Response of the Tropical Tree Species Astronium graveolens to Meteorological Conditions and Ground-Level Ozone in São Paulo, Brazil

Astronium graveolens is a native tree species from Atlantic Forest considered sensitive to O 3 . This study aimed to determine which environmental factors, including air quality and meteorological conditions, have the most significant influence on gas exchange and the appearance of visible foliar symptoms in this species. Saplings were potted and exposed in a standardized manner in an open area in the southeastern city of São Paulo, Brazil. Gas exchange was measured weekly in the morning (9 am to 10 am), midday (11 am to 12 pm), and afternoon (2 pm to 3 pm) during the spring and summer seasons ( n = 10). Data on O 3 concentration and meteorological conditions were obtained on-site. Principal component analysis identified that the morning hours provide the most favorable meteorological conditions for gas exchange. High temperature and VPD reduced gas exchange in the midday and afternoon. Although the AOT40 was high, there were no visible foliar symptoms, which was an unexpected result. We propose that the meteorological conditions, mainly the VPD and temperature, caused stomatal closure, and consequently prevented the absorption of O 3 ; therefore, there was no association between O 3 and reduction of gas exchange, nor manifestation of foliar visible symptoms. We consider that more studies are necessary for the proper use of A. graveolens as an O 3 bioindicator species.