Effect of fungal infection on leaf gas-exchange and chlorophyll fluorescence in Quercus ilex

Experiments were conducted to study the susceptibility to infection by two fungal pathogens, Cryphonectria parasitica or Phomopsis spp. of undisturbed holm oaks (Quercus ilex) and the resprout from the stump of trees after ex cision of the shoot. Leaf gas-exchange and chlorophyll a fluorescence were recorded on plants growing in natural conditions for two years, as markers of disease progress at the first stages of infection. In infected plants, p athogen-induced stomatal closure limited photosynthesis and increased contr ibution of energy dissipating processes protecting PSII integrity, as shown by higher non-photochemical quenching (NPQ). Excision treatment reduced su sceptibility to infection and favoured water availability in resprouts, whi ch showed higher gas-exchange rates.