Plant Growth Substrate Research Articles

The role of organo-zeolitic material in supporting phytoremediation of a copper mining waste dump

The effect of applying organo-zeolitic (OZ) amendment in supporting phytoremediation of a copper mine waste dump, using a substrate obtained from Ľubietová, Central Slovakia, was studied. Three plant growth substrates were prepared: (i) the untreated substrate sample from the contaminated site (D–O), (ii) the contaminated sample treated with OZ material, with 82% D–O and 18% OZ (DO + OZ), (iii) the soil from a reference site (R). The largest amount of dry biomass was obtained from the DO + OZ sample. Whole plants grown on the original substrate (D–O) were accumulating a high concentration of Cu (3057 mg kg−1). The plants root grown on DO + OZ sample accumulated highest Cu concentrations (3127 mg kg−1), but in their aerial part, only 83.54 mg kg−1 was accumulated. The translocation factor’s lower than the unit values prove that these plant species do not transfer heavy metals from root to shoot, this is why their heavy metal excluder role is evident. The value of the bioconcentration factor of the DO + OZ root/substrate obtained to be greater than the unit for Cu, Pb, Zn, Cd, Co, Ni, and Mn, suggests the OZ material’s positive contribution in the phytoremediation process that can be applied for these waste dumps.

Physicochemical Properties and Plant Coverage of Wood-based Growing Media on Slopes

The use of wood waste as substrate for plant growth exemplifies a strategy for turning waste into resources. The overall objective of this research was to evaluate the effects of wood-based growing media on plant cover in a slope area. Moreover, we tried to find out what physicochemical properties affect plant cover on a slope. For treatments, we tested natural soil, soil mixed with wood-based growing medium (1:1, w/w), and wood-based growing medium by itself. Physical and chemical characteristics were evaluated after four months from the date of treatment application to the experimental slope site. Soil coverage with seedlings of Lespedeza cyrtobotrya was measured for plant growth evaluation. Physicochemical properties were altered by mixing the natural soil with wood-based growing medium. Particularly, soil moisture and organic matter contents were significantly changed in soils treated with wood-based growing medium compared to soil alone. We confirmed that plant coverage rate was high when wood-based growing medium was mixed with the natural soil. There was a significant linear relationship between moisture content and CEC (Cation Exchange Capacity) of all growth media tested and plant coverage. This result was expected, as moisture content tends to increase with organic matter content, such as in wood-based growing medium. In conclusion, the high moisture content of the wood-based growing medium was considered effective for plant growth in the experimental slope site, and this wood-based growing medium provides a means to improve the harmony between the slope and the surrounding environment.

Plant growth-promoting rhizobacteria as an alternative to mineral fertilizers in assisted bioremediation - Sustainable land and waste management

The challenge of environment management is a sustainable development of both environmental systems and the green economy. The main objective of this study was the optimization and testing of plant growth-promoting rhizobacteria soil biopreparation and soil amendments as the alternative to or to help offset use of mineral soil fertilizers. A field study was conducted on a degraded area to improve plant biomass yield using inoculated bacteria. Moreover, organic additives (sewage sludge) and inorganic fertilizers were also used to compare their effectiveness. The conducted study investigated the combined effect of immobilized microbial consortium and soil substrates for plant growth (red fescue) on degraded areas and confirmed synergistic interactions between plants, microorganisms and soil substrates in the process of phytoremediation. The formulation consisted of immobilized bacterial consortia having mechanisms for the synthesis of compounds preferably affecting growth and development of (crop) plants. The conducted studies confirmed that the PGPR bacteria used in the experiment have the potential to promote plant growth, increase organic nitrogen the bioavailable P pool in soil.The results of the field study (synergy effect of alternative fertilization and bacteria) can be used to create effective methods in assisted soil bioremediation. This approach has a high social acceptance and reduces resource consumption of fertilizers having an impact on sustainable development. Implementing methods of supporting plant growth using microorganisms can undoubtedly contribute to the development of ‘green’ resource management.

