Fisiologia Vegetal
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/185
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Resultados da Pesquisa
Item Photorespiratory changes and induced resistance on tomato against septoria leaf spot by a phosphite combined with free amino acids(Universidade Federal de Viçosa, 2022-10-05) Silva, Bruno do Nascimento; Rodrigues, Fabrício Ávila; http://lattes.cnpq.br/1954041792535980Septoria leaf spot (SLS), caused by Septoria lycopersici, is a destructive disease in tomato. Infection of plants by pathogens causes changes in photosynthesis, photorespiration and respiration that will affect defense responses. The first study investigated the impacts caused on photorespiration in tomato leaves by S. lycopersici infection. Infection reduced photosynthesis and pigment concentration and increased respiration and the photorespiration/crude photosynthesis ratio increased in infected leaves. S. lycopersici infection caused great oxidative damage as demonstrated by increased concentrations of malonaldehyde, superoxide anion and hydrogen peroxide. We evaluated the expression of genes involved in the photorespiratory pathway (GOX1, GOX2, SHMT2, SMHT3 and GLYK), nitrogen metabolism (Fd-GOGAT) and stress acclimatization (mMDH1, mMDH2 and CAT) and observed an up- regulation during the process of S. lycopersici infection. A better understanding of the physiological changes that occur in the leaves of tomato plants infected by S. lycopersici at the level of photorespiration may contribute to the development of cultivars more efficiently to cope with the fungal infection. In the second study, we investigated the use of potassium phosphite combined with free L-α-amino acids (called stimulus induced resistance (IR)) to increase tomato defense responses against S. lycopersici infection. Plants that received the RI stimulus showed a reduction in the severity of SLS and less colonization of leaf tissue by S. lycopersici (lower expression of TEF-1α). Plants sprayed with IR stimulus showed lower concentrations of malonaldehyde, hydrogen peroxide and superoxide anion radical, while sucrose, fructose and starch concentrations and high ascorbate peroxidase, catalase, glutathione reductase and superoxide dismutase activities increased when compared to plants sprayed with IR stimulus. water in response to S. lycopersici infection. The photosynthetic apparatus was less compromised, which resulted in higher concentrations of chlorophyll a+b and carotenoids in plants sprayed with RI stimulus. We observed that genes involved in host defense reactions (CHI3, CHI9, GLU, PAL3, POX3, PPOB and PPOF) and those related to acquired systemic resistance (PAL3 and ICS) or induced systemic resistance ((ethylene production - ACO2, ACO3, ACO5 and ACO4) and the jasmonic acid signaling pathway (LOX1.1, LOXB, LOXC andPDF1.2)) and we observed an up-regulation for plants infected and sprayed with RI stimulus. These findings highlight the potential of using this IR stimulus for the management of SLS. Keywords: Antioxidative metabolism. Foliar disease. Host defense responses. Induced resistance. Necrotrophic pathogen.Item Thermal oscillations provoke physiological and biochemical changes on wheat plants infected by Pyricularia oryzae(Universidade Federal de Viçosa, 2019-07-25) Silva, Bruno do Nascimento; Rodrigues, Fabrício Ávila; http://lattes.cnpq.br/1954041792535980Wheat blast, caused by Pyricularia oryzae, is the most important wheat disease nowadays. High temperatures, as a consequence of climatic changes, can potentially cause physiological and biochemical changes on plants by altering their resistance to diseases. This study aimed to determine whether thermal oscillations could cause physiological and biochemical changes on wheat plants when infected with P. oryzae. Plants were submitted to different thermal acclimations (19°C and 28°C) for five days before being inoculated with P. oryzae. After inoculation, plants were kept at 25°C for 24 h and then either transferred to the initial temperature conditions or transferred to different temperature combinations (19oC→28°C and 28°C→19°C) during three days. Non-inoculated plants were submitted to these same conditions. Blast development was reduced on plants submitted to thermal acclimatization of 19oC→19oC compared to plants exposed to 28°C→28°C. There was no significant difference for blast severity between the thermal acclimations of 19oC→28°C and 28°C→19°C. Plants submitted to 28°C before or after inoculation showed impairments on photosynthesis with lower values for maximum photosystem PSII photochemical efficiency and effective PSII quantum yield, but high values for quantum yield of non-regulated energy dissipation besides lower concentration of pigments, reduction on stomatal conductance and an increase in the internal CO 2 concentration. There was high superoxide dismutase and lower ascorbate peroxidase activities for inoculated plants submitted to thermal acclimatization of 28°C→28°C. Low and high concentrations of superoxide anion and hydrogen peroxide, respectively, occurred for inoculated plants acclimated at 28°C→28°C. High chitinase, phenylalanine ammonia-lyase, and peroxidase activities occurred for inoculated plants acclimated at 28°C→28°C and 19°C→28°C. Polyphenoloxidase activity was lower for inoculated plants submitted to 28°C after or before fungal inoculation. Lipoxygenase increased on inoculated plants exposed at thermal acclimatization of 19oC→19oC. The malondialdehyde concentration was high for inoculated plants submitted to 28°C after or before fungal inoculation. In conclusion, blast development was favored on plants pre-acclimated at 28°C before fungal inoculation and kept at this same temperature during fungal infection process. By contrast, blast development was quite similar on plants pre-acclimated at 19 and 28°C before inoculation with P. oryzae and submitted, respectively, to temperatures of 28 or 19°C after inoculation. Wheat plants exposed at 28°C during the fungal infection process showed damage to the photosynthetic apparatus, a less efficient antioxidative system, and a minor contribution of the enzymes related to host defense. Key words: Defense enzymes. High temperatures. Host resistance. Photosynthesis. Wheat blast