Meteorological conditions, ozone concentration and leaf age affect gas exchange in Psidium guajava ‛Palumaʼ

ABSTRACT This study aimed to investigate the importance of leaf age, meteorological conditions and ozone concentration (O3) on gas exchange of Psidium guajava ‛Paluma'. Saplings were grown and exposed in standard conditions in the city of São Paulo, in six periods of three months with weekly measurements in young and mature leaves. Gas exchanges were higher in young leaves for almost the entire experiment. Mature leaves showed greater reduction in gas exchange. The multivariate analysis of biotic and abiotic variables indicated that vapor pressure deficit (VPD), O3 concentration and radiation were the main variables associated with gas exchange decrease in young leaves. In mature leaves the influence of VPD is lower, but the temperature importance is higher. Moreover, the opposition between assimilation and O3 is more evident in mature leaves, indicating their greater sensitivity to O3.