Toxicity assessment of cobalt ferrite nanoparticles on wheat plants

ABSTRACTCobalt ferrite nanoparticles (NPs) have received increasing attention due to their widespread therapeutic and agricultural applicability. In the environmental field, dry powder- and ferrofluid-suspended cobalt ferrite NPs were found to be useful for removing heavy metals and metalloids from water, while diluted suspensions of cobalt ferrite NP have been promisingly applied in medicine. However, the potential toxicological implications of widespread exposure are still unknown. Since cobalt ferrite NPs are considered residual wastes of environmental or medical applications, plants may serve as a point-of-entry for engineered nanomaterials as a result of consumption of these plants. Thus, the aim of this study was to assess the effects of dry powder and fresh cobalt ferrite NP on wheat plants. Seven-day assays were conducted, using quartz sand as the plant growth substrate. The toxicity end points measured were seed germination, root and shoot lengths, total cobalt (Co) and iron (Fe) accumulation, photosynthetic pigment production, protein (PRT) production, and activities of catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (GPX). Increasing total Co and Fe in plant tissues indicated that wheat plants were exposed to cobalt ferrite NP. Seed germination and shoot length were not sufficiently sensitive toxicity end points. The effective concentration (EC50) that diminished root length of plants by 50% was 1963 mg/kg for fresh ferrite NPs and 5023 mg/kg for powder ferrite NP. Hence, fresh ferrite NPs were more toxic than powder NP. Plant stress was indicated by a significant decrease in photosynthetic pigments. CAT, APX, and GPX antioxidant enzymatic activity suggested the generation of reactive oxygen species and oxidative damage induced by cobalt ferrite NP. More studies are thus necessary to determine whether the benefits of using these NPs outweigh the risks.

Quantification and colonisation dynamics of Escherichia coli O157:H7 inoculation of microgreens species and plant growth substrates

Microgreens are edible plants used in food preparation for their appealing flavours and colours. They are grown beyond the point of harvest of sprouted seeds, and normally include the cotyledons and first true leaves. Their method of production is similar to sprouted seeds, which is known to be favourable for growth of microbial pathogens, although there is little data on the potential of food-borne pathogens such as Shigatoxigenic Escherichia coli (STEC) to colonise these plants. We found colonisation of nine different species of microgreen plants by STEC (isolate Sakai, stx−), with high levels of growth over five days, of approximately 5 orders of magnitude, for plants propagated at 21 °C. STEC (Sakai) formed extensive colonies on external tissue, with some evidence for internalisation via stomatal pores. Several factors impacted the level of colonisation: (1) plant tissue type such that for broccoli microgreens, the highest levels of STEC (Sakai) occurred on cotyledons compared to the true leaf and hypocotyl; (2) the route of contamination such that higher levels occurred with contaminated irrigation water compared to direct seed contamination; (3) inoculation dose, although only at low levels of inoculation (3 log10) compared to medium (5 log10) or high (7 log10) levels; (4) environmental factors, including to some extent humidity, but also plant growth substrate types. It was also evident that a starvation response was induced in STEC (Sakai) in low-nutrient plant irrigation medium. Together these data show that microgreens represent a potential hazard of contamination by food-borne pathogens, and to mitigate the risk, they should be considered in the same manner as sprouted seeds.

Biostimulant Action of Protein Hydrolysates: Unraveling Their Effects on Plant Physiology and Microbiome.

