Effects of biochar and freeze‒thaw cycles on the bacterial community and multifunctionality in a cold black soil area.

Global climate change has altered soil freeze‒thaw cycle events, and little is known about soil microbe response to and multifunctionality regarding freeze‒thaw cycles. Therefore, in this study, biochar was used as a material to place under seasonal freeze-thaw cycling conditions. The purpose of this study was to explore the ability of biochar to regulate the function of freeze-thaw soil cycles to ensure spring sowing and food production. The results showed that biochar significantly increased the richness and diversity of soil bacteria before and after freezing-thawing. In the freezing period, the B50 treatment had the greatest improvement effect (2.6% and 5.5%, respectively), while in the thawing period, the B75 treatment had the best improvement effect. Biochar changed the composition and distribution characteristics of the bacterial structure and enhanced the multifunctionality of freeze-thaw soil and the stability of the bacterial symbiotic network. Compared with the CK treatment, the topological characteristics of the bacterial ecological network of the B50 treatment increased the most. They were 0.89 (Avg.degree), 9.79 (Modularity), 9 (Nodes), and 255 (Links). The freeze-thaw cycle decreased the richness and diversity of the bacterial community and changed the composition and distribution of the bacterial community, and the total bacterial population decreased by 658 (CK), 394 (B25), 644 (B50) and 86 (B75) during the thawing period compared with the freezing period. The soil multifunctionality in the freezing period was higher than that during the thawing period, indicating that the freeze-thaw cycle reduced soil ecological function. From the perspective of abiotic analysis, the decrease in soil multifunctionality was due to the decrease in soil nutrients, enzyme activities, soil basic respiration and other singular functions. From the perspective of bacteria, the decrease in soil multifunctionality was mainly due to the change in the Actinobacteriota group. This work expands the understanding of biochar ecology in cold black soil. These results are conducive to the sustainable development of soil ecological function in cold regions and ultimately ensure crop growth and food productivity.

Mid- and long-term effects of biochar on soil improvement and soil erosion control of sloping farmland in a black soil region, China.

Biochar has been widely used as a soil conditioner, but research on the mid-and long-term effects of biochar on soil structure and soil erosion is still seriously lacking. To investigate the effects of mid- and long-term applications of biochar on soil improvement and soil erosion, a 4-year experiment was carried out on a field runoff plot of 3° sloping farmland in the black soil region of Northeast China. By examining the influence of different biochar application amounts (0, 25, 50, 75, and 100 t ha-1) on annual runoff, annual soil erosion, soil water retention curves, unsaturated hydraulic conductivity and unsaturated water diffusivity over four consecutive years, the optimal biochar application rate was determined. The results showed that the biochar application amount, year and their interaction imposed significant effects on soil structure, annual runoff, annual soil erosion, and moisture characteristic parameters. When the water content exceeded a certain value (0.28 cm3 cm-3), biochar improved the soil hydraulic conductivity. biochar inhibited the horizontal diffusion of water, while Pearson correlation analysis indicated that soil structure improvement encouraged soil water holding capacity enhancement and prevented soil erosion. Based on the analysis of the soil structure and soil erosion during the four-year period, the best biochar application rate for water and soil improvement of the sloping farmlands in the black soil area was proposed, namely, biochar application at 50 t ha-1 for two consecutive years. The research results provide practical application for combat soil erosion of sloping land.

Photochemical performance of thylakoid membrane in lead-treated Nymphoides peltatum.

Photochemical responses in the thylakoid membrane of Nymphoides peltatum to increasing lead (Pb) concentrations were investigated after 5 days of exposure. Pb accumulation increased in a concentration-dependent manner, with a maximum of 118.44 µg g(-1) at 100 µM. Nutrients (Zn, Mg, Mo, Ca, Fe and Mn), ATPase activity and pigment generally increased progressively at Pb concentrations of 12.5 and 25 µM, but then declined at concentrations of 50 and 100 µM. Moreover, Pb stress induced an increase in chlorophyll (Chl) a/b ratio in a different extent. No outstanding changes were observed in several Chl a fluorescence parameters at low Pb concentrations (12.5 and 25 µM), while significant changes (p < 0.05) were observed in these parameters at higher concentrations. The alterations of nutrients, ATPase activity and pigment content were associated with disturbances in the thylakoid membrane, indicated by the quenching of Chl a fluorescence. These results were indicative of a disarray in photochemical activities exerted by Pb phytotoxicity.

