SiO3(2 to 6 mM)either individually or in combination with PEG led to an improvement in all morphological and biochemical characteristics.The activities of CAT,POD,and PPO enzymes increased significantly compared to control.Furthermore,the lowest PPO,CAT,and POD activity were achieved.Additionally,K2SiO3 treatments under drought stress successfully enhanced the leaf stomatal behavior.Our results suggest that K2SiO3 can help to maintain plant integrity in the tested cultivar under drought stress.

Cd and Hg Mediated Oxidative Stress,Antioxidative Metabolism and Molecular Changes in Soybean(Glycine max L.)

Cadmium(Cd)and Mercury(Hg)is among the heavy metals most hazardous for plant and human health.Known to induce oxidative stress in plants and disbalance equilibrium in the antioxidant defence system,these metals alter plant growth and cause damage at the cellular and molecular levels.Soybean is an important oilseed crop that is raised in soils often contaminated by Cd and Hg.The comparative studies on the deleterious effect of Cd and Hg and the defence system of antioxidants were not studied earlier in soybean plant.In this study,soybean plants were exposed to Cd(100μM CdCl_(2))and Hg(100μM HgCl_(2))and studied for physiological,biochemical and molecular responses.Both Cd and Hg treatment increased the magnitude of oxidative stress.Activities of antioxidant enzymes were significantly upregulated in response to Cd and Hg stress.Quantitative and qualitative assessment of isolated RNA showed significant differences in RNA under stress.Integrity values of RNA confirmed alterations.Transcript level of the Actin gene,involved in the morphogenesis of plants and also used as referenced gene in expression studies was analyzed using qRT-PCR just to check its stability and response under heavy metal stress.Results showed significant upregulation of the gene in the presence of Cd.It can be concluded that both Cd and Hg caused oxidative damage to plants,and adversely affected the quality of RNA.However,soybean tried to limit the adverse impacts of Cd and Hg stress by elevating the antioxidant system and upregulating Actin gene.

Metal natural product complex Ru-procyanidins with quadruple enzymatic activity combat infections from drug-resistant bacteria

Bacterial infection hampers wound repair by impeding the healing process.Concurrently,inflammation at the wound site triggers the production of reactive oxygen species(ROS),causing oxidative stress and damage to proteins and cells.This can lead to chronic wounds,posing severe risks.Therefore,eliminating bacterial infection and reducing ROS levels are crucial for effective wound healing.Nanozymes,possessing enzyme-like catalytic activity,can convert endogenous substances into highly toxic substances,such as ROS,to combat bacteria and biofilms without inducing drug resistance.However,the current nanozyme model with single enzyme activity falls short of meeting the complex requirements of antimicrobial therapy.Thus,developing nanozymes with multiple enzymatic activities is essential.Herein,we engineered a novel metalloenzyme called Ru-procyanidin nanoparticles(Ru-PC NPs)with diverse enzymatic activities to aid wound healing and combat bacterial infections.Under acidic conditions,due to their glutathione(GSH)depletion and peroxidase(POD)-like activity,Ru-PC NPs combined with H2O2 exhibit excellent antibacterial effects.However,in a neutral environment,the Ru-PC NPs,with catalase(CAT)activity,decompose H2O2 to O2,alleviating hypoxia and ensuring a sufficient oxygen supply.Furthermore,Ru-PC NPs possess exceptional antioxidant capacity through their superior superoxide dismutase(SOD)enzyme activity,effectively scavenging excess ROS and reactive nitrogen species(RNS)in a neutral environment.This maintains the balance of the antioxidant system and prevents inflammation.Ru-PC NPs also promote the polarization of macrophages from M1 to M2,facilitating wound healing.More importantly,Ru-PC NPs show good biosafety with negligible toxicity.In vivo wound infection models have confirmed the efficacy of Ru-PC NPs in inhibiting bacterial infection and promoting wound healing.The focus of this work highlights the quadruple enzymatic activity of Ru-PC NPs and its potential to reduce inflammation and promote bacteria-infected wound healing.

