Description: Background   D-amino acids are far less abundant in nature than L-amino acids. Both L- and D-amino acids enter soil from different sources including plant, animal and microbial biomass, antibiotics, faeces and synthetic insecticides. Moreover, D-amino acids appear in soil due to abiotic or biotic racemization of L-amino acids. Both L- and D-amino acids occur as bound in soil organic matter and as “free“ amino acids dissolved in soil solution or exchangeably bound to soil colloids. D-amino acids are mineralized at slower rates compared to the corresponding L-enantiomers. Plants have a capacity to directly take up “free“ D-amino acids by their roots but their ability to utilize them is low and thus D-amino acids inhibit plant growth. Scope   The aim of this work is to review current knowledge on D-amino acids in soil and their utilization by soil microorganisms and plants, and to identify critical knowledge gaps and directions for future research. Conclusion   Assessment of “free“ D-amino acids in soils is currently complicated due to the lack of appropriate extraction procedures. This information is necessary for consequent experimental determination of their significance for crop production and growth of plants in different types of managed and unmanaged ecosystems. Hypotheses on occurrence of “free“ D-amino acids in soil are presented in this review. Content Type Journal Article Category Review Article Pages 1-19 DOI 10.1007/s11104-011-1059-5 Authors Valerie Vranova, Department of Geology and Soil Science, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zemedelska 3, 613 00 Brno, the Czech Republic Helena Zahradnickova, Department of Analytical Biochemistry, Institute of Entomology, Biology Centre, v.v.i., Academy of Sciences of the Czech Republic, Branisovska 31, 370 05 Ceske Budejovice, the Czech Republic Dalibor Janous, CzechGlobe—Global Change Research Centre AS CR, v.v.i., Belidla 986/4a, 603 00 Brno, the Czech Republic Keith R. Skene, Biosphere Research Institute, Letham, Angus, DD8 2PY Scotland, UK Avtar S. Matharu, Green Chemistry Centre of Excellence, Department of Chemistry, University of York, York, England YO10 5DD, UK Klement Rejsek, Department of Geology and Soil Science, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zemedelska 3, 613 00 Brno, the Czech Republic Pavel Formanek, Department of Geology and Soil Science, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zemedelska 3, 613 00 Brno, the Czech Republic Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   The objective of this study was to investigate the role of transpiration on accumulation and distribution of thallium (Tl) in young durum wheat ( Triticum turgidum L. var ‘Kyle’) and spring canola ( Brassica napus L. cv ‘Hyola 401’) plants. Methods   Seedlings were grown hydroponically and exposed to Tl(I) under different high relative humidity (RH) conditions which resulted in different rates of transpiration among treatments. Plants were harvested prior to exposure, after a dark period of 9 (wheat) or 10 h (canola), and after 24 h of exposure. Harvested plant material was digested and analyzed for Tl by GFAAS. Results   Our results indicated that accumulation and distribution of Tl by plants was dependent on plant species, Tl(I) dose, duration of exposure and RH, but that the effect of RH was influenced by plant species and Tl dose. Plants exposed to Tl(I) under different RH conditions did not accumulate more Tl overall. In wheat, shoots with higher transpiration rates contained a higher Tl concentration. In canola, the rate of transpiration did not consistently affect the concentration of Tl in shoots. Conclusions   Overall, our results suggest that accumulation and translocation of Tl by plants is influenced by environmental factors that affect transpiration, in addition to soil characteristics. Content Type Journal Article Category Regular Article Pages 1-10 DOI 10.1007/s11104-011-1058-6 Authors Heidi Renkema, School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada Julie Kikkert, School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada Beverley Hale, School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada Edward Berkelaar, Department of Environmental Science, Redeemer University College, Hamilton, Ontario L9K 1J4, Canada Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Intra-specific variation in root system architecture and consequent efficiency of resource capture by major crops has received recent attention. The aim of this study was to assess variability in a number of root traits among wild genotypes of narrow-leafed lupin ( Lupinus angustifolius L.), to provide a basis for modelling