Hydrogen peroxide mediates cadmium accumulation in the root of a high cadmium-accumulating rice (Oryza sativa L.) line.

Hydrogen peroxide (H2O2) is a vital signaling molecule in response to cadmium (Cd) stress in plants. However, the role of H2O2 on Cd accumulation in root of different Cd-accumulating rice lines remains unclear. Exogenous H2O2 and 4-hydroxy-TEMPO (H2O2 scavenger) were applied to investigate the physiological and molecular mechanisms of H2O2 on Cd accumulation in the root of a high Cd-accumulating rice line Lu527-8 through hydroponic experiments. Interestingly, it was found Cd concentration in the root of Lu527-8 increased significantly when exposed to exogenous H2O2, while reduced significantly when exposed to 4-hydroxy-TEMPO under Cd stress, proving the role of H2O2 in regulating Cd accumulation in Lu527-8. Lu527-8 showed more Cd and H2O2 accumulation in the roots, along with more Cd accumulation in cell wall and soluble fraction, than the normal rice line Lu527-4. In particular, more pectin accumulation, especially low demethylated pectin, was observed in the root of Lu527-8 when exposed to exogenous H2O2 under Cd stress, resulting in more negative functional groups with greater capacity to binding Cd in the root cell wall of Lu527-8. It indicated that H2O2-induced cell wall modification and vacuolar compartmentalization contributes greatly to more Cd accumulation in the root of the high Cd-accumulating rice line.

Aggregate-associated carbon compositions explain the variation of carbon sequestration in soils after long-term planting of different tea varieties.

Strategies to increase carbon (C) sequestration in tea plantation soils are pertinent to mitigating global climate change, but little is known about the variation in C sequestration in soils planted with different tea varieties. In the current study, we collected 0-20 and 20-40 cm layer soil samples from a tea plantation planted with four tea varieties (Chuancha No.3 (CC3), Chuanmu No. 217 (CM217), Chuannong Huangyazao (CN), and C. sinensis 'Fuding Dabaicha' (FD)). Soil organic carbon (SOC) stock and composition in the bulk soil and aggregate fractions, as well as the SOC stability index (SI), were investigated. Both SOC stock and composition in the bulk soil or aggregate fractions were variable among the soils after planting different tea varieties. Overall, the highest SOC stock (0-40 cm) was observed in FD soil, followed by CN, CC3, and CM217 soil. This difference was dominated by the SOC stock associated with macroaggregates, and the highest macroaggregate-associated SOC stock was detected in FD soil in both soil layers. Moreover, FD soil showed the highest proportion of macroaggregates in both soil layers, accumulated the greatest recalcitrant organic carbon (ROC) and further contributed to the highest SI values of SOC associated with most aggregate fractions. In contrast, CN topsoil (0-20 cm) accumulated the greatest labile organic carbon (LOC) in most aggregate fractions, which had a positive correlation with the amount of C return by pruning litter. Ultimately, long-term planting of FD promoted macroaggregate formation, and ROC accumulation in aggregates greatly contributed to maintaining high C sequestration in the tea plantation soils and showed a high potential for future C budgets; in contrast, the tea plantation soil planted with CN could be a potential C source because of high C return.

Evaluation for phosphorus accumulation and removal capability of nine species in the Polygonaceae to excavate amphibious superstars used for phosphorus-phytoextraction.

Reducing excessive phosphorus (P) from both soils and eutrophic waters is attractive to achieve environmental P balance, and P-phytoextraction by amphibious plants with great biomass and P uptake is an amazing method, as already reported for P-accumulating plant, Polygonum hydropiper. However, it is still unknown how widespread high P tolerance and great P accumulation is among species in the Polygonaceae, and if there are new amphibious superstars used for P-phytoextraction. We used six Polygonum species and three non-Polygonum species to compare P accumulation and removal capability in hydroponics and soils with different P treatments. In high P hydroponics, all species showed superiority in growth and P accumulation without P toxicity, except for F. multiflora. In high P soils, all species showed much better growth performance with green leaves at 8 weeks, with shoot biomass being 3.60-29.49 g plant-1. At 8 weeks, Polygonum species displayed obviously higher shoot P accumulation (31.32-152.37 mg plant-1), P extraction ratio (3.16%-15.36%), maximum potential P removal (13.89-67.59 kg ha-1), and much lower plant effective number (7-32) than non-Polygonum species under high P soils. Besides, P. lapathifolium, P. divaricatum and P. orientale ranked the top three in growth with P concentration more than 10 mg g-1 dry weight in hydroponics and showed dominant advantage in P accumulation and P removal from high P soils. Through the cluster analysis, P. lapathifolium was always separated into a class, and P. divaricatum and P. orientale more likely clustered together. It is therefore that P. lapathifolium, P. divaricatum and P. orientale are tolerant to high P and attractive in P accumulation and P removal from high P waters and soils, and thus can be used as new amphibious superstars for P-phytoextraction, particularly P. lapathifolium.