Gene cloning,protein expression,and enzymatic characterization of a double-stranded RNA degrading enzyme in Apolygus lucorum

RNA interference(RNAi)is a powerful tool that post-transcriptionally silences target genes in eukaryotic cells.However,silencing efficacy varies greatly among different insect species.Recently,we met with little success when attempting to knock down genes in the mirid bug Apolygus lucorum via dsRNA injection.The disappearance of double-stranded RNA(dsRNA)could be a potential factor that restricts RNAi efficiency.Here,we found that dsRNA can be degraded in midgut fluids,and a dsRNase of A.lucorum(AldsRNase)was identified and characterized.Sequence alignment indicated that its 6 key amino acid residues and the Mg2+-binding site were similar to those of other insects’dsRNases.The signal peptide and endonuclease non-specific domain shared high sequence identity with the brown-winged green stinkbug Plautia stali dsRNase.AldsRNase showed high salivary gland and midgut expression and was continuously expressed through the whole life cycle,with peaks at the 4th instar ecdysis in the whole body.The purified AldsRNase protein obtained by heterologously expressed can rapidly degrade dsRNA.When comparing the substrate specificity of AldsRNase,3 specific substrates(dsRNA,small interfering RNA,and dsDNA)were all degraded,and the most efficient degradation is dsRNA.Subsequently,immunofluorescence revealed that AldsRNase was expressed in the cytoplasm of midgut cells.Through cloning and functional study of AldsRNase,the enzyme activity and substrate specificity of the recombinant protein,as well as the subcellular localization of nuclease,the reason for the disappearance of dsRNA was explained,which was useful in improving RNAi efficiency in A.lucorum and related species.

Preliminary investigation on the role of microorganisms in the production of phosphine

The relationships between the phosphine content and various microbial populations,activities of different enzymes were investigated firstly.The results indicated that the phosphine content of samples from various environments was positively related to total anaerobic microorganisms,organic phosphate compound-dissolving bacteria,denitrifying bacteria,and the activities of alkaline phosphatase and dehydrogenase,with correlation coefficients (R^2) up to 0.93,0.90,0.69,0.79,and 0.82,respectively.Results also sh...

Effective remediation of aged HMW-PAHs polluted agricultural soil by the combination of Fusarium sp, and smooth bromegrass (Bromus inermis Leyss.)

Fusarium sp. strain ZH-H2 is capable to degrade high molecular weight polycyclic aromatic hydrocarbons （HMW-PAHs）, smooth bromegrass （Bromus inermis Leyss.） can also degrade 4- to 6-ring PAHs. Pot experiments were conducted to investigate how bromegrass and different inoculum sizes of ZH-H2 clean up HMW-PAHs in agricultural soil derived from a coal mine area. The results showed that, compared with control, different sizes of inocula of ZH-H2 effectively degraded HMW-PAHs, with removal rates of 19.01, 34.25 and 29.26% for 4-, 5- and 6-ring PAHs in the treatment with 1.0 g kg-1ZH- H2 incubation after 90 d. After 5 mon of cultivation, bromegrass reached degradation rate of these compounds by 12.66, 36.26 and 36.24%, respectively. By adding strain ZH-H2 to bromegrass, HMW-PAHs degradation was further improved up to 4.24 times greater than bromegrass （W）, in addition to the degradation rate of Bbf decrease. For removal rates of both 5- and 6-ring PAHs, addition of 0.5 g kg-1 Fusarium ZH-H2 to pots with bromegrass performed better than addition of 0.1 g kg-1, while the highest concentration of 1.0 g kg-1 Fusarium ZH-H2 did not further improve degradation. Degradation of4-ring PAHs showed no significant difference among different ZH-H2 incubations with bromegrass treatments. We found that the degradation rates of 4-, 5- and 6-ring PAHs in all treatments are significantly correlated in a positive, linear man- ner with activity of lignin peroxidase （LIP） （t=0.8065, 0.9350 and 0.9165, respectively）, while degradation of 5- and 6-ring PAHs is correlated to polyphenoloxidase （PPO） activity （r=0.7577 and 07806）. Our findings suggest that the combination of Fusarium sp. ZH-H2 and bromegrass offers a suitable alternative for phytoremediation of aged PAH-contaminated soil in coal mining areas, with a recommended inoculation size of 0.5 g Fusarium sp. ZH-H2 per kg soil.