of root structure. Methods   A subset of 111 genotypes of L. angustifolius was selected from a large germplasm pool based on similarity matrices calculated using Diversity Array Technology markers. Plants were grown for 6 weeks in the established semi-hydroponic phenotyping systems to measure the fine-scale features of the root systems. Results   Root morphology of wild L. angustifolius was primarily dominated by the taproot and first-order branches, with the presence of densely or sparsely distributed second-order branches in the late growth stage. Large variation in most root traits was identified among the tested genotypes. Total root length, branch length and branch number in the entire root system and in the upper roots were the most varied traits (coefficient of variation CV 〉0.50). Over 94% of the root system architectural variation determined from the principal components analysis was captured by six components (eigenvalue 〉1). Five relatively homogeneous groups of genotypes with distinguished patterns of root architecture were separated by k -means clustering analysis. Conclusions   Variability in the fine-scale features of root systems such as branching behaviour and taproot growth rates provides a basis for modelling root system structure, which is a promising path for selecting desirable root traits in breeding and domestication of wild and exotic resources of L. angustifolius for stressful or poor soil environments. Content Type Journal Article Category Regular Article Pages 1-15 DOI 10.1007/s11104-011-1050-1 Authors Ying Long Chen, Soil Science and Plant Nutrition, School of Earth and Environment (M087), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia Vanessa M. Dunbabin, Tasmanian Institute of Agricultural Research, The University of Tasmania, Private Bag 54, Hobart, TAS 7000, Australia Art J. Diggle, The Department of Agriculture and Food, Western Australia, Locked Bag 4, Bentley, WA 6983, Australia Kadambot H. M. Siddique, The UWA Institute of Agriculture, The University of Western Australia (M082), 35 Stirling Highway, Crawley, WA 6009, Australia Zed Rengel, Soil Science and Plant Nutrition, School of Earth and Environment (M087), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Soil temperature influences nitrogen (N) diffusion in soil but until now, such effects have been difficult to quantify. This study aimed at estimating the effect of temperature on the diffusive fluxes of plant-available N forms in two contrasting soils. Methods   Using a novel technique based on micro-dialysis, we established relationships between diffusive fluxes and temperature in aqueous solutions and in soil samples. Results   Averaged for all compounds, the decreases of diffusive fluxes from the soil to the microdialysis sampler were 3.8 and 4.7% per degree Celsius in an agricultural and a boreal forest soil, respectively. The temperature-related shift of diffusive flux was, however, significantly dependent on molecular weight of the N compound. In accordance with established functions for temperature effects on diffusive fluxes, the non-linearity of this relationship resulted in a greater temperature response for small N compounds compared to larger compounds. Conclusions   Our results show that, all other factors being equal, the relative contribution of smaller N compounds to the diffusive flux of total plant-available N increases with increasing soil temperatures. Content Type Journal Article Category Regular Article Pages 1-7 DOI 10.1007/s11104-011-1061-y Authors Erich Inselsbacher, Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), SE-901 83 Umeå, Sweden Torgny Näsholm, Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), SE-901 83 Umeå, Sweden Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background   Composts with different feedstocks may have differential effects on soil properties and plant growth which, may be further modulated by soil texture. Materials and methods   In a 77-day pot experiment in the glasshouse, we investigated the effect of a single application as mulch of six types of composts derived from different starting feedstocks in two soils (13% and 46% clay, referred to as S13 and S46) on soil physical, chemical and biological properties, plant growth and nutrient uptake. Composts were placed as 2.5 cm thick mulch layer on the soil surface and wheat plants were grown and harvested at 42 days and at 77 days (grain filling). Results   Composts differed in total and available N and P and particle size with C1, C3, C4 and C5 being fine-textured, whereas C2 and C6 were coarse-textured. Compost addition as mulch increased soil total organic C and EC, but had no effect on