Hydrogen peroxide contributes to cadmium binding on root cell wall pectin of cadmium-safe rice line (Oryza sativa L.).

Cell wall pectin is essential for cadmium (Cd) accumulation in rice roots and hydrogen peroxide (H2O2) plays an important role as a signaling molecule in cell wall modification. The role of H2O2 in Cd binding in cell wall pectin is unclear. D62B, a Cd-safe rice line, was found to show a greater Cd binding capacity in the root cell wall than a high Cd-accumulating rice line of Wujin4B. In this study, we further investigated the mechanism of the role of H2O2 in Cd binding in root cell wall pectin of D62B compared with Wujin4B. Cd treatment significantly increased the H2O2 concentration and pectin methyl esterase (PME) activity in the roots of D62B and Wujin4B by 22.45-42.44% and 12.15-15.07%, respectively. The H2O2 concentration and PME activity significantly decreased in the roots of both rice lines when H2O2 was scavenged by 4-hydroxy-Tempo. The PME activity of D62B was higher than that of Wujin4B. The concentrations of high and low methyl-esterified pectin in the roots of D62B significantly increased when exposed to Cd alone but significantly decreased when exposed to Cd and exogenous 4-hydroxy-Tempo. No significant difference was detected in Wujin4B. Exogenous 4-hydroxy-Tempo significantly decreased the Cd concentration in the cell wall pectin in both rice lines. The modification of H2O2 in Cd binding was further explored by adding H2O2. The maximum Cd adsorption amounts on the root cell walls of both rice lines were improved by exogenous H2O2·H2O2 treatment significantly influenced the relative peak area of the main functional groups (hydroxyl, carboxyl), and the groups intensely shifted after Cd adsorption in the root cell wall of D62B, while there was no significant difference in Wujin4B. In conclusion, Cd stress stimulated the production of H2O2, thus promoting pectin biosynthesis and demethylation and releasing relative functional groups involved in Cd binding on cell wall pectin, which is beneficial for Cd retention in the roots of Cd-safe rice line.

Sufficient nitrogen promoted high phosphorus tolerance and phosphorus-accumulating capability of Polygonum hydropiper in relation to changes of phytohormones and phenols.

Nitrogen (N) application is efficient to enhance phosphorus (P)-phytoextraction efficiency of P-accumulating plants. However, there is little available information on growth, P uptake and physiological changes of P-accumulating plants in high P media with different N application, and that whether the improved growth or P uptake is related with changes of phytohormones and phenols. This study investigated growth, P-accumulating capability, phytohormones and phenols of a mining ecotype (ME) and a non-mining ecotype (NME) of Polygonum hydropiper in high P media (400 mg L-1) with sufficient N (SN, 50 mg L-1) and low N (LN, 12.5 mg L-1) supply. SN supply greatly increased tissue biomass, P-accumulating capability of P. hydropiper in high P media, and the ME showed higher P bioaccumulation coefficient, and tissue P accumulation than the NME. The greatest tissue biomass and P accumulation was found at 5 weeks. At 5 weeks, SN supply greatly decreased concentrations of indole-3-acetic acid (IAA), zeatin, abscisic acid (ABA), total phenolic and flavonoid in tissues of P. hydropiper, compared with LN supply. The ME produced lower concentrations of IAA, zeatin, ABA, total phenolic and flavonoid than the NME in leaf and stem in high P media with N supply. Significantly negative correlations were found between IAA, zeatin, ABA, flavonoid concentrations and biomass as well as P accumulation in leaf. Thus, SN supply promoted high P tolerance and P-accumulating capability of the ME in relation to modulating phytohormones and phenols to suitable concentrations, ultimately improving P-phytoextraction ability.

