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It is increasingly believed that soil nematodes play an important role in the soil community and have a pronounced influence on the evaluation of soil health and the monitoring of soil food web changes. Soil aggregates provide habitable pore space and resource availability for soil organisms. The distribution of soil nematodes, which are relatively small soil fauna, may be related to the degree of soil aggregates. Soil nematode communities were studied with different soil components: large macro-aggregates (> 2 mm), medium macro-aggregates (2–1 mm), small macro-aggregates (1–0.25 mm), and micro-aggregates (< 0.25 mm) extracted from the same crop variety plantings (Sichuan tea) of different ages (19 years, 26 years, 34 years, and 56 years) in Sichuan province, southwestern China, in 2018. The results showed that the tea plantation with 26 years of cultivation was more suitable for the propagation of nematode communities, and the numbers of total nematodes were highest in the > 2 mm fractions. Compared with other tea plantations, the Margalef index (SR) of 26-year-old tea plantation was significantly higher than that within the large and medium macro-aggregates, and the maturity index (MI) was higher in the large and small macro-aggregates in the 26-year-old tea plantation. In the large macro-aggregates, the value of functional metabolic footprints decreased with the tea plantation age. In addition, the functional metabolic footprints increased with the increase in soil aggregate size. Our finding suggests that nematode communities are limited by resource availability and resource quality played an important role in determining nematode communities. Moreover, the soil food web was degenerated with the age of tea cultivation. Therefore, in the study area, it is necessary to pay attention to the rational allocation and application of organic fertilizer in the late stage of tea planting, so as to maintain the soil fertility and soil food web structure of the tea garden. [ABSTRACT FROM AUTHOR]

Background: Tea (Camellia sinensis L) has efficient aluminum (Al) accumulation mechanisms, Al accumulation in different tea varieties is affected by the distribution of Al fractions in soil. However, little is known about the changes in Al fractions based on the aggregates in soils of different tea varieties. Methods: The distribution of Al fractions in aggregates collected from soils planted with four tea varieties (C. sinensis 'Fuding Dabaicha' (FD), Chuancha No. 3 (CC3), Chuanmu No. 217 (CM217) and Chuannong Huangyazao (CN)) was investigated by continuous extraction method. Results: Results showed significant differences in the distributions of Al fractions among the soils. The FD soil had the highest organic matter-bound Al (Or-Al) concentration, which was related to its high proportion of > 5 mm aggregates and the high Or-Al concentration in the > 5 mm aggregates. The CC3 soil had the highest concentrations of total aluminum (T-Al), water-soluble aluminum (Ws-Al) and exchangeable aluminum (Ex-Al), and the accumulation of T-Al, Ws-Al and Ex-Al depended on the highest concentrations of T-Al, Ws-Al and Ex-Al in the > 5 mm and < 0.25 mm aggregates among the four soils. Therefore, these differences in the Al fraction distributions among the soils were related to the changes in soil aggregate compositions and the aggregate-associated Al fractions. Conclusions: This study helps elucidate the mechanisms of Al sequestration, and provides evidence for developing appropriate management plans to prevent an increase in Al concentrations in the soils of CC3 and FD by adjusting the soil aggregate composition and the Al concentration of aggregates. [ABSTRACT FROM AUTHOR]

Background: Soil microbial community diversities and compositions are sensitive indicators of soil quality, but little is known about the changes in community diversity and composition of fungi in soils after planting different tea varieties. Methods: The differences in soil fungal community between the four tea varieties (Chuancha No.3 (CC3), Chuanmu No.217 (CM217), Chuannong Huangyazao (CN), and C. Sinensis 'Fuding Dabaicha' (FD)) were investigated by high-throughput sequencing. Results: Results showed significant differences in soil fungal β diversity, fungal community composition, and functional guilds in the soils planted with the four tea varieties, except α diversity. FD soil had the lowest number of phylum and class but the greatest relative abundance of Ascomycota; this occurred in conjunction with both a lower pH and soil organic carbon (SOC), total nitrogen (TN), and total phosphorous (TP) concentrations, but with a greater bulk density. A lower relative abundance of pathotroph-saprotroph-symbiotroph was detected in both CM217 and CN soils. A higher relative abundance of both saprotroph and saprotroph-symbiotroph was detected in both CM217 and CN soils; these fungal trophic modes had significantly positive correlations with soil pH, TN, and TP concentrations. CM217 and CN soils indicated the highest potential for maintaining the diversity of fungal communities and enhancing soil organic C and N accumulation. Conclusions: Soil properties play important roles in explaining the differences in soil fungal community composition and functional guild within a tea plantation system. Over 15 years tea planting, the soils grown with CM217 and CN tea varieties showed better soil quality. [ABSTRACT FROM AUTHOR]

Chelant-assisted phytoremediation may modify plant rhizosphere, which is closely related to heavy metal (HM) accumulation in plants. This work focused on the effects of nitrilotriacetic acid (NTA) on rhizosphere characteristics to investigate the mechanisms of lead (Pb) accumulation in Athyrium wardii (Hook.) Makino with exposure to 800 mg kg−1 Pb. After NTA application, Pb accumulation in the underground part of A. wardii increased by 14.3%, accompanying with some changes for the rhizosphere soils. Soil pH decreased by 0.37 units, and the dissolved organic carbon (DOC) content in the rhizosphere soils significantly increased by 7.6%. The urease, acid phosphatase, and catalase activities in the rhizosphere soils significantly increased by 104.8%, 19.7%, and 27.1%, respectively. However, a slight inhibition on microbial activities was observed in the rhizosphere of A. wardii after NTA application. Soil respiration decreased by 8.9%, and microbial biomass carbon decreased by 8.9% in the rhizosphere soils, indicating that NTA addition might recruit some microorganisms to maintain rhizosphere functions in Pb-contaminated soils while inhibiting others with low tolerance to Pb. Results suggest that lower pH, more DOC exudation, and higher soil enzyme activities after NTA application contributed to the increase of Pb accumulation in A. wardii. This study gave some preliminary evidence for NTA-assisted Pb remediation by A. wardii by modifying rhizosphere characteristics. [ABSTRACT FROM AUTHOR]

