Shuxin Tu

Effects of elevated CO2 on growth, photosynthesis, elemental composition, antioxidant level, and phytochelatin concentration in Lolium mutiforum and Lolium perenne under Cd stress

The objective of this study was to investigate combined effects of Cd and elevated CO(2) on growth, physiological and physiochemical characteristics, elemental compositions in Lolium mutiforum and Lolium perenne grown in soils amended with three Cd concentrations (0, 25, 100 mg kg(-1)) under two CO(2) levels (375, 810 microLL(-1)). Elevated CO(2) increased net assimilation rate and internal CO(2) concentration, and consequently increased total plant biomass by 51 to 31%. At same spiked Cd level, malondialdehyde content in leaves was lower under elevated than under ambient CO(2), whereas superoxide dismutase activity was higher. Elevated CO(2) decreased Cd, S, and phytochelatin concentrations in roots and shoots to a various degree, depending on plant species and element, but the PC-Cd ratio was not affected. It was concluded that elevated CO(2) ameliorated Cd toxicity in both Lolium species under Cd stress, and that the increase of plant biomass and the alleviation of Cd toxicity with elevated CO(2) for the Lolium species may be more dependent on increased photosynthesis and enhanced antioxidant capacity. Results of the study may provide insights into the interaction between soil Cd contamination and atmospheric CO(2) concentration with regard to plant ability to grow and remove the Cd from soils.

Silicon occurrence, uptake, transport and mechanisms of heavy metals, minerals and salinity enhanced tolerance in plants with future prospects: A review

Recently, heavy metals pollution due to industrialization and urbanization, use of untreated wastewater and unreasonable use of pesticides and fertilizers is increasing rapidly, resulting in major threat to the environment and contaminate soils. Silicon (Si) is the second most abundant element in the earth crust after oxygen. Although its higher accumulation in plants, yet Si has not been listed as essential nutrient however, considered as beneficial element for growth of plants particularly in stressed environment. Research to date has demonstrated that silicon helps the plants to alleviate the various biotic and abiotic stresses. This review article presents a comprehensive update about Si and heavy metals, minerals and salinity stresses, and contained the progress about Si so far done worldwide in the light of previous studies to evaluate the ecological importance of Si. Moreover, this review will also be helpful to understand the Si uptake ability and its benefits on plants grown under stressed environment. Further research needs for Si-mediated mitigation of heavy metals and mineral nutrients stresses are also discussed.

The Accumulation and Subcellular Distribution of Arsenic and Antimony in Four Fern Plants

In the present study, Pteris cretica ‘Albo-Lineata’ (PC), Pteris fauriei (PF), Humata tyermanii Moore (HT), and Pteris ensiformis Burm (PE), were selected to explore additional plant materials for the phytoremediation of As and Sb co-contamination. To some extent, the addition of As and Sb enhanced the growth of HT, PE, and PF. Conversely, the addition of As and Sb negatively affected the growth of PC and was accompanied with the accumulation of high levels of As and Sb in the roots. The highest concentration of Sb was recorded as 6405 mg kg−1 in the roots of PC, and that for As was 337 mg kg−1 in the rhizome of PF. To some degree, As and Sb stimulated the uptake of each other in these ferns. Arsenic was mainly stored in the cytoplasmic supernatant (CS) fraction, followed by the cell wall (CW) fraction. In contrast, Sb was mainly found in the CW fraction and, to a lesser extent, in the CS fraction, suggesting that the cell wall and cytosol play different roles in As and Sb accumulation by fern plants. This study demonstrated that these fern plants show a good application potential in the phytoremediation of As and Sb co-contaminated environments.

Growth, V uptake, and antioxidant enzymes responses of chickpea (Cicer arietinum L.) genotypes under vanadium stress

AimsHeavy metals pollution is one of the most challenging problems to the environment and agricultural soils in recent decades. The purpose of the present work was to elucidate the effects of vanadium (V) on growth, V uptake, protein content and enzymes activity to sort out the V-tolerant and the sensitive genotypes of chickpea under hydroponic conditions.MethodsThe activities of antioxidant enzymes (SOD, CAT, POD, and GSH, MDA) and protein contents were determined by using UV-1600 Spectrophotometer, and V concentration was determined by using GFAAS (GTA 120).ResultsThe findings show that V significantly increased the enzymes activities in all chickpea genotypes however, V significantly reduced the protein contents, and more accumulation of V was observed in roots than shoots in all genotypes. The plant biomass and lengths of roots and shoots were also significantly reduced by V. Moreover, NH4VO3 caused more toxicity than Na3VO4.ConclusionsThe previous studies report that higher activities of enzymes increase the tolerance of plants against stress. The obtained data of present study indicated that Noor–2009 and C–44 are tolerant and G–1 and Balkasar are sensitive genotypes of chickpea against V stress.

