Ozone effects in coffee (Coffea arabica L.) plants: Cultivar-specific responses and risk assessment

Abstract

The environmental sustainability of agricultural production faces critical challenges due to climate change, with tropospheric ozone (O₃) being a significant concern. This study investigates the dose-response (DR) relationship between O₃ exposure and leaf biomass (LB, as a proxy of coffee production) reduction in three coffee cultivars (Coffea arabica L. cv. Geisha, IAC99, and IAC62) using both exposure- (AOT40) and flux-based (POD_Y) indices. Experiments were conducted in a Free-Air Controlled Exposure (FACE), where plants were exposed to ambient air (AA), 1.5 × AA, and 2.0 × AA O₃ levels. The study reports the O₃ visible foliar injury (O₃_VFI) on C. arabica leaves for the first time. It also reveals that O₃ significantly reduced total LB in the Geisha and IAC62 cultivars compared to the less affected IAC99. The stomatal conductance model was parametrized to estimate stomatal O₃ uptake and understand each cultivar's physiological response to O₃ stress. The Geisha and IAC62 cultivars exhibited higher stomatal O₃ uptake due to relatively high maximum stomatal conductance (g_max) values compared to IAC99, leading to greater biomass loss under elevated O₃ conditions. The DR analysis identified POD_1.5 as the most appropriate index for assessing critical O₃ levels (CLs) for LB losses. Linear regression was suitable for representing the DR relationships, and the O₃ CL for a 4 % and 10 % LB reduction was estimated at 0.29 and 0.73 mmol m⁻² POD_1.5, respectively. These findings underscore the necessity of cultivar-specific studies for accurate O₃ risk assessment and management in coffee production.