High Zn concentration does not impair biomass, cutting radial growth, and photosynthetic activity traits in Populus alba L

Purpose: Evaluate the efficiency of Populus alba clone Villafranca in the uptake and translocation of Zn from contaminated soils. Materials and methods: The effects of 48 days of zinc treatment (Znt) on the growth and the photosynthetic activities of P. alba L. clone Villafranca were studied using ZnSO4 (375 ppm per unit of soil dry weight) added in sand and peat moss substrate at the beginning of the treatment (T0) and again after 30 days (T1) in order to reach a target Zn concentration of 375 ppm at T0 and 750 ppm at T1 per unit of soil dry weight. Results and discussion: Zn uptake in the different organs was analyzed after 30 (T1) and 48 days (T2) from the beginning of treatment, showing the following order: root ≫ leaves ≥ woody cutting = stem. The leaf area increased by 12 % in comparison to control plants at the end of second treatment (48 days). Cutting radial growth showed a high synchronicity in the growth rate fluctuation among control and Znt plants, but a higher increase in radial diameter of Znt cutting was observed starting from day 38 (after 8 days of second Znt) reaching after 48 days 38 % higher than control plants. Conclusions: Although our data of leaf Zn concentration were in the range usually reported as toxic for plants, Villafranca clone in Znt substrate were unaffected in terms of net CO2 assimilation and stomatal conductance to water vapor.