Comparative Effects of Biochar, Slag and Ferrous–Mn Ore on Lead and Cadmium Immobilization in Soil

A variety of remediation approaches have been applied to the heavy metals-contaminated soils, however, the immobilization of metals in co-contaminated soils still not cleared. Therefore, an incubation study was conducted to evaluate the instantaneous effects of different concentrations of biochar (BC), slag (SL) and Fe–Mn ore (FMO) on immobilization of Pb and Cd through the Toxicity Characteristic Leaching Procedure (TCLP) by following the the European Community Bureau of Reference (BCR), CaCl2 and NH4NO3. The sequential extraction of BCR showed decrease in acid soluble fractions, while the residual proportions of Pb and Cd were enhanced with increasing concentrations of SL and BC. Addition of BC significantly lowered the extractable fractions of both metals by TCLP, NH4NO3 and CaCl2 as compared to SL and FMO. Among all amendments, BC incorporation into co-contaminated soil offered promising results for Pb and Cd immobilization. Overall, all amendments showed positive and long-term impact on the reclamation of co-contaminated soil with heavy metals and could deserve advance monitoring studies on a field scale.

Nitric oxide induces rice tolerance to excessive nickel by regulating nickel uptake, reactive oxygen species detoxification and defense-related gene expression

Soil contamination with nickel (Ni) is a persistent threat to crop production worldwide. The present study examined the putative roles of nitric oxide (NO) in improving Ni-tolerance in rice. Our findings showed that application of exogenous sodium nitroprusside (SNP), a NO donor, significantly improved the growth performance of rice seedlings when grown under excessive Ni. The enhanced Ni-tolerance of rice prompted by SNP could be ascribed to its ability to regulate Ni uptake, decrease Ni-induced oxidative stress as evidenced by reduced levels of hydrogen peroxide, malondialdehyde, and electrolyte leakage in Ni-stressed plants. The positive roles of NO against Ni-toxicity also reflected through its protective effects on photosynthetic pigments, soluble proteins and proline. SNP also boosted antioxidant capacity in Ni-stressed plants by maintaining increased levels of ascorbate, enhanced activities of ROS-detoxifying enzymes, particularly peroxidase (POD) and catalase (CAT) in both roots and shoots compared with Ni-stressed alone plants. Moreover, SNP treatment also upregulated the transcript levels of CAT, POD, ascorbate peroxidase, glutathione reductase and superoxide dismutase genes in shoots under Ni-stress. Using different sulfide compounds and NO scavenger cPTIO, we also provided evidence that NO, rather than other byproducts of SNP, contributed to the improved performance of rice seedlings under Ni-stress. Collectively, our results conclude that exogenous SNP-mediated modulation of endogenous NO enhanced rice tolerance to Ni-stress by restricting Ni accumulation, maintaining photosynthetic performance and reducing oxidative damage through improved antioxidant system, thereby suggesting NO as an effective stress regulator in mitigating Ni-toxicity in economically important rice, and perhaps in other crop plants.

Chinese Milk Vetch Improves Plant Growth, Development and 15 N Recovery in the Rice-Based Rotation System of South China

Chinese milk vetch (CMV) is vital for agriculture and environment in China. A pot experiment combined with 15N labeling (including three treatments: control, no fertilizer N and CMV; 15N-labeled urea alone, 15NU; substituting partial 15NU with CMV, 15NU-M) was conducted to evaluate the impact of CMV on plant growth, development and 15NU recovery in rice-based rotation system. The 15NU-M mitigated oxidative damage by increasing antioxidant enzymes activities and chlorophyll content while decreased malondialdehyde content in rice root and shoot, increased the biomass, total N and 15N uptake of plant shoots by 8%, 12% and 39% respectively, thus inducing a noticeable increase of annual 15N recovery by 77% versus 15NU alone. Remarkable increases in soil NH4+ and populations of bacteria, actinomycetes and azotobacter were obtained in legume-rice rotation system while an adverse result was observed in soil NO3− content versus fallow-rice. CMV as green manure significantly increased the fungal population which was decreased with cultivating CMV as cover crop. Therefore, including legume cover crop in rice-based rotation system improves plant growth and development, annual N conservation and recovery probably by altering soil nitrogen forms plus ameliorating soil microbial communities and antioxidant system which alleviates oxidative damages in plants.