The disparity of tolerance in plants in response to Cd stress is associated with multiple physiological processes. A pot experiment was conducted to investigate the physiological properties involved in Cd tolerance of a high-cadmium (Cd)-accumulating rice line (Lu527-8) in comparison with a normal rice line (Lu527-4) under different levels of Cd exposure. Lu527-8 showed higher biomass and Cd concentrations compared with Lu527-4. The tolerance index (TI), bioconcentration factor (BCF), and translocation factor (TF) of Lu527-8 could be up to 3.08, 1.48, and 4.50 times these of Lu527-4, respectively. The two rice lines owned a uniform strategy to reduce Cd toxicity in root and stem by Cd deposition in cell wall and compartmentalization in vacuoles instead of keeping Cd in organelles. For Lu527-8, the higher distribution proportions of Cd combined with cell wall in leaf was linked to its higher Cd tolerance in comparison with Lu527-4. Lu527-8 showed a lower decline in membrane stability, antioxidation, photosynthetic parameters, and pigments than Lu527-4 when exposed to Cd stress. Taken together, the results demonstrated that higher Cd tolerance in high-Cd-accumulating rice Lu527-8 is closely linked to its greater abilities of cell wall fixation in leaf, oxidation resistance, as well as osmotic regulation and photosynthesis. [ABSTRACT FROM AUTHOR]

There are some key processes that regulate cadmium (Cd) accumulation in rice. Understanding the characteristics and mechanisms of Cd accumulation in high Cd-accumulating rice lines benefits for excavating relevant genes. Cd accumulation and distribution in roots of Lu527-8, a high Cd-accumulating rice line, were investigated by a hydroponic experiment, with a control of a normal rice line (Lu527-4). Lu527-8 showed significantly higher Cd concentrations in roots than Lu527-4. More than 81% of Cd in roots of two rice lines is distributed in soluble fraction and cell wall. In soluble fraction, there were more organic acids, amino acids, and phytochelatins in Lu527-8, benefiting Cd accumulation. Pectin and hemicellulose 1 (HC1), especially pectin, were main polysaccharides in cell wall. Lu527-8 showed more pectin and HC1 along with higher pectin methylesterase (PME) activity compared with Lu527-4, promoting Cd accumulation. Besides, Lu527-8 showed higher Cd translocation from root to shoot due to more amounts of ethanol-extractable Cd in roots than Lu527-4. In conclusion, specific characteristics of Cd chemical forms and subcellular distribution in roots of high Cd-accumulating rice line are important for Cd accumulation and translocation. [ABSTRACT FROM AUTHOR]

Purpose: Being the most widespread soil in the Chengdu Plain in Sichuan Basin, China, paddy soil has a great importance in agriculture and ecology. Anthropogenic activities alter the concentrations and stoichiometric ratios (C:N, C:P, and N:P) of carbon (C), nitrogen (N), and phosphorus (P) in paddy soil. This study aims to investigate whether the cycling of C, N, and P in paddy soil is influenced by cropping system and pedogenic process (the subtype of paddy soil). Materials and methods: In this study, we collected 1080 soil samples at 0–20 cm from five cropping systems (rice monoculture (RM), vegetable monoculture (VM), rice and vegetable rotation (RVR), rice and wheat rotation (RWR), rice and oilseed rape rotation (ROR)) and six subtypes (bleached paddy soil (BPS), gleyed paddy soil (GPS), percogenic paddy soil (PPS), degleyed paddy soil (DPS), submergienc paddy soil (SPS), and hydromorphic paddy soil (HPS)) of paddy soil in Chengdu. Soil organic carbon (SOC), soil total nitrogen (TN), and soil total phosphorus (TP) concentrations were determined to calculate the stoichiometric ratios. Results and discussion: Our results indicated that the concentrations of SOC, TN, and TP of paddy soil were higher than those of cropland on a global scale. There are similar stoichiometric ratios between paddy soil in Chengdu Plain and the cropland in the global scale. The cropping system and subtype significantly altered the soil nutrient concentrations and stoichiometric ratios. The concentrations of soil TN under rotation systems (RV, RW, and RO) were significantly higher than those of VM. The soil with the subtypes of BPS and GPS were related to low TP concentration. Conclusions: The cropping system of VM showed soil N consumption compared with the traditional cropping system (rotation systems, such as RV, RW, and RO). In addition, subtype also significantly influenced the element balance in paddy soil. The balance of soil C, N, and P is mainly affected by fertilizer application of N and P. [ABSTRACT FROM AUTHOR]

Reducing cadmium (Cd) accumulation in flue-cured tobacco is the main degree to reduce the harm of Cd to human health. In this study, a rhizobag experiment was conducted to investigate the characteristics of dissolved organic matter (DOM) in the rhizosphere of a low-Cd-accumulating tobacco line (RG11) and its role in the processes of Cd accumulation by plants. Cd concentrations in the roots and leaves of RG11 were 24.09–25.30 and 31.08–34.41% lower, respectively, than those of Yuyan5 under Cd stress. Cd exposure promoted DOM accumulation in the rhizosphere soils of the two tobacco lines. DOM concentrations in the rhizosphere soils of RG11 were 8.29–14.31% lower than those of Yuyan5 under Cd stress. RG11 presented less hydrophilic acid and hydrophilic base fractions, along with more hydrophobic acid and hydrophobic base fractions of DOM in the rhizosphere than those of Yuyan5 under Cd exposure. Fourier transform infrared spectroscopy results showed that RG11 exhibited less O–H, C–H, C=C, COO–, and C–O functional groups in rhizosphere DOM than those of Yuyan5 under Cd stress. Thus, the DOM in the rhizosphere of RG11 showed lower ability to solubilize Cd in soils, resulting in less Cd uptake by roots. This could be considered to be one of the important mechanisms of low Cd accumulation in leaves of RG11. [ABSTRACT FROM AUTHOR]

