Uso de imagens termais no monitoramento de condutância estomática, potencial hídrico foliar e disponibilidade de água no solo em mudas de eucalipto
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Data
2025-02-26
Autores
Oliveira, Lorena Lacerda de
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Universidade Federal do Espírito Santo
Resumo
Eucalyptus, widely cultivated in Brazil and globally to meet the demand of the pulp and paper industry, has been planted in regions with varying soil and climatic conditions. In areas with low and irregular rainfall, water scarcity may lead to stomatal closure, adversely affecting transpiration, gas exchange, photosynthesis, and consequently, plant development. The use of innovative technologies, such as thermographic imaging, has proven to be a promising tool for monitoring plant water stress. This study aimed to evaluate the potential use of thermographic images of eucalyptus leaves in determining stomatal conductance, leaf water potential, and soil water content under different atmospheric demand and soil water availability conditions.The experiment was conducted in an open area at the Laboratory of Meteorology and Forest Ecophysiology, Federal University of Espírito Santo, located in Jerônimo Monteiro, Espírito Santo, Brazil. Three field campaigns were carried out in April, May, and August 2024, with the aim of collecting data under varying atmospheric conditions, particularly solar radiation, temperature, and atmospheric vapor pressure deficit. Seedlings of the hybrid Eucalyptus urophylla × Eucalyptus grandis clone I144 were planted in 12-liter pots and grown for approximately 30 days, with irrigation initially maintained near 90% of the maximum soil water retention capacity (MWRC). During each campaign, once the plants reached approximately 0.5 m² of leaf area, irrigation was suspended for a subset of plants, and the following water supply levels were implemented: full irrigation, moderate water restriction, and severe water restriction. These levels were defined by maintaining the substrate at 90%, 60%, and 30% of the MWRC, respectively. Five replicates were adopted, totaling 15 plants per campaign. On the final day of each campaign, water consumption, gas exchange, stomatal conductance, leaf water potential, and leaf temperature were measured to characterize plant physiological responses. Additionally, throughout the campaigns, daily measurements were taken at 10 a.m. for soil water content, stomatal conductance, and leaf temperature, while predawn leaf water potential was measured to model the physiological variables and soil water content as a function of leaf temperature and the temperature difference between air and leaf . Data were subjected to analysis of variance, and when significant differences were found using the F-test at the 5% level, means were compared using Tukey's test at the same significance level. For modeling purposes, second-order polynomial models were fitted to describe the relationships among variables, and two regression algorithms were employed: Random Forest Regressor (RFR) and K-Nearest Neighbors Regressor (KNN). Model accuracy was assessed using the coefficient of determination (R²), standard error of estimate (SEE), and root mean square error (RMSE). The results demonstrated a significant impact of water restriction on the ecophysiology of eucalyptus by the end of the campaigns, with stomatal closure emerging as the primary control mechanism. Furthermore, thermographic imaging proved useful in determining leaf water potential, soil moisture content, and particularly stomatal conductance, highlighting its applicability in assessing plant water status
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Mudanças climáticas , Déficit hídrico , Eucalipto , Climate change , Water deficit , Eucalyptus