Describing and modelling ozone-dependent variation in flavonoid content of bean (Phaseolus vulgaris cv. Bergamo) leaves: a particular dose–response relationship analysis

Abstract

We investigated the ozone-dependent variation in the amount of a flavonoid accumulated by bean leaves (Phaseolus vulgaris L. cv. Bergamo). The phenolic response was modelled with special regard to different ozone exposure indexes. Using open-top chamber technology, six atmospheres of increasing ozone concentration were tested. Four successive harvests were carried out during a 33-d experiment. Primary and first trifoliate leaves were collected. Visible foliar injuries were recorded and the quantification of an ozone-responsive flavonoid was achieved by HPLC. Ozone significantly increased the amount of kaempferol glucuronide, which normally decreased with leaf ageing. Depending on the leaf type, this increase occurred either before or after the appearance of visible foliar damage. A linear regression could account for the ozone dose–phenolic response relationship. However, with respect to leaf type, the agreement between the model and observed values was influenced by the way in which ozone dose was calculated. Among the ozone exposure indexes tested, only the index with the highest threshold (AOT60) was appropriate to make the phenolic response linear in the case of primary leaves while in the case of first trifoliate leaves, this index always displayed the poorest adjustment compared with SUM00, SUM60, and AOT40 indexes. The study of the relationship suggests that sensitivity to ozone could be dependent on leaf type.