Fig. 7
From: Macro- and microscopic leaf injury triggered by ozone stress in beech foliage (Fagus sylvatica L.)
Conceptual model of O3 injury variation by the end of vegetation season and in relation to O3 uptake. The spectrum of visible symptoms and microscopic markers of O3 stress late in the vegetation season depends on the yearly O3 uptake (each grey line). Degenerative or disruptive microscopic injury appears at lower O3 dose than the overlying visible symptoms. The term discoloration indicates a change in foliage hue or colour (e.g. photobleaching or bronzing, reddening) as a consequence of chlorophyll degradation or accumulation of compounds from the secondary metabolism. The induction of cellular responses (ACS, HR-like) depends on the species-specific exceedance of O3 uptake threshold, tending to more variable values later in the vegetation season as a consequence of varying foliage phenology. Application range: broadleaved trees and shrubs in temperate and tropical biomes