Ozone-induced stomatal sluggishness develops progressively in Siebold's beech (Fagus crenata)

We investigated the effects of ozone and leaf senescence on steady-state stomatal conductance and stomatal response to light variation. Measurements were carried out in a free-air ozone exposure experiment on a representative deciduous broadleaved tree species in Japan (Fagus crenata). Both steady-state and dynamic stomatal response to light variation varied intrinsically with season due to leaf senescence. Ozone induced the decrease in steady-state leaf gas exchange and the sluggish stomatal closure progressively. These findings suggest that ozone reduces the ability of plants to adapt to a fluctuating light environment under natural conditions, and therefore impairs plant growth and ability to control water loss.

► We investigated the effects of ozone and leaf senescence on stomatal response to light variation.
► Measurements were carried out in a free-air ozone exposure experiment on Siebold's beech.
► Stomatal response to light variation varied intrinsically with season due to leaf senescence.
►  Steady-state stomatal conductance was reduced under elevated ozone.
► Ozone increased time for stomatal closing and reduced light-saturated photosynthesis progressively.