Aplicação da deteção remota à avaliação nutricional de fruteiras

Dissertação de mest., Geomática (Análise de Sistemas Ambientais), Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2012Devido à necessidade de encontrar técnicas mais rápidas e eficazes de diagnóstico de deficiências nutricionais em campo, torna-se importante explorar a potencialidade do uso de imagens de satélite com método de monitorização da clorose férrica em citrinos na região do Algarve, através do processamento de imagens determinando os índices de vegetação mais adequados ao diagnóstico e se possível ainda antes do aparecimento de sintomas para que as correções desta deficiência sejam feitas atempadamente. Para tal selecionaram-se dois pomares de citrinos da cultivar Newhall e utilizou-se um total de 152 árvores para a calibração do modelo e um terceiro pomar para a validação do modelo da cultivar Valencia late, localizados no município de Tavira, Portugal. O modelo foi elaborado utilizando medições de clorofila pelo método não destrutivo através da utilização do aparelho SPAD-502 e posterior conversão destes valores em clorofila total através de uma curva de calibração. Colheram-se entre 20 a 30 folhas sãs por árvore e realizaram-se as leituras de clorofila numa amostragem de 15 folhas por árvore. Adquiriu-se uma imagem de satélite/sensor multiespectral RapidEye com uma área de 625 km2, uma resolução espacial de 5 m de pixel e uma resolução espectral de 5 bandas (em nm): 440-510, 520-590, 630-685, 690-730 e 760-850 respetivamente para: azul, verde, vermelho, red edge e infravermelho próximo. De modo a avaliar a potencialidade na utilização desta imagem para um diagnóstico precoce de clorose férrica foram analisados índices de vegetação como: o NDVI, o NDVIr, o SPADI, o SPADIr, o MCARI, o TCARI e o OSAVI, determinados por combinações aritméticas de duas ou mais bandas. Verificou-se que o índice SPADIr foi o modelo mais apropriado na estimação dos conteúdos em clorofila total nas folhas de laranjeira desta cultivar e que possui capacidade de diagnosticar cloroses em campo que foi comprovado através da validação

Is there a relationship between ferric-chelate reductase activity in roots of poncirus trifoliata and leaf chlorophyll contents?

Poncirus trifoliata is a citrus rootstock very sensitive to Fe deficiency. This deficiency is very common in crops grown in calcareous soils due to the detrimental effect of bicarbonate ion. Higher plants have distinct behaviours when faced with Fe chlorosis, and several mechanisms may be activated under Fe shortage. The aim of this study was to investigate the activity of ferric-chelate reductase (FC-R), a key enzyme in Fe uptake, and to verify whether relationships with leaf chlorophyll contents could be established. Plants were grown in nutrient solutions without Fe (0 μM Fe), with 1 μM Fe, with 120 μM Fe and with 120 μM Fe plus CaCO3 (1 g L-1). Total leaf chlorophyll in young and mature leaves was determined using a calibration model based on a relationship between SPAD readings and concentration of chlorophyll (r2=0.95; P<0.01). The activity of FC-R was determined in roots apexes and several biomass parameters in shoots (number of leaves, height, dry and fresh weight) and roots (dry and fresh weight) were evaluated at the end of the experiment. The activity of FC-R increased in plants grown without iron (0 μM Fe). The results about the relations between root FC-R and leaf chlorophyll are discussed.info:eu-repo/semantics/publishedVersio

Nannochloropsis oceanica biomass enriched by electrocoagulation harvesting with promising agricultural applications

ABSTRACT: Electrocoagulation is a promising technology to harvest and concentrate microalgae while saving costs on secondary dewatering steps. However, the sacrificial electrodes release salts that impact the media and the harvested biomass. This study evaluated the effects of Fe, Zn, and Mg electrodes on Nannochloropsis oceanica harvesting and elementary composition of biomass and supernatants. Moreover, plant bioavailability of electrocoagulation minerals attached to biomass was assessed in the tomato plant model Solanum lycopersicum (cv. ‘Cherry’). Fe electrodes had better performance at lower power consumption and operation costs, followed by Zn and Mg. Electrocoagulation changes biomass and supernatant nutrient composition. Electrodes precipitated Mg and Ca from the nutrient media, enriching N. oceanica biomass, but increased Pb 2–4 times and depleted P in supernatants. Finally, Fe and Mg electrode metals in the biomass were proven bioavailable to S. lycopersicum seedlings, making electrocoagulation harvested biomass a promising bioresource to agricultural applications.info:eu-repo/semantics/publishedVersio