Effects of biochar and compost on microbial community assembly and metabolic processes in glyphosate, imidacloprid and pyraclostrobin polluted soil under freezethaw cycles.

Biochar and organic compost are widely used in agricultural soil remediation as soil immobilization agents. However, the effects of biochar and compost on microbial community assembly processes in polluted soil under freezingthawing need to be further clarified. Therefore, a freezethaw cycle experiment was conducted with glyphosate (herbicide), imidacloprid (insecticide) and pyraclostrobin (fungicide) polluted to understand the effect of biochar and compost on microbial community assembly and metabolic behavior. We found that biochar and compost could significantly promote the degradation of glyphosate, imidacloprid and pyraclostrobin in freezethaw soil decrease the half-life of the three pesticides. The addition of immobilization agents improved soil bacterial and fungal communities and promoted the transformation from homogeneous dispersal to homogeneous selection. For soil metabolism, the combined addition of biochar and compost alleviated the pollution of glyphosate, imidacloprid and imidacloprid to soil through up-regulation of metabolites (DEMs) in amino acid metabolism pathway and down-regulation of DEMs in fatty acid metabolism pathway. The structural equation modeling (SEM) results showed that soil pH and DOC were the main driving factors affecting microbial community assembly and metabolites. In summary, the combined addition of biochar and compost reduced the adverse effects of pesticides residues.

Financial Development and Health Outcomes: Do Financial Globalization Matter in Selected Asian Economies?

The importance of health is well documented in the development economics literature because of its increasing effects on economic growth in the long-run. Financial development and financial globalization are essential resources for health. This study examines the role of financial development and financial globalization in the rapid rise of life expectancy in China, India, and Japan by using the annual data covering the period of 1991-2019. The ARDL bounds testing approach confirm the long-run relationship between financial development, financial globalization, and life expectancy in the presence of GDP, health expenditure, and the internet. The long-run findings indicate that financial development positively affects life expectancy by 0.599% in China. The novel findings also indicate that financial globalization positively affects life expectancy by 1.247% in Japan and 1.121% in India. Our findings offer new empirical insights to policymakers crucial to improving life expectancy in China, India, and Japan.

Transcriptome profiles of high-lysine adaptation reveal insights into osmotic stress response in Corynebacterium glutamicum.

Corynebacterium glutamicum has been widely and effectively used for fermentative production of l-lysine on an industrial scale. However, high-level accumulation of end products inevitably leads to osmotic stress and hinders further increase of l-lysine production. At present, the underlying mechanism by which C. glutamicum cells adapt to high-lysine-induced osmotic stress is still unclear. In this study, we conducted a comparative transcriptomic analysis by RNA-seq to determine gene expression profiles under different high-lysine stress conditions. The results indicated that the increased expression of some metabolic pathways such as sulfur metabolism and specific amino acid biosynthesis might offer favorable benefits for high-lysine adaptation. Functional assays of 18 representative differentially expressed genes showed that the enhanced expression of multiple candidate genes, especially grpE chaperon, conferred high-lysine stress tolerance in C. glutamicum. Moreover, DNA repair component MutT and energy-transducing NADH dehydrogenase Ndh were also found to be important for protecting cells against high-lysine-induced osmotic stress. Taken together, these aforementioned findings provide broader views of transcriptome profiles and promising candidate targets of C. glutamicum for the adaptation of high-lysine stress during fermentation.

Calmodulin bound to stress fibers but not microtubules involves regulation of cell morphology and motility.

Calmodulin (CaM) is a major cytoplasmic calcium receptor that performs multiple functions including cell motility. To investigate the mechanism of the regulation of CaM on cell morphology and motility, first we checked the distribution of CaM in the living cells using GFP-CaM as an indicator. We found that GFP-CaM showed a fiber-like distribution pattern in the cytosol of living Potorous tridactylis kidney (PtK2) cells but not in living HeLa cells. The endogenous CaM in heavily permeabilized HeLa was also found to display a fiber-like distribution pattern. Further examination showed that the distribution pattern of GFP-CaM was same as that of stress fibers, but not microtubules. Co-immunoprecipitation also showed that CaM can interact with actin directly or indirectly. The microinjection of trp peptide, a specific inhibitor of CaM, attenuated the polymerization of stress fibers and induced the alteration of cell morphology. A wound-healing assay and a single cell tracking experiment showed that CaM in PtK2 cells could increase cell motility. The data we have got from living cells suggested that CaM affect cell morphology and motility through binding to stress fibers and regulate f-actin polymerization.

