[Two-stage Inhibition Effects of Burkholderia sp. Y4 Application on Cadmium Uptake and Transport in Wheat].

In order to evaluate the feasibility of using Burkholderia sp. Y4 as a cadmium （Cd）-reducing bacterial agent in contaminated wheat fields， the changes in the rhizosphere soil microbial community and Cd available state， as well as the content and transport characteristics of Cd in the wheat root， basal node， internode， and grain under the treatment of strain Y4 were tested using microbial high-throughput sequencing， step-by-step extraction， subcellular distribution， and occurrence analyses. The results showed that root application of strain Y4 significantly reduced the root and grain Cd content of wheat by 7.7% and 30.3%， respectively， compared with that in the control treatment. The Cd content and Cd transfer factor results in wheat vegetative organs showed that strain Y4 reduced the Cd transfer factor from basal node to internode by 79.3%， and Cd content in the wheat internode stem also decreased by 50.9%. The study of Cd occurrence morphology showed that strain Y4 treatment increased the proportion of residual Cd in roots and basal ganglia， decreased the contents of inorganic and water-soluble Cd in roots， and increased the content of residual Cd in basal ganglia. Further examination of the subcellular distribution of Cd showed that the Cd content in root cell walls and basal ganglia cell fluid increased by 21.3% and 98.2%， respectively， indicating that the Cd fixation ability of root cell walls and basal ganglia cell fluid was improved by the strain Y4 treatment. In the rhizosphere soil， it was found that the microbial community structure was changed by strain Y4 application. Under the Y4 treatment， the relative abundance of Burkholderia increased from 9.6% to 11.5%， whereas that of Acidobacteriota decreased. Additionally， the relative abundance of Gemmatimonadales， Pseudomonadales， and Chitinophagales were also increased by strain Y4 treatment. At the same time， the application of strain Y4 increased the pH value of rhizosphere soil by 8.3%. The contents of exchangeable Cd， carbonate-bound Cd， and iron-manganese oxide-bound Cd in the soil decreased by 44.4%， 21.7%， and 15.9%， respectively， whereas the proportion of residual Cd reached 53.6%. Root application of strain Y4 increased the contents of nitrate nitrogen and ammonium nitrogen in the soil by 22.0% and 21.4%， respectively， and the contents of alkaline nitrogen also increased to a certain extent. In conclusion， the root application of strain Y4 not only improved soil nitrogen availability but also inhibited Cd transport and accumulation from contaminated soil to wheat grains in a "two-stage" manner by reducing Cd availability in rhizosphere soil and improving Cd interception and fixation capacity of wheat roots and basal nodes. Therefore， Burkholderia Y4 has application potential as a Cd-reducing and growth-promoting agent in wheat.

[Effects of Exogenous Melatonin Treatment on the Growth and Antioxidant System of Rice Seedlings Under Antimony Stress].

To investigate the effect of exogenous application of melatonin (MT) on rice seedlings under antimony (Sb) stress, hydroponic experiments were carried out with rice seedlings (Huarun No.2). The fluorescent probe localization technology was used to locate the reactive oxygen species (ROS) in the root tips of rice seedlings, and the root viability, malondialdehyde (MDA) content, ROS (H2O2 and O2-·) content, antioxidant enzyme (SOD, POD, CAT, and APX) activities, and antioxidant (GSH, GSSG, AsA, and DHA) contents in the roots of rice seedlings were analyzed. The results showed that exogenous addition of MT could alleviate the adverse effects of Sb stress on the growth and increase the biomass of rice seedlings. Compared with the Sb treatment, the application of 100 µmol·L-1 MT increased rice root viability and total root length by 44.1% and 34.7% and reduced the content of MDA, H2O2, and O2-· by 30.0%, 32.7%, and 40.5%, respectively. Further, the MT treatment increased the activities of POD and CAT by 54.1% and 21.8%, respectively, and also regulated the AsA-GSH cycle. This research indicated that exogenous application of 100 µmol·L-1MT can promote the growth and antioxidant ability of rice seedlings and alleviate the damage of lipid peroxidation by Sb stress, thus improving the resistance of rice seedlings under Sb stress.