Nickel stressed responses of rice in Ni subcellular distribution, antioxidant production, and osmolyte accumulation

Nickel has been found a key pollutant in farmlands of central and south China, and understanding of Ni toxicity in rice is of great significance in safety production of rice and remediation of Ni polluted paddy soils. The present study aimed to investigate the uptake and subcellular distribution of Ni, antioxidant production, and osmolyte accumulation of rice (Oryza sativa L., cv. yangliangyou 6) plants exposed to excessive Ni concentrations to gain an insight into Ni-induced phytotoxicity. Results revealed that exposure of rice seedlings to high Ni concentrations resulted a decline in root and shoot lengths and fresh weight (FW) and dry weight (DW) of rice plants, which are in connection with the depletion of the contents of photosynthetic pigments. Measurement of Ni concentrations in the roots and shoots showed that Ni was mainly accumulated in roots followed by shoots. Moreover, Ni was mainly deposited in soluble fraction and cell wall, than cell organelle, which suggests that both compartments act as crucial defensive barriers against Ni toxicity in rice plants. Ni also induced its toxicity by damaging oxidative metabolism, as indicated by increased level of hydrogen peroxide and malondialdehyde content. Furthermore, Ni stress also showed a desynchronized antioxidant system by increasing the activities of catalase, peroxidase, and the contents of ascorbic acid and glutathione, whereas decreasing the activity of superoxide dismutase in the roots and shoots of rice plants. Ni stress also triggered the rate of proline accumulation and decreasing the contents of soluble protein and soluble sugar. In crux, our results suggests that excessive Ni inhibited rice growth and induced oxidative stress through inducing ROS formation, while stimulated enzymatic and non-enzymatic antioxidants system appeared as adaptive mechanisms of rice plants against Ni-induced oxidative stress. Furthermore, majority of Ni was located in soluble fraction and modulation in osmolyte accumulation under Ni stress seemed to provide additional defense against oxidative stress.

Chinese Milk Vetch as Green Manure Mitigates Nitrous Oxide Emission from Monocropped Rice System in South China

Monocropped rice system is an important intensive cropping system for food security in China. Green manure (GM) as an alternative to fertilizer N (FN) is useful for improving soil quality. However, few studies have examined the effect of Chinese milk vetch (CMV) as GM on nitrous oxide (N2O) emission from monocropped rice field in south China. Therefore, a pot-culture experiment with four treatments (control, no FN and CMV; CMV as GM alone, M; fertilizer N alone, FN; integrating fertilizer N with CMV, NM) was performed to investigate the effect of incorporating CMV as GM on N2O emission using a closed chamber-gas chromatography (GC) technique during the rice growing periods. Under the same N rate, incorporating CMV as GM (the treatments of M and NM) mitigated N2O emission during the growing periods of rice plant, reduced the NO3- content and activities of nitrate and nitrite reductase as well as the population of nitrifying bacteria in top soil at maturity stage of rice plant versus FN pots. The global warming potential (GWP) and greenhouse gas intensity (GHGI) of N2O from monocropped rice field was ranked as M<NM<FN. However, the treatment of NM increased rice grain yield and soil NH4+ content, which were dramatically decreased in the M pots, over the treatment of FN. Hence, it can be concluded that integrating FN with CMV as GM is a feasible tactic for food security and N2O mitigation in the monocropped rice based system.

Impact of different amendments on biochemical responses of sesame (Sesamum indicum L.) plants grown in lead-cadmium contaminated soil

Soil co-contamination with lead (Pb) and cadmium (Cd) is a tenacious risk to crop production globally. The current experiment observed the roles of amendments [biochar (BC), slag (SL), and ferrous manganese ore (FMO)] for enhancing Pb and Cd tolerance in sesame (Sesamum indicum L.). Our results revealed that application of amendments significantly enhanced the nutrient level of sesame seedlings developed under extreme Pb and Cd conditions. The higher Pb and Cd-tolerance in sesame encouraged by amendments might be credited to its capability to restrict Pb and Cd uptake and decreased oxidative damage induced by Pb and Cd that is also demonstrated by lesser production of hydrogen peroxide (H2O2), malondialdehyde (MDA), and reduced electrolyte leakage (EL) in plant biomass. The added amendments relieved Pb and Cd toxicity and improved photosynthetic pigments, soluble protein, and proline content. Not only this amendments also decreased the antioxidant bulk, such as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in sesame plants compared to control when exposed to Pb and Cd. Moreover, the added amendments = down-regulated the genes expression which regulate the SOD, POD, and CAT activity in sesame under Pb and Cd-stress. Furthermore, supplementation of amendments to the soil, reduced the bio accessibility (SBET), leachability (TCLP), and mobility (CaCl2) of Pb and Cd. Collectively, our findings conclude that the application of amendments enhanced sesame tolerance to Pb and Cd stress by restricting Pb and Cd accumulation, maintained photosynthetic presentation and dropped oxidative loss through enhanced antioxidant system, thus signifying amendments as an operational stress regulators in modifying Pb and Cd-toxicity that is highly important economically in all crops including sesame.