Effects of simulated acid rain on the growth of five Brazilian tree species and anatomy of the most sensitive species (Joannesia princeps)

Seedlings and young saplings of some woody species were exposed to simulated low-pH acid rain, in order to develop a response screening for tropical tree species by determination of the symptoms of foliar injury and growth responses, as well as to identify anatomical alterations in the leaf blade of the most sensitive species. Gallesia integrifolia (Spreng.) Harms, Genipa americana L., Joannesia princeps Vell., Mimosa artemisiana Heringer & Paula and Spondias dulcis Forst.f. were exposed daily to 20 min of acid rain, pH 3.0, for 10 consecutive days. The degree of leaf damage and the anatomical alterations observed were efficient parameters to determine the sensitivity to acid rain. At the end of the experiment J. princeps was the most sensitive species as determined by foliar injury and seedling growth. The degree of leaf damage was similar among the seedlings, except in S. dulcis, which showed reduced percentage of foliar injury. Necrotic and chlorotic spots on the leaf blade occurred. In the most sensitive species, J. princeps, necrotic blade tissues showed accumulation of phenolic compounds, hypertrophy and collapsed cells. Most of the structural alterations were observed in the adaxial epidermis, the palisade parenchyma and spongy parenchyma and the abaxial epidermis. Long-term experiments with seedlings of S. dulcis and saplings of G. integrifolia are suggested, to characterise the response of these species that presented fewer symptoms but whose growth was affected under acid rain.