Response of Survival,Growth and Some Morpho-Physiological and Biochimical Characteristics of Populus caspica Bornm. Seedling to Salinity

Salinity is an important abiotic stress affecting the seedling growth in saline soils. In this research,Populus caspica Bornm. potted seedlings were examined under control environment in five salinity levels (0, 5, 100, 150, and 200 mM NaCl) as RCBD with three replicates for 45 days.  The results showed salinity significantly reduced the survival rate, stem growth, collar diameter growth, leaf number, root length, total biomass, net photosynthesis, photosystem II photochemical, leaf water potential and enhanced free proline content. In 100 mM salinity, 74 percent of seedlings survived while they increased the stem growth by 40 mm. In 50 mM salinity, even though collar diameter growth and stem growth decreased a little (0.6 mm and 0.8 cm, respectively) but survival rate was still 100 percent. In general, the tolerance threshold for salinity of P. caspica seedlings, from viewpoint of survival, can be estimated to be 50 mM. This implies that in coastal areas and/or deforested lowland sites of northern Iran where the soil salinity is < 50 mM, plantation of P. caspica can be employed. Further studies in longer periods will raise the strength and accuracy of this statement.