Movimento e sinalização do ferro em plantas com estratégia I

A deficiência de Fe provocou decréscimos no teor de clorofila total, acréscimos na atividade da QFR, alterações morfológicas a nível radicular, diminuição de absorção e translocação de Fe nos diferentes órgãos. No morangueiro o decréscimo do Fe incidiu nas raízes, na coroa e nas flores. No Poncirus o teor de Fe diminuiu nas raízes. Como alternativa à absorção de Fe ocorreu uma acumulação dos metais Zn, Mn e Cu especialmente nas raízes e folhas novas. No morangueiro os compostos orgânicos acumularam nas folhas velhas e jovens e diminuíram nas raízes. O pulso de Fe fornecido na solução nutritiva a plantas cloróticas de morangueiro levou à recuperação da deficiência em 12 dias. A partição de Fe foi direcionada para a coroa e para as flores, associado a acumulação de ácidos sucínico e cítrico ao nível radicular e permitiu maior absorção de Fe. Foram estudadas as alterações no mecanismo de resposta em plantas com o gene FRO1 silenciado. Em plantas silenciadas a deficiência de Fe levou à redução da expressão do gene, decréscimo da atividade QFR e diminuição na síntese de clorofila. Em Nicotiana o padrão de distribuição do Fe entre folhas velhas e jovens foi alterado e não foi possível recuperar as plantas silenciadas, as plantas não conseguiram retomar o metabolismo na síntese de clorofila nem ativar a enzima QFR. Foi estudado o comportamento de porta-enxertos de Poncirus com a estratégia redutora e as adaptações fisiológica ativas quando transplantadas para solo calcário. Estas plantas apresentaram desempenho semelhante em relação às plantas que cresceram numa primeira fase sem limitação de Fe indicando que os mecanismos de adaptação e o aumento nutricional induzidos pela deficiência de Fe podem ser utilizados como uma ferramenta de defesa que contribuirá para as plantas tolerarem melhor as diferentes restrições do solo em condições de campo.Fe deficiency caused decreases in total chlorophyll, increases in ferric chelate reductase activity, morphological alterations at the root level and decreases in Fe absorption and translocation in different organs. In strawberry plants, Fe content decreased in the roots, the crown and the flowers. In Poncirus, the Fe content decreased in the roots. As an alternative to Fe absorption, an accumulation of Zn, Mn and Cu metals occurred especially in roots and young leaves. In strawberry organic compounds accumulated in mature and young leaves and lowered in the roots. The Fe pulse added to the nutrient solution of chlorotic strawberry plants led to Fe deficiency recovery after 12 days. Fe partitioning was directed to the crown and flowers, associated with the accumulation of succinic and citric acids at the root level, which allowed higher Fe absorption. Changes to the response mechanism in plants with the FRO1 gene silenced were studied. In silenced plants, Fe deficiency led to reduced gene expression, decreased FCR activity and decreased chlorophyll synthesis. In Nicotiana, the pattern of Fe distribution between mature and young leaves was altered and silenced plants were unable to recover after Fe resupply, the plants were unable to resume chlorophyll synthesis nor activate the ferric chelate reductase enzyme. The behaviour of Poncirus rootstocks with the reduction-based strategy induced was analysed when transplanted to calcareous soil. These plants presented similar performance in regard to plants that grew in a first stage with Fe sufficient conditions indicating that physiological and morphological adaptations and the nutritional increase induced by Fe deficiency can be used as a defence tool that may contribute to more tolerant plants to different soil environments under field conditions

Correction to: Can bicarbonate enhance the performance of carob seedlings grown in nutrient solutions with different Fe concentrations?

Correction to: Journal of Soil Science and Plant Nutrition https://doi.org/10.1007/s42729-019-00100-4info:eu-repo/semantics/publishedVersio

Responses of tomato (Solanum lycopersicum L.) plants to iron deficiency in the root zone

Iron deficiency induces a yellowing in the aerial part of plants, known as iron chlorosis, and reduces the growth, yield, and quality of the fruits. Understanding plant response to iron deficiency is essential for agronomic management. This study decoded the temporal response of tomato plants (Solanum lycopersicum L.) to iron deficiency by quantifying different vegetative parameters. Subapical root swelling in the first 2.0 mm and several shoot and root growth parameters were measured in plants grown in a nutrient solution with and without Fe, on different dates designated as days after transplantation (DAT). Correlations between the total chlorophyll concentration in young leaves and 22 morphological and physiological parameters were also calculated. The plants grown in the absence of Fe had a higher number of secondary roots at 3 DAT, compared to control plants. On the same date, subapical root swelling was also observed, particularly at 1.5 and 2.0 mm from the root tip. Those plants also had a lower chlorophyll content in young leaves and a higher ferric-chelate reductase activity (FCR; EC 1.16.1.17) in the roots. At 9 DAT, the overall vegetative performance (plant height, fresh weight of stems and leaves) was negatively affected. At the end of the experiment (14 DAT), significant correlations were found between chlorophyll and the studied parameters. In conclusion, tomato plants experienced a cascade of responses to Fe deficiency throughout nine days: firstly, root lateralization increased; later, root swelling was observed, and a decrease in leaf chlorophyll content was registered associated with an increase in root FCR. At the end, the biomass of tomato plants decreased.info:eu-repo/semantics/publishedVersio

The root ferric-chelate reductase of Ceratonia siliqua (L.) and Poncirus trifoliata (L.) Raf. responds differently to a low level of iron

