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Toxicidad de cadmio en plantas de pimiento y brócoli. Evaluación de tratamientos paliativos


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Title:
Toxicidad de cadmio en plantas de pimiento y brócoli. Evaluación de tratamientos paliativos
Authors:
Pérez Millán, Rafael
Tutor:
García-Sánchez, Francisco  
Simon Grao, Silvia  
Editor:
Universidad Miguel Hernández de Elche
Department:
Departamentos de la UMH::Producción Vegetal y Microbiología
Issue Date:
2023-04-27
URI:
https://hdl.handle.net/11000/30034
Abstract:
La contaminación ambiental por cadmio (Cd) se ha incrementado drásticamente en la naturaleza debido principalmente a la intensificación de las actividades industriales, la aplicación de fertilizantes fosfatados y al uso de lodos de depuradora. Estas actividades han llevado a la contaminación a gran...  Ver más
Environmental contamination by cadmium (Cd) has increased drastically in nature mainly due to the intensification of industrial activities, the application of phosphate fertilizers and the use of sewage sludge. These activities have led to large-scale contamination of agricultural soils. Cadmium is a heavy metal with no biological function, which is toxic at low concentrations in humans, animals and plants. In agricultural crops, Cd is absorbed and transported from root to shoot efficiently, and can be accumulated in tissue, affecting growth and development. Cd causes abnormalities in the nutrient absorption and vegetative development, affects cellular metabolism at the enzymatic, photosynthetic, stomatic and hydric. All this induces the production of a high oxidative stress which prevents and limits growth and decreases agricultural crop yield. In humans, the deposition of Cd in the body is a consequence of the consumption of foods with Cd accumulation that do not present apparent phytotoxic symptoms, being able to cause serious health problems, such as cancer. For all these reasons, it is necessary to develop simple and sustainable techniques for agriculture, which allow blocking the effect of Cd and decrease absorption, transport, accumulation and symptoms in crop plants in order to to improve agricultural production and food security. Currently, the use of biostimulants in order to reduce the effect of Cd on the plant development has been studied. However, the results vary depending on different factors, such as the composition of the molecules evaluated, the dose used, the manner and time of application. Therefore, this thesis has been developed with the main objective to evaluate the effect of the application of different biostimulant substances on plants grown in Cd stress conditions. For this, 3 experiments have been carried out to elucidate what application form inhibited the toxicity of Cd more effectively and decreased its damage and accumulation in the plant. The crops selected for the experiments were pepper and broccoli, due to their importance in agriculture. In addition, the pepper has a low-medium tolerance to Cd, since it accumulates in its tissues (mainly the root), showing fast visual symptoms. And the broccoli is a crop with medium tolerance, that accumulates Cd in its tissues, mainly in the leaves and in the inflorescence. In the first experiment, it was evaluated if the application of selenium (Se) inhibited the absorption, accumulation and toxicity of Cd in pepper plants grown under hydroponic conditions with nutrient solution enriched with Cd. For this reason, four treatments were carried out (−Cd/−Se, +Cd/−Se, +Cd/+SeF and +Cd/+SeR) to determine the most adequate type of application of Se (foliar route and/or root route) in terms of reducing the toxic effects of Cd in the plants. In the second experiment, it was analyzed whether the beneficial effect of the application of Se in the decrease of Cd toxicity, in pepper plants grown in hydroponics in Cd phytotoxicity conditions with four treatments (−Cd/−Se, +Cd/−Se, +Cd/+SeF and +Cd/+SeR), was a consequence of the fact that Se improves the efficiency of nitrogen metabolism and of carbon. For this purpose, the following parameters were analysed in the tissues of leaves and roots: the concentrations of anions related to this metabolism, such as nitrates, nitrites and ammonium; the activities of different enzymes such as nitrate reductase, nitrite reductase and glutamate synthase; polyamines in their different forms; salts of organic acids; amino acids and sugars. Lastly, in the third experiment, the effect of exogenous applications of Biocat G (fulvic/humic acids), selenium (Se) and chitosan was evaluated in roots and leaves of broccoli plants exposed to Cd stress. The treatments applied were: (i) T1: nutrient solution Hoagland (NS), (ii) T2: NS + Cd at 3 mg L-1 (NS + Cd), (iii) T3: NS + Cd + application root application of Biocat G (NS + Cd + BioG), (iv) T4: NS + Cd + foliar application of Se (NS + Cd + Se1), (v) T5: NS + Cd + root application of Se (NS + Cd + Se2), (vi) T6: NS + Cd + foliar application of chitosan (NS + Cd + chitosan1), and (vii) T7: NS + Cd + application root chitosan (NS + Cd + chitosan2). From these experiments, the most relevant conclusions were: First experiment: The results obtained showed that the excess of Cd in the nutrient solution resulted in a decrease in the total dry biomass of the plants grown under these conditions, and that this decrease was due to the reduction in shoot growth (48% +Cd/−Se, 45% +Cd/+SeF, and 38% +Cd/+SeR, relative to −Cd/−Se). This growth reduction was due to: (i) the toxicity of Cd itself and (ii) the nutritional imbalance suffered by the plants. It seems that under hydroponic conditions, the addition of Se to the nutrient solution, and therefore its absorption through of the roots (lower antioxidant activity, superoxide dismutase, H2O2 and higher catalase activity), delayed and greatly reduced the toxic effects of Cd on pepper plants, unlike the foliar application of this element. Second experiment: The results showed the superiority of the treatment +Cd/+SeR with respect to the +Cd/+SeF treatment, as shown by the increase in the conjugated polyamines, decreased glutamate and phenylalanine, and increased malate and chlorogenic acid. Data from the metabolic study indicated that the foliar treatment with Se caused some damage to pepper plants or triggered a series of metabolic responses different from those observed in SeR plants. The results indicated that the SeR decreased the accumulation and toxicity of Cd as polyamine homeostasis improved, defense mechanisms such as phenylpropanoid increased and the entry of Cd into the plants was blocked. Third experiment: The results showed that the exogenous application of Biocat G and Se (T3 and T5) ameliorated the adverse effects caused by Cd toxicity and the rate plant growth. In addition, Biocat G was able to limit the transport of Cd from the leaves to the inflorescences, reducing the content of Cd in the edible part. These treatments (T3 and T5) gave the best results, act on the plants deactivating Cd toxicity, but did not affect its accumulation in the plant tissue. In addition, Biocat G limits the transport of Cd from the non-edible part to the edible. Biocat G was able to limit the transport of Cd from the leaves to the inflorescences, reducing the Cd content in the edible part
Notes:
Programa de Doctorado en Recursos y Tecnologías Agrarias, Agroambientales y Alimentarias
Keywords/Subjects:
Cadmio
Fertilidad del suelo
Protección de cultivos
Toxicidad de los alimentos
Knowledge area:
CDU: Ciencias aplicadas: Agricultura. Silvicultura. Zootecnia. Caza. Pesca: Agricultura. Agronomía. Maquinaria agrícola. Suelos. Edafología agrícola
Type of document:
info:eu-repo/semantics/doctoralThesis
Access rights:
info:eu-repo/semantics/openAccess
Appears in Collections:
Tesis doctorales - Ciencias e Ingenierías



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