Characteristics of cadmium immobilization in the cell wall of root in a cadmium-safe rice line (Oryza sativa L.).

Cultivating cadmium (Cd)-safe rice lines, which show low Cd accumulation in brown rice, is generally beneficial to ensure food safety. The Cd retention in root of Cd-safe rice line D62B plays an important role in its low Cd translocation from root to shoot. To understand the mechanism of Cd retention in root, a hydroponic experiment was conducted to investigate the subcellular distribution of Cd and the contribution of polysaccharides to Cd binding to the root cell wall of a Cd-safe rice line D62B with a common rice line Luhui17 as a control material. D62B retained more Cd in the root by sequestrated a higher proportion of Cd in the cell wall, further it transferred less Cd to shoot. Close to half of the Cd in the root cell wall of D62B was accumulated in the hemicellulose 1 (HC1), and the proportions of HC1 in it were 1.2-1.7 times higher than these of Luhui17. The proportion of Cd in the pectin showed a dose-dependent increase in two rice lines. D62B contained significantly higher uronic acid concentrations of the pectin and greater pectin methyl esterase (PME) activities than Luhui17 in the root cell wall. These results indicated that a superior Cd binding capacity of the cell wall polysaccharides in D62B played an important role in its Cd retention in root.

Transport of colloidal phosphorus in runoff and sediment on sloping farmland in the purple soil area of south-western China.

Colloidal particles in runoff could play an important role in phosphorus (P) transfer from sloped farmland to waterbodies. We investigated the distribution of P in different-size particles from a purple soil and colloidal phosphorus (CP) loss in runoff and sediment from sloped farmland in south-western China. The profile distribution of P showed obvious surface accumulation. The risk of P loss in topsoil was greater than those of the other soil layers on sloping farmland of purple soil. The concentration of soil particles of < 0.002 mm in purple soil profiles was low, but the total phosphorus (TP) and available phosphorus (AP) concentrations of soil particles of < 0.002 mm were high. During a rainfall event, CP loss is significantly power function related to the runoff yield rate, and is linearly related to the sediment yield rate. The majority of P in runoff was CP. The total loss of CP in runoff was 139.52 g ha-1, in which surface runoff accounted for 64.3%. CP loss can be controlled by controlling runoff from sloping farmland, especially surface runoff. Our results suggest that CP loss should be valued in the process of nutrient loss, as well as CP transfer should be given greater consideration in the mechanistic studies of the P transfer process.

Effect of tea plantation age on the distribution of glomalin-related soil protein in soil water-stable aggregates in southwestern China.

Glomalin-related soil protein (GRSP) is crucial for the accumulation of soil organic carbon (SOC), and contributes to the formation of soil aggregates. However, it remains unclear whether GRSP is involved in altering the stability of soil aggregates in the long-term tea planting process. The relationship between the distribution of GRSP and soil aggregates in tea plantations is poorly studied. We compared the distribution of SOC and GRSP in aggregates in tea plantations of different ages (18, 25, 33, and 55 years) and those in an abandoned land and investigated their potential contribution to the soil aggregate stability. Tea plantation was found to be beneficial for the accumulation of SOC and GRSP compared to the abandoned land. The content of SOC significantly increased after tea plantation, especially in surface soil (0-20 cm), and the increase range was 21.79%-46.51%, due to the centralized management of tea plantations. The content of total glomalin-related soil protein (T-GRSP) and easily extractable glomalin-related soil protein (EE-GRSP) varied with the increasing tea plantation age. The T-GRSP content was higher in 25-year-old tea plantation, while EE-GRSP was gradually decreased with the increasing age of the tea plantation, and T-GRSP had better correlation with SOC than EE-GRSP. Long-term tea plantation (after 33 years) was not conducive to the preservation of GRSP. The distribution of GRSP in the tea plantation soils differed greatly among the aggregates, with the 0.25-1-mm aggregate having less GRSP, which might be related to the distribution of soil fungi in the aggregates. There was a significant correlation between T-GRSP and mean weight diameter (MWD; P < 0.05) in the whole soil, whereas EE-GRSP had no correlation with the MWD of the aggregates. The T-GRSP content was correlated closely with the stability of soil aggregates in the tea plantations, and their relationship was dependent on the aggregate scale. Our results show that the T-GRSP content in the tea plantation soils has important effects on the formation and stability of aggregates in this region, which was one of the factors affecting the structure and quality of tea plantation soil. Improving GRSP is an effective way for the both SOC sequestration and soil health after long-term tea plantation.

