Effects of drought on photoprotective mechanisms in European beech (Fagus sylvatica L.) seedlings from different provenances

The effects of drought on photoprotection mechanisms of three beech provenances from three contrasting climatic origins have been studied. Morphology differed among provenances, with a lower leaf area/fine roots ratio in the xeric populations (Moncayo). This characteristic allowed this provenance to respond later than the others to a drought-stress treatment. However, in desiccating leaves the stability of PSII was higher in the plants from the stressful climate of the Pyrenees (Belagoa). Drought resulted in a reduction in pigment content (except in Belagoa) with simultaneous increases in antheraxanthin, zeaxanthin and tocopherol pools. These molecules play an important photoprotective role and reached similar values in stressed leaves from the three provenances. These antioxidants also protected the leaves from paraquat-induced oxidation. It is concluded that drought tolerance in the studied xeric ecotype is based to a greater extent on morphological characteristics than on a better photoprotective system.