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Master's Dissertation
DOI
https://doi.org/10.11606/D.11.2019.tde-20191218-133555
Document
Author
Full name
Luciana Santos Rodrigues
Institute/School/College
Knowledge Area
Date of Defense
Published
Piracicaba, 1996
Supervisor
Title in Portuguese
Efeito de fungos endolíticos no metabolismo fotossintético de plantas de banana (Musa Cavendish) e milho (Zea mays L.)
Keywords in Portuguese
BANANA
FOTOSSÍNTESE
FUNGOS ENDOFÍTICOS
METABOLISMO
Abstract in Portuguese
Fungos endofíticos são aqueles que ocorrem no interior das plantas e causam infecções assintomáticas em tecidos. O trabalho teve por objetivo estudar o efeito de fungos endofíticos no metabolismo fotossintético de plantas de banana (Musa cavendish) e milho (Zea mays L.). O desempenho fotossintético das plantas axênicas e inoculadas com fungos endofíticos foi avaliado através de parâmetros como fixação de CO2 e evolução de O2, fluorescência da clorofila, conteúdo de clorofila total, conteúdo de carboidratos (amido e sacarose) e conteúdo de metabólitos. Os resultados mostraram a existência de diferenças na capacidade fotossintética, em função do aumento da intensidade de luz. As plantas axênicas de ambas espécies apresentaram uma taxa fotossintética maior que as plantas inoculadas. O conteúdo de clorofila total nas plantas axênicas foi superior ao encontrado em plantas inoculadas. Os parâmetros de fluorescência da clorofila mostraram que as plantas inoculadas de banana (ϕpopen) e de milho estão sofrendo algum tipo de estresse provavelmente devido à presença do fungo. Plantas inoculadas de milho mostraram elevado conteúdo de ácido 3-fosfoglicérico quando comparadas com as plantas axênicas e controle. Os valores de fosfoenolpiruvato e piruvato das plantas axênicas e inoculadas foram superiores aos das plantas controle. As alterações no conteúdo de metabólitos das plantas inoculadas sugerem mudanças na atividade de enzimas do ciclo C4 e do ciclo de Calvin, possivelmente devido à alterações no metabolismo da planta induzidas pelo fungo. As plantas inoculadas de milho apresentaram ainda menor conteúdo de carboidratos totais e um aumento na taxa respiratória quando comparadas com as plantas axênicas. Estes resultados sugerem que a presença do fungo pode estar alterando o processo de partição de carbono nas plantas inoculadas e dessa forma diminuindo a capacidade fotossintética nessas plantas. A redução na capacidade fotossintética das plantas inoculadas poderia ainda ser provocada pelo metabolismo do próprio fungo, absorvendo produtos fotoassimilados e produzindo toxinas
Title in English
Effect of endophytic fungi on the photosynthetic metabolism of banana (Musa Cavendish) and maize (Zea mays L.) plants
Abstract in English
Endophytic fungi occur inside plants causing asymptomatic infections in tissues. The present study focuses on the effect of endophytic fungi on the photosynthetic metabolism of banana (Musa Cavendish) and maize (Zea mays L.) plants. The photosynthetic performance of axenic and endophytic inoculated plants was assessed by determining CO2 fixation and O2 evolution, chlorophyll fluorescence, total chlorophyll content, carbohydrate contents (starch and sucrose) and metabolite content. The results showed differences in photosynthetic capacity, with increasing light intensity. Axenic plants of both species display higher photosynthetic rates than inoculated plants. Total chlorophyll content was generally higher in axenic plants than inoculated plants. Fluorescence results indicate that inoculated banana (ϕpopen) and maize plants are under some form of stress, possibly due to the presence of the fungus. Inoculated maize plants exhibited an elevated levei of 3-phosphoglyceric acid compared to the axenic and control plants. Phosphoenolpyruvate and pyruvate values for axenic and inoculated plants were higher than those for control plants. Metabolite contents were also different for the inoculated plants, suggesting changes in the enzymatic activities of the C4 pathway and Calvin cycle, probably due to alterations in plant metabolism caused by the presence of the fungus. Inoculated maize plants also had lower total carbohydrate content and higher respiratory rates relative to axenic plants. These combined results suggest that the fungus may be altering carbon partitioning in inoculated plants, decreasing the photosynthetic capacity of the plants. The decrease in photosynthetic capacity for inoculated plants could also be caused by the fungus' metabolic activities, consuming photoassimilates and producing toxins.
 
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Publishing Date
2019-12-19
 
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