Soil-vegetation relationships in Mediterranean forests after fire

Background:Wildfires are one of the major environmental concerns in Mediterranean ecosystems.Thus,many studies have addressed wildfire impacts on soil and vegetation in Mediterranean forests,but the linkages between these ecosystem compartments after fire are not well understood.The aim of this work is to analyze soil-vegetation relationships in Mediterranean burned forests as well as the consistency of these relationships among forests with different environmental conditions,at different times after fire,and among vegetation with different functional traits.Results:Our results indicate that study site conditions play an important role in mediating soil-vegetation relationships.Likewise,we found that the nature of soil-vegetation relationships may vary over time as fire effects are less dominant in both ecosystem compartments.Despite this,we detected several common soil-vegetation relationships among study sites and times after fire.For instance,our results revealed that available P content and stoichiometry(C:P and N:P)were closely linked to vegetation growth,and particularly to the growth of trees.We found that enzymatic activities and microbial biomass were inversely related to vegetation growth rates,whereas the specific activities of soil enzymes were higher in the areas with more vegetation height and cover.Likewise,our results suggest that resprouters may influence soil properties more than seeders,the growth of seeders being more dependent on soil status.Conclusions:We provide pioneer insights into how vegetation is influenced by soil,and vice-versa,in Mediterranean burned areas.Our results reflect variability in soil-vegetation relationships among study sites and time after fire,but consistent patterns between soil properties and vegetation were also detected.Our research is highly relevant to advance in forest science and could be useful to achieve efficient post-fire management.

Relationships between leaf color changes,pigment levels,enzyme activity,photosynthetic fluorescence characteristics and chloroplast ultrastructure of Liquidambar formosana Hance

Liquidambar formosana Hance is an attractive landscape tree species because its leaves gradually change from green to red,purple or orange in autumn.In this study,the red variety of L.formosana was used to establish a quantitative model of leaf color.Physiological changes in leaf color,pigment levels,enzyme activity,photosynthetic fluorescence characteristics and chloroplast ultrastructure were monitored.The relationship between leaf color and physiological structure indices was quantitatively analyzed to systematically explore the mechanisms behind leaf color.Our data showed that with a decrease in external temperatures,chloroplast numbers and sizes gradually decreased,thylakoid membranes became distorted,and chlorophyll synthesis was blocked and gradually decreased.As a result,chloroplast membranes could not be biosynthesized normally;net photosynthesis,maximum and actual photochemical efficiency,and rate of electron transfer decreased rapidly.Excess light energy caused leaf photoinhibition.With intensification of photoinhibition,leaves protected themselves using two mechanisms.In the first,anthocyanin synthesis was promoted by increasing chalcone isomerase and flavonoid glycosyltransferase activities and soluble sugar content so as to increase anthocyanin to filter light and eliminate reactive oxygen species to reduce photoinhibition.In the second,excessive light energy was consumed in the form of heat energy by increasing the non-photochemical quenching coefficient.These processes tuned the leaves red.

Start-up performances of dry anaerobic mesophilic and thermophilic digestions of organic solid wastes

Two dry anaerobic digestions of organic solid wastes were conducted for 6 weeks in a lab-scale batch experiment for investigating the start-up performances under mesophilic and thermophilic conditions. The enzymatic activities, i.e., β-glucosidase, N-α-benzoyl-Largininamide （BAA）-hydrolysing protease, urease and phosphatase activities were analysed. The BAA-hydrolysing protease activity during the first 2-3 weeks was low with low pH, but was enhanced later with the pH increase. β-Glucosidase activity showed the lowest values in weeks 1-2, and recovered with the increase of BAA-hydrolysing protease activity. Acetic acid dominated most of the total VFAs in thermophilic digestion, while propionate and butyrate dominated in mesophilic digestion. Thermophilic digestion was confirmed more feasible for achieving better performance against misbalance, especially during the start-up period in a dry anaerobic digestion process.

Response of soil catalase activity to chromium contamination

The impact of chromium（Ⅲ） and （Ⅵ） forms on soil catalase activity was presented. The Orthic Podzol, Haplic Phaeozem and Mollic Gleysol from different depths were used in the experiment. The soil samples were amended with solution of Cr（Ⅲ） using CrCl3, and with Cr（Ⅵ） using K2Cr2O7 in the concentration range from 0 to 20 mg/kg, whereas the samples without the addition of chromium served as control. Catalase activity was assayed by one of the commonly used spectrophotometric methods. As it was demonstrated in the experiment, both Cr（Ⅲ） and Cr（Ⅵ） have an ability to reduce soil catalase activity. A chromium dosage of 20 mg/kg caused the inhibition of catalase activity and the corresponding contamination levels ranged from 75% to 92% for Cr（Ⅲ） and 68% to 76% for Cr（Ⅵ）, with relation to the control. Catalase activity reached maximum in the soil material from surface layers （0-25 cm）, typically characterized by the highest content of organic matter creating favorable conditions for microorganisms.