Estado hídrico de mudas de Eucalyptus urophylla na fase de rustificação identificado por meio de espectroscopia de infravermelho próximo e médio
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Data
2022-04-29
Autores
Manzato, Caroline Lourenço [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O Brasil se destaca no cenário mundial por possuir excelente desempenho no setor florestal, fruto das condições climáticas e da tecnologia desenvolvida pelas empresas e instituições de pesquisa do país. Porém, um plantio florestal de qualidade e que atenda e supra a demanda por seus serviços é necessário obter mudas de qualidade e bem desenvolvidas. A obtenção de mudas com qualidade é possível, devido principalmente aos manejos hídrico e nutricional adotados nos viveiros florestais. Visando aumentar a produtividade no campo, é necessário fornecer às plantas condições nutricionais e hídricas ainda na fase de mudas, para que ao serem plantadas a campo obtenham maior êxito. Para tornar essas condições favoráveis às mudas, os viveiros florestais adotam medidas visando melhorar a taxa de sobrevivência das plantas após o plantio em campo. Essa prática é conhecida como rustificação, onde as mudas são preparadas para se aclimatarem as condições desfavoráveis de campo, com o intuito de se obter melhor desenvolvimento e sobrevivência. Entretanto, no processo de irrigação há um alto consumo de água, por isso é de extrema importância um manejo hídrico mais adequado na produção de mudas florestais que supra a demanda hídrica das plantas sem comprometer sua qualidade e produtividade, aliado ao consumo consciente, para que esse recurso natural vital a qualquer tipo de vida (humana, animal e vegetal) no planeta, seja conservado e não falte em quantidade e qualidade. As técnicas de sensoriamento remoto, como a espectrorradiometria são capazes de fornecer informações sobre as plantas a nível celular por meio da reflectância foliar espectral. O presente trabalho teve por objetivos avaliar os efeitos de diferentes níveis de estresse hídrico no processo de rustificação de mudas de Eucalyptus urophylla sobre as variáveis fisiológicas e morfológicas e avaliar por meio do espectrorradiômetro as mudanças no comportamento da reflectância espectral foliar das mudas de eucalipto. Ao analisar os gráficos da curva média de reflectância espectral com as variáveis fisiológicas das mudas de eucalipto submetidas aos diferentes tratamentos, foi possível identificar aos 7 dias, que a curva média da reflectância das mudas submetidas ao tratamento T4 (irrigação uma vez ao dia, a cada dois dias) apresentou os maiores valores de reflectância nas regiões espectrais do infravermelho próximo (970nm e 1190nm) e médio (1450nm) se comparado com os demais tratamentos. Esses resultados indicam, que as mudas do tratamento T4 foram submetidas às menores quantidades de água. As variáveis fisiológicas que apresentaram comportamento semelhante ao da reflectância foliar foram assimilação de carbono (A), transpiração (E) e eficiência no uso da Rubisco (A/Ci), onde as mudas submetidas ao mesmo tratamento (T4) apresentaram aos 7 dias, os menores valores médios dessas variáveis, diferindo estatisticamente entre os demais tratamentos pelo teste de Tukey-Kramer (p<0,05). Ou seja, as mudas submetidas a menor disponibilidade hídrica apresentaram os maiores valores médios da reflectância foliar, devido à baixa absorção da radiação eletromagnética pela água presente nos tecidos celulares das mudas, e consequentemente, os menores valores médios das variáveis fisiológicas assimilação de CO2 (A), transpiração (E), eficiência no uso da água (EUA) e eficiência no uso da Rubisco (A/Ci).