pH. In all treatments, cumulative soil respiration was higher in S13 than in S46 and was increased by compost addition with the greatest increase with C2 and C6. Compared to the unamended soil, most compost mulches (except C2) increased macroaggregate stability. Compost mulches significantly increased available P and N in both soils, except for C2. Compost mulches increased available N up to 6-fold in both soils with the strongest increase by C5. Most composts also increased wheat growth and shoot P and N concentrations with the greatest effect on plant N concentration by C5 and on plant P concentration by C4. However, C2 decreased shoot N and P concentrations compared to the unamended soil. Most compost mulches (except C2) increased mycorrhizal colonization by up to 50% compared to the unamended soil. Conclusions   Fine-textured compost mulches generally had a greater effect on soil properties and plant growth than coarse-textured composts. Despite distinct differences between the soils with respect to clay content, TOC and available P, the effect of the compost mulches on soil and plant properties was quite similar. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1007/s11104-011-1056-8 Authors Tra T. T. Duong, School of Agriculture, Food and Wine, The Waite Research Institute, University of Adelaide, DX 650 DP 636, Adelaide, SA 5005, Australia Chris Penfold, School of Agriculture, Food and Wine, The Waite Research Institute, University of Adelaide, DX 650 DP 636, Adelaide, SA 5005, Australia Petra Marschner, School of Agriculture, Food and Wine, The Waite Research Institute, University of Adelaide, DX 650 DP 636, Adelaide, SA 5005, Australia Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Phenanthrene is one of the ubiquitous, persistent organic pollutants commonly found in soil and sediments. The study will provide insight regarding the feasibility of nitrogen-assisted phytoremediation. Methods   To study the effects of various nitrogen forms on cucumber seedling phenanthrene tolerance, hydroponic experiments were conducted in a greenhouse. Results   Under phenanthrene stress, decreases in plant growth and biomass were more pronounced with a nitrate supply than with ammonium. In addition, phenanthrene concentrations in plants fed with ammonium were higher than those fed with nitrate. The reduction in plant protein and sugar, increases in nitrogen and phosphate concentrations, and increased activity of antioxidative enzymes may contribute to the phenanthrene stress response and adaptation. Higher peroxidase, superoxide dismutase, and catalase activities were found in ammonium-fed plants as compared to nitrate-fed plants under phenanthrene stress. Moreover, the reduction in soluble protein content and increases in phenanthrene transport and accumulation in non-photosynthetic organs may enable ammonium-fed plants to adapt more effectively to adverse conditions. Conclusions   Overall, these results suggest that ammonium nutrition could provide a useful tool to improve the growth and adaption of plants under phenanthrene stress. Content Type Journal Article Category Regular Article Pages 1-11 DOI 10.1007/s11104-011-1054-x Authors Xinping Yang, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095 China Shiwei Guo, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095 China Lingling Guo, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095 China Changzhou Wei, Key Laboratory of Oasis Eco-Agriculture, College of Agriculture, Shihezi University, Shihezi, 832003 China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Rice ( Oryza sativa L.) is the primary source of carbohydrate for the majority of the World's population. Herbaspirillum seropedicae is a diazotroph that lives within and on the surface of rice roots. It can promote the growth of rice, partly by supplying it with fixed nitrogen. Methods   To better understand the rice– H. seropedicae interaction, cDNA libraries from rice roots either inoculated (RRCH) or uninoculated (RRSH) with the diazotroph were obtained and analysed. Results   Potential differentially expressed genes identified from the libraries encoded a metallothionein-like protein type 1, a NOD26-like membrane integral protein ZmNIP2-1, a thionin family protein, an oryzain gamma chain precursor, stress-associated protein 1 (OsISAP1), probenazole-inducible protein PBZ1 and auxin- and ethylene-responsive genes. Differential expression was analysed by qRT-PCR for some of these genes and confirmed in most cases. The expression of stress- and defence-related genes coding for thionins, PBZ1 and OsISAP1 was repressed, while expression of a metallothionein gene was induced by inoculation with H. seropedicae . In contrast, expression of auxin-responsive genes was repressed, while expression of ethylene genes was either repressed or induced. The possible involvement of these and other genes in plant-bacterial interactions is discussed. Conclusions   The decrease in expression of the defence-related proteins PBZ1 and thionins in the rice– H. seropedicae association, suggests that the bacteria modulate plant defence responses during colonisation. The expression of genes responsive to auxin and ethylene also appears to be regulated by the bacteria. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1007/s11104-011-1044-z Authors L. C. C. Brusamarello-Santos, Departamento de Genética, Universidade Federal do Paraná, Rua Coronel Francisco Heráclito dos Santos, C. Postal 19071, 81531-980 Curitiba, PR, Brazil F. Pacheco, Departamento de Bioquímica, Universidade Federal do Paraná, Curitiba, PR, Brazil S. M. M. Aljanabi, Apollo Bramwell Hospital, Royal Road, Moka, Mauritius R. A. Monteiro, Departamento de Bioquímica, Universidade Federal do Paraná, Curitiba, PR, Brazil L. M. Cruz, Departamento de Bioquímica, Universidade Federal do Paraná, Curitiba, PR, Brazil V. A. Baura, Departamento de Bioquímica, Universidade Federal do Paraná, Curitiba, PR, Brazil F. O. Pedrosa, Departamento de Bioquímica, Universidade Federal do Paraná, Curitiba, PR, Brazil E. M. Souza, Departamento de Bioquímica, Universidade Federal do Paraná, Curitiba, PR, Brazil R. Wassem, Departamento de Genética, Universidade Federal do Paraná, Rua Coronel Francisco Heráclito dos Santos, C. Postal 19071, 81531-980 Curitiba, PR, Brazil Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Few studies have focused on changes in the physical and chemical properties of soils that are induced by grazing at high altitudes. Our aim was to identify potential responses of soil to grazing pressure on the semiarid steppe of the northern Tibetan Plateau and their probable causes. Methods   Fractal geometry to describe soil structure, soil dynamics, and physical processes within soil is becoming an increasingly useful tool that allows a better understanding of the performance of soil systems. In this study, we sampled four experimental areas in the northern part of the Tibetan Plateau under different grazing intensities: ungrazed, lightly grazed, moderately grazed and heavily grazed plots. Fractal methods were applied to characterise particle-size distributions and pore patterns of soils under different grazing intensities. Results   Our results reveal a highly significant decrease in the fractal dimensions of particle size distributions ( D 1 ) and the fractal dimensions of all pores ( D 2 ) with increasing grazing intensity. Soil organic carbon (SOC), total N and total P concentrations increased significantly with decreasing grazing intensity. We did not find differences in soil pH in response to grazing. Conclusions   Grazing induced a significant deterioration of the physical and chemical topsoil properties in the semiarid steppe of the northern Tibetan Plateau. Fractal dimensions can be a useful parameter for quantifying soil degradation due to human activities. Content Type Journal Article Category Regular Article Pages 1-11 DOI 10.1007/s11104-011-1053-y Authors Xiaodan Wang, Key Laboratory of Mountain Environment Evolvement and Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Science, No.9, section 4 of Renming South Road, Chengdu, 610041 China Yan Yan, Key Laboratory of Mountain Environment Evolvement and Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Science, No.9, section 4 of Renming South Road, Chengdu, 610041 China Yingzi Cao, Key Laboratory of Mountain Environment Evolvement and Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Science, No.9, section 4 of Renming South Road, Chengdu, 610041 China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   The aim of this study is on the one hand to identify the most determining variables predicting the site productivity of pedunculate oak, common beech and Scots pine in temperate lowland forests of Flanders; and on the other hand to test whether the accuracy of site productivity models based exclusively on soil or forest floor predictor variables is similar to the accuracy achieved by full ecosystem models, combining all soil, vegetation, humus and litterfall composition related variables. Methods   Boosted Regression Trees (BRT) were used to model in a climatically homogeneous region the relationship between environmental variables and site productivity. A distinction was made between soil (soil physical and chemical), forest floor (vegetation and humus) and ecosystem (soil, forest floor and