[Effects of Exogenous Jasmonic Acid on Arsenic Accumulation and Response to Stress in Roots of Rice Seedlings].

Arsenic (As) pollution has a toxic effect on crop growth, leading to reduced crop quality and yield. Therefore, it is urgent to explore safe and effective strategies to reduce its toxicity. In this experiment, hydroponics, fluorescent probe locating technology, differential centrifugation, and Fourier infrared spectroscopy (FTIR) analysis were used to research the effect of exogenous jasmonic acid (JA) on the accumulation and stress resistance of rice seedlings. The results showed that JA application reduced the As content in the roots and shoots of rice by 31.4% and 51.4%, respectively, and significantly reduced As content in the cell wall and soluble fractions of rice roots. JA changed the distribution ratio of As in the subcellular components. The distribution ratio of As in the cell wall increased by 16.4%, and the distribution ratio of soluble fractions decreased by 17.3%. JA enhanced the fixation of As by the cell wall and reduced the As content in the soluble fraction. Furthermore, JA increased the levels of SOD, CAT, GSH, and PEPC in root cells and reduced the contents of H2O2 and MDA, indicating that JA reduced lipid peroxidation damage, regulated carbon and nitrogen metabolism, and alleviated As toxicity. This research provides a new approach for the prevention and control of rice As pollution.

[Effect of Chelating Agents and Organic Acids on Remediation of Cadmium and Arsenic Complex Contaminated Soil Using Xanthium sibiricum].

In order to improve the phytoextraction efficiency of Xanthium sibiricum on farmland soil that had been contaminated by Cd and As, this study explored the effects of chelating agents and organic acids (EDTA, SAP, CA, and MA) on the extraction of Cd and As heavy metals using X. sibiricum. The results showed that the four different chelating agents and organic acids had little effect on the biomass of the roots, stems, and leaves of X. sibiricum. However, they had different effects on the concentrations and accumulation of Cd and As in various organs of X. sibiricum. Compared with the those in the CK treatment, EDTA, SAP, CA, and MA significantly increased the Cd concentrations in the leaves of X. sibiricum by 44.1%, 32.4%, 41.2%, and 38.2% and the As concentrations in the roots of X. sibiricum by 89.6%, 7.4%, 94.8%, and 61.5%, respectively. The four treatments (EDTA, SAP, CA, and MA) improved the total Cd accumulation of X. sibiricum, with increasing ranges, respectively, of 70.2%, 29.4%, 28.9%, and 33.1%, and the As accumulation increased by 67.0%, 19.6%, 81.9%, and 40.8%, respectively, compared with that of the CK treatment. The four chelating agents and organic acids had different effects on the Cd and As bioconcentration factor and transfer factor of various organs of X. sibiricum. Treatments with EDTA, SAP, CA, and MA resulted in a decrease of 32.7%-38.2% in soil Cd concentrations and a decrease of 14.6%-20.5% in soil As concentrations. These four chelating agents can be used for enhancing the efficiency of extraction Cd and As heavy metals by X. sibiricum.

[Effects of Burkholderia sp. Y4 on Cadmium Damage and Uptake in Rice Seedlings].