Changes in P accumulation, tissue P fractions and acid phosphatase activity of Pilea sinofasciata in poultry manure-impacted soil.

Pilea sinofasciata is a promising phytoextraction material to remove excess phosphorus (P) from manure-impacted soil. However, little information is available on its physiological response to animal manure treatments. Here, P accumulation, tissue P fractions and acid phosphatase activity were investigated in a mining ecotype (ME) and a non-mining ecotype (NME) of P. sinofasciata at different poultry manure (PM) treatments (0, 25, 50, 75, 100 and 125 g kg-1). Biomass and P accumulation of the ME increased up to 50 g kg-1, after which they significantly decreased; while P accumulation of the NME increased up to 100 g kg-1. But, shoot and root P accumulation of the ME were significantly higher than those of the NME at all PM treatments, showing 1.13-2.92 and 1.11-2.89 times higher values, respectively. Inorganic P and nucleic P dominated in tissues of both ecotypes. Besides, the ME maintained higher concentrations of inorganic P and ester P in leaves and ester P, nucleic P and residual P in roots than the NME. Acid phosphatase activity in leaves and roots increased by increasing PM treatments, except in root at 125 g kg-1. Acid phosphatase activity in leaves of the ME was positively correlated with concentrations of inorganic P, ester P and nucleic P, while that of the NME only correlated with inorganic P concentration. Probably, the optimized P fractions allocation and higher tissue acid phosphatase allow the ME to grow well and efficiently accumulate P in PM-impacted soil.

Subcellular distribution and chemical form of phosphorus involved in alleviating phosphorus toxicity of the phosphorus-accumulator Polygonum hydropiper.

Polygonum hydropiper is a dominant plant species in Shifang phosphorus (P) mine area and is a promising P-accumulator used for P-phytoextraction. To date, little information is available on the physiological response involved in alleviating P toxicity of P. hydropiper under high P. A pot experiment was carried out to investigate growth, P subcellular distribution, chemical forms in two ecotypes of P. hydropiper under high levels (1, 4, and 8 mmol P L-1) of inorganic P (Pi) and organic P (Po), supplied as KH2PO4 and myo-inositol hexaphosphoric acid dodecasodium salt, respectively. The mining ecotype (ME) showed a greater ability to tolerate high P than the non-mining ecotype (NME), as shown by its superior growth with undamaged leaf anatomical structure. The ME showed 1.3-2.2 times greater shoot P accumulation than the NME. More than 93% of P accumulated in tissue cell wall and soluble fraction. The increasing P treatments increased all tissue P forms, especially Pi form. The ME showed significantly higher ester P, nucleic P and insoluble P in tissues than the NME at 8 mmol L-1; however, it demonstrated lower Pi, expect for roots at 5 weeks. The percentages of Pi and nucleic P in roots of the ME were higher than other P forms, and the percentages of nucleic P dominated in the leaves. Probably, the combination of preferential distribution of P in cell wall and soluble fraction in tissues and storage of P in low activity as nucleic P in leaves allows the ME to adapt high P.

[Influence of Rhubarb extract on the expression of NGAL and IL-18 in the kidney of rabbits after CPR].

