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Nitrate metabolism in leaves of lettuce plants grown in floating system with different nitrate concentrations
No full textNITRATE METABOLISM IN LETTUCE AND ROCKET
Full text linkAbstract
Intensive farming techniques with highly fertilization management lead to produce leafy vegetables with high accumulation of nitrates. The Reg. UE 1258/2011 imposes threshold on nitrate content beyond which the vegetables (lettuce, rocket and spinach) cannot be placed on the market. It is so important to adopt strategies which reduce nitrate levels in leaves. This objective can be achieved through the studies on the metabolism of nitrates in model and greatest commercial interest species. This study focuses on cultivation in floating system because was shown that this cultivation technique has the ability to reduce the intake of macronutrients in the nutrient solution, making more efficient the assimilation of nitrogen by the plants and so reducing the level of nitrates in vegetables (Rouphael et al., 2004). Two leafy vegetables were chosen as study-species, lettuce (Lactuca sativa L.) and rocket (Diplotaxis tenuifolia L.) that have different efficiency of use and organication of nitrates. Some researchers have found levels of nitrate in Diplotaxis higher than 9300 mg*kg-1 FW (Santamaria et al., 1999; Cerutti et al., 1996), in fact rocket it is considerate a hyper accumulator of nitrates. This research focuses on comparative biology studies between the two species and on their nitrate metabolism to understand which are the factors that make the difference in the nitrate accumulation. Nitrate reductase, NR, (E.C.1.7.1.1-3) is the first enzyme from which start NO3- organication. Concentration in nitrates in the nutrient solution and other abiotic factors like light intensity and exposure, diurnal alternation of light and dark, temperature, CO2 levels, hormones (cytokinin, ethylene) (Dordas, 2009), anoxia, availability of sugars and nitrogen metabolites such as glutamine all play regulatory roles in NR activity (Crawford, 1995). The growing experiments performed for this thesis were planned to characterize the nitrate metabolism in lettuce and rocket plants grown in nutrient solutions containing different nitrate concentrations and under different light exposure. To achieve this objective the plants were cultivated, on the one hand, in conditions very similar to reals one, in greenhouse and with nutrient solution containing 2, 10 and 20 mM NO3-, but also with nutrient solution with low nitrate concentrations, 0.25, 0.5, 1 and 2 mM NO3-, gave after 1 day of nitrogen starvation, to highlight the high sensitiveness of nitrate transporters, and consequently on nitrate reductase, at small differences of nitrate in the nutrient solution. On the other hand the cultivations were carried out in a growth chamber in order to eliminate the influence on the results of some environmental parameters, which are difficult to evaluate in an uncontrolled environment and the aforesaid low nitrate concentrations were tested.
The qualitative parameters, as content of chlorophylls, carotenoids, nitrates, nitrites, sucrose, reducing and total sugars were determinate to understand the status of the plants sampled at different environmental conditions and to evaluate how the different concentration of nitrates in the nutrient solutions affect these parameters. Then the activity of NR was measured using two different assays to understand the response of this enzyme at the different conditions used and to be correlated with the qualitative parameters, in order to deepen the mechanisms that affect the first step of reduction of the nitrates and, consequently, their organication to glutamate and amino acids.
The study was integrated with the gene expression analysis for the main enzymes involved in the nitrate metabolism of lettuce and rocket: nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase and nitrate transporter (NTR). These analysis were performed using quantitative retro-transcriptase PCR (qRT-PCR) to study the transcriptional regulation under the different nitrate concentrations availability
Diurnal pattern of nitrate reductase in leaves of rocket (Diplotaxis tenuifolia L.) plants
No full textONE, concime completo per la lattuga coltivata in orti famigliari e urbani
No full textThe cultivation of vegetables in the garden or on the balcony for own production is often performed as hobby from persons without any agricultural knowledge. Therefore the good agricultural practies are not followed. The most part of the growing practices are approximate, in particular fertilization. In this work a complete fertilizer has been evaluated for providing the mineral nutrients required from vegetables and stimulate the nutrient use efficiency. The product tested is ONE® commercialized from Valagro S.p.A. compared with control fertilized with the minimum lettuce requirements and solutions having the same concentrations of macro-nutrients present in ONE®. In order to separate the nutritional effect from the biostimulant effects.
Results showed that ONE treatments were able to speed up the growing rate of plants and these reached the commercial maturity earlier than other treatments. The yield in ONE® treatments were higher reaching 320 g/plant or 3 kg/m2 compared to 141 g/plant or 1.3 kg/m2 of the control. The chlorophyll content was higher in ONE treatments having a positive effect on the visual appearance of the vegetables. The nitrate content was very low below 500 mg/kg FW, much lower than the commercialization law limits. The sucrose content was higher in outer leaves compared the inner leaves, while opposite results were found for total sugars. In conclusion considering the yield and quality parameters the ONE at the 50% of the dose suggested on the label gave the best results in Iceberg lettuce
Variazione dei componenti della qualità e marcatori per la caratterizzazione degli ortaggi di IV gamma
No full textThe quality of fresh-cut or minimally
processed or ready-to-eat vegetables depend from
many internal and external parameters. Some are
very labile (i.e. vitamin C) while others, instead, are
very stable and do not significantly change during the
shelf life even if the appearance of the product is
compromised. Quality changes are mainly due to the
product quality at the harvesting and the storage conditions
during the postharvest period. During the storage
period, a fast decline of ascorbic acid and some
chlorophyll components related to electron flux in the
photosynthetic activity occur. Contemporary other
processes increase such as lipid peroxidation, membrane
degradation and ethylene production. Usually
ethylene increase in the packages or boxes containing
the vegetables until to reach a plateau. In the
leafy vegetables the stress conditions can be measured
by monitoring the chlorophyll a fluorescence
and the derived JIP test indexes. These parameters
are calculated on the intermediate data points on the
fluorescence induction curve. The increase of consumer’s
safety several researches have been carrying
out for identifying molecular markers associated
with the senescence process that might be used for
assessing the quality of product at any point of the
distribution chain. Microarrays of tomato have been
used for identifying genes up-regulated or down-regulated
to cut operations (wounds). The genes differential
expressed will be evaluated if they can be used as
molecular markers of quality in the fresh-cut distribution
chain
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
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