1,720,983 research outputs found
Effects of Selenium Enrichment of Tomato Plants on Ripe Fruit Metabolism and Composition
No full textThe effects of selenium (Se) addition on production and quality traits of Solanum lycopersicon ‘Red Bunch’ were investigated. Se was added as sodium selenate at the rate of 0, 0.5 and 1 mg Se L-1 to the nutrient solution. Se was absorbed by roots and accumulated in leaves and fruits, and at the tested concentrations, it did not affect yield. Se concentration followed a gradient, decreasing from the basal
to the apical part of the plant. At red ripe stage, the fruits on the lower trusses accumulated higher amount of Se than the fruits of the higher trusses. ß-carotene and lutein significantly decreased only at 1.0 mg Se L-1. Lycopene increased either in 0.5 and, less markedly, 1.0 mg Se L-1-treated fruits where a pronounced increase in quercetin was also observed
Absorption of selenium by Lactuca sativa as affected by carboxymethylcellulose
No full textSeveral organic compounds of high molecular weight present in soil interact with selenium and may act as active binding agents affecting its availability in soil, and, consequently, selenium uptake by plants. This study is aimed at investigating the effects of polysaccharides on selenium speciation in soil and on selenium absorption by Lactuca saliva L. plants. Three-week-old seedlings were transplanted into pots filled with soil, and sodium selenite at rates of 1.5 and 5 mg Se kg(-1) of soil, or sodium selenate at a rate of 1.5 mg Se kg(-1) of soil were applied. Carboxymethylcellulose (CMC) was added to the soil at rates of 0, 3 and 30 mg kg(-1) of soil. After 48 and 110 d from transplanting plants were harvested, separated into root and shoot, and fresh and dry matter weights were recorded. Total selenium was determined in both soil and plant samples. A sequential extraction was used to investigate the different Se oxidation states and assess the availability of Se in soil after the final harvesting. Both selenite and selenate were absorbed by roots, but plants amended with SeVI+ showed higher selenium concentration than plants amended with SeIV+. Selenite appears to be less mobile than selenate both in soil and plants. The addition of carboxymethylcellulose to soil decreased the amount of selenium absorbed by plants. CMC interacted with Se, making it less mobile as evidenced by the increase in the insoluble fractions. The insoluble Se forms in soil may represent environmental Se sinks potentially available for plants if the substrate is re-used for subsequent growth cycles and selenium species are mobilized as a result of biological and chemical processes. (c) 2006 Elsevier Ltd. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Effects of conventional and alternative management systems on soil phosphorus content, soil structure, and corn yield
No full textConventional management practices have been associated with increased soil erosion and organic matter loss and the contamination of surface and ground water. Alternative agriculture systems which minimize external chemical inputs and degradation of soil and water resources represent alternatives to conventional management practices. Four different management practices were compared on an alluvial silty loam soil cultivated to grow corn (Zea mays L.). The effects of conventional and reduced tillage and of different chemical inputs on the distribution of phosphorus (P) concentration and on soil porosity were investigated. Results showed that the highest P content was detected in the topsoil (0–10 cm) of the minimum tilled plots even though the amount of P fertilizer added was much lower than the amount added in the conventionally tilled plots. The total porosity was significantly higher in the minimum tilled soil and was related only to the tillage technique. Since the higher porosity was mainly due to the higher proportion of elongated and regular pores, the minimum tilled soil appeared to be more resistant to physical stresses and characterized by a higher biological activity
Effects of phosphate and thiosulphate on arsenic accumulation in Brassica juncea plants grown in soil and in hydroponic culture
No full textArsenic is recognised as a toxic metalloid and a strong pollutant in soils of many countries. Thus, the reclamation
of contaminated areas is fundamental in order to protect both human health and agricultural production.
This study is focused on the assisted phytoextraction, a technology for reclaiming polluted soils that takes
advantage of the capability of some plants to extract inorganic elements from soils with the aid of additive agents.
The nutrients phosphorus, as phosphate, and sulphur, as thiosulphate, can compete with the form more oxidised of
arsenic, both in soil and plant.
This study examined the capability of thiosulphate (Th) and phosphate (Ph) to promote the release of As from soil
surfaces in order to improve the phytoavailability and thus the absorption of As by Brassica juncea plants.
In the first experiment B. juncea plants were grown on a soil that had been sampled from an industrial area
strongly contaminated by As (790 mg As kg-1 soil). The second experiment was carried out in hydroponics where
As has been added at a concentration (100 microM) similar to the As available concentration measured in soil.
In both trials ammonium thiosulphate (at the concentration of 0.27 M in soil, and 400 microM in hydroponics)
and potassium hydrogen phosphate (at the concentration of 0.05 M in soil, and 112 microM in hydroponics)
were added. The biomass of B. juncea was determined and the accumulation of P, S and As in root and in the
above-ground tissues have been analyzed.
Our results showed that thiosulphate and phosphate acted either as nutrients and detoxifying agents, due to the
stimulation of plant defensive systems, and influenced either the biomass production and the As accumulation in
plant tissues.
In the plants grown in soil, As accumulated at higher levels in the above-ground part than in the roots and the
addition of Th induced a higher biomass production and a higher total As accumulation (concentration x biomass)
in the above-ground tissues. This might be due to the detoxifing capacity of sulphur and suggests the presence of
interactions between the pollutant and the competitor elements both in soil and plant. Brassica juncea showed a
potential as suitable specie in terms of assisted phytoextraction of As.
Further clarifications of the existing relations between nutrients and plants are future goals in order to develop a
more efficient technique of phytoremediation
Soil microbial characteristics and mineral nitrogen availability as affected by olive oil waste water applied to cultivated soil.
No full textWaste disposal is an urgent problem in those Italian areas devoted to olive oil production where a large amount of olive oil waste is produced in a short period of time. Given the high organic matter and macronutrient content of olive oil waste water, its use in agriculture could help to solve the disposal problem and, at the same time, to improve the physiochemical characteristics of intensely cultivated soils. However, olive oil waste water contains noteworthy quantities of phenols, which are toxic and have bacteriostatic activity. The effects of repeated spreading of olive oil waste water on alfalfa, on soil microbial properties, and on the availability of mineral nitrogen were determined. Doses of 0, 80, and 160 m3 ha−1 of olive oil waste water (OW) were spread over experimental plots sown with 3rd year alfalfa. Soil samples were collected at various intervals after OW application. The biomass, respiratory activity, metabolic quotient, mineralization index, and the potential nitrification activity (PNA) of the soil were measured. Polyphenol, organic carbon, and mineral nitrogen contents were measured on the same soil samples. In general, the spreading of OW caused slightly positive modifications to the soil microbial biomass and metabolic quotient. These modifications were temporary and disappeared as early as a few months after the treatment. The PNA, as well as the nitrate and nitrite contents, were lower in the treated plots during the vegetative cycle of alfalfa and after the last harvest, and appeared to be negatively correlated with polyphenols. The results of this experiment confirmed that the spreading of olive oil waste water on cultivated soil could be an eco‐compatible practice. Despite their origin, the OW had no toxic effects on the soil microflora, and in fact, stimulated growth and reproduction of cells. Only the PNA proved to be slightly reduced, but the yield was not negatively affected
Earthworms as useful bioindicators of agroecosystem sustainability in orchards and vineyards with different inputs
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