PHYSIOLOGICAL RESPONSES OF Bauhinia purpurea L. TO HEAT STRESS IN THE CONTEXT OF CLIMATE CHANGE
2025
Meloni, Diego Ariel | Lescano, Julia Andrea | Bezerra da Silva, José Aliçandro
The response of trees to heat waves is uncertain, although crucial in forest and urban ecosystems. Bauhinia purpurea is a multipurpose woody species, and its tolerance to heat stress is unknown. The aim of this study was to determine the effect of heat stress on photosynthesis, reactive oxygen species (ROS) production and antioxidant enzyme activity in B. purpurea. One-year-old seedlings were placed in a growth chamber at 27°C/27°C, 38°C/27°C or 43°C/27°C, day and night, respectively, for seven days. At the end of the trial, measurements of gas exchange, chlorophyll a fluorescence emission, and biochemical variables of oxidative stress were determined. A completely randomized experimental design with 10 replicates was used, and results were analyzed with ANOVA and Tukey's test. Heat stress inhibited net photosynthesis, but did not affect internal CO2 concentration. It altered variables of chlorophyll a fluorescence emission, with a decrease in the rate of electron transport and photochemical quenching. Heat stress produced a low response in antioxidant enzymes, increasing malondialdehyde production and electrolyte loss. It is concluded that heat stress produces a non-stomatic inhibition of CO2 fixation by inhibiting the photochemical stage of photosynthesis. Regimes of 43°C/27°C also produce photoinhibition and compromise light absorption. The species has an inefficient antioxidant enzyme response, resulting in oxidative stress and damage to cell membranes.
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