TOLERANCE TO SODIUM CHLORURE AND NA K SEL ECTIVITY IN 3 PROVENANCES OF MARITIME PINE (PINUS-PINASTER AIT)/

Because of a maritime pine forest dieback on the west coast of France, 3 geographic provenances were tested for their tolerance to sodium ch lorure and for their Na/K selectivity. Young seedlings (I month old) w ere cultivated on aerated nutrient solution containing NaCl (0 to 150 mM/l). After 10 days of treatment, the 3 provenances differed in their sensibility to salinity, and the observed classification was found to be identical to the behavior of the frees in forest: this result supp orts the hypothesis of sodium as one of the factors responsible for th e dieback. For these young plants, tolerance to Na was essentially due to a higher selectivity for K over Na, so that growth was maintained. A greater production of biomass would also allow these genotypes to d elay the toxic effects of Na, by dilution of this cation. These physio logical mechanisms, noted at an early growth stage, are to be confirme d on older plants.