litterfall composition jointly) predictors. Results   Our results have illustrated the strength of BRT to model the non-linear behaviour of ecological processes. The ecosystem models, based on all collected variables, explained most of the variability and were more accurate than those limited to either soil or forest floor variables. Nevertheless, both the soil and forest floor models can serve as good predictive models for many forest management practices. Conclusions   Soil granulometric fractions and litterfall nitrogen concentrations were the most effective predictors of forest site productivity in Flanders. Although many studies revealed a fertilising effect of increased nitrogen deposition, nitrogen saturation seemed to reduce species’ productivity in this region. Content Type Journal Article Category Regular Article Pages 1-16 DOI 10.1007/s11104-011-1052-z Authors Wim Aertsen, Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Celestijnenlaan 200E, Box 2411, BE-3001 Leuven, Belgium Vincent Kint, Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Celestijnenlaan 200E, Box 2411, BE-3001 Leuven, Belgium Bruno De Vos, Research Institute for Nature and Forest, Gaverstraat 4, BE-9500 Geraardsbergen, Belgium Jozef Deckers, Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Celestijnenlaan 200E, Box 2411, BE-3001 Leuven, Belgium Jos Van Orshoven, Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Celestijnenlaan 200E, Box 2411, BE-3001 Leuven, Belgium Bart Muys, Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Celestijnenlaan 200E, Box 2411, BE-3001 Leuven, Belgium Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   In the field, high ambient temperature inevitably leads to high root zone temperature, especially for seedlings. It is reported that maintaining a non-stressful root temperature is beneficial to improving tolerance of shoot to heat stress. However, our recent studies found that 1-year-old seedlings of smooth-pit peach grew poorly at non-stressful root zone temperature under field conditions in summer. To explore the mechanisms underlying the observations, we studied the physiological responses of seedlings of smooth-pit peach ( Prunus mira Koehne), a heat-sensitive species, to high ambient temperatures (37 and 42°C) under varying root zone temperatures. Methods   One-year-old seedlings of smooth-pit peach were divided into two groups subjected to two temperatures: non-stressful root temperature (25 ± 2°C, NRT), and high root zone temperature (HRT). The root and ambient temperatures were controlled by a root zone temperature chamber and light incubator. During this process, the responses of leaf water status (RWC), chlorophyll a fluorescence, activities of antioxidant enzymes, and abscisic acid (ABA) content to high ambient temperature were investigated. Results   Under the high ambient temperature, seedlings exposed to NRT had higher RWC than those subjected to HRT. Interestingly, high ambient temperature induced more severely damage to the primary photochemistry of photosystem II (PSII) in seedlings under NRT than those under HRT. These results were consistent with the results of activities for antioxidant enzymes. Seedlings exposed to NRT exhibited a significantly lower leaf ABA contents than those exposed to HRT under high ambient temperatures. Further studies demonstrated that, in seedlings treated with NRT, exogenous application of ABA enhanced the activities of antioxidant enzymes and significantly alleviated the damage to the primary photochemistry of PSII caused by high ambient temperature. Conclusions   Our findings demonstrate that exposure of smooth-pit peach seedlings to non-stressful root temperature maintained leaf water status under high ambient temperature, but it enhanced the sensitivity of PSII to heat stress. The enhanced accumulation of ABA in leaves of smooth-pit peach seedlings triggered by HRT may contribute to the improvement of the thermo-tolerance of PSII. Content Type Journal Article Category Regular Article Pages 1-12 DOI 10.1007/s11104-011-1037-y Authors Hai-Ping Hao, Institute of Botany, Chinese Academy of Sciences, No.20 Nanxincun, Xiangshan, Beijing, 100093 China Chuang-Dao Jiang, Institute of Botany, Chinese Academy of Sciences, No.20 Nanxincun, Xiangshan, Beijing, 100093 China Shou-Ren Zhang, Institute of Botany, Chinese Academy of Sciences, No.20 Nanxincun, Xiangshan, Beijing, 100093 China Yu-Dan Tang, Institute of Botany, Chinese Academy of Sciences, No.20 Nanxincun, Xiangshan, Beijing, 100093 China Lei Shi, Institute of Botany, Chinese Academy of Sciences, No.20 Nanxincun, Xiangshan, Beijing, 100093 China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X