Plant-derived protein hydrolysates (PHs) have gained prominence as plant biostimulants because of their potential to increase the germination, productivity and quality of a wide range of horticultural and agronomic crops. Application of PHs can also alleviate the negative effects of abiotic plant stress due to salinity, drought and heavy metals. Recent studies aimed at uncovering the mechanisms regulating these beneficial effects indicate that PHs could be directly affecting plants by stimulating carbon and nitrogen metabolism, and interfering with hormonal activity. Indirect effects could also play a role as PHs could enhance nutrient availability in plant growth substrates, and increase nutrient uptake and nutrient-use efficiency in plants. Moreover, the beneficial effects of PHs also could be due to the stimulation of plant microbiomes. Plants are colonized by an abundant and diverse assortment of microbial taxa that can help plants acquire nutrients and water and withstand biotic and abiotic stress. The substrates provided by PHs, such as amino acids, could provide an ideal food source for these plant-associated microbes. Indeed, recent studies have provided evidence that plant microbiomes are modified by the application of PHs, supporting the hypothesis that PHs might be acting, at least in part, via changes in the composition and activity of these microbial communities. Application of PHs has great potential to meet the twin challenges of a feeding a growing population while minimizing agriculture’s impact on human health and the environment. However, to fully realize the potential of PHs, further studies are required to shed light on the mechanisms conferring the beneficial effects of these products, as well as identify product formulations and application methods that optimize benefits under a range of agro-ecological conditions.

Do the plants in functional green walls contribute to their ability to filter particulate matter?

Indoor air quality has become a growing concern as people are spending more time indoors, combined with the construction of highly sealed buildings that promote thermal efficiency. Particulate matter (PM) is a common indoor air pollutant, with exposure to high concentrations associated with several detrimental health outcomes. Active botanical biofilters or functional green walls are becoming increasingly efficient and have the potential to mitigate high suspended PM concentrations. These systems, however, require further development before they become competitive with industry standard in-room air filters. Whilst the plant growth substrate in active biofilters can act as a filter medium, it was previously not known whether the plant component of these systems played a function in PM filtration. This study thus examines the influence of the botanical component on active green wall PM single pass removal efficiency (SPRE), with a focus on evaluating the air filtration features of different plant species in green wall modules. All tested botanical biofilters outperformed biofilters that consisted only of substrate. Green walls using different plant species had different single pass removal efficiencies, with fern species recording the highest removal efficiencies across all measured particle sizes (Nephrolepis exaltata bostoniensis SPRE for PM0.3-0.5 and PM5-10 = 45.78% and 92.46% respectively). Higher removal efficiencies were associated with increased pressure drop across the biofilter. An assessment of plant morphological data suggested that the root structure of the plants strongly influenced removal efficiency. These findings demonstrate the potential to enhance active botanical biofiltration technology with appropriate plant species selection.

Evaluation of pyritic mine tailings as a plant growth substrate

At the Kidston gold mine, Australia, the direct establishment of vegetation on tailings was considered as an alternative to the use of a waste rock cover. The tailings acid/base account was used to predict plant growth limitation by acidity, and thus methods capable of identifying tailings that would acidify to pH 4.5 or lower were sought. Total S was found to be poorly correlated with acid-generating sulfide, and total C was poorly correlated with acid-neutralizing carbonate, precluding the use of readily determined total S and C as predictors of net acid generation. Therefore, the selected approach used assessment of sulfide content as a predictor of acid generation, and carbonate content as a measure of the acid-neutralizing capacity available at pH 5 and above. Using this approach, the majority of tailings (67%) were found to be non-acid generating. However, areas of potentially acid-generating tailings were randomly distributed across the dam, and could only be located by intensive sampling. The limitations imposed by the large sample numbers, and costly analysis of sulfide and carbonate, make it impractical to identify and ameliorate acid-generating areas prior to vegetation establishment. However, as only a small proportion of the tailings will acidify, a strategy of re-treating acid areas following oxidation is suggested. The findings of the present study will assist in the selection of appropriate methods for the prediction of net acid generation, particularly where more conservative measurements are required to allow vegetation to be established directly in tailings.

