Fisiologia Vegetal
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/185
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Resultados da Pesquisa
Item Nickel and glyphosate on the potentiation of the soybean resistance against infection by Phakopsora pachyrhizi(Universidade Federal de Viçosa, 2020-03-18) Einhardt, Andersom Milech; Rodrigues, Fabrício de Ávila; http://lattes.cnpq.br/8666942935119852In this study, the effects of nickel (Ni) (60 g ha -1 Ni) and glyphosate (Gl) (960 g ha -1 e.a. Gl) spray on the antioxidative, defense, and ethylene metabolisms of soybean plants inoculated with P. pachyrhizi were evaluated. In the first experiment, the severity of Asian soybean rust (ASR) decreased by 35% in plants of cv. TMG 135 treated with Ni (+Ni). The malondialdehyde (MDA) concentration was higher in plants not treated with Ni (-Ni) than in +Ni plants and was linked to ASR severity and extensive colonization of the palisade and spongy parenchyma cells by fungal hyphae. The lignin concentration, β-1,3-glucanase (GLU) activity, and expression of the URE gene and the defense-related genes PAL1.1, PAL2.1, CHI1B1, and PR-1A were up- regulated in +Ni infected plants. Taken together, the information provided in this study showed the great potential of Ni to increase the basal level of soybean resistance to ASR and to complement other control methods within the context of sustainable agriculture. In the second experiment, ASR severity in plants of cv. TMG 135 decreased by 34% due to Ni supply. In inoculated plants, the MDA concentration and superoxide (O2-) and hydrogen peroxide (H2O2) accumulation were lower for +Ni plants in comparison to -Ni plants. The antioxidant enzymes activities were inefficient to avoid the high reactive species of oxygen (ROS) accumulation on -Ni inoculated plants. The photosynthetic pigments, maximum photochemical efficiency of photosystem II (PSII), effective yield of PSII, electron transport rate, rate of net carbon assimilation, stomatal conductance to water vapor, and transpiration rate values were higher and the yield for other non-regulated losses and internal CO2 concentration values were lower for +Ni inoculated plants in comparison to -Ni inoculated plants. High ROS production and the great damage to the photosynthetic apparatus damage caused by P. pachyrhizi infection on -Ni plants affected the synthesis of the sugars and increased the energetic consumption limiting therefore, the plant energetic reserves faster in contrast to +Ni plants. In conclusion, the cellular oxidative damage and the impairment on the photosynthetic apparatus of soybean plants caused by P. pachyrhizi infection were alleviated by supplying Ni foliarly. In the thirst experiment, ASR severity was lower by 37, 68, and 77% in plants of cv. TMG 132 supplied with Ni, Gl, and Ni and Gl (Ni+Gl) in comparison to plants supplied with water (control). The inoculation caused largest and fastest increase in the concentration of ROS and MDA in control plants in comparison to Ni and Gl plants. In inoculated plants, the Ni and Gl increased phenylalanine ammonia lyase and GLU activities and phenolics concentration. Additionally, Ni-treated plants showed a fasted cell wall lignification than control plants. Polyphenoloxidase activity was increased by Gl at 5 days after inoculation, regardless of P. pachyrhizi infection. In conclusion, this study demonstrated that Ni and Gl regulate differently the activity of defense enzymes and did not affect the antioxidant enzymes in soybean plants infected by P. pachyrhizi. In the fourth experiment, the ASR severity was reduced on plants of cv. TMG 132 sprayed with Ni and Gl. Carotenoids and chlorophylls concentrations were preserved for Ni, Gl, and Ni+Gl inoculated plants in comparison to that in control plants. Parameters of chlorophyll a fluorescence revealed photosynthetic apparatus damage and lowest destination of energy to photochemistry process on inoculated plants from the control treatment. Limitations on the photosynthetic machinery capacity of inoculated plants to capture light and use the absorbed energy by PSII reflected on their capacity to reduce the CO2 as indicated by the high values for internal CO2 concentration and low values for rate of net carbon assimilation. Low sugars concentration on inoculated plants from the control treatment was linked to their reduced photosynthetic capacity due to the high ASR severity. For non-inoculated plants, ethylene concentration was not affected by Ni and Gl, but its concentration decreased for inoculated plants being more pronounced for plants from the control treatment. In conclusion, this study sheds light into the role played by both Ni and Gl on ASR control from a physiological point of view. Soybean plants exposed to Ni and Gl were able to maintain their photosynthetic capacity and the great ethylene concentration during the infection process of P. pachyrhizi. Keywords: Plant nutrition. Herbicide. Host defense. Photosynthesis. Asian Soybean Rust.Item Ethylene and nickel in the resistance of maize against the infection by Exserohilum turcicum(Universidade Federal de Viçosa, 2020-11-27) Oliveira, Lillian Matias de; Rodrigues, Fabrício Ávila; http://lattes.cnpq.br/0139096690634343Diseases cause a negative impact on maize yield worldwide, and the northern leaf blight (NLB), caused by the hemibiotrophic fungus Exserohilum turcicum, is one of the most important. Considering