In order to investigate the effects of Burkholderia sp. Y4 on rice seedlings under cadmium (Cd) stress, seed germination and vermiculite culture experiments were conducted using low Cd-accumulation xiangzaoxian 24 (X24) and high Cd-accumulation Tyou 705 (T705) varieties. The effects of Burkholderia sp. Y4 on rice growth, oxidative damage caused by Cd, and Cd accumulation were studied. Additionally, the Cd2+ flux rates in the elongation zone of rice roots under Burkholderia sp. Y4 application were detected using non-invasive micro-test technology. Burkholderia sp. Y4 alleviated the inhibition effect of Cd on rice seed germination by 13.8%. After inoculation with Burkholderia sp. Y4 for 7 d, the length of rice roots and buds increased by 83.3% and 12.2%, and their dry weight increased by 56.8% and 12.5%, respectively; those in the 10 d Y4 inoculation group increased by 28.6% and 20.0% in length and by 113.2% and 46.0% in dry weight, respectively. Burkholderia sp. Y4 inoculation also alleviated rice oxidative stress damage caused by Cd. The application of strain Y4 significantly reduced the content of the oxidative damage product malondialdehyde (MDA) in the shoots and roots of rice seedlings by 21.5% and 16.9%, respectively. Under Burkholderia sp. Y4 inoculation, the significant changes in antioxidant enzyme SOD and CAT activities caused by Cd stress disappeared in rice roots; those in shoots also decreased from 176.9% and 74.8% to 53.3% and 21.5%, respectively. Conversely, Burkholderia sp. Y4 inhibited Cd uptake by rice seedlings with different genotypes, including the low Cd-accumulation variety X24 and high Cd-accumulation variety T705. The root application of strain Y4 significantly reduced Cd accumulation in the shoots and roots of rice seedlings by 79.2% and 62.7% in T705 and by 57.3% and 24.1% in X24, respectively. The Cd2+ flux rate of high Cd-accumulation variety T705 was significantly higher than that of low Cd-accumulation variety X24. Under Burkholderia sp. Y4 inoculation, the yellow membrane was formed on the root surface of rice seedlings, and the Cd2+ flux rate in the elongation zone of T705 and X24 roots decreased by 36.0% and 35.0% in 3-day-old seedlings, as well as by 44.6% and 24.9% in 10-day-old seedlings, respectively. In conclusion, Burkholderia sp. Y4 inoculation inhibited the toxic effects of Cd on rice seedling growth through alleviating oxidative stress and damage caused by Cd. Furthermore, the root application of Burkholderia sp. Y4 effectively decreased the Cd2+ flux rate in the elongation zone of roots to inhibit the Cd uptake and accumulation in roots and shoots of rice seedlings. This study provides theoretical basis and data support for the application of Burkholderia sp. Y4 as a Cd-reducing and growth-promoting agent for rice in contaminated farmland.

[Isolation and Identification of the Plant Endophyte R-13 and Its Effect on Cadmium Accumulation in Solanum nigrum L.]

The combination of endophytes and hyperaccumulator plants can significantly improve the efficiency of heavy metal phytoremediation in contaminated soil. A plant endophyte named Herbaspirillum R-13 was isolated from rice roots in a cadmium (Cd) contaminated paddy field. This strain exhibited a strong tolerance to Cd2+ and could grow on a solid medium with a Cd2+ concentration of 300 mg·kg-1. The R-13 strain was able to produce siderophores and Indole acetic acid (IAA), through color reactions. In addition, Pikovskaya's and Ashby's solid medium tests showed that the R-13 strain had a lower capacity for dissolving phosphorus but a higher capacity for fixing nitrogen. In the pot experiment, high-throughput sequencing technology was used to track the colonization of the R-13 strain in Solanum nigrum L. roots. Three days after inoculation, the relative abundance of Herbaspirillum in the root of Solanum nigrum L. had increased by 201.88% compared to the blank control (CK) and after two inoculations, the relative abundance of Herbaspirillum in the root of Solanum nigrum L. had increased by 1182.44% compared to CK. The relative abundance of Herbaspirillum in the root of Solanum nigrum L. began to decrease significantly from 5 days after inoculation. Inoculation with 20 mL·pot-1 of R-13 fermentation broth resulted in no significant effects on the Cd content of roots, stems, leaves, or fruits of S. nigrum L. With 40 mL·pot-1 of fermentation broth, the Cd content of vegetative organs and fruits was significantly increased. When it reached 200 mL·pot-1, the Cd content of vegetative organs was the highest, with Cd concentrations in the roots, stems, leaves, and fruits increasing by 84.42%, 43.67%, 64.06%, and 20.29%, respectively. In conclusion, root inoculation with endophytic Herbaspirillum R-13 can significantly increase the relative content of Herbaspirillum in the root system and enhance Cd absorption of S. nigrum L. Therefore, this strain has excellent prospects for application in the phytoremediation of soil contaminated with Cd.

[Foliar Application of L-Cysteine: Effects on the Concentration of Cd and Mineral Elements in Rice].

