Effect of temperature and salinity on germination and seedling establishment of Ailanthus altissima (Mill.) Swingle (Simaroubaceae)

The tree of heaven Ailanthus altissima (Mill.) Swingle is a multipurpose tree in forestry. However, it is considered an invasive and dangerous plant for native species, and in particular for national parks, where many studies have recorded their involvement in the disturