Ecophysiological aspects of Eucalyptus saligna seedlings subjected to a heat wave associated with water restriction


Publication date: 31/10/2023

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Summary: Climate change can make eucalyptus clones unsuitable for cultivation due to changes in temperature and precipitation. Among the eucalyptus species, Eucalyptus saligna stands out, the species most planted in the southern region of the country. In this context, the objective was to evaluate the ecophysiological responses of young E. saligna plants subjected to the effects of heat waves and different levels of water deficit in the soil. The experiment was carried out in greenhouses with controlled temperature and relative humidity, at the Laboratory of Meteorology and Forest Ecophysiology, belonging to the Federal University of Espírito, in Jerônimo Monteiro - ES. 24 seedlings were transplanted into 12 liter pots, filled with substrate. Initially, the seedlings were grown for 48 days at a maximum temperature (Tmax) of 32ºC, with daily replacement at the level of 90% of the maximum water retention capacity (WRC). Sequentially, two associated heat wave days were simulated in seedlings at three soil water levels. The experimental design consisted of a completely randomized design in a 2 x 3 factorial scheme, with six treatments: normal temperature condition (Tmax = 32°C) and heat wave (Tmax = 43ºC), combined with three levels of water in the soil: restriction severe water (35% of WRC), intermediate (62% of WRC) and absent (90% of WRC). They were adopted with four replications, where each repetition represents one plant, totaling 24 plants. Water restriction was induced gradually, starting the cut at the lowest target WRC, followed by the intermediate level and upon reaching the desired levels, temperature treatments were applied, with subsequent recovery to normal temperature conditions. Analyzes of water consumption, height, diameter, gas exchange, water status, water stress index, number of leaves, leaf area, dry mass of the shoot and root were carried out. The data were subjected to the normality assumption verification test (Shapiro – Wilk), analysis of variance. When verifying significant differences, F test at 5%, the means were compared using the Tukey test at 5%. The results showed that water consumption is directly affected by the severe level of water restriction, with no full recovery even after maximum water availability in the soil. The reduction in photosynthetic rate and stomatal conductance combined with increased transpiration are quick responses to conditions of low soil water availability and the occurrence of heat waves. The species of Eucalyptus saligna studied proved to be resistant to heat waves when it does not suffer from water deficit. The heat wave intensified the impact of water restrictions.

Keywords: Climate changes, Water déficit, Heat wave, Eucalipto.

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