OBJECTIVE: To study the preventive effect and mechanism of Rhubarb extract on renal injury after cardiopulmonary resuscitation (CPR) in rabbits with cardiac arrest (CA). METHODS: Twenty-four male Japanese big-ear rabbits were divided into sham operation group, CPR model group and Rhubarb pretreatment group by random number table method, with 8 rabbits in each group. The rabbits in Rhubarb pretreatment group were treated with Rhubarb extract 5 mL×kg-1×d-1 for 7 days; and those in sham operation group and CPR model group were fed with 0.9% normal saline 10 mL/d for 7 days. After 7 days, ventricular fibrillation (VF) was produced in CPR model group and Rhubarb pretreatment group by 50 V alternating currents stimulation through bottom of the heart leads to the apex to prepare CPR model. The rabbits of the CPR model group and Rhubarb pretreatment group were sacrificed at 2 hours after successful resuscitation, and the animals in the sham operated group were sacrificed directly after anesthesia. The levers of blood urea nitrogen (BUN) and creatinine (Cr) in serum were examined by automatic biochemical analyzer. The positive expression area of neutrophil gelatinase-associated lipocalin (NGAL) and interleukin-18 (IL-18) in kidney were examined by immunohistochemistry. RESULTS: Compared with the sham operation group, the levels of BUN and Cr were significantly increased in the CPR model group and Rhubarb pretreatment group [BUN (mmol/L): 15.53±3.90, 10.51±3.16 vs. 7.03±2.23, Cr (µmol/L): 137.20±12.23, 86.80±7.67 vs. 66.39±5.47, both P < 0.05]. Compared with the CPR model group, the levels of BUN and Cr were significantly decreased in the Rhubarb pretreatment group [BUN (mmol/L): 10.51±3.16 vs. 15.53±3.90, Cr (µmol/L): 86.80±7.67 vs. 137.20±12.23, both P < 0.05]. Immunohistochemical staining showed that the expression of NGAL and IL-18 mainly existed in glomerular and tubular cells in patina. Compared with the sham operation group, the positive expression areas of NGAL and IL-18 in kidney were significantly increased in the CPR model group and Rhubarb pretreatment group [NGAL (µm2): 208.26±7.58, 136.74±5.33 vs. 98.93±7.83, IL-18 (µm2): 256.48±4.64, 113.22±6.98 vs. 77.06±6.47, all P < 0.05]. Compared with the CPR model group, the positive expression areas of NGAL and IL-18 were significantly decreased in the Rhubarb pretreatment group [NGAL (µm2): 136.74±5.33 vs. 208.26±7.58, IL-18 (µm2): 113.22±6.98 vs. 256.48±4.64, both P < 0.05]. CONCLUSIONS: CA can lead to acute kidney injury (AKI). Rhubarb extract can reduce the expression of NGAL and IL-18 in kidney of rabbits after CPR, and protect the kidney after CPR.

Dynamics of soil organic carbon mineralization in tea plantations converted from farmland at Western Sichuan, China.

Climate warming and land use change are some of the drivers affecting soil organic carbon (SOC) dynamics. The Grain for Green Project, local natural resources, and geographical conditions have resulted in farmland conversion into tea plantations in the hilly region of Western Sichuan. However, the effect of such land conversion on SOC mineralization remains unknown. In order to understand the temperature sensitivity of SOC decomposition in tea plantations converted from farmland, this study considered the different years (i.e., 2-3, 9-10, and 16-17 years) of tea plantations converted from farmland as the study site, and soil was incubated for 28 days at 15°C, 25°C, and 35°C to measure the soil respiration rate, amount, and temperature coefficient (Q10). Temperature and land use type interactively affected the SOC mineralization rate, and the cumulative amount of SOC mineralization in all the plots was the largest at 35°C. SOC mineralization was greater and more sensitive to temperature changes in the farmland than in the tea plantations. Compared with the control, tea plantation soils showed lower SOC mineralization rate and cumulative mineralization amount. The 16-17-year-old tea plantation with a low SOC mineralization amount and high SOC content revealed the benefits of carbon sequestration enhancement obtained by converting farmland into tea plantations. The first-order kinetic equation described SOC mineralization dynamics well. Farmland conversion into tea plantations appeared to reduce the potentially mineralizable carbon pool, and the age of tea plantations also had an effect on the SOC mineralization and sequestration. The relatively weak SOC mineralization temperature sensitivity of the tea plantation soils suggested that the SOC pool of the tea plantation soils was less vulnerable to warming than that of the control soils.

P accumulation and physiological responses to different high P regimes in Polygonum hydropiper for understanding a P-phytoremediation strategy.

Phosphorus (P) accumulators used for phytoremediation vary in their potential to acquire P from different high P regimes. Growth and P accumulation in Polygonum hydropiper were both dependent on an increasing level of IHP (1-8 mM P) and on a prolonged growth period (3-9 weeks), and those of the mining ecotype (ME) were higher than the non-mining ecotype (NME). Biomass increments in root, stem, and leaf of both ecotypes were significantly greater in IHP relative to other organic P (Po) sources (G1P, AMP, ATP), but lower than those in inorganic P (Pi) treatment (KH2PO4). P accumulation in the ME exceeded the NME from different P regimes. The ME demonstrated higher root activity compared to the NME grown in various P sources. Acid phosphatase (Apase) and phytase activities in root extracts of both ecotypes grown in IHP were comparable to that in Pi, or even higher in IHP. Higher secreted Apase and phytase activities were detected in the ME treated with different P sources relative to the NME. Therefore, the ME demonstrates higher P-uptake efficiency and it is a potential material for phytoextraction from P contaminated areas, irrespective of Pi or Po contamination.