Aims: Endophytes are significant for their ecological role in plants and potential applications in phytoremediation. Endophytic bacteria with plant-growth-promoting (PGP) characteristics are isolated as inoculants to enhance phytoremediation efficiency; however, few attempts have been made to isolate bacteria from phosphorus (P)-accumulating plants and study their roles in P-phytoextraction. Method: Endophytic bacteria of P-accumulating herb Polygonum hydropiper were isolated and identified. The PGP traits including indole-3-acetic acid (IAA), siderophores, phosphate-solubilization etc. were characterized. Some endophytes were selected as the inoculants for a pot experiment in high P soil to investigate their role in P-phytoextraction. Results: Thirty-five isolates were tolerant of high P and classified into 10 taxonomic groups. The production of indole-3-acetic acid into IAA acid and siderophores was dependent on strain species. Tricalcium phosphate (TCP)-solubilizing activity of these strains was associated with a decrease of pH but increases of organic acids production, while phytin-solubilizing activity was associated with a decrease of pH but increases of acid and alkaline phosphatase activities. In the six inoculants, five strains promoted stem and leaf growth of Polygonum hydropiper except for SLs08. P. hydropiper with inoculation of SLr02, SLr15, SLs13 and SLs18 showed significantly higher root length and surface area than the control plants. The inoculation with SLr15, SLs13 and SLs18 significantly enhanced stem and leaf P accumulation of P. hydropiper. Conclusions: Endophytic bacteria with PGP traits exist in Polygonum hydropiper and strains SLr15, SLs13 and SLs18 greatly promoted plant growth and shoot P accumulation, offering the most potential as PGP inoculants for assisting P. hydropiper in P-phytoextraction. [ABSTRACT FROM AUTHOR]

Purpose: Phosphorus (P) and sediment loss through runoffs to surface and ground water represent a risk to human and environmental health. The objective of this work was to understand the mechanisms of P loss under heavy rain from the purple soil of sloping farmlands. Materials and methods: The work was carried out with simulated rainfall experiment at different maize growth stages. The combination of three factors was studied: tillage methods (flat planting, longitudinal ridge, and cross-ridge), slope gradients (10°, 15°, and 20°), and maize growth stages (seedling stage, elongation stage, tasseling stage, and maturity stage). Surface runoff, subsurface runoff, sediment, P content in runoff, and sediment were determined. Results and discussion: The rate of sediment yield was positively and non-linearly correlated with the runoff shear force and increased quickly when using the longitudinal ridge tillage method. Longitudinal ridge and 20° slope croplands showed greater erodibility, which resulted in higher runoff, sediment yield, and associated P loss. Total phosphorus (TP) and available phosphorus (AP) losses during the entire growth period were 17.58 mg m−2 and 32.86 mg m−2, in the longitudinal ride on 20° slope. Cross-ridge treatment can effectively prevent the loss of P. The P loss occurred violently on 20° slope, and there was little difference in the P loss between 10° and 15° slopes. Dissolved total phosphorus (DTP) loss dominated the TP loss in runoff, accounting for more than 55.58% of the DTP losses in all the treatments. Conclusions: These results indicate the application of flat planting and cross-ridge tillage in croplands with less than 20° slope, as these will minimize the pollution of soil and water resources by reducing P loss in runoff and sediment. [ABSTRACT FROM AUTHOR]

Better understanding of microbial activity in the rhizosphere soils associated with lead (Pb) uptake by plants may help with the phytoremediation of Pb-contaminated soils. In this work, the effects of Pb exposure (0, 200, 400, 600, 800 mg kg−1) on Pb accumulation and soil microbial activity in the rhizosphere of the mining ecotype (ME) and corresponding non-mining ecotype (NME) of Athyrium wardii (Hook.) Makino were investigated through a pot experiment. Although the plant growth of the two ecotypes was inhibited under Pb stress, the ME showed a less biomass decrease (12.6–44.0%) for aboveground than the NME, showing a greater tolerance to Pb stress. Pb concentrations as well as Pb accumulation in the two ecotypes showed an increasing trend with increasing soil Pb concentrations. The ME presented greater Pb accumulation ability than the NME, especially in underground parts. Pb availability in the rhizosphere soils of the two ecotypes after harvest decreased compared with those before transplantation. Available Pb in the rhizosphere of the ME was 1.4–4.8 times higher than that of the NME under exposure to 200–800 mg kg−1 Pb. The ME shows a greater ability to mobilize Pb in the rhizosphere soils. Pb exposure resulted in an inhibition of microbial activity in the rhizosphere of the two ecotypes. The ME demonstrated greater soil respiration and microbial biomass carbon (MBC) in the rhizosphere than the NME when treated with 200–800 mg kg−1 Pb. The ME showed a less decrease for MBC and a less increase for metabolic quotient in the rhizosphere soils than the NME when exposed to Pb generally. Microorganisms in the rhizosphere soils of the ME seem to be much more adapted to Pb stress, thus showing a great benefit for Pb accumulation and the phytostabilization of Pb-contaminated soils by the ME. [ABSTRACT FROM AUTHOR]

