Psidium guajava 'Paluma' (the guava plant) as a new bio-indicator of ozone in the tropics

Psidium guajava 'Paluma' saplings were exposed to carbon filtered air (CF), ambient non-filtered air (NF), and ambient non-filtered air +40 ppb ozone (NF + O-3) 8 h per day during two months. The AOT40 values at the end of the experiment were 48, 910 and 12 895 ppb h(-1), respectively for the three treatments. After 5 days of exposure (AOT40 = 1497 ppb h(-1)), interveinal red stippling appeared in plants in the NF + O-3 chamber. In the NF chamber, symptoms were observed only after 40 days of exposure (AOT40 = 880 ppb h-1). After 60 days, injured leaves per plant corresponded to 86% in NF + O-3 and 25% in the NF treatment, and the average leaf area injured was 45% in NF + O-3 and 5% in the NF treatment. The extent of leaf area injured (leaf injury index) was explained mainly by the accumulated exposure of ozone (r(2) = 0.91; p < 0.05). (C) 2006 Elsevier Ltd. All rights reserved.