To evaluate the feasibility of applying L-cysteine (L-Cys) as a foliar conditioner for Cd reduction in rice, a field experiment was conducted to investigate the concentration of Cd and mineral elements in rice after the foliar application of L-Cys. The variation in Cd distribution and morphology in key rice organs was examined to study the Cd reduction mechanisms of spraying L-Cys on rice. The results showed that foliar application of L-Cys at the rice-flowering stage significantly decreased Cd concentration in grains, in a concentration dependent manner, without inhibiting the accumulation of mineral elements Ca, Mg, K, Mn, and Zn. With a 10 mmol ·L-1 L-Cys application, Cd concentration in rice grains decreased by 59.2%, to below 0.2 mg ·kg-1, which is the maximum safety limit in China. Foliar application of L-Cys also inhibited Cd accumulation in rice vegetative organs, including rachises, first nodes, neck-panicles, flag leaves, second internodes, second nodes, second leaves, stalks, and roots (58.3%, 56.0%, 62.7%, 67.0%, 59.3%, 61.5%, 60.2%, 54.9%, and 50.3%, respectively). After transfer factor calculation, first nodes were found to be the key organ for Cd blocking in rice. The application of L-Cys increased Cd transfer from flag leaves and second internodes to first nodes (105.4% and 45.8%, respectively), but decreased Cd transfer from first nodes up to neck-panicles (27.5%). In rice first nodes, the concentrations of Cd in the inorganic, water soluble, and residue states were all lower following L-Cys application, and the proportion of residual Cd increased to 94.4%. Therefore, foliar application of L-Cys significantly inhibited Cd transport and accumulation in rice grains, by decreasing the Cd concentrations of various vegetative organs and improving Cd interception in the first nodes. This is a promising way to produce rice with lower Cd concentrations and normal mineral element concentrations in Cd-contaminated paddy fields.

[Mechanism of S-allyl-L-cysteine Alleviating Cadmium Stress in Seedling Roots and Buds of Rice Seedlings].

Cd has toxic effects on rice seed germination and plant growth, which may eventually lead to decreased yield and excessive Cd content in rice grains. The potential mechanism of S-allyl-L-cysteine (SAC), a natural sulfur compound derived from garlic extract, in alleviating Cd2+ stress in young roots and buds of rice seedlings was studied by a seed germination experiment. "Zhong zao 35", one of the main rice varieties in Southern China, was selected as the test material. Firstly, the alleviating effect of SAC on Cd2+ stress in rice seedling roots and buds was studied. Following this, the physiological mechanism of Cd2+ stress alleviation by SAC was examined based on the expression of the Cd transporter coding gene using real-time fluorescent quantitative PCR. The results showed that when the Cd2+ stress concentration reached 50 µmol·L-1, the young roots and buds of rice seedlings were significantly inhibited, and when the SAC concentration reached 200 µmol·L-1, Cd2+ stress was significantly alleviated. Compared to a Cd2+ stress treatment group, the total root length, surface area, and volume of young roots was increased by 173.5%, 65.52%, and 37.04%, respectively; CAT and SOD activity in young roots and buds was increased by 212.42% and 110.76%, and 31.41% and 47.31%, respectively; MDA and GSH content was decreased by 43.09% and 34.12%, and 33.97% and 35.74%, respectively; and Cd content was decreased by 35.91% and 28.86%, respectively. The results of quantitative real-time PCR showed that the relative expression levels of OsNramp5 and OsHMA2 were significantly reduced by 33.38% and 34.99% compared with the Cd2+ stress group, respectively. However, the relative expression level of OsHMA3 was significantly increased by 33.96%. From the above experimental results, the main mechanism by which SAC reduces Cd2+ stress in the young roots and buds of rice is via the regulation of Cd transporter-encoding genes, reducing Cd2+ transport to young roots and buds, and increasing transport to vacuoles.

[Effects of Different Exogenous Plant Hormones on the Antioxidant System and Cd Absorption and Accumulation of Rice Seedlings Under Cd Stress].