An assessment of the atmospheric particle removal efficiency of an in-room botanical biofilter system

In addition to the growing requirement to reduce building energy needs, demand has arisen to find sustainable methods of improving indoor air quality. Recent advances in green wall technology have led to the development of activated systems, termed botanical biofilters, that move air through the plant growth substrate to increase the rate at which the interior atmospheric environment is exposed to the components of the plant-substrate system that are active in air pollutant removal. Development of this technology is moving towards green wall integration within building air conditioning and ventilation systems. The work presented here describes an evaluation of several parameters essential for determining the functionality of a modular botanical biofilter, as well as experiments to systematically determine the filtration performance of the device, specifically the single-pass particulate rem filtration efficiency was evaluated and defined. The maximum filtration efficiency for total suspended particulate matter peaked at an air flow rate of 11.25 L s−1 through the 0.25 m2 filter, with any increases in air flow rate met with a reduction in efficiency. The system recorded removal efficiencies were 53.35 ± 9.73% for total suspend particles, 53.51 ± 15.99% for PM10, and 48.21 ± 14.71% for PM2.5. Comparisons were made against the single pass efficiency of the system without the botanical component, as well as a common in-duct pleated panel air filter, indicating that further development is required to enhance the filtration capacity of the system if it is match current air filtration standards.

Phytostabilization of Zn-Pb ore flotation tailings with Dianthus carthusianorum and Biscutella laevigata after amending with mineral fertilizers or sewage sludge

Zinc-lead mining wastes remain largely unvegetated and prone to erosion for many years because of phytotoxic levels of residual heavy metals, low nutrient status and poor physical structure. The optimal solution for these areas is to restore plant cover using species which spontaneously appear on the spoils. These species are adapted to the conditions of tailings, and their establishment will promote further vegetation by increasing soil organic matter and development of a soil system capable of supporting the nutrient and water requirements of plants and microoorganisms. The potential of Dianthus carthusianorum and Biscutella laevigata to stabilize mine spoils was analysed in a three-year pot experiment. Post-flotation wastes accumulated after Zn and Pb recovery from ores, were collected from tailings and used as a substrate for plant growth. Seeds for seedling production were collected from plants growing spontaneously on mine tailings. Prior to the establishment of the three-year pot experiment, the substrate was amended with fertilizer NPK or municipal sewage sludge, supplemented with K2O (SS). Substrate samples were collected for chemical analyses, dehydrogenase and urease activities measurements each year at the end of the growing season. The plants were harvested three years after the amendments. Both tested plant species were equally suitable for revegetation of the tailings. The amendment including both SS and NPK resulted in an increase of Corg, Nt, available P, K, Mg contents, an increase of dehydrogenase (DHA) and urease activities and a decrease in the concentrations of the soluble forms of Zn, Pb and Cd. However, nutrient content, DHA activity and plant biomass were higher with SS than NPK addition. NPK application enhanced the substrate properties after the first growing season, while positive effects of SS use were still observed after three years. A longer-lasting positive effect of SS than NPK application was probably due to the high organic matter content in SS, which was gradually decomposing and releasing nutrients.

An assessment of the potential fungal bioaerosol production from an active living wall

Active living walls, or indoor air biofilters, have been proposed as a sustainable and aesthetic means of improving indoor air quality. However these systems have yet to be adequately assessed for their potential contribution to airborne fungal proliferation in indoor spaces. The current work represents a simulation study to determine, under realistic office conditions, whether a typical active living wall makes a quantifiable contribution to the airborne aeromycota. We found that the living wall studied made no significant contribution to the density or diversity of airborne culturable fungi in a test room. Few organisms of concern to public health were identified. We conclude that active biofilters are unlikely to make hazardous contributions to indoor fungi; however, further work that documents the bioaerosol generation rate with variations in temperature, airflow, plant varieties, planting densities, maintenance schedule, age of plants, plant growth substrates and substrate moisture content need further elucidation.