Polyamines content and physiological and biochemical responses to ladder concentration of nickel stress in Hydrocharis dubia (Bl.) Backer leaves.

Influence of ladder concentration of nickel (Ni) on the leaves of Hydrocharis dubia were studied after 3 days treatment. The accumulation of Ni, the content of polyamines, proline, malondialdehyde (MDA) and soluble protein, as well as the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in the leaves were investigated. The result indicated that the toxicity of Ni manifested in respective aspect of physiological and biochemical characters. Significant increase of Ni concentration in the leaf tissue was observed, which was concentration dependent. Visible symptoms of Ni toxicity: chlorosis and necrosis occurred following the 3rd day. Meantime, treatment with Ni resulted in the increase in the generation rate of O2(*-) in the leaves. SOD and CAT activities decreased significantly in response to Ni treatment, it was possibly the reason of accumulation of O2(*-). However, a several-fold decrease in POD activities was found. Our results indicated that because of prolonged increases in O2(*-) level, oxidative damage, measured as the level of lipid peroxidation, occured in the leaves of Ni treated fronds. The changes of the content of polyamines (PAs) were also investigated in the leaves of Hydrocharis dubia. Ni treatment significantly increased the putrescine (Put) level and lowered spermidine (Spd) and spermine (Spm) levels, thereby significantly reducing the ratio of free (Spd + Spm)/Put in leaves, which has been considered as the signal under stress. Although the trend that PS-conjugated PAs and PIS-bound PAs changed the same as free PAs, they changed in more less extent.

Exogenous polyamines enhance copper tolerance of Nymphoides peltatum.

The protective effects of polyamines (PAs) against copper (Cu) toxicity were investigated in the leaves of Nymphoides peltatum. Cu treatment increased the putrescine (Put) level and lowered spermidine (Spd) and spermine (Spm) levels, thereby reducing the (Spd+Spm)/Put ratio in leaves. Exogenous application of Spd or Spm markedly reversed these Cu-induced effects for all three PAs and partially restored the (Spd+Spm)/Put ratio in leaves. It also significantly enhanced the level of proline, retarded the loss of soluble protein, decreased the rate of O2*- generation and H2O2 content, and prevented Cu-induced lipid peroxidation. Furthermore, exogenous Spd and Spm reduced the accumulation of Cu and effectively maintained the balance of nutrient elements in plant leaves under Cu stress. These results suggest that exogenous application of Spd or Spm can enhance the tolerance of N. peltatum to Cu by increasing the levels of endogenous Spd and Spm as well as the (Spd+Spm)/Put ratio.

Physiological responses of Alternanthera philoxeroides (Mart.) Griseb leaves to cadmium stress.

Aquatic macrophytes were found to be the potential scavengers of heavy metals from aquatic environment. In this study, several physiological responses of Alternanthera philoxeroides (Mart.) Griseb leaves to elevated concentrations of cadmium (up to 10mM) were investigated. It was found that A. philoxeroides was able to accumulate cadmium in its leaves. The pigment contents decreased with the increase of the Cd concentrations. The Cd could induce rise of the activity of peroxidase (POD) at lower concentration (<5mM), however, when the concentration of Cd rose up to 10mM, the POD activity declined. The changes of superoxide dismutase (SOD) and Catalase (CAT) activities were exactly opposite to that of POD. In the leaves of Cd-treated fronds, the amounts of three polypeptides with apparent molecular weights 80, 39 and 28kDa, respectively, were became visible in SDS-PAGE. The nature of these polypeptides remains to be determined.

Adverse Effects of Hydroalcoholic Extracts and the Major Components in the Stems of Impatiens balsamina L. on Caenorhabditis elegans.

Impatiens balsamina L. (Balsaminaceae), an annual herb found throughout China, has been extensively used in traditional Chinese medicine (TCM). However, our knowledge regarding the adverse effects of I. balsamina in vivo is very limited. In this present study, the nematode Caenorhabditis elegans model was employed to fully assess the adverse effects of hydroalcoholic (EtOH 55%) extracts of I. balsamina stems (HAEIBS) in vivo. After exposure to 10 mg/mL HAEIBS, the major organism-level endpoints of C. elegans of percent survival, frequency of head thrash and body bends, and reproduction had decreased by 24%, 30%, and 25%, respectively. The lifespan of C. elegans was also greatly reduced after HAEIBS exposure compared to the controls. The active compounds in HAEIBS were separated using high speed countercurrent chromatograph (HSCCC) and characterized by high performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR). Two compounds, lawsone and 2-methoxy-1,4-naphthoquinone (MNQ), and their adverse effects were then more thoroughly detailed in this study. It was found that lawsone is the major toxin in HAEIBS with a higher toxicity than MNQ in terms of negative impact on C. elegans mortality, locomotion, reproduction, and lifespan. Our data also suggests that the C. elegans model may be useful for assessing the possible toxicity of other Chinese medicines, plant extracts, and/or compounds.