In order to explore the effects of the exogenous addition of plant hormones on the antioxidant system and Cd absorption and accumulation of rice seedlings under Cd stress, the transportation and accumulation of Cd was reduced in plants to alleviate the stress of Cd on the rice. With the rice seedlings of Zhongjiazao 17 as the research object, a hydroponic experiment was carried out with three Cd concentration treatments (0, 5, and 25 µmol·L-1), and four exogenous plant hormone treatments:no plant hormones, 100 µmol·L-1 melatonin (MT), 0.2 µmol·L-1 2,4-epibrassinolide (EBL), and 0.2 µmol·L-1 jasmonic acid (JA), for a total of 12 treatments, each treatment repeated three times. The contents of Cd in the rice seedlings were analyzed, as well as the content of MDA, POD, CAT, and reduced GSH in the shoots and roots of the rice seedlings. The results indicated that under the stress of 5 µmol·L-1 and 25 µmol·L-1 Cd, the addition of MT, EBL, and JA significantly reduced the MDA content of the shoots by 11%-24%, and the roots and shoots were healthy. On the contrary, the addition of the three exogenous substances all caused an increase in the MDA content in the root system, but the effects of MT and EBL were obvious. Under the 5 µmol·L-1 Cd stress, compared with CK, the MDA contents increased by 45.5% and 20.0% respectively; under 25 µmol·L-1 Cd stress, they increased by 46.2% and 19.8%. The exogenous addition of plant hormones can significantly increase the activity of POD and CAT in the shoots and underground parts of the rice seedlings and reduce the contents of GSH and Cd. Under the 5 µmol·L-1 Cd stress, the Cd content in the shoots of rice plants decreased by 39.4%, 40.1%, and 51.6%, the roots were reduced by 38.9%, 40.2%, and 7.0%. Under the 25 µmol·L-1 Cd stress, the aboveground Cd content was reduced by 18.9%, 14.5%, and 35.6%, and the roots were reduced by 85.3%, 81.1%, and 56.5%. By exogenously adding low-concentration plant hormones MT, EBL, and JA, the stress of Cd on the rice can be alleviated, and the toxic effect of Cd on rice can be reduced.

[Effects of Exogenous Spermidine on Seed Germination and As Uptake and Accumulation of Rice Under As5+ Stress].

As pollution in farmland has a toxic effect on the growth of crops, which reduces their yield and quality. The effects of exogenous spermidine (Spd) on rice seed germination and seedling growth under As5+ stress were studied. The results showed that exogenous Spd could promote the germination of rice seeds under As5+ stress, improve the germination potential and germination rate of seeds, and promote the growth of seedling roots. The addition of Spd could increase the activity of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) of rice seedlings and roots under As5+ stress, and reduce the content of malondialdehyde (MDA) in rice buds and roots. When As5+ concentration was 25 µmol·L-1, adding 500 µmol·L-1 and 1000 µmol·L-1 Spd, MDA content in rice roots was decreased by 12.3% and 31.3% and CAT activity of rice shoots was increased by 105.1% and 101.4%, and CAT activity of rice roots was increased by 29.9% and 57.1%, respectively. The addition of Spd also affected the uptake and accumulation of As in rice. When the concentration of As5+ was 25 µmol·L-1, adding 500 µmol·L-1 and 1000 µmol·L-1 Spd, the concentration of As in rice shoots decreased by 69.4% and 75.1%, and As concentration in rice roots decreased by 7.6% and 24.4%, respectively. Spd could therefore effectively alleviate the toxic effect of As5+ on rice.

[Effects of Foliar Spraying of 2,3-dimercaptosuccinic Acid on Cadmium Uptake, Transport, and Antioxidant System in Rice Seedlings].

Rice contaminated by Cd has aroused widespread public concern. It is of great importance to find effective ways to reduce Cd translocation from roots to shoots and alleviate Cd stress in rice to ensuring food quality and safety. In this study, 2,3-dimercaptosuccinic acid (DMSA) was sprayed onto the leaves of rice seedlings to evaluate the feasibility of DMSA reducing Cd translocation to rice shoots and alleviating Cd stress. Therefore, seedlings of Zhongzao 35, one of the main rice cultivars in southern China, were used to study the effects of different concentrations of DMSA on the uptake and transport of Cd in rice seedlings by hydroponics. The effects of DMSA on MDA and GSH content, and activities of antioxidant enzymes such as CAT and SOD in rice seedlings, were also investigated. The results showed that after four iterations of foliar application of DMSA at concentrations of 0.2, 0.4, and 1.0 mmol·L-1, the Cd concentration in the rice seedling shoots decreased significantly with increasing DMSA spraying concentration. Compared with the control, the Cd concentration in shoots decreased by 22.1%, 39.7%, and 43.5%, respectively, but had no significant effect on the root Cd concentration. There was no significant effect on the concentrations of K, Ca, Mg, Fe, Zn, or Mn in the shoot or root. The content of MDA and GSH in the shoots of rice seedlings decreased significantly after four spraying times of DMSA and the activity of CAT and SOD increased significantly, which shows that spraying DMSA alleviated the stress effect of Cd on rice seedlings. Foliar application of DMSA can significantly reduce the accumulation of Cd in rice shoots but has no significant effect on the content of six common mineral elements, and can effectively relieve the oxidative damage caused by Cd stress. DMSA has the potential to develop a foliar modulator for reducing rice grain Cd content.