Waste or substrate for metal hyperaccumulating plants — The potential of phytomining on waste incineration bottom ash

Phytomining could represent an innovative low-cost technology for the selective recovery of valuable trace elements from secondary resources. In this context the potential of phytomining from waste incineration bottom ash was tested in a pot experiment. Fresh bottom ash was acidified, leached to reduce salinity and amended with organic material to obtain a suitable substrate for plant growth. Two hyperaccumulator species, Alyssum serpyllifolium subsp. lusitanicum and Sedum plumbizincicola as well as three metal tolerant species, Brassica napus, B. juncea and Nicotiana tabacum were tested for their phytomining potential on the pre-treated and amended bottom ashes from municipal solid waste and hazardous waste incineration. The hyperaccumulators had severe difficulties to establish on the bottom ash and to produce sufficient biomass, likely due to salinity and Cu toxicity. Nevertheless, concentrations of Ni in A. serpyllifolium and Zn in S. plumbizincicola were high, but total metal removal was limited by the low biomass production and was clearly less than on metalliferous soils. The Brassica species proved to be more tolerant to salinity and high Cu concentrations and produced considerably higher biomass, but total metal removal was limited by rather low shoot concentrations. The observed limitations of the phytomining process along with currently low market prices of Ni and Zn suggest that further optimisation of the process is required in order to make phytomining economically feasible on the tested waste incineration bottom ashes.

Complete pituitary infarction associated with hypothermia and brain death

Coal waste disposal areas demand proper rehabilitation activities because several environmental impacts are related to them, such as acid mine drainage, loss of biohabitats, water pollution, and soil degradation. The most common strategy is to cover them with an impermeable layer followed by a new soil layer as soon as possible, while maximizing plant growth and avoiding water and wind erosion. This study examines the possibility of transforming coal waste itself into a substrate for plant growth, namely technosol, assuming its own use for progressive rehabilitation and revegetation of waste deposits. The coal waste is amended with other residues in an integrated waste management approach: rice husk ash, steel slag, and sewage sludge to adjust physical structure, pH, and nutrient availability, respectively. The raw material composition, fertility, metals bioavailability, plant growth, and nutrients in plant tissue are analyzed after successive growth of lopsided oats (Avena strigosa) and maize (Zea mays). The results show that coal waste allows a fertile plant substrate after being amended in accordance to experimental conditions. The soil metal concentration is found to fall within the limits of natural variation for soils in the study area and nutrients in plant tissue are found to be consistent with lopsided oats and maize standards. The proposed waste mixture results in a technosol capable of adequately promoting plant growth, that is, it is a potential resource to accelerate revegetation and natural succession in coal waste disposal areas.

Magnetite nanoparticle (NP) uptake by wheat plants and its effect on cadmium and chromium toxicological behavior

The aim of this work was to assess the uptake of citrate-coated magnetite nanoparticles (NPs) by wheat plants and its effect on the bioaccumulation and toxicity of individual and joint Cd2+ and Cr6+ levels. Seven-day assays were conducted using quartz sand as the plant growth substrate. The endpoints measured were seed germination, root and shoot lengths, and heavy metal accumulation. Magnetite exhibited very low toxicity, regardless of the wheat seedling NP uptake and distribution into roots and shoots. The seed germination and shoot length were not sensitive enough, while the root length was a more sensitive toxicity endpoint. The root length of wheat seedlings exposed to individual metals decreased by 50% at 2.67mgCd2+kg−1 and 5.53mgCr6+kg−1. However, when magnetite NPs (1000mgkg−1) were added, the root length of the plants increased by 25 and 50%. Cd2+ and Cr6+ showed similar and noninteractive joint action, but strongly impaired the wheat seedlings. In contrast, an interactive infra-additive or antagonistic effect was observed upon adding magnetite NPs. Thus, cadmium and chromium accumulation in vegetable tissues was considerately diminished and the toxicity alleviated.

