Derivation of ozone flux-yield relationships for lettuce: A key horticultural crop

Ozone flux-response relationships were derived for lettuce, employing a multiplicative approach to model the manner in which stomatal conductance is influenced by key environmental variables, using a dataset collected during field experimentation in Crete and yield-response relationships derived from parallel open-top chamber experiments. Regional agronomic practices were adopted throughout. Computed versus measured data revealed that the derived model explained 51% (P < 0.001) of the observed variation in stomatal conductance. Concentration-based indices were compared with flux-based indices. Analyses revealed a significant relationship between accumulated stomatal ozone flux and yield employing flux threshold cut-offs up to 4 nmol m−2 s−1. Regressions employing very low or zero flux thresholds resulted in the strongest yield-flux relationships (explaining ≈80% (P < 0.05) of the variation in the dataset).