Effects of dietary asafoetida (Ferula sinkiangensis K. M. Shen) levels on feeding attraction activity, growth performance, healthiness, and digestive enzyme activity in juvenile Lateolabrax japonicus.

The study was to investigate effects of asafoetida (Ferula sinkiangensis K. M. Shen) powder on feeding attraction activity (FAA), growth performance, healthiness, and digestive enzyme activity of juvenile Lateolabrax japonicus. Six concentration levels (0, 5, 10, 15, 20, and 25 g/kg diets) were formulated for luring and feeding experiment. Results showed that asafoetida could stimulate the appetite of L. japonicus at the dietary levels from 10 to 25 g/kg; reduce the feed conversion ratio (FCR) and feed intake (FI) at 10-20 g/kg; increase the weight gain (WG) and specific growth rate (SGR) at 5-10 g/kg; increase the hepatosomatic index (HSI), body crude lipid content, serum total protein (TP) content, and lysozyme activity at 10-15 g/kg; decrease the moisture at 10-15 g/kg; and increase the serum total superoxide dismutase (T-SOD) activity at 5-15 g/kg, when compared with the control group (p < 0.05). Digestive enzyme activities including amylase (AMS) and trypsin in the intestine were significantly affected by the asafoetida powder (p < 0.05). Regression analyses between the FAA, FCR, WG, SGR, HSI, LZM, T-SOD, AMS, trypsin, and the dietary asafoetida powder levels showed that the optimal additional amount was 16.95, 13.65, 8.36, 8.15, 15.45, 9.94, 8.75, 11.77, and 7.07 g/kg, respectively, indicating that the optimal amount of asafoetida powder was located in 7.07-16.95 g/kg diet. However, combined with the significant difference analyses obtained from the current study, we would suggest the additive suitable dosage was 10 g/kg.

Rice vegetative organs alleviate cadmium toxicity by altering the chemical forms of cadmium and increasing the ratio of calcium to manganese.

Altering Cd chemical form is one of the mechanisms to alleviate Cd toxicity in rice plant. Field experiments were carried out in this study to investigate the potential of rice vegetative organs in altering Cd into insoluble chemical forms in the natural environment. Experimental results showed that more than 80% of Cd in rice roots existed in the insoluble forms. Uppermost nodes altered Cd into insoluble form preferentially and generally had higher content of insoluble Cd than other organs. Rachises displayed a slow increasing trend in soluble Cd when total Cd in roots was less than 1.8 mg kg-1. However, when Cd content in roots exceeded 2.8 mg kg-1, the ratio of insoluble to soluble Cd remained stable at 85:15 in rachises and roots, and at 75:25 in uppermost nodes and flag leaves. Cd concentration in grains was greatly lower than that in vegetative organs, and closely correlated with the content of soluble Cd in rachises (r = 0.991**) as well as in uppermost nodes. Soluble Cd in the uppermost nodes displayed a much lower mobility than that in other organs. Accumulation of soluble Cd was always companied by decrease of Ca and increase of Mn in roots, uppermost nodes and rachises. A small increase of soluble Cd from 0.05 to 0.1 mg kg-1 caused a sharp decline of Ca:Mn ratio in roots and rachises. Roots and nodes had much higher Ca:Mn ratio than rachises when soluble Cd was less than 0.5 mg kg-1 in them. These results indicate that vegetative organs have a great potential to alter more than 75% Cd into insoluble forms and increasing Ca:Mn ratio may be another way to alleviate Cd toxicity by establishing new ionic homeostasis in rice plants.