Iron (Fe) deficiency is a common nutritional disorder in several crops grown in calcareous soils, but some species are well adapted to these conditions. A hydroponic experiment was conducted to compare the response of a calcicole species Ceratonia siliqua L. (carob) and of Poncirus trifoliata (L.) Raf., a citrus rootstock very sensitive to Fe deficiency. Rootstocks from both species were grown in nutrient solutions without Fe (0 M Fe), with 1 M Fe, and with 10 M Fe (carob) or 40 M Fe (P. trifoliata). A low level of Fe or its absence in the nutrient solution led to a significant decrease in P. trifoliata vegetative growth and in SPAD readings. The root activity of ferric-chelate reductase (FC-R), a key enzyme in Fe uptake, was low in the absence or with high levels of Fe. Its highest values were in roots exposed to a low level of Fe as described in several sensitive species. In contrast, the activity of FC-R was very high in carob in the absence of Fe and was decreased sharply even when only a low level of Fe was present in the nutrient solution. Plant growth and SPAD readings in the leaves of carob were similar in all treatments. Carob seems to maintain a large activity of root FC-R that may ensure enough Fe to satisfy plant demand. The fact that it presents a slow growing pattern may also contribute to the tolerance of this species to low levels of external Fe

The memory of iron stress in strawberry plants

Research ArticleTo provide information towards optimization of strategies to treat Fe deficiency, experiments were conducted to study the responses of Fe-deficient plants to the resupply of Fe. Strawberry (Fragaria ananassa Duch.) was used as model plant. Bare-root transplants of strawberry (cv. ‘Diamante’) were grown for 42 days in Hoagland's nutrient solutions without Fe (Fe0) and containing 10 mM of Fe as Fe-EDDHA (control, Fe10). For plants under Fe0 the total chlorophyll concentration of young leaves decreased progressively on time, showing the typical symptoms of iron chlorosis. After 35 days the Fe concentration was 6% of that observed for plants growing under Fe10. Half of plants growing under Fe0 were then Fe-resupplied by adding 10 mM of Fe to the Fe0 nutrient solution (FeR). Full Chlorophyll recovery of young leaves took place within 12 days. Root ferric chelate-reductase activity (FCR) and succinic and citric acid concentrations increased in FeR plants. Fe partition revealed that FeR plants expressively accumulated this nutrient in the crown and flowers. This observation can be due to a passive deactivation mechanism of the FCR activity, associated with continuous synthesis of succinic and citric acids at root level, and consequent greater uptake of Fe.info:eu-repo/semantics/publishedVersio

Brief characterisation of Fe chlorosis in chia (Salvia hispanica L.) plants grown in nutrient solution

Chia (Salvia hispanica L.) plant is a well-known plant due to the nutraceutical value of its seeds. The aim of this preliminary study was to assess the response of Chia plants to Fe deficiency. Chia plants were grown for 12 days in Hoagland's nutrient solutions without Fe (Fe0) and with Fe (Fe10-10 mu M Fe). Biomass parameters and root ferric chelate-reductase activity (FC-R; EC 1.16.1.17) were determined at the end of the experiment. Chlorophyll estimations (expressed as SPAD readings) decreased progressively, showing the typical symptoms of iron chlorosis. In addition, iron-deficient chia plants exhibit smaller biomass (number of leaves, root, and shoot growth reduction) compared to control plants. These plants also showed morphological changes in roots. Furthermore, root FC-R activity was significantly lower in Fe0 plants.info:eu-repo/semantics/publishedVersio

Characterization and correction of Fe deficiency in strawberry: novel approaches

Iron (Fe) is abundant in soils and although it is required in small amounts by plants the incidence of iron chlorosis (Fe deficiency) is very common in a number of crops and requires massive soil application of Fe-chelates to correct it. In this work, we present the most important results obtained in several experiments conducted with strawberry to study the physiological and biochemical response mechanisms to Fe deficiency, and the assessment of novel alternatives to control this nutritional disorder. In all experiments, conducted in hydroponic systems, symptoms were induced by withdrawing Fe from the solution and the results were compared to a control treatment grown with Fe. The degree of chlorosis and symptoms recovery was estimated using SPAD values. The activity of iron chelate reductase, the enzyme responsible for Fe reduction in roots, was determined in root apices by colorimetric quantification of the BPDS complex. The Fe concentration in leaves and roots was quantified by atomic absorption spectrophotometry after treatments at 450 ºC and acid digestion of the ashes obtained. Strawberry plants that grew always without Fe, presented Fe chlorosis and morphological external root modifications associated with increases of the activity of the Fe-reductase enzyme. The recovery of chlorotic plants was achieved by application of Fe sulphate either to leaves or to the nutrient solution. In plants recovered by using Fe in the solution, the enzyme maintained a large activity, suggesting a strategy to increase plant Fe pools. As an alternative to synthetic Fe chelates, we also tested a foliar application of a plant extract obtained from fresh grass clippings (national patent PT/103584-2009 of UALG, and international patent PCT/PT2007/000041-2008, UALG and ADPFertilizantes), which was effective in chlorosis recovery after three applications. The results are discussed in order to highlight the practical implications of these responses under a perspective of optimization of crop Fe fertilizatio