Lead tolerance mechanism in sterilized seedlings of Potamogeton crispus L.: subcellular distribution, polyamines and proline.

The effects of increasing concentrations of lead (Pb) on malondialdehyde (MDA) content, soluble protein, Pb accumulation, nutrients, polyamines (PAs) and proline metabolism were investigated in sterilized seedlings of Potamogeton crispus L. after 5d exposure. Significant oxidative stress was not caused, indicated by a little induction of MDA content and soluble proteins. Pb accumulation increased in a concentration-dependent manner and most of Pb was stored in the cell wall. Total P, Mg, Na and Zn rose and total Fe fell; total Ca increased at 25 µM Pb but then declined. The nutrients in cell wall fraction changed in the same pattern as total nutrients, whereas those in soluble and organelle fraction declined. Total putrescine (Put) decreased markedly, while total spermidine (Spd), spermine (Spm) and (Spd+Spm)/Put ratio increased progressively but then declined. The trends for free, perchloric acid soluble conjugated (PS-conjugated) and perchloric acid insoluble bound (PIS-bound) PAs were similar to those on total PAs, except that PIS-bound Spm increased significantly. Arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) activities rose gradually, while diamine oxidase (DAO) initially increased but then declined. Proline content increased initially only to decline later, due to the increase of r-glutamyl kinase (GK) activity. Meanwhile, ornithine-d-aminotransferase (OAT) activity gradually reduced, while no significant change was observed in proline dehydrogenase (PDH) activity. Our results indicated that the tolerance of P. crispus to Pb stress was based on cell wall compartmentalization combined with increase of nutrients, alterations of PAs, and induction of proline.

[Effects of exogenous spermidine on resistance of Nymphoides peltatum to Hg2+ stress].

Effects of different exogenous spermidine concentrations on the activities of some enzymes (SOD, CAT, POD, APX), O(-)(2) generation rate, the MDA, chlorophyll, soluble protein and polyamine contents in leaves of Nymphoides peltatum without Hg(2+) stress or under Hg(2+) stress were studied. The results showed that: (1) The spermidine (Spd) and spermine (Spm) content dropped significantly under Hg(2+) (3 mg/L) stress 4 d, while that of putrescine (Put) was increased markedly. Exogenous Spd could increase the Spd and Spm content in leaves, while that of Put lowered at first and rose later. (2) Hg(2+) 3 mg/L decreased drastically the activities of SOD, CAT and APX, increased the O(-)(2) generation rate, led to the accumulation of a large amount of MDA and loss of chlorophyll and soluble protein. Exogenous Spd could enhance the activities of SOD, CAT and APX, decrease O(-)(2) generation rate and reduce the MDA content. In addition, Spd could also decrease the loss of chlorophyll and soluble protein content induced by Hg(2+) stress, enhance the ability of Nymphoides peltatum to resist Hg(2+) stress. The most suitable concentration of Spd was in the range 0.1-0.5 mmol/L.

[Study on sequence difference and SNP pheomenon of rDNA ITS region in F type and H type population of Dendrobium officinale].

OBJECTIVE: To study rDNA ITS sequence differences between F type and that of H type of Dendrobium officinale in main habitat of China. METHOD: The population differences of the rDNA ITS region (including ITS1, ITS2, 5.8S) sequences of D. officinale were studied by the method of DNA sequences analysis. RESULT: There were two different sites between the rDNA ITS sequence of F type and that of H type. One was in ITS1 region, and the other was in 5.8S region. It was proved that there was some relativity between the character of rDNA ITS region and the life type of the populations. The phenomenon of single nucleotide polymorphism (SNP) existed in 5.8S region of rDNA ITS region between F type and H type. The sequences of rDNA ITS region of D. officinale were reported for the first time, and the sequences of ITS region ranged 634 bp (ITS1 231 bp, ITS2 240 bp, 5.8S 163 bp). CONCLUSION: The analysis of rDNA ITS of D. officinale deeply reveal the population differences of D. officinale of F type and H type.

Biochemical defense strategies in sterilized seedlings of Nymphoides peltatum adapted to lead stress.