[Alleviation Effects of Exogenous Melatonin on Ni Toxicity in Rice Seedings].

The alleviation effect of exogenous melatonin (MT) on Ni toxicity in rice seedings was investigated. The results showed that low concentration of Ni stress (10, 50 µmol·L-1) had little effect on the growth of root of rice seedings, while higher concentration of Ni stress (100-1000 µmol·L-1) significantly inhibited the growth of rice root. Compared with the control treatment, the addition of 100 and 1000 µmol·L-1 Ni would decrease the total length and surface area of root by 63.3%-98.0% and 56.9%-96.3%, respectively. The results showed that addition of exogenous melatonin had a positive effect on the growth of rice seedings under Ni stress. This kind of positive effect was even more obvious in the root of rice seedings. The total length of rice root decreased by 58.4%-83.8% at Ni concentration of 100 µmol·L-1, whereas it decreased by only 8.7%-29.1% when 100 µmol·L-1 Ni and 10 µmol·L-1 MT were added, compared with the control treatment. The addition of exogenous melatonin had significant alleviation effects on oxidative stress in rice seedings caused by Ni. Compared with the 100 µmol·L-1Ni treatment, addition of 10 µmol·L-1 exogenous MT could significantly decrease the production rate of O2-· by 43.2%-50.2% and the relative electrolytic leakage by 25.7%-31.6%, whereas increase the activities of CAT by 21.9%-33.7% and the soluble protein content by 82.6%-84.6%. The results suggested that application of exogenous melatonin could effectively alleviate the toxic effects of Ni on rice seedings.

[Effects of exogenous melatonin on accumulation and chemical form of Cd in rice]. / è¤ªé»‘ç´ å¯¹æ°´ç¨»é•‰ç§¯ç´¯åŠå ¶åŒ–å­¦ç»“åˆå½¢æ€çš„å½±å“.

Effects of exogenous melatonin on accumulation and chemical form of Cd in rice seedlings were investigated. The results showed that Cd stress significantly decreased the biomass of shoots and roots, and the chlorophyll content in rice leaves. The addition of exogenous melatonin could remarkably increase the biomass of rice and significantly decreased Cd content in the shoots and roots. At Cd concentration of 5 Μmol·L-1, addition of 20 Μmol·L-1 exogenous melatonin could decrease Cd content in rice shoots and roots by 48.4% and 16.9% respectively, compared with the control. When the concentration of exogenous melatonin rose to 100 Μmol·L-1, Cd content in rice shoots and roots decreased by 67.5% and 47.9% respectively. Furthermore, the addition of exogenous melatonin obviously decreased the Cd-translocation efficiency of rice seedlings. When the Cd concentration was 20 Μmol·L-1, addition of 20 and 100 Μmol·L-1 exogenous melatonin could decrease the Cd-translocation efficiency by 24.4% and 46.8% respectively. The chemical form of Cd in rice seedlings was analyzed by using sequential extraction. The results showed that exogenous melatonin addition increased the proportion of NaCl-extractable Cd, while decreased the proportion of ethanol-extractable Cd and water-extractable Cd in rice seedlings. It was suggested that the addition of exogenous melatonin could promote the transfer of Cd from strong to weak mobility form, thereby reducing the uptake and transport of Cd in rice seedlings.

[Effect of Boron-antimony Interaction on the Uptake and Accumulation of Antimony and Boron by Rice Seedling].

