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It is known that the coffee (Coffea arabica L.) plant which is originally from shade habitats would have a limited ability to grow under full sun. Previous work has shown that nitrogen fertilisation can reduce the leaf damage when the plants are exposed to high light intensities during several days. In the present work we aimed to study the effects of the high irradiance during the first hours and evaluate the positive contribution of nitrogen fertilisation in the case of short‐term exposure to strong light. Young plants (1.5–2 years old) grown in 1.5 kg of a mixed soil were supplemented with a nutrient solution containing 15 mM nitrogen in the form of NH4NO3, every 7 days (2N treatment), 15 days (1N treatment) and 45 days (0N treatment). Top mature leaves were exposed to a photosynthetic photon flux density of 1 500 μmol m−2 s−1 for a maximal period of 8 h, and changes in photosynthesis and pigment composition were monitored along the period of high light exposure. Photosynthetic capacity, leaf conductance to water vapour, electron transport capacity and maximum carboxylation activity, as well as some leaf fluorescence parameters (minimal fluorescence, photochemical efficiency of PSII and quantum yield of photosynthetic electron transport) were reduced by the stress, with a generally stronger impact observed in the 0N plants. The photochemical quenching was affected only in the 0N plants, while the non‐photochemical quenching increased in 2N plants but decreased in the 0N ones. The results showed that 2N plants presented a better initial status of the photosynthetic parameters and of the content of photoprotective pigments. Those plants showed ability to trigger some protective mechanisms, as observed by the tendency to increase the xanthophyll pool content, specially in zeaxanthin and in non‐photochemical quenching. Also, protein content presented a tendency to increase after 1.5 h, which was maintained until the end of the high light period. We conclude that nitrogen availability is a key factor in the acclimation process to high light.

Young coffee plants (Coffea arabica L. cv. Catuaí), originally from a shaded habitat, were separated in three groups to be grown under different levels of N fertilization: 0.3 mmol N supplements were given to the soil every 7 days (high N treatment, 2N), every 15 days (medium N treatment, 1N) and every 45 days (low N treatment, 0N). These plants were later exposed to a high sunlight irradiance (noon PPFD up to 1500 µmol m–2 s–1 ) for a period of 12 or 15 days. Among others, the values of electron trans-port capacity, maximum carboxylation activity, photosynthetic capacity (Amax) and several fluorescence parameters (Fv/Fm, Fv´/Fm´, qP, &phis;e) first showed a reduction (until the 4th–7th day) in all N treatments, followed by an N-dependent recovery. The 2N plants were less affected in the first few days and, at the end of the stress period, showed a better recovery for most of the studied parameters and the highest increase in the saturating PPFD for net photosynthesis and A max . The present work shows that the ability to acclimate displayed by the mature leaves of 2N plants was accompanied by an increase in energy dis-sipation mechanisms. These include an increase in the ‘high energy’ quenching and, mostly, the presence of higher contents of some xanthophylls (zeaxanthin and lutein) and carotenes, which helped to decrease the energetic overcharge in the photosystems. Pigment changes in mature leaves suggest that N can promote specific mechanisms of acclimation others than those that might be expected from a preferential partition of the element N into photosynthetic components.

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