Purpose: Chelate-assisted phytoremediation with biodegradable chelates has been considered to be a promising technique to enhance phytoremediation efficiency, while little information is available on phytostabilization. This study aims to assess NTA-assisted phytostabilization of Pb-contaminated soils by Athyrium wardii (Hook.). Materials and methods: A pot experiment was carried out to investigate the effects of different application days (1, 3, 5, 7, 10, 14, 21) of nitrilotriacetic acid (NTA) on plant growth, Pb accumulation, and Pb availability in rhizosphere soils of A. wardii grown in soils contaminated with low (200 mg kg−1) and high (800 mg kg−1) concentrations of Pb. Results and discussion: With the application of NTA, better growth for A. wardii was observed when treated with NTA for 5–14 days for both low and high Pb soils, suggesting potential harvest time. Pb concentrations and Pb accumulation in underground parts of A. wardii grown in low and high Pb soils increased with increasing application time of NTA generally. Similar changes were also found for bioaccumulation coefficients (BCFs) of A. wardii. The greatest remediation factors (RFs) for underground parts and whole plant of A. wardii were observed for NTA application time of 7 and 5 days for low and high Pb soils, suggesting the greatest remediation efficiency. Furthermore, plant growth, BCF, and RF of A. wardii grown in low Pb-contaminated soils were greater than those grown in high Pb-contaminated soils. Pb availability in rhizosphere soils of A. wardii grown in low Pb soils was lower than those in high Pb-contaminated soils. Conclusions: It seems to be the optimum for A. wardii to phytostabilize slightly Pb-contaminated soils with the application of NTA for 7 days as taking plant growth, Pb remediation efficiency, and environmental risk into consideration. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Aims: Plants can optimize the allocation of phosphorus (P) among their foliar P fractions to increase the P utilization efficiency (PUE). Identifying the genetic relationships between foliar P fractionation and PUE could provide opportunities to improve the P efficiency of barley (Hordeum vulgare L.). Methods: The differences in the concentrations and proportions of inorganic P, ester P, nucleic acid P and insoluble P between a wild barley cultivar CN4027 and a commercial cultivar Baudin were studied, and their quantitative trait loci (QTLs) at normal P (NP) and low P (LP) fertilisations were mapped. The PUE that was determined in the previous study was used to analyze the relationship between PUE and foliar P fractionation in this research. Results: Both cultivars of barley could increase their metabolic P fractions as an LP stress tolerance strategy to ensure their continued metabolic activities in response to LP stress. Cultivar CN4027 showed higher nucleic acid P concentration (NPC), nucleic acid P proportion (NPP) and insoluble P proportion (IPP) than cultivar Baudin under LP stress. This abundant organic P (Po) pool of CN4027 ensured the normal functioning of its metabolic pathways under LP stress. The close relationships between the foliar P fractionation and PUE could be explained by two QTL clusters, Cl-3H.02 and Cl-5H.01. The QTL cluster Cl-3H.02 is flanked by the markers bPb3256099-bPb3255630 on chromosome 3H and controls the ester P concentration (EPC), ester P proportion (EPP), insoluble P concentration (IPC) and IPP. Conclusions: The QTL cluster Cl-3H.02 might have great potential for the future genetic improvement of barley PUE and may offer clues for the genetic relationships between the foliar P fractionation and PUE. [ABSTRACT FROM AUTHOR]

Aims: The selection and breeding of low grain-cadmium (Cd)-accumulating rices is a promising approach for reducing the Cd concentration in grains. A cadmium-safe rice line designated D62B (Oryza Sative L.) accumulated a low Cd concentration in brown rice for safe consumption (< 0.2 mg kg−1). D62B was a great potential breeding material with a weaker translocation capacity of Cd to shoot compared with common rice lines. A prior understanding of the Cd translocation mechanisms in D62B offered theoretical basis for breeding new low-Cd-accumulating rice cultivars in the future. Methods: A pot experiment was conducted to investigate the changes of non-protein thiols in shoot and root of D62B in comparison with a common rice line (Luhui17), and then the relationship between the Cd translocation via xylem and organic acids in xylem sap of two rice lines was explored by a hydroponic experiment. Results: D62B showed lower Cd translocated to shoot in comparison with Luhui17. The translocation factor (TF) of D62B varied from 0.11 to 0.15. Cd exposure promoted the synthesis of non-protein thiols in two rice lines, particularly in roots. Syntheses of glutathione (GSH) and phytochelatins (PCs) in root of D62B were greater than those of Luhui17. Cd concentration in xylem sap of D62B was significant positively correlated with the malic acid, citric acid and tartaric acid concentrations. The citric acid and tartaric acid concentrations in xylem sap of D62B were significantly lower than those of Luhui17. There was no significant difference for malic acid between two rice lines. Conclusions: More GSH and PCs in root of D62B was beneficial to Cd retention in root. Furthermore, the involvement of lower citric acid and tartaric acid in Cd translocated in xylem sap of D62B resulted in lower Cd accumulation in shoot. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Interactions between heavy metals in soil could affect soil heavy metal availability and plant uptake. Thus, in this study, Cd and Pb accumulation as well as plant growth of the mining ecotype (ME) and non-mining ecotype (NME) of Athyrium wardii (Hook.) in response to the exposure of Cd and Pb was investigated by a pot experiment. Although the exposure of Cd in combination with Pb further inhibited the growth of the two ecotypes in comparison with the exposure of single Cd or Pb, the ME presented lower biomass decline for the whole plant (22.0%-70.0%) than the NME among most treatments. The presence of Pb promoted Cd accumulation both in above-ground and under-ground parts of the ME. Cd concentrations in under-ground parts of the ME decreased when exposed to higher concentrations of Pb (> 600 mg kg−1). Meanwhile, the presence of Cd inhibited Pb accumulation in above-ground parts of the ME and promoted Pb accumulation in under-ground parts of the ME. Pb concentrations in under-ground parts of the ME decreased when soil Cd concentrations were more than 25 mg kg−1. The partial correlation analysis further demonstrated that the interactions between Cd and Pb stimulated Cd accumulation both in above-ground and under-ground parts of the ME and Pb accumulation in under-ground parts of the ME, while inhibited Pb accumulation in above-ground parts of the ME, showing great benefit for Pb phytostabilization by the ME. Among treatments, the bioaccumulation coefficients for Cd and Pb of the ME, varying from 2.71-31.05 and 20.09-78.06, were much higher than those of the NME. The translocation factors for Cd and Pb of the ME, varying from 0.26-0.52 and 0.01-0.10, were lower than those of the NME. These results indicate that the ME presented greater potential for the phytostabilization of soil contamination with Cd and Pb, especially for Pb. [ABSTRACT FROM AUTHOR]