不同刈割频度对大针茅草原群落特征及土壤元素含量的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 不同刈割频度对大针茅草原群落特征及土壤元素含量的影响 DOI: 10.5846/stxb201507121473 作者: 作者单位: 内蒙古大学生命科学学院，中国农业科学院农业环境与可持续发展研究所,内蒙古大学生命科学学院,中国农业科学院农业环境与可持续发展研究所,内蒙古大学，中国农业科学院农业环境与可持续发展研究所,内蒙古大学，中国农业科学院农业环境与可持续发展研究所,内蒙古大学,中国农业科学院农业环境与可持续发展研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 内蒙古自然科学基金项目（2014ZD02）；农业部资助项目（国家牧草现代产业技术体系，CARS-35）；国家科技支撑计划专题项目（2013BAC09B03-2） Effects of different mowing frequency on the community characteristics and soil element contents in a Stipa grandis steppe ecosystem Author: Affiliation: School of Life Sciences, Inner Mongolia University,School of Life Sciences, Inner Mongolia University,,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在草原生态系统中，土壤是植物生长发育最重要的基质，对植物群落动态有显著的影响。刈割是内蒙古典型草原区除放牧外最重要的利用方式。研究不同刈割频度对典型草原区群落特征和若干土壤性质的影响及土壤因子与群落特征的相关性，旨在得出对群落多样性最有利并最适宜生产利用的刈割频度。研究区设置在内蒙古锡林浩特市东部以大针茅建群的典型草原；在2009-2013年进行不同频度的刈割处理，共设置处理，一年两次刈割、一年一次刈割、两年一次（割一年休一年）刈割、围封，在2013年8月采集测定土壤养分的样品。刈割对群落多样性影响显著，割一年休一年Shannon-Wiener多样性指数、Pielou均匀度指数、丰富度指数均高于其他刈割处理（P<0.05）；不同频度刈割下，一年两次刈割处理下土壤20-30cm和30-40cm的有机质含量显著高于其他处理（P<0.05）；不同频度刈割处理下土壤中的速效磷和速效氮的含量没有显著差异；一年两次处理的土壤全氮含量显著高于其他处理（P<0.05）。Shannon-Wiener多样性指数与有机质含量、全氮含量呈显著负相关；Pielou均匀度指数与土壤元素间无显著相关关系；Richness指数与有机质含量呈显著负相关，与全氮含量为极显著负相关关系。割一年休一年刈割处理下土壤元素含量呈现更好的状态，结合群落物种多样性及生产利用的角度，割一年休一年为最合理的刈割频度。 Abstract:In grassland ecosystems, soil is the most important substrate for plant growth and has a significant impact on Plant community dynamics. Mowing is the most important way to use steppes in Inner Mongolia, except for grazing. In the present study, the impact of different mowing frequencies on the community characteristics and soil properties, and the correlation between soil factors and community characteristics were studied. The aim was to determine the most efficient and suitable mowing system for enhanced productivity and community diversity. The study area is a typical steppe primarily based on Stipa grandis, located in the Maodeng pasture of eastern Xilinhaote City, Inner Mongolia, the mowing frequency were set four gradient(TAY:Twice a year;OAY:Once a year; OTY:Once two year; NM:No mowing). Different mowing treatments were conducted in 2009-2013, soil samples were collected and analyzed in August 2013. The results indicated that the mowing treatments significantly affected plant community diversity(P<0.05). The Shannon-Wiener diversity index, Pielou evenness index, and species richness index for the mowing once-in-two-years treatment were higher than those for the other treatments. The organic matter contents of 20-30 cm and 30-40 cm soil in the mowing twice-in-one-year treatment were significantly higher than those in other treatments(P<0.05). There were no significant differences in the available nitrogen and phosphorus contents of soil between the different treatments. In addition, the soil total nitrogen in the mowing twice-in-one-year treatment was significantly higher than that in other treatments(P<0.05). The correlation analysis showed the Shannon-Wiener diversity and species richness indices were significantly negatively correlated with organic matter and total nitrogen contents, where as the Pielou evenness index had no correlation with soil element content, Richness index was significantly negatively correlated with total nitrogen content and organic matter content. Fencing was significantly beneficial to soil nutrients, but not conducive to the growth of dominant species, plant community species diversity, and increasing the plant community density. Combining the results for species diversity and production, an annual mowing interval was the most efficient mowing method for the steppe ecosystem. 参考文献 相似文献 引证文献

