Effect of soil salinity on morphology and gas exchange of two Paulownia hybrids

A pot experiment was carried out to investigate the effect of salinity on growth, leaf anatomy and gas exchange characteristics in two Paulownia hybrid lines ( Paulownia tomentosa × fortunei -TF and Paulownia elongata × elongata -T4). The distribution of Mg, Ca, Na, K and Fe between water available fractions from non-saline, saline soils, and different organs showed acropetal concentration gradient for metal accumulation, excepting Ca. Selective uptake of K over Na was enhanced slightly with increasing salinity, where K/Na ratio was reduced in Paulownia elongata × elongata -T4 and rose in Paulownia tomentosa × fortunei -TF. The reduction in the total plant leaf area and in the values of the intrinsic components of photosynthesis-maximal Rubisco catalyzed carboxylation velocity, maximal electron transport rate and triose phosphate utilization rate was observed only in Paulownia tomentosa × fortunei -TF. The CO 2 compensation point rose to Paulownia tomentosa × fortunei -TF and declined in Paulownia elongata × elongata -T4, while the stomatal factor values were enhanced in both hybrid lines. Under saline conditions, the stomatal component was more limiting to photosynthesis than its biochemical components. It was concluded that Paulownia elongata × elongata -T4 was more resistant to salinity because its growth and gas exchange characteristics were less affected in comparison with Paulownia tomentosa × fortunei -TF.