[Effects of tobacco garlic crop rotation and intercropping on tobacco yield and rhizosphere soil phosphorus fractions].

A field plot experiment was conducted to investigate the tobacco yield and different forms of soil phosphorus under tobacco garlic crop rotation and intercropping patterns. The results showed that compared with tobacco monoculture, the tobacco yield and proportion of middle/high class of tobacco leaves to total leaves were significantly increased in tobacco garlic crop rotation and intercropping, and the rhizosphere soil available phosphorus contents were 1.3 and 1.7 times as high as that of tobacco monoculture at mature stage of lower leaf. For the inorganic phosphorus in rhizosphere and non-rhizosphere soil in different treatments, the contents of O-P and Fe-P were the highest, followed by Ca2-P and Al-P, and Ca8-P and Ca10-P were the lowest. Compared with tobacco monoculture and tobacco garlic crop intercropping, the Ca2-P concentration in rhizosphere soil under tobacco garlic crop rotation at mature stage of upper leaf, the Ca8-P concentration at mature stage of lower leaf, and the Ca10-P concentration at mature stage of middle leaf were lowest. The Al-P concentrations under tobacco garlic crop rotation and intercropping were 1.6 and 1.9 times, and 1.2 and 1.9 times as much as that under tobacco monoculture in rhizosphere soil at mature stages of lower leaf and middle leaf, respectively. The O-P concentrations in rhizosphere soil under tobacco garlic crop rotation and intercropping were significantly lower than that under tobacco monoculture. Compared with tobacco garlic crop intercropping, the tobacco garlic crop rotation could better improve tobacco yield and the proportion of high and middle class leaf by activating O-P, Ca10-P and resistant organic phosphorus in soil.

[Characteristics of phosphorus uptake and use efficiency of rice with high yield and high phosphorus use efficiency].

A total of twenty seven middle maturing rice varieties as parent materials were divided into four types based on P use efficiency for grain yield in 2011 by field experiment with normal phosphorus (P) application. The rice variety with high yield and high P efficiency was identified by pot experiment with normal and low P applications, and the contribution rates of various P efficiencies to yield were investigated in 2012. There were significant genotype differences in yield and P efficiency of the test materials. GRLu17/AiTTP//Lu17_2 (QR20) was identified as a variety with high yield and high P efficiency, and its yields at the low and normal rates of P application were 1.96 and 1.92 times of that of Yuxiang B, respectively. The contribution rate of P accumulation to yield was greater than that of P grain production efficiency and P harvest index across field and pot experiments. The contribution rates of P accumulation and P grain production efficiency to yield were not significantly different under the normal P condition, whereas obvious differences were observed under the low P condition (66.5% and 26.6%). The minimal contribution to yield was P harvest index (11.8%). Under the normal P condition, the contribution rates of P accumulation to yield and P harvest index were the highest at the jointing-heading stage, which were 93.4% and 85.7%, respectively. In addition, the contribution rate of P accumulation to grain production efficiency was 41.8%. Under the low P condition, the maximal contribution rates of P accumulation to yield and grain production efficiency were observed at the tillering-jointing stage, which were 56.9% and 20.1% respectively. Furthermore, the contribution rate of P accumulation to P harvest index was 16.0%. The yield, P accumulation, and P harvest index of QR20 significantly increased under the normal P condition by 20.6%, 18.1% and 18.2% respectively compared with that in the low P condition. The rank of the contribution rates of P efficiencies to the yield was in order of P uptake efficiency > P utilization efficiency > P transportation efficiency. The greatest contribution rate of P accumulation to the yield was noticed at the jointing-heading stage with the normal P application while it reached the maximal value at the tillering-jointing stage with the low P application. Therefore, these two stages may be the critical periods to coordinate high yield and high P efficiency in rice.

Influence of swine manure on growth, P uptake and activities of acid phosphatase and phytase of Polygonum hydropiper.

