No abstract

The Brazilian native tree species Astronium graveolens was indicated as sensitive to ozone in a fumigation experiment. Thus, the objective of this study was to evaluate how sensitive A. graveolens is to ozone under realistic conditions in the field. Eighteen saplings were exposed to ozone in a contaminated area and in a greenhouse with filtered air during two exposure periods of approximately 63 days each (March-May 2012 and September-October 2012). Leaf injury was analyzed by means of its incidence and severity, the leaf injury index (LII) and the progression of leaf abscission. These variables were monitored weekly, whereas growth and lipid peroxidation were monitored monthly. Plants exposed to ozone showed significant growth decrease and visible leaf injury increase, but lipid peroxidation and leaf abscission remained unchanged. These results indicated that plants subjected to ozone possibly diverted energy from growth to the production of antioxidants necessary to cope with ozone-induced oxidative stress.

-(Gas exchange and visible leaf injuries in saplings of Astronium graveolens Jacq. fumigated with ozone). Astronium graveolens Jacq. is a tree species of large occurrence in the Atlantic and the semideciduous forests. As ozone (O 3 ) concentrations in São Paulo State are phytotoxic, it was decided to determine some physiological and biochemical responses of this species to O 3 due to its importance in reclamation programs. Saplings were kept in two closed chambers: filtered air (FA) and filtered air enriched with O 3 (AF + O 3 , 100 ppb, 4 h day -1 , 7 days, n = 9). Leaf injury was assessed daily and at the end of the fumigation, carbon assimilation (A), stomatal conductance (gs), evapotranspiration (E), internal CO 2 concentration (Ci), maximum carbon assimilation (Amax), lipid peroxidation (LP), and relative permeability of electrolytes (RPE) were established. O 3 induced the appearance of leaf injuries and reduced A, gs, E, and Amax and did not change Ci, LP, and RPE. The species is moderately sensitive to O3. Long-term experiments should be conducted to verify if gas exchange reduction may adversely affect growth and hence affecting its use in reforestation programs. Keywords: Air pollution, tropical tree species, tropospheric ozone RESUMO -(Trocas gasosas e injúrias foliares visíveis em plantas jovens de Astronium graveolens Jacq. fumigadas com ozônio). Astronium graveolens Jacq. é uma espécie arbórea de grande ocorrência na floresta atlântica de encosta e do interior do Estado de São Paulo. Como as concentrações de ozônio (O 3 ) no Estado de São Paulo são fitotóxicas, decidiu-se avaliar algumas respostas fisiológicas e bioquímicas da espécie ao O 3 devido sua importância em programas de recuperação de áreas degradadas. Plantas jovens foram mantidas em câmaras fechadas, uma com ar filtrado (AF) e outra com ar filtrado enriquecido com O 3 (AF + O 3 , 100 ppb, 4 h dia -1 , 7 dias, n = 9). As injúrias foliares foram avaliadas diariamente e ao final da fumigação foram determinadas a assimilação de carbono (A), condutância estomática (gs), transpiração (E), concentração interna de CO2 (Ci), assimilação máxima de carbono (Amax), peroxidação de lipídios (PL) e permeabilidade relativa de eletrólitos (PRE). O O 3 induziu o surgimento de injúrias foliares e reduziu A, gs, E e Amax, porém não alterou Ci, PL e PRE. A espécie é medianamente sensível ao O3. Experimentos de longa duração devem ser realizados para verificar se a redução nas trocas gasosas pode prejudicar o crescimento a ponto de reduzir sua aplicação em programas de reflorestamento. Palavras-chave: espécies arbóreas tropicais, ozônio troposférico, poluição do ar 1. Instituto de Botânica, Núcleo de Pesquisa em Ecologia, Avenida Miguel Stéfano, 3.687, 04301-902 São Paulo, SP, Brasil 2. Autor para correspondência: regmorae@yahoo.com.br IntroduçãoA atividade antrópica introduz na atmosfera diferentes gases e partículas que modificam as proporções de seus compostos naturais, alterando suas características e comprometendo suas propriedades e funções. As...