Purpose: Establishing tea plantations (Camellia sinensis L.) can markedly change the pools of soil inorganic phosphorus (P) especially in water-stable aggregates. However, the effects of different chronosequence phases on the quantity and quality of inorganic P fractions in such plantations are poorly understood.Materials and methods: This study investigated the inorganic P fractions including the Al bound-P (Al-P), Fe bound-P (Fe-P), occluded-P (O-P), and Ca bound-P (Ca-P) in water-stable aggregates (WSAs) of soil from tea plantations converted from farmland. The investigations included 2–3 (CT2-3), 9–10 (CT9-10), and 16–17 years (CT16-17) and one abandoned land as contrast (CK), which is close to the three different-aged sites of soil from tea plantations converted from farmland in Zhongfeng Township of Mingshan County, Sichuan, southwest China.Results and discussion: The dominant size fraction was the aggregate with 0.5–0.25 mm. Content of > 1 mm fraction gradually increased with the increasing age in tea plantations. The contribution rate is closely related to the content of WSAs. The highest content of Al-P was observed in the aggregate with < 1 mm, Fe-P and Ca-P mainly existed in the aggregate with > 2 mm, and the distribution of O-P was uniform in soil from tea plantations converted from farmland at 0–20 and 20–40 cm soil depths, indicating that aggregate size fractions can influence the concentration of P in different P fractions. The contents of Al-P and Fe-P increased with the increasing age in tea plantations, whereas the contents of O-P and Ca-P decreased in CT16-17.Conclusions: The results of this study show that the distribution of inorganic P fractions can be influenced by aggregate size and inorganic P fractions which had low activity and are transformed into highly available fractions with the increasing age in tea plantations. [ABSTRACT FROM AUTHOR]

Aim: This study focused on P acquisition mechanisms of Hordeum spontaneum from P-impoverished soil by measuring plant growth, P acquisition and rhizosphere properties.Methods: Two P-efficient genotypes (IS-22-30 and IS-22-25) and a P-inefficient genotype (IS-07-07) were subjected to a P supply of 0, 30 mg kg−1 (deficient P) and 60 mg kg−1 (sufficient P) in a rhizobag experiment. After 60 days, biomass, P concentration, and P uptake were analyzed. Changes in pH, P fractions and acid phosphatase activity in soil at different distances from the roots were determined, using a slicing technique.Results: P-efficient genotypes showed greater biomass and plant P content, but lower plant P concentration than the P-inefficient genotype. The average seed P content was 113 and 176 μg P per seed of P-efficient genotypes and P-inefficient genotype, respectively. P-efficient genotypes showed P uptake of 3.0 and 7.9 mg pot−1 at 0 and 30 mg P kg−1; while that of P-inefficient genotype was 1.0 and 5.3 mg pot−1, respectively. Acid phosphatase activity was significantly enhanced in the soil-root interface and P-efficient genotypes demonstrated 54% greater activity of rhizosphere acid phosphatase than the P-inefficient genotype. Rhizosphere P fractions showed that P utilized by the two genotypes mainly came from H2O-Pi, NaHCO3-Pi, and NaOH-Pi, while the P-efficient genotypes markedly depleted NaHCO3-Po, NaOH-Po and HCl-Pi, and the depletion zone extended to 4 mm under P deficiency.Conclusions: These results indicate the potential to sustain more growth and greater P acquisition by P-efficient genotypes of wild barley from P-deficient soil through changes of rhizosphere P fractions and enhancing rhizosphere acid phosphatase activity. [ABSTRACT FROM AUTHOR]

This study investigated phosphorus (P) accumulation and rhizosphere characteristics of Polygonum hydropiper under high levels (400, 800, and 1600 mg P kg) of inorganic P (Pi) and organic P (Po), supplied as KHPO and myo-inositol hexaphosphoric acid dodecasodium salt, respectively. Mining (ME) and non-mining (NME) ecotypes were used since they differed in the capacity of nutrient acquisition. Biomass and P accumulation in shoots and roots of the ME increased by increasing Pi levels, whereas they decreased by increasing Po concentrations. Rhizosphere pH declined by 0.15-0.45 U for the ME and 0.04-0.14 U for the NME. Orthophosphate was the most abundant form, and it depleted greatly in the rhizosphere, with higher effect by the ME than by the NME. Glycerophosphate and inositol hexakisphosphate concentrations increased in the rhizosphere under high Po treatments with higher effect by the ME than by the NME. Rhizosphere acid phosphomonoesterase, alkaline phosphomonoesterase, and phytase activities of both ecotypes were higher in high P treatments than the treatment without P, whereas phosphodiesterase activity decreased. Significantly higher enzyme activities were observed in the rhizosphere soil of the ME than the NME. Probably, the ME might obtain higher shoot P than the NME from P-enriched soils through changes in rhizosphere properties. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) pollution has threatened severely to food safety and human health. A pot experiment and a field experiment were conducted to investigate the difference of Cd accumulation between rice ( Oryza sativa L.) lines and F hybrids in Cd-contaminated soils. The adverse effect on biomass of rice lines was greater than that of F hybrids under Cd treatments in the pot experiment. The variations of Cd concentration among rice cultivars in different organs were smaller in stem and leaf, but larger in root and ear. Average proportion of Cd in root of F hybrids was 1.39, 1.39, and 1.16 times higher than those of rice lines at the treatment of 1, 2, and 4 mg Cd kg soil, respectively. Cd concentrations in ear of F hybrids were significantly lower than rice lines with the reduction from 29.24 to 50.59%. Cd concentrations in brown rice of all F hybrids were less than 0.2 mg kg at 1 mg Cd kg soil, in which Lu98A/YaHui2816, 5406A/YaHui2816, and C268A/YaHui2816 could be screened out as cadmium-safe cultivars (CSCs) for being safe even at 2 mg Cd kg soil. C268A/YaHui2816 showed the lowest Cd concentration in root among F hybrids, while Lu98A/YaHui2816 and 5406A/YaHui2816 showed lower capability of Cd translocation from root to shoot under Cd exposure, which eventually caused the lower Cd accumulation in brown rice. The lower level of Cd translocation contributed to reducing the accumulation of Cd in brown rice had been validated by the field experiment. Thus, Lu98A/YaHui2816, 5406A/YaHui2816, and C268A/YaHui2816 could be considered as potential CSCs to cultivate in Cd-contaminated soils (<2 mg Cd kg soil). [ABSTRACT FROM AUTHOR]