Analysis of soil microbiome indicators in processes of soil formation, organic matter transformation and processes involved with fine regulation of vegetative processes

At the current stage of soil microbiology development the study of the entire complex of microorganisms inhabiting the soil became possible, which helps finding the optimal combination of factors resulting in the formation of soil fertility as well as the development of stable and stress resistant phytocenosis. Soil metagenome is the largest genetic depository for all purposes, from the soil formation processes - transformation of barren rock into a substrate for plant growth and development, to the temporary adaptations in the short-term interests of the plant. The investigation of genetic potential of soil metagenome and its mobilization are the main goals of this project. Such studies should be comprehensive and solve actual issues: 1) the study of the mechanisms of soil-forming processes and the analysis of the evolution of metagenomes due to the special features of pedogenesis; 2) investigation of microbiome participation in organic residues decomposition and efficient transformation of soil organic matter; 3) screening of the associative plant-protective and growth promoting microorganisms. The object for the analysis of microbiome evolutionary potential in the process of soil formation may be the technogenic dumps resulting from mining operations, which are chronosequences of soils of different ages. Samples of paleosols are also of particular interest in the evolutionary aspect of the analysis of the soil metagenome. The project is expected to reveal a group of soil microorganisms, which take the most active part in the formation of soil fertility and effectively implement growth-stimulating and protective functions for the plant. The data may be of value for both fundamental science and serve as a base for the design of environmentally friendly high-productive phytocenoses based on the use of the adaptive potential of soil microbiota.

Screening for new accumulator plants in potential hazards elements polluted soil surrounding Peruvian mine tailings

Tailings usually provide an unfavorable substrate for plant growth because of their multi-stress environment. Plants growing on naturally metal-enriched soils are of particular interest in this perspective, since they are genetically tolerant to high metal concentrations and have an excellent adaptation to extreme conditions. Soil and plant samples were taken in Peru, at a polymetallic mine (mainly Ag, Pb and Cu) in Cajamarca Province, Hualgayoc district. Top soils (0–20cm) were analyzed for physical and chemical properties by standard methods. Total As, Cu, Pb and Zn concentrations in top soils were determined by ICP–OES. Similar metals in plants were analyzed separately (aerial and root system) by ICP–MS. Translocation Factor (TF) and Shoot Accumulation Factor (SAF) were determined to assess the tolerance strategies developed by these species and to evaluate their potential for phytoremediation purposes. The non-polluted soils had near neutral pH (6.8±0.1), a great content of organic carbon (42±4.0gkg−1) and a silt loamy texture. Soil and plant samples were taken at four locations (CA1, CA2, CA3, CA4) as well as the local reference topsoil (CA0). The range of total soil values in mg kg−1 is as follows: As 280–1029; Cu 256–2070; Pb 3992–16,060 and Zn 11,550–28,059, respectively. Unusual elevated concentrations of Pb (over 1000mgkg−1) and TF greater than one were detected in shoots of six different plants species (Ageratina sp., Achyrocline alata (Kunth) DC., Cortaderia hapalotricha Pilg., Epilobium denticulatum Ruiz & Pav., Taraxacum officinale Weber and Trifolium repens Walter). Ageratina sp and E. denticulatum also showed elevated concentrations of Zn (over 10,000mgkg−1) and TF greater than one in some studied locations. However, the SAF was smaller than one. Controlled-environment studies must be performed to definitively confirm the Pb hyperaccumulation character of the cited plant species.