Brazil stands out on the world stage for having excellent performance in the forestry sector, as a result of climatic conditions and technology developed by companies and research institutions in the country. However, a quality forest planting that meets and supplies the demand for its services is necessary to obtain quality seedlings, well developed and this is only possible through the irrigation process. Aiming to increase productivity in the field, it is necessary to provide the plants with nutritional and water conditions still in the seedling stage (GOMES et al., 2002), so that when planted in a field, they can achieve greater success. To make these conditions favorable to the seedlings, the forest nurseries adopt to improve the rate of plant areas after planting in the field, this practice is known as rustification, where the seedlings are prepared to adapt to unfavorable field conditions, in order to obtain the best development and technologies. However, in the irrigation process there is a high consumption of water, so it is extremely important to have more adequate water management in the production of forest seedlings that meet the water demand of the plants without compromising their quality and productivity, combined with conscious consumption, so that this natural resource vital to any type of life (human, animal and plant) on the planet, be conserved and do not lack in quantity and quality. Remote sensing techniques such as spectroradiometrics are able to provide information about plants at the cellular level through spectral leaf reflectance. The present work aimed to evaluate the effects of different levels of water stress in the rustification process of Eucalyptus urophylla seedlings on physiological and morphological variables and to evaluate through a spectroradiometer the changes in the behavior of the leaf spectral reflectance of eucalyptus seedlings. By analyzing the graphs of the average spectral reflectance curve with the physiological variables of eucalyptus seedlings subjected to different treatments, it was possible to identify at 7 days that the average reflectance curve of seedlings submitted to treatment T4 (irrigation once a day, the every two days) showed the highest reflectance values in the near (970 and 1190 nm) and medium (1450 nm) infrared spectral regions compared to the other treatments. These results indicate that the T4 treatment seedlings were subjected to the smallest amounts of water. The physiological variables that showed behavior similar to leaf reflectance were carbon assimilation (A), transpiration (E) and efficiency in the use of Rubisco (A/Ci), where seedlings submitted to the same treatment (T4) showed at 7 days, the lowest mean values of these variables, differing statistically between the other treatments by the Tukey-Kramer test (p<0.05). That is, seedlings subjected to lower water availability had the highest mean values of leaf reflectance, due to the low absorption of electromagnetic radiation by the water present in the cellular tissues of the seedlings, and consequently, the lowest mean values of the physiological variables CO2 assimilation (A), transpiration (E), water use efficiency (USA) and Rubisco use efficiency (A/Ci).
Brazil stands out on the world stage for having excellent performance in the forestry sector, as a result of climatic conditions and technology developed by companies and research institutions in the country. However, a quality forest planting that meets and supplies the demand for its services is necessary to obtain quality seedlings, well developed and this is only possible through the irrigation process. Aiming to increase productivity in the field, it is necessary to provide the plants with nutritional and water conditions still in the seedling stage (GOMES et al., 2002), so that when planted in a field, they can achieve greater success. To make these conditions favorable to the seedlings, the forest nurseries adopt to improve the rate of plant areas after planting in the field, this practice is known as rustification, where the seedlings are prepared to adapt to unfavorable field conditions, in order to obtain the best development and technologies. However, in the irrigation process there is a high consumption of water, so it is extremely important to have more adequate water management in the production of forest seedlings that meet the water demand of the plants without compromising their quality and productivity, combined with conscious consumption, so that this natural resource vital to any type of life (human, animal and plant) on the planet, be conserved and do not lack in quantity and quality. Remote sensing techniques such as spectroradiometrics are able to provide information about plants at the cellular level through spectral leaf reflectance. The present work aimed to evaluate the effects of different levels of water stress in the rustification process of Eucalyptus urophylla seedlings on physiological and morphological variables and to evaluate through a spectroradiometer the changes in the behavior of the leaf spectral reflectance of eucalyptus seedlings. By analyzing the graphs of the average spectral reflectance curve with the physiological variables of eucalyptus seedlings subjected to different treatments, it was possible to identify at 7 days that the average reflectance curve of seedlings submitted to treatment T4 (irrigation once a day, the every two days) showed the highest reflectance values in the near (970 and 1190 nm) and medium (1450 nm) infrared spectral regions compared to the other treatments. These results indicate that the T4 treatment seedlings were subjected to the smallest amounts of water. The physiological variables that showed behavior similar to leaf reflectance were carbon assimilation (A), transpiration (E) and efficiency in the use of Rubisco (A/Ci), where seedlings submitted to the same treatment (T4) showed at 7 days, the lowest mean values of these variables, differing statistically between the other treatments by the Tukey-Kramer test (p<0.05). That is, seedlings subjected to lower water availability had the highest mean values of leaf reflectance, due to the low absorption of electromagnetic radiation by the water present in the cellular tissues of the seedlings, and consequently, the lowest mean values of the physiological variables CO2 assimilation (A), transpiration (E), water use efficiency (USA) and Rubisco use efficiency (A/Ci).
Descrição
Palavras-chave
manejo hídrico, viveiros florestais, estresse hídrico, reflectância foliar, NIRS, water management, forest nurseries, hydrical stress, leaf reflectance