Phosphorus (P) deficiency in soil is a major factor that limits barley yield production. Increasing the tolerance to P-deficiency of barley is one of the most cost-effective solutions. Quantitative trait loci (QTLs) controlling P acquisition, P utilization efficiency and biomass at the seedling stage were identified using a population of recombinant inbred lines (RILs) subjected to two P concentrations (low P (LP), 25 µM and normal P (NP), 250 µM). The population was derived from a cross between Baudin and CN4027, which is a Hordeum spontaneum accession. In two hydroponic trials conducted in 2014 and 2016, seventeen QTLs were detected on chromosomes 2H, 3H, 4H and 5H at the two P concentrations. Eight of these QTLs influenced P acquisition efficiency (PAE). Phenotypic variation explained by a particular PAE-related QTL ranged from 13.3 to 39.9%. One QTL designated as Qspue.sau- 3H.01 was related to P utilization efficiency (PUE); the phenotypic variation explained by this QTL was 12.5% (NP concentration) and 13.1% (LP concentration), respectively. Strong associations were observed between biomass and P efficiency-related traits in our study. Two QTL clusters controlling biomass, PAE- and PUE-related traits simultaneously were stably identified in the intervals bPb3263664-bPb3931069 and bPb3264570-bPb4786261 on chromosome 3H at both P concentrations in both trials. The QTLs related to PAE, PUE and biomass are important for the P-tolerant phenotype and may offer valuable clues for fine mapping and map-based cloning of barley. [ABSTRACT FROM AUTHOR]

Splash erosion of soil particles by raindrops impacting a soil surface is the initiating mechanism of water erosion. To evaluate the effects of splash erosion on maize, spatial distribution of rainfall intensity and splash erosion rate were measured under maize cover in different growth stages. The relation between splash erosion rate under the maize canopy and rainfall intensity was analyzed. The results indicated that, the average rainfall intensity under the maize canopy gradually increased with the increase in rainfall intensity during the whole growth stage, and splash erosion rate under the maize canopy showed the same change. The average rainfall intensity and splash erosion rate under rainfall of 2.0 mm min were significantly higher than those of the rainfall of 1.0 mm min. Under the same rainfall intensity, the minimum of splash erosion rate appeared in the jointing stage, while the maximum appeared in the tasseling stage. Compared with the seedling stage, the average splash erosion rates of the jointing stage showed the reduction of 23.9, 24.2, and 41.1 % the corresponding rainfall of 1.0, 1.5 and 2.0 mm min, respectively, under the maize canopy. Under rainfall of 1.0 and 1.5 mm min, there was a significant negative correlation between rainfall intensity under the canopy and splash erosion rate of every spot at the maize tasseling stage. Under rainfall of 2.0 mm min, there was also a significant negative correlation between rainfall intensity and splash erosion rate under the canopy of every spot at maize seedling stage and mature stage. The distribution of splash erosion rate was concentrated at maize seedling stage and mature stage. However, the dispersion degree of splash erosion rate was obvious at jointing stage and tasseling stage of maize. Splash erosion rates showed great difference under the canopy at every period of maize growth. Under rainfall of 1.0 mm min, the high splash erosion rate appeared at two spots, while under rainfall of 1.5 and 2.0 mm min, splash erosion rate was only concentrated in a spot. This study would provide theoretical guidance for soil erosion control based on crop growth and coverage. [ABSTRACT FROM AUTHOR]

The application of organic amendments into heavy metal contaminated soil is considered as an environmentally friendly technique to promote the potential of phytoremediation. A pot experiment was carried out to evaluate the effect of humic substances on growth, cadmium (Cd) accumulation and phytostabilization potential of the mining ecotype (ME) and the corresponding non-mining ecotype (NME) of Athyrium wardii (Hook.) grown in Cd-contaminated soils. The addition of the humic substances demonstrated great promotion for the growth and Cd uptake of ME. Both plant biomass and Cd concentration significantly increased with the increasing application of the humic substances up to 100 g kg, beyond which no significant change of underground part biomass and Cd concentrations in underground part of A. wardii was observed. The maximum Cd concentration in underground part of ME was 180 mg kg when 150 g kg humic substances were applied. The ME showed greater Cd accumulation capability in underground part (0.47-0.68 mg plant) than that of NME (0.27-0.45 mg plant). Increasing bioaccumulation coefficient (BCF) values of A. wardii was observed with increasing application of the humic substances. The BCF values of ME were higher than those of NME. However, the use of the humic substances exhibited little impact on translocation factors (TFs) of ME, and the TF values of ME were less than NME. Furthermore, the application of the humic substances improved the remediation factors (RFs) of A. wardii. The RF values in underground part of ME ranging from 0.73 to 0.91 % were apparently higher than those of NME. These results indicated that the humic substances can be a potential candidate for enhancing the phytostabilization of A. wardii grown in Cd-contaminated soils. [ABSTRACT FROM AUTHOR]

Phytoextraction is a promising technique to remove cadmium (Cd) from contaminated soils. In this research, the two different Cd accumulation rice lines of Lu527-8 (the high Cd accumulating rice line) and Lu527-4 (the normal rice line) were grown in soils with different Cd treatments (0, 5, 10, and 20 mg kg soil) to evaluate Cd accumulation characteristics and Cd removal potentials. When the concentration of Cd in soil increased, Lu527-8 showed less symptoms of phytotoxicity when compared to Lu527-4. Furthermore, Lu527-8 demonstrated greater shoot Cd accumulation (321.17-964.95 mg plant) than Lu527-4 (50.37-201.66 μg plant) at the jointing and filling stages. The soil available Cd content of Lu527-8 significantly decreased by 26.92-38.97 and 27.77-63.44 % at the jointing and filling stages, respectively. Meanwhile, the total Cd content in soil also reduced by 11.64-46.75 and 21.41-54.11 % at jointing and filling stages, respectively. When the Cd concentration in soil was 20 mg kg, the Cd extraction rate in shoots of Lu527-8 reached 2.12 and 2.85 % which increased 10.60 and 6.48 times compared with that of Lu527-4 at the jointing and filling stages, respectively. In conclusion, this study demonstrates that Lu527-8 shows great abilities of Cd accumulation and Cd removal potential from contaminated soils with different Cd treatments and it is a promising species for phytoextraction of Cd-contaminated soils. [ABSTRACT FROM AUTHOR]