Substrate biofortification in combination with foliar sprays of plant growth promoting bacteria and humic substances boosts production of organic tomatoes

Global demand for organic produce has increased by ca. 20% annually as consumers express increasing concerns over pesticide residues in their food. Organic tomato farming under tropical conditions is limited, and studies of production for industrial processing are relatively rare. In this study, we aimed to evaluate a new biotechnological tool with the potential to accelerate the conversion from conventional to organic industrial tomato production by combining the benefits of (i) the plant growth-promoting bacteria (PGPB) Herbaspirillum seropedicae and (ii) humates. This novel biofertilizer was first applied in plant growth substrate to stimulate seedling growth under greenhouse conditions; subsequently, it was used as a foliar spray following the transplantation of greenhouse seedlings to field conditions. The benefits of vermicompost plus PGPB and humate were evident in both seedling growth and development. Fruit biomass increased significantly relative to control plants after changes in plant metabolism during early growth stages. After transplantation to the field, foliar spraying of PGPB and humates enhanced nitrate uptake and nitrate reductase activity; it also stimulated the secondary metabolic phenylalanine ammonia lyase pathway. This new generation of biological products based on vermicompost, soluble organic matter and selected beneficial microorganisms provides opportunities for effectively increasing biological inputs to sustainable food, fiber and energy production.

Use of nursery potting mixes amended with local Trichoderma strains with multiple complementary mechanisms to control soil-borne diseases

This study was performed to isolate and characterize Trichoderma species from the rhizosphere of holm oak, olive and lavender in a nursery to select effective antagonistic and growth-promoting agents and use them to amend nursery plant growth substrates. Among the isolated Trichoderma species, three from olive (T. asperellum T2, T. hamatum T3, and T. harzianum T6), three from holm oak (T. hamatum T19, T. asperellum T20, and T. virens T21) and two from lavender (T. asperellum T12 and T. harzianum T14) were selected for the in vitro antagonism test against the plant pathogens Sclerotinia sclerotiorum, Rhizoctonia solani, Verticillium dahliae, Phytophthora nicotianae and P. cinnamomi. The mycelial growth of each target species was differently and directly affected by each Trichoderma isolate and its volatile and non-volatile metabolites, suggesting multiple mechanisms in the antagonistic activity. The ability of Trichoderma isolates to trigger defense pathways in Arabidopsis was evaluated in an in vitro system by assessing the activation of the R2R3-MYB-like transcription factor gene myb72. The activation of myb72 induced by the isolates was significantly different from the control, with T. asperellum T20 as the most effective. The application of a mixture of Trichoderma isolates decreased the root rot that was caused by the artificial inoculation of R. solani and S. sclerotiorum but to a lesser extent. The highest efficacy against the oomycete P. nicotianae was shown by T. harzianum T6 alone, which produced antibiotic compounds that were effective in vitro against oomycetes. The application of a combination of local antagonists through the amendment of potting soil may have potential in the sustainable production of nursery plants.

Trichoderma harzianum T-78 supplementation of compost stimulates the antioxidant defence system in melon plants.

Compost is emerging as an alternative plant growing medium in efforts to achieve more sustainable agriculture. The addition of specific microorganisms such as Trichoderma harzianum to plant growth substrates increases yields and reduces plant diseases, but the mechanisms of such biostimulants and the biocontrol effects are not yet fully understood. In this work we investigated how the addition of citrus and vineyard composts, either alone or in combination with T. harzianum T-78, affects the antioxidant defence system in melon plants under nursery conditions. Compost application and/or Trichoderma inoculation modulated the antioxidant defence system in melon plants. The combination of citrus compost and Trichoderma showed a biostimulant effect that correlated with an increase in ascorbate recycling enzymes (monodehydroascorbate reductase, dehydroascorbate reductase) and peroxidase. Moreover, the inoculation of both composts with Trichoderma increased the activity of antioxidant enzymes, especially those involved in ascorbate recycling. Based on the long-established relationship between ascorbic acid and plant defence responses as well as plant growth and development, it can be suggested that ascorbate recycling activities play a major role in the protection provided by Trichoderma and its biostimulant effect and that these outcomes are linked to increases in antioxidant enzymes. We can conclude that the combination of citrus compost and T. harzianum T-78 constitutes a viable, environmentally friendly strategy for improving melon plant production.