Effect of interactions between boron (B) and antimony on the uptake and accumulation by rice (Oryza sativa L.) seedling was investigated in solution culture. The results showed that Sb(III) and Sb(V) could inhibit rice growth and Sb(III) was more toxic than Sb(V). Concentrations of B in rice roots and shoots were significantly affected by the addition of Sb(III) and Sb(V). The addition of 30 µmol x L(-1) Sb(III) could significantly decrease B of rice shoots and roots by 57.6% and 75.6%, and 30 µmol x L(-1) Sb(V) could decrease B of rice roots by 16.0%, compared with the control treatment, when the B concentration was 0.5 mg x L(-1). Equally, adding B also significantly affected the concentrations of Sb in rice roots and shoots. The addition of 2.0 mg x L(-1) B could decrease the concentrations of Sb in rice roots and shoots,by 39.1% and 9.2%, respectively, compared with 0.5 mg x L(-1) B, when the Sb(III) concentration was 10 µmol x L(-1). Adding 2.0 mg x L(-1) B could decreasd Sb concentrations in rice roots by 13.9%, compared with 0.5 mg x L(-1) B, when the Sb(V) concentration was 10 µmol x L(-1). Furthermore, adding B had significant effect on bioaccumulation factor and distribution ratio of Sb in rice roots and shoots. The results of the study demonstrated that Sb pollution in farmland could be alleviated by adding B fertilizer, thus protecting human health from Sb pollution.

Characterization of a prophenoloxidase from hemocytes of the shrimp Litopenaeus vannamei that is down-regulated by white spot syndrome virus.

Previously, a prophenoloxidase (proPO) gene (named proPO-a here) from hemocytes of Litopenaeus vannamei was isolated. Here, a proPO-b gene was also identified and characterized from hemocytes of L. vannamei. The cDNA sequences of proPO-a and proPO-b were compared, and it was found that both proPOs had a microsatellite DNA site near the 3' end of the open reading frame (ORF). However, the microsatellite DNA of proPO-b contained a compound imperfect simple sequence repeats (SSR) ((CT)(38)(CA)(8)(AA)(CA)(3)(TA)(CA)(14)), which was different from the perfect one ((CT)(20)) of proPO-a, and the cDNA sequences of proPO-a and proPO-b prior to the microsatellite DNA were almost identical, but differed after the microsatellite DNA. ProPO-b (3232 bp) was longer than proPO-a (2471 bp). The 3' UTR sequence after SSR of proPO-a was not detected in shrimp randomly collected from five different geographically separate populations by reverse-transcription polymerase chain reaction (RT-PCR). On the contrary, the 3' UTR sequence of proPO-b was detected in all five groups of shrimps. Northern blot analysis showed that a transcript at approximately 3.2kb, but not 2.5kb, was detected mainly in hemocytes, and also present in midgut, gill, heart, stomach, posterior midgut cecum, and cuticular epidermis, but no signal was detected in hepatopancreas and musculature. RT-PCR and quantitative real-time RT-PCR analysis showed similar results of the proPO-b expression profile in these shrimp tissues. We also observed that proPO-b expression was down-regulated in shrimp challenged with white spot syndrome virus (WSSV). Our results suggest that proPO-b is a main transcript form of proPO gene in L. vannamei, and it may play a role in defence against WSSV virus.

catena-Poly[[bis-(pyridine-κN)nickel(II)]-µ-oxalato-κO,O:O,O].

The title compound, [Ni(C(2)O(4))(C(5)H(5)N)(2)](n), was synthesized under hydro-(solvo)thermal conditions. The Ni(II) atom, lying on a twofold rotation axis, has an octa-hedral coordination geometry involving two N atoms from two pyridine ligands and four O atoms from two oxalate ligands. The Ni atoms are connected by the tetra-dentate bridging oxalate ligands into a one-dimensional zigzag chain.

[Detection carbamate pesticides residue in cucumber by immobilized acetyicholinesterase enzyme].

A novel method was described for detection carbamate pesticides residue in cucumber by immobilizing acetylcholinesterase enzyme in a micro-screen plate with 96 wells based on GA-BSA-gelatin gels. The concentrations of BSA, GA and gelatin in enzyme immobilization solution were optimized and the best concentrations were 5%, 0.5% and 0.1%, respectively. To analyze the pesticides residue 5g cucumber sample was homogenized with 10 mL acetone then an aliquot of 5mL extract was collected in a 10 mL test tube with a cap, into which 2g sodium chloride and 2mL dichloromethane were added in sequence. After shaking, 1 mL of the supernatant aliquot was evaporated by a blower in a small beaker and dissolved by 20% methanol-water solution then 50 microL was piped to a sample well. After incubation 10 minutes the absorbance was detected. The proposed method offered a rapid, simple and inexpensive means to in screen of batch samples. The minimum detection limit of this method was in a range of 0.1-0.2 mg/kg for cucumber samples.