Purpose: Long-term tea plantation ( Camellia sinensis L.) could markedly change the pools of total fluoride (T-F) in soil extractable fractions. However, the effects of different chronosequence phases on the changes of fluoride fractions in these plantations are poorly understood. Materials and methods: In this study, we have investigated the distribution of extractable fluoride fractions in four differently aged tea plantations (16, 23, 31, and 53 years old, respectively), in Zhongfeng Township of Ming-shan County, Sichuan, Southwest China. This study aimed to determine the effects of the age of various tea plantations with respect the contents of T-F, also considering the water-soluble fluoride (Ws-F), the exchangeable fluoride (Ex-F), the Fe/Mn oxide-bound fluoride (Fe/Mn-F), the organic matter-bound fluoride (Or-F), and the residual fluoride (Res-F) within soil aggregates. Results and discussion: The T-F, Ws-F, Ex-F, and Res-F contents increased with the decreasing of particle size except for Fe/Mn-F and Or-F. Along with the increase of tea plant life, the contents of Ws-F and Ex-F within soil aggregates gradually increased. In addition, the trends of extractable Fe/Mn-F and Or-F were opposite to that of highly available fluoride after 23 years. Conclusions: The results of this study show that fluoride is easily transformed into highly available phases in long-term tea plantations, improving the absorption of fluoride for tea plants. [ABSTRACT FROM AUTHOR]

A pot experiment was conducted to evaluate the rhizosphere characteristics of the mining ecotype (ME) of Athyrium wardii and the non-mining ecotype (NME) with rhizobags when exposed to Pb-contaminated soils for 40 days. The results showed that the ME was more tolerant to Pb and more efficient in Pb uptake than the NME. Available Pb concentrations in the rhizosphere of ME and NME increased by 1.2-2.3 times and 1.7-2.7 times when compared to those in the bulk soil, whereas available Pb concentrations in rhizosphere of ME were lower than those of NME. Significant depletion of exchangeable Pb, Pb bound to carbonate and Pb bound to organic matter was observed in the rhizosphere of ME. No statistical change of Pb bound to Fe-Mn oxides was observed in the rhizosphere of both ecotypes. pH values in the rhizosphere of ME decreased by 0.02-0.16 units compared to the bulk soil, and the dissolved organic carbon concentrations in the rhizosphere of ME were 1.1-1.5 times higher than those in the bulk soil. Microorganism numbers in rhizosphere of both ecotypes reduced with increasing Pb treatments, and the sensitivity order of microbial community to Pb was: bacteria > fungi > actinomycetes. Microorganism number in the rhizosphere of ME was higher than that of NME and bulk soil. In conclusion, the ME was more effective in Pb uptake and showed greater capability in mobilizing Pb from non-mobile fraction to mobile fractions likely due to its specific rhizosphere characteristics. [ABSTRACT FROM AUTHOR]

Athyrium wardii is one of the dominant plant species flourishing on the Pb-Zn mine tailings in Sichuan Province, China. A greenhouse pot experiment was conducted to evaluate the chemical forms, subcellular distribution, and thiol compounds in A. wardii under different Pb treatments. The results showed that plants of the mining ecotype (ME) of A. wardii were more tolerant to Pb than those of the non-mining ecotype (NME) in spite of accumulation of higher Pb concentrations. The Pb concentrations in shoots and roots of the ME were 3.2∼8.6 times and 3.0∼24.6 times higher than those of the NME, respectively. The ME was more efficient in Pb uptake than the NME. Moreover, 27.8∼39.0 % of the total Pb in ME was sodium chloride (NaCl) extractable and 38.0∼48.5 % was acetic acid (HAc) extractable, whereas only a minority of total Pb was in ethanol and HO extractable. In subcellular level, 77.4∼88.8 % of total Pb was stored in the cell walls of ME and 9.0∼18.9 % in soluble fractions. Increasing Pb concentrations enhanced sequestration of Pb into the cell walls and soluble fractions of ME tissues to protect organelles against Pb. Synthesis of non-protein thiols (NP-SH) and phytochelatins (PCs) in roots of ME significantly enhanced in response to Pb stress, and significant increases in glutathione (GSH) were observed in shoots of ME. Higher levels of NP-SH, GSH, and PCs were observed in roots of the ME comparing with NME, especially under high Pb treatments. The results indicated that Pb was localized mainly in cell wall and soluble fraction of ME plants with low biological activity by cell wall deposition and vacuolar compartmentalization, which might be the important adapted Pb detoxification mechanisms of ME. [ABSTRACT FROM AUTHOR]

The Cadmium (Cd) accumulation capacity and subcellular distribution in the mining ecotype (ME) and non-mining ecotype (NME) of Kyllinga brevifolia Rottb were investigated in pot experiments. The results showed that average Cd contents in shoots of the two ecotypes of K. brevifolia were higher than those in roots, whereas Cd concentrations in roots were greater than those in shoots. Also, shoot Cd contents in NME of K. brevifolia were 1.65-45.45 times greater than those in ME when the plants were grown at 5, 25, 50, and 100 mg Cd kg soil. Moreover, Cd contents in the roots in NME were 1.75-45.45 times higher than those in ME. Subcellular distribution of Cd demonstrated that the majority of Cd in the two ecotypes of K. brevifolia was distributed in the cell walls and soluble fraction, and a small percentage of Cd existed in organelle fraction. In addition, proportions of Cd distributed in shoots and roots cell walls of NME were greater than those in ME. It could be assumed that compared with ME, NME of K. brevifolia has better Cd accumulation capacity, and the subcellular distribution of Cd might be one of the mechanisms to explain such phenomena. [ABSTRACT FROM AUTHOR]