Excessive application of animal manure to the farmland results in enrichment of P in the soil. Phytoremediation is a promising strategy for extracting excess P from manure impacted soil. P uptake characteristics of a mining ecotype (ME) and a non-mining ecotype (NME) of Polygonum hydropiper were investigated in this study by adopting soil culture containing various concentrations of swine manure (0-200 g swine manure kg(-1) soil). A peak value in the biomass of P. hydropiper was determined in 100 g kg(-1) soil. Significant increase of P content in tissues of two ecotypes was noticed with an increase in swine manure concentration. Maximum P accumulation in shoots and roots was observed at the concentration of 100 g kg(-1) soil, however, the ME accumulated more P as compared to the NME. The ME showed a lower plant effective number and a higher P extraction ratio compared to the NME. Both acid phosphatase and phytase activities of P. hydropiper were obviously enhanced under swine manure impacted soil compared with control, while those of ME higher than the NMEs. Therefore, the two ecotypes of P. hydropiper can accumulate P from soil amended with swine manure and establishes the foundation for phytoremediation.

[Effects of phosphorus sources on phosphorus fractions in rhizosphere soil of wild barley genotypes with high phosphorus utilization efficiency].

High P-efficiency (IS-22-30, IS-22-25) and low P-efficiency (IS-07-07) wild barley cultivars were chosen to evaluate characteristics of phosphorus uptake and utilization, and properties of phosphorus fractions in rhizosphere and non-rhizosphere in a pot experiment with 0 (CK) and 30 mg P · kg(-1) supplied as only Pi (KH2PO4), only Po (phytate) or Pi + Po (KH2PO4+ phytate). The results showed that dry matter and phosphorus accumulation of wild barley in the different treatments was ranked as Pi > Pi + Po > Po > CK. In addition, dry matter yield and phosphorus uptake of wild barley with high P-efficiency exhibited significantly greater than that with low P-efficiency. The concentration of soil available phosphorus was significantly different after application of different phosphorus sources, which was presented as Pi > Pi + Po > Po. The concentration of soil available phosphorus in high P-efficiency wild barley was significantly higher than that of low P-efficiency in the rhizosphere soil. There was a deficit in rhizosphere available phosphorus of high P-efficiency wild barley, especially in Pi and Pi+Po treatments. The inorganic phosphorus fractions increased with the increasing Pi treatment, and the concentrations of inorganic phosphorus fractions in soil were sorted as follows: Ca10-P > O-P > Fe-P > Al-P > Ca2-P > Ca8-P. The contents of Ca2-P and Ca8-P for high P-efficiency wild barley showed deficits in rhizosphere soil under each phosphorus source treatment. In addition, enrichment of Al-P and Fe-P was observed in Pi treatment in rhizosphere soil. The concentrations of organic phosphorus fractions in soil were sorted as follows: moderate labile organic phosphorus > moderate resistant, resistant organic phosphorus > labile organic phosphorus. The labile and moderate labile organic phosphorus enriched in rhizosphere soil and the greatest enrichment appeared in Pi treatment. Furthermore, the concentrations of moderate resistant organic phosphorus and resistant organic phosphorus decreased in rhizosphere soil. The concentrations of labile and moderate labile organic phosphorus in rhizosphere soil of high P-efficiency wild barley were significantly higher than that of low P-efficiency wild barley in each phosphorus source treatment. However, moderate resistant organic phosphorus and resistant organic phosphorus concentrations had no significant difference between the two genotypes. Wild barley with high P-efficiency demonstrated a greater ability of mobilization and uptake Ca2-P, Ca8-P, Al-P and labile organic phosphorus than that with low P-efficiency under Pi deficiency.

[Screening of wild barley genotypes with high phosphorus use efficiency and their rhizosphere soil inorganic phosphorus fractions].

