Differential physiological and genetic responses of five European Scots pine provenances to induced water stress.

Pinus sylvestris L. (Scots pine) is the conifer with widest natural distribution area. Portugal constitutes its westernmost limit of distribution. Most of the Portuguese populations were planted but two autochthonous populations were recently ascribed to 'Serra do Gerês' (NW Portugal), and seem to be well adapted to the temperate climate. However, the ongoing climate changes may compromise their survival. With this study we intend to evaluate the anatomic-physiological and genetic responses of Scots pine from five European provenances ('Gerês', 'Puebla de Lillo', 'Montes Universales', Germany and Sweden) to three water availability regimes, in order to determine which one(s) present higher resistance to drought. Individuals from 'Gerês' presented the highest stability in photosynthetic reactions as well as the better photochemical and metabolic behaviours under drought (T3). Hence, the relative expression ratio of three water stress-responsive genes during drought was lower and gradual in 'Gerês', compared to all other provenances, followed by Germany. The results achieved in 'Gerês' and Germany provenances are very interesting since they reflected that the native populations of 'Gerês' along with the Portuguese Scots pine planted populations with a probable German provenance, have ability and high adaptive potential to respond to situations of water deficit. Moreover, the present genetic and physiological data demonstrated the urgent demand for the conservation of Portuguese Scots pine genetic resources as well as its use in plantation/afforestation of areas where the warming and drought has been affecting the survival of this species.