Phytostabilization has great practical significance and flexibility in the ecological restoration of mining tailings and remediation of heavy metals polluted soils. However, potential use of metallophytes in phytostabilization is limited by a lack of knowledge of many basic plant processes. A mining ecotype (ME) Athyrium wardii, Pb/Cd phytostabilizer, and a non-mining ecotype (NME) A. wardii were grown in a pot experiment to investigate the chemical characteristics of the rhizosphere when exposed to the Cd polluted soils. Rhizobags were used to collect rhizosphere and bulk soils, separately. The results indicated that the ME A. wardii was more efficient in Cd accumulation in the root than NME after growing in Cd polluted soils for 50 days in a green house. Soil solution pH and dissolved organic carbon (DOC) concentration in the rhizosphere of ME A. wardii were higher than in the bulk soil and initial values (before planting), whereas the increment in the ME A. wardii were greater than NME. Owing to the increasing of rhizosphere soil pH, exchangeable Cd significantly decreased, whereas the other Cd species were increased with increasing soil DOC values. It is assumed that the ME A. wardii was effective in stabilizing Cd from the mobile fraction to non-mobile fractions. Results from this study suggest that rhizosphere alkalinization and the exudation of high amounts of dissolved organic matter (DOM) to reduce heavy metal mobility might be the two important mechanisms involved in the metal tolerance/accumulation of ME A. wardii. [ABSTRACT FROM AUTHOR]

The objectives of the present study were to compare nine dominant plant species growing in mine tailings and nonmining areas in terms of biomass and Cd concentrations and to search for Cd accumulation and tolerance. Also, more detailed experiments were conducted on Athyrium wardii using a pot experiment to assure its Cd-accumulation ability and tolerance as a potential phytostabilizer of Cd-polluted soils. Nine dominant plant species growing on Pb/Zn mine tailings and their corresponding nonmining ecotypes were investigated for their potential to phytostabilize Cd. The performance of A. wardii exposed to high levels of Cd was investigated under controlled conditions. A field study revealed that the Cd concentrations in the roots of these plants ranged from 0.21 to 251.07 mg kg, and the highest concentrations were found in A. wardii, which reached a concentration of 69.78, 251.07, and 126.35 mg kg during the early growth stage (May), vigorous growth stage (August), and late growth stage (October), respectively. The Cd concentrations of roots among the nine mining ecotypes were positively correlated with available content of Cd in the rhizosphere soils, whereas a negative correlation was observed in the nonmining ecotypes. A pot experiment showed that the mining ecotype of A. wardii had a higher biomass production and Cd retention capacity in roots than that of the nonmining ecotype. Due to the relatively high tolerance to Cd and the capacity of roots to retain this metal, A. wardii may be useful for the phytostabilization of soils contaminated by Cd. [ABSTRACT FROM AUTHOR]

Background, aim and scope: Lead (Pb) accumulation in soils affects plants primarily through their root systems. The aim of this study was to investigate early symptoms of the loss of membrane integrity and lipid peroxidation in root tissues and physiological adaptation mechanism to Pb in accumulating ecotypes (AE) and non-accumulating ecotypes (NAE) of Sedum alfredii under Pb stress in hydroponics. Methods and results: Histochemical in situ analyses, fluorescence imaging, and normal physiological analysis were used in this study. Pb accumulation in roots of both AE and NAE increased linearly with increasing Pb levels (0-200 μM), and a significant difference between both ecotypes was noted. Both loss of plasma membrane integrity and lipid peroxidation in root tissues became serious with increasing Pb levels, maximum tolerable Pb level was 25 and 100 μM for NAE and AE, respectively. Pb supplied at a toxic level caused a burst of reactive oxygen species (ROS) in root cells in both ecotypes. However, the root cells of AE had inherently higher activities of superoxide dismutase (SOD), guaiacol peroxidase (POD), and lipoxygenase (LOX) in control plants, and the induction response of these antioxidant enzymes occurred at lower Pb level in AE than NAE. AE plants maintained higher ascorbic acid and HO concentrations in root cells than NAE when exposed to different Pb levels, and Pb induced more increase in dehydroascorbate (DHA), catalase (CAT), and ascorbate peroxidase (APX) in AE than NAE roots. Discussion and conclusion: Results indicate that histochemical in situ analyses of root cell death and lipid peroxidation under Pb short-term stress was sensitive, reliable, and fast. Higher tolerance in roots of accumulating ecotype under Pb stress did depend on effective free oxygen scavenging by making complex function of both constitutively higher activities and sensitive induction of key antioxidant enzymes in root cells of S. alfredii. [ABSTRACT FROM AUTHOR]

Screening out plants that are hyper-tolerant to certain heavy metals plays a fundamental role in remediation of mine tailing. In this study, nine dominant plant species growing on lead-zinc mine tailing and their corresponding non-mining ecotypes were investigated for their potential phytostabilization of lead. Lead concentration in roots of these plants was higher than in shoots, and the highest concentrations of lead were found in Athyrium wardii: 15542 and 10720 mg kg in the early growth stage (May) and vigorous growth stage (August) respectively, which were 426 and 455 times higher than those of the non-mining ecotypes. Because of poor lead translocation ability, lead accumulation in roots reached as high as 42 mg per plant. Available lead in the rhizosphere soils of A. wardii was 310 mg kg, which was 17 times higher than that of the non-rhizosphere soil. Lead concentrations of roots for the nine mining ecotypes were positively correlated with available lead in the rhizosphere soils, whereas a negative correlation was observed in the non-mining ecotypes. These results suggest that A. wardii was the most promising candidate among the tested species for lead accumulation in roots, and it could be used for phytostabilization in lead polluted soils. [ABSTRACT FROM AUTHOR]