A pot experiment was conducted to investigate the differences of 16 wild barley genotypes in phosphorus (P) uptake and use efficiency under the same P supply levels and the characteristics of inorganic P fractions in rhizosphere and non-rhizosphere soils of high P use efficiency genotypes. There existed greater differences in the P use efficiency for dry matter production at jointing stage (CV = 11.6%) and flowering stage (CV = 12.4%), and in the P use efficiency for grain yield at maturing stage (CV = 13.7%) among the genotypes. The biomass, P accumulation amount, and P use efficiency for dry matter production of high P use efficiency genotypes (IS-22-30 and IS-22-25) were significantly higher than those of low P use efficiency genotype (IS-07-07), and the grain yield of IS-22-30 and IS-22-25 was 3.10 and 3.20 times of that of IS-07-07, respectively. When supplied 0 and 30 mg x P kg(-1), the concentrations of available P and water soluble P in rhizosphere soils were significantly lower than those in non-rhizosphere soils, especially for the water soluble P. The concentrations of inorganic P fractions in the rhizosphere and non-rhizosphere soils were in the order of Ca10-P > O-P > Fe-P > Al-P > Ca2-P > Ca8-P. When supplied 30 mg x P kg(-1), the Ca8-P concentration in high P use efficiency genotypes rhizosphere soils at jointing and flowering stages was significantly lower than that in low P use efficiency genotype rhizosphere soil, but the Ca2-P concentration was in adverse. When no P was supplied, the concentrations of Ca2-P and Ca8-P in high P use efficiency genotypes rhizosphere soils were significantly higher than those in low P use efficiency genotype rhizosphere soil, and the Ca10-P concentration in the rhizosphere soils of all genotypes decreased. When supplied 30 mg x P kg(-1), the Fe-P and O-P concentrations in high P use efficiency genotypes rhizosphere soils were significantly higher than that in low P use efficiency genotype rhizosphere soil, but the Al-P concentration presented an opposite trend. Under no P supply, the Al-P, Fe-P, and O-P concentrations in high P use efficiency genotypes rhizosphere soils were significantly lower than those in low P use efficiency genotype rhizosphere soil. It was suggested that under low P stress, the capabilities of high P use efficiency genotypes in activating and absorbing soil A1-P and Ca2-P were stronger than those of low P use efficiency genotype.

[Differences in phosphorus utilization efficiency among wheat cultivars].

A pot experiment was conducted to study the differences in the biomass, phosphorus concentration, phosphorus use efficiency for dry matter, and phosphorus use efficiency for grain yield among different wheat cultivars under low phosphorus supply, aimed to screen the wheat varieties with high phosphorus use efficiency. For the test cultivars, their biomass per plant at tillering, jointing, flowering, and maturing stages was 0.46-1.09, 0.85-2.10, 3.00-7.00, and 3.85-12.88 g, and their phosphorus concentration was 2.21-4.26, 2.38-4.42, 2.44-4.96, and 1.30-5.09 mg x g(-1), respectively. From tillering to maturing stages, the phosphorus accumulation in plant and the phosphorus use efficiency for dry matter displayed a decreasing effect on the biomass formation. Significant differences were observed in the phosphorus use efficiency for dry matter (tillering stage CV = 16.3%, jointing stage CV = 15.0%, and flowering stage CV = 13.3%) and in the phosphorus use efficiency for grain yield (maturing stage CV = 20.5%) among the cultivars. The cultivars CD1158-7 and Sheng A3 Yi 034 had higher phosphorus use efficiency for dry matter and phosphorus use efficiency for grain yield, while the Yu 02321 was in adverse. The phosphorus concentration in the cultivars with high phosphorus use efficiency was significantly lower than that in the cultivars with low phosphorus use efficiency, and the grain yield of CD1158-7 and Sheng A3 Yi 03-4 was 0.98 times and 0.78 times higher than that of Yu 02321.

Uptake and accumulation of phosphorus by dominant plant species growing in a phosphorus mining area.

Phosphorus accumulation potentials were investigated for 12 dominant plant species growing in a phosphorus mining area in Shifang, as well as their corresponding non-mining ecotypes growing in Ya'an, China. High phosphorus concentrations were observed in the seedling and flowering stages of two species, Pilea sinofasciata and Polygonum hydropiper, up to 16.23 and 8.59 g kg(-1), respectively, which were 3.4 and 7 times higher than in the non-mining ecotypes. Available phosphorus levels in the respective rhizosphere soils of these plants were 112.84 and 121.78 mg kg(-1), 12 and 4 times higher than in the non-rhizosphere soil. Phosphorus concentrations in shoots of the mining ecotypes of all 12 species were significantly negatively correlated with available phosphorus in the rhizosphere soils (p<0.05), whereas a positive correlation was observed in the non-mining ecotypes. The biomass in shoot of the mining ecotype of P. hydropiper was nearly 2 times that in the non-mining ecotype. The results suggested that P. sinofasciata and P. hydropiper were efficient candidates among the tested species for phosphorus accumulation in shoots, and that further studies should be conducted to investigate their potential to be adopted as phosphorus accumulators.