In order to study potential antioxidant defense mechanisms, the effects of increasing concentrations of lead (Pb) on polyamines (PAs), various thiols, vitamins C and E, and proline contents in sterilized seedlings of Nymphoides peltata (S.G. mel.) Kuntze were investigated after 5 days of exposure. The levels of total putrescine (Put), spermidine (Spd), and spermine (Spm) decreased significantly, while the ratio of (Spd + Spm)/Put first increased but then declined as the concentration of Pb increased. The trends for free, perchloric acid soluble-conjugated (PS-conjugated), and perchloric acid insoluble-bound (PIS-bound) PAs were similar to the trend seen for total PAs. Moreover, reduced glutathione (GSH), nonprotein thiols (NP-SH), phytochelatins (PCs), and vitamin C were induced at high Pb concentrations. No significant change was observed in vitamin E. An initial decline in proline content was followed by an increase as the Pb concentration rose. The reduced level of Put and elevated contents of GSH, NP-SH, PCs, vitamin C, and proline were found to be associated with antioxidant efficiency, which supports the hypothesis that they could play a significant role in the adaptation mechanisms of N. peltatum under Pb stress.

Lead-induced oxidative damage in steriled seedlings of Nymphoides peltatum.

The effects of increasing concentrations of lead (Pb) on Pb accumulation and its influence on nutrient elements, malondialdehyde (MDA) content, generation of superoxide anion (O2(-·)), hydrogen peroxide (H2O2) content, antioxidant enzymes activities, soluble protein, and photosynthetic pigment, as well as chloroplast ultrastructure in steriled seedlings of Nymphoides peltata (S. G. Gmel.) Kuntze were investigated in order to understand Pb-induced toxicity. The accumulation of Pb was found to increase in a concentration-dependent manner. Nutrient elements (Ca, K, Fe, Mn, and Mo) were also affected. MDA content and O2(-·) generation rate increased progressively, while H2O2 content first boosted up at a low Pb concentration of 12.5 µM but then declined. Guaiacol peroxidase and catalase activities increased alternately, while superoxide dismutase activity gradually fell. Negative correlations were found between Pb and soluble protein and photosynthetic pigment. Moreover, Pb exposure resulted in a significant damage of chloroplasts. Taken together, these findings supported the hypothesis that Nymphoides peltatum underwent oxidative stress induced by Pb. In addition, both the disorder of nutrient elements and the damage to the ultrastructure of chloroplasts were indicative of general disarray in the cellular functions exerted by Pb.

Physical localization and DNA methylation of 45S rRNA gene loci in Jatropha curcas L.

In eukaryotes, 45S rRNA genes are arranged in tandem arrays of repeat units, and not all copies are transcribed during mitosis. DNA methylation is considered to be an epigenetic marker for rDNA activation. Here, we established a clear and accurate karyogram for Jatropha curcas L. The chromosomal formula was found to be 2n=2x=22=12m+10 sm. We found that the 45S rDNA loci were located at the termini of chromosomes 7 and 9 in J. curcas. The distribution of 45S rDNA has no significant difference in J. curcas from different sources. Based on the hybridization signal patterns, there were two forms of rDNA - dispersed and condensed. The dispersed type of signals appeared during interphase and prophase, while the condensed types appeared during different stages of mitosis. DNA methylation analysis showed that when 45S rDNA stronger signals were dispersed and connected to the nucleolus, DNA methylation levels were lower at interphase and prophase. However, when the 45S rDNA loci were condensed, especially during metaphase, they showed different forms of DNA methylation.

[Subcellular distribution and phytotoxicity of cadmium in Alternanthera philoxeroides leaves].

