Assessment of salt tolerance in Populus alba clones using chlorophyll fluorescence

Cuttings of five Populus alba clones (S18 F1-26, Al29 F8-35, J3 F1-4, GU1 F16-36, PO9 F21-88), Populus euphratica, and Populus×euramericana (I-214) were submitted during 45 d to regular watering with NaCl solutions of electrical conductivity of 7 and 14 dS m⁻¹. Chlorophyll a fluorescence in response to the salinity stress was assessed, using F₀ and F_v/F_m. Differences in reaction to the salt were found in P. alba clones, F₀ and F_v/F_m being the fluorescence parameters used to check out this stress. Minimal constant fluorescence of dark-adapted plants (F₀) showed a better correlation with the disease index exhibited by plants and also with salinity dose than the parameter F_v/F_m. Some of the P. alba clones showed the same behaviour, assessed through fluorescence parameters, as P. euphratica, which was previously defined as salt tolerant, while the rest exhibited the same characteristics as I-214, which was very sensitive.