Tolerância a baixas temperaturas e zoneamento agroclimático de espécies forrageiras para o Estado do Paraná
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Data
2017-03-02
Autores
Manetti Filho, João [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A ocorrência de geadas nas pastagens causa perdas de alimento para os animais, reduzindo a produção de leite e carne. Existe uma diversidade de espécies forrageiras com grande potencial produtivo e ampla adaptação térmica, que podem ser cultivadas em áreas de risco desse fenômeno. No entanto é necessário caracterizar a tolerância dessas espécies a baixas temperaturas e as regiões com condições climáticas adequadas. Os métodos de avaliação de danos por baixas temperaturas são predominantemente qualitativos, baseados em critérios visuais que têm o viés da subjetividade. Esta tese teve como objetivos determinar as temperaturas mínimas de início de danos para sete espécies forrageiras e efetuar o zoneamento de risco de geadas para o estado do Paraná. Foram incluídas no estudo as forrageiras: Alfafa (Medicago sativa), Sorgo (Sorghum bicolor), Aveia Preta (Avena strigosa), Brachiaria brizantha cv. Marandu, Milheto (Pennisetum glaucum), capim Mombaça (Panicum maximum) e Tifton 85 (Cynodon spp). As plantas foram conduzidas em vasos em casa de vegetação até 60 dias e submetidas a baixas temperaturas no interior de uma câmara de crescimento com condições de luminosidade e temperatura controladas, atingindo valores mínimos de 0,2 -0,9, -1,8, -2,7, -4,1, -4,6 e -6,2oC, durante uma hora. Foram realizadas avaliações quantitativas pós testes de fluorescência da clorofila, condutividade elétrica de solução embebida com discos de folhas e atividade das enzimas ascorbato peroxidase (APX), catalase (CAT) e superóxido dismutase (SOD), por meio de espectrofotometria. As espécies apresentaram respostas em função da temperatura, que possibilitaram diferenciar a tolerância e nível de dano de cada uma delas. Análises da anatomia foliar comprovaram os danos em função da tolerância de cada espécie. Com base nos resultados desses estudos, foram estabelecidos critérios baseados na temperatura crítica de cada espécie e realizado o zoneamento de risco de geadas no estado do Paraná. Os resultados apresentados nesta tese constituem uma inovação em termos de metodologias de análise de danos por baixas temperaturas em forrageiras.
The occurrence of frosts in the pastures causes loss of food for the animals, reducing the production of milk and meat. There is a diversity of forage species with great productive potential and wide thermal adaptation, which can be cultivated in areas at risk of this phenomenon. However, it is necessary to characterize the tolerance of these species at low temperatures and regions with adequate climatic conditions. The methods of evaluation of low temperature damages are predominantly qualitative, based on visual criteria that have the bias of subjectivity. This thesis had as objectives to determine the minimum temperatures of beginning of damages for seven forage species and to carry out the risk zoning of frosts to the state of Paraná. The forages studied were: alfalfa (Medicago sativa), sorghum (Sorghum bicolor), black Oat (Avena strigosa), Brachiaria brizantha cv. Marandu, millet (Pennisetum glaucum), Mombasa grass (Panicum maximum) and Tifton 85 (Cynodon spp). The plants were conducted in pots in a greenhouse up to 60 days and subjected to low temperatures inside a growth chamber with controlled light and temperature conditions, reaching the minimum temperatures of 0,2, -0,9 -1,8, -2,7, -4,1, -4,6 and -6,2°C for one hour. Quantitative evaluations were performed after tests, based on chlorophyll fluorescence, electric conductivity on leaf discs and activity of the enzymes ascorbate peroxidase (APX), catalase (CAT) and superoxide dismutase (SOD) by means of spectrophotometry. The species showed responses as a function of temperature, which made it possible to differentiate the tolerance and level of damage of each one of them. Leaf anatomy analysis allowed visualizing the damage as a function of the tolerance of each species. Based on the results of these studies, criteria based on the critical temperature of each species were established to perform the risk zoning of frosts in the state of Paraná. The results presented in this thesis are an innovation in terms of methodologies for the analysis of damages caused by low temperatures in forages.
The occurrence of frosts in the pastures causes loss of food for the animals, reducing the production of milk and meat. There is a diversity of forage species with great productive potential and wide thermal adaptation, which can be cultivated in areas at risk of this phenomenon. However, it is necessary to characterize the tolerance of these species at low temperatures and regions with adequate climatic conditions. The methods of evaluation of low temperature damages are predominantly qualitative, based on visual criteria that have the bias of subjectivity. This thesis had as objectives to determine the minimum temperatures of beginning of damages for seven forage species and to carry out the risk zoning of frosts to the state of Paraná. The forages studied were: alfalfa (Medicago sativa), sorghum (Sorghum bicolor), black Oat (Avena strigosa), Brachiaria brizantha cv. Marandu, millet (Pennisetum glaucum), Mombasa grass (Panicum maximum) and Tifton 85 (Cynodon spp). The plants were conducted in pots in a greenhouse up to 60 days and subjected to low temperatures inside a growth chamber with controlled light and temperature conditions, reaching the minimum temperatures of 0,2, -0,9 -1,8, -2,7, -4,1, -4,6 and -6,2°C for one hour. Quantitative evaluations were performed after tests, based on chlorophyll fluorescence, electric conductivity on leaf discs and activity of the enzymes ascorbate peroxidase (APX), catalase (CAT) and superoxide dismutase (SOD) by means of spectrophotometry. The species showed responses as a function of temperature, which made it possible to differentiate the tolerance and level of damage of each one of them. Leaf anatomy analysis allowed visualizing the damage as a function of the tolerance of each species. Based on the results of these studies, criteria based on the critical temperature of each species were established to perform the risk zoning of frosts in the state of Paraná. The results presented in this thesis are an innovation in terms of methodologies for the analysis of damages caused by low temperatures in forages.
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Palavras-chave
Risco climático, Pastagens, Geadas, Avaliação de danos, Fluorescência da clorofila, Condutividade elétrica, Ascorbato peroxidase (APX), Catalase (CAT), Superóxido dismutase (SOD), Sazonalidade, Pastures, Frost, Damage assessment, Fluorescence of chlorophyll, Electric conductivity, Climatic risk, Seazonality