the harmful effects of E. turcicum infection in the leaves of maize plants, the objectives of this study were to investigate the alterations in the photosynthesis (parameters related to leaf gas exchange and chlorophyll a fluorescence), the foliar concentration of micronutrients, and reactive oxygen species (ROS), production of ethylene, activities of both defense and antioxidant enzymes, and the expression of the genes related to the production of hormones. The first study investigated the role of ethylene (ET) in increasing the resistance of maize plants against NLB at physiological, biochemical, and molecular levels. Maize plants were sprayed with ET, aminooxyacetic acid (AOA) (an ET inhibitor), and water (control). The ET application increased its concentration in the leaf tissues and contributed to the expansion of NLB lesions. Also, high NLB severity resulted in lower values for net carbon assimilation rate, stomatal conductance, transpiration rate, and maximum quantum yield of photosystem II (F v/F m) at advanced stages of fungal infection. Lower concentration of pigments and higher concentrations of malonaldehyde (MDA) and hydrogen peroxide (H2O2) were noticed for ET- sprayed plants infected by E. turcicum. Great NLB development in the leaves of ET-sprayed plants can probably be attributed to the lower activities of antioxidative (ascorbate peroxidase, glutathione reductase, and superoxide dismutase) and defense (chitinase, β-1,3-glucanase, lipoxygenase, and phenylalanine ammonia-lyase) enzymes. The second study was carried out to investigate the effect of foliar nickel (Ni) spray on the potentiation of maize resistance against E. turcicum infection by examining alterations at biochemical and physiological levels. In the in vitro assay, Ni efficiently inhibited the mycelial growth of E. turcicum. For Ni-sprayed and inoculated plants, there were higher foliar concentrations of manganese and Ni. These plants exhibited significant decreases of 33 and 24%, respectively, for NLB severity at 12 and 16 days after inoculation. There were lower MDA and H2O2 concentrations in the leaves of +Ni inoculated plants. The decrease in NLB severity for Ni-sprayed plants was related to its direct effect against E. turcicum infection or through the potentiation of host defense responses such as high lipoxygenase and polyphenoloxidase activities as well as great production of phenolics and lignin. Keywords: Antioxidative metabolism. Host defense responses. Northern leaf blight. Plant nutrition. Plant hormone. Photosynthesis.Item Effects of salt stress on growth and metabolism of tomato (Solanum lycopersicum L.) plants associated with high concentration of carbon dioxide(Universidade Federal de Viçosa, 2020-11-06) Brito, Fred Augusto Lourêdo de; Ribeiro, Dimas MendesSoil salinity is an important environmental factor that limits the crop yield. On the other hand, the elevated CO2 concentration (e[CO2]) is able to mitigate the negative effects of salt stress on crop yield by stimulating photosynthetic rate in many C3 species, including Solanum lycopersicum. However, the impact of soil salinization on the relationship between biomass allocation, hormone biosynthesis and the primary metabolism of tomato plants under e[CO2] are hitherto not well understood. In this context, tomato plants grown under salt stress showed high Na+ concentration in tissues under both ambient [CO2] (a[CO2]) and e[CO2]. Under a[CO2], plants treated with NaCl showed lower accumulation of biomass compared to untreated plants. However, e[CO2] restored the growth of tomato plants under saline stress by reducing concentration of abscisic acid (ABA) and the ethylene precursor 1-aminocyclopropane-1- carboxylic acid in leaves and roots. In addition, plants treated with NaCl under a[CO2] showed reduction of the concentration of Krebs Cycle intermediates and increase of amino acids glycine and serine, while the plants under e[CO2] treated with NaCl presented the recovery of these parameters to the levels of the control plants. These findings led to a new questioning whether plants with alterations in ABA biosynthesis present differential strategies of tolerance to saline stress under e[CO2]. Thus, we analyzed tomato plants cv. Micro-Tom (MT), ABA-deficient mutant notabilis (not) and plants with high ABA concentration (NCED) submitted to salt stress. The growth of not plants was more affected in relation to MT and NCED plants, mainly under conditions of salt stress under both [CO2]. On the other hand, e[CO2] led to increases in total biomass and leaf area for all genotypes under saline stress, compared to a[CO2]. In addition, NCED mutants showed greater growth in relation to the MT and not genotypes under e[CO2] in control and saline conditions. e[CO2] caused an increase in photosynthesis and reduction of photorespiration in the MT, not and NCED treated with NaCl compared to a[CO2]. In addition, e[CO2] induced changes in the primary metabolism which were associated with increases in dark respiration, especially of MT and not genotypes under saline stress. Taken together, our results suggest that e[CO2] alleviates the effects of saline stress on plants through increased photosynthesis, reduced photorespiration and reprogrammed primary metabolism by mechanisms independent of ABA concentration. Keywords: Photosynthesis. Respiration. Primary metabolism. Hormonal regulation. Salt stress. Tomato plant