A hydroponic experiment was conducted to study the subcellular distribution of Cd and mineral elements in Alternanthera philoxeroides leaves and the leaves anti-oxidative capacity and chlorophyll, soluble protein, and phytochelatins (PCs) contents under the stress of different concentration (0, 0.05, 0.1, 0.2, 0.4 mmol x L(-1)) Cd. With the increasing concentration of Cd in culture medium, the Cd content in all subcellular components of A. philoxeroides leaves increased significantly, and mainly distributed in cell wall, followed by in soluble fractions, and in chloroplast and mitochondria. When the Cd concentration in the medium exceeded 0.2 mmol x L(-1), the Cd was more allocated in soluble fractions than in cell wall. Cd stress resulted in an obvious imbalance of mineral elements uptake. With the increasing concentration of Cd, the Ca content in all subcellular components, especially in cell wall, increased significantly, whereas the P and K contents in cell wall and soluble fractions as well as the Mg and Fe contents in chloroplast decreased. In the meantime, the soluble protein and chlorophyll contents showed a decreasing trend, the glutathione and ascorbic acid contents decreased after an initial increase, the total anti-oxidative capacity (T-AOC) increased progressively, and the PCs accumulated in large quantity. These results suggested that A. philoxeroides had definite resistance to the water body Cd, and there was a dosage-effect relationship between the Cd enrichment in the subcellular components of A. philoxeroides leaves and the phytotoxicity of Cd. The imbalance of the mineral elements in subcellular components and the decrease of soluble protein and chlorophyll contents in chloroplast indicated the obvious phytotoxicity of Cd, while the massive accumulation of Ca in cell wall and the increased levels of PCs and T-AOC suggested the stronger resistance of A. philoxeroides to Cd stress. There was a definite correlation between the PCs production by A. philoxeroides and the toxicity of Cd, suggesting that the PCs could be considered as a sensitive biomarker for estimating the Cd phytotoxicity.

Changes of polyamine levels in roots of Sagittaria sagittifolia L. under copper stress.

INTRODUCTION: The goal of the present study was to investigate the effects of Cu contamination on the above-mentioned biochemical and physiological parameters in order to explore possible prevention strategies against heavy metal stress. MATERIALS AND METHODS: Effects of copper (Cu) on the roots of Sagittaria sagittifolia L. were studied after 10 days of treatment at five concentration levels. The accumulation of Cu, the generation rate of O(2) (·-), the contents of thiobarbituric acid reactive substances (TBARS) and polyamines, as well as the activities of arginine decarboxylase (ADC) and polyamine oxidase (PAO) in the roots were measured and analyzed. RESULTS AND DISCUSSION: It was observed that endogenous Cu content increased in roots of S. sagittifolia L. in a concentration-dependent manner, along with an increased production of O(2) (·-). TBARS content increased progressively up to 5 µmol l(-1) Cu. A constant increase in ADC activity was also observed. The results indicated that lower Cu concentrations (2.5 and 5 µmol l(-1), respectively) had greater enhancing effect on the contents of free Put and perchloric acid-soluble conjugated (PS-conjugated) putrescine (Put), while Cu treatments at different concentration levels had similar enhancing effect on the content of perchloric acid-insoluble bound Put. In total, Put content in each Cu-treated group was higher than that in the control group. PAO activity was inhibited up to 10 µmol l(-1) Cu but enhanced at higher Cu concentrations (20 and 40 µmol l(-1)). This explained the initial rise and subsequent decline of the contents of all forms of spermine (Spm), free and PS-conjugated spermidine (Spd). However, with the increase of Cu concentration, total Spm content increased gradually while total Spd content decreased. Our results suggest that Cu is phytotoxic to the roots of S. sagittifolia L. at high concentrations, and that the increased Spm level is not sufficient to resist Cu-induced oxidative damages.

Involvement of polyamines in adaptation of Potamogeton crispus L. to cadmium stress.

The effects of increasing concentrations of cadmium (Cd) on the ultrastructure, Cd accumulation, generation of O(2)(-), contents of ascorbate (AsA), reduced glutathione (GSH) and polyamines (PAs), as well as the activities of polyamine oxidase (PAO) (EC 1.5.3.3) and diamine oxidase (DAO) (EC 1.4.3.6) were investigated in the leaves of Potamogeton crispus. Cd exposure resulted in significant damage in chloroplasts and mitochondria, suggesting that Cd hastened the senescence of the tested plants. The accumulation of Cd was found to increase in a concentration-dependent manner, accompanied by increased production of O(2)(-). AsA content increased progressively up to 70µM Cd, followed by a decline at higher concentration. GSH content slightly increased up to 70µM Cd and then declined. In addition, Cd treatment increased the putrescine (Put) content, while decreasing spermidine (Spd) and spermine (Spm) contents, which reduced the ratio of free (Spd+Spm)/Put in the leaves. PS-conjugated PAs changed in the same pattern as free PAs, while PIS-bound PAs was different. PIS-bound Put content enhanced with the increase of Cd concentration up to 50µM and then decreased, and PIS-bound Spd and Spm contents decreased to a lesser extent. Moreover, the activities of PAO and DAO increased significantly with the increase of the Cd concentrations, reaching the peak values at 70µM Cd. Our results suggested that certain PAs and PAs forms could play a significant role in the adaptation mechanism of P. crispus under Cd stress.