Anthocyanins and tannins: is the urban air pollution an elicitor factor?

(Anthocyanins and tannins: is the urban air pollution an elicitor factor?) In order to survive in highly adverse conditions, plants have evolved a genetic capacity for compensating drastic environmental changes, by producing antioxidants that neutralize the effects of stress, such as those caused by oxidant pollutants. One example is Psidium guajava cv. Paluma (guava), which is described as an efficient bio-indicator of tropospheric ozone, by displaying typical foliar injury, characterized by reddening on the adaxial surface. The aim of this study was to investigate alterations in phenolic compounds content (anthocyanins and tannins) in P. guajava on a field condition of atmospheric pollutants at São Paulo city. Four field exposure assays were performed to investigate the alterations on phenolic contents under pollution stress and under seasonal variations. Principal components and regression analysis indicated that the concentrations of ozone and phenolic compounds accumulation can be highly correlated. Accumulated precipitation during the field exposures showed significant correlations with tannin contents. Contents of foliar proanthocyanidins were correlated to precipitation, global solar radiation, and leaf injury. On a field condition, many factors can elicit response on phenolic contents, e.g., presence of other pollutants, climatic conditions, and biotic factors. Urban air pollution seems to be an elicitor factor to the production of phenolic compounds on P. guajava, specially anthocyanins and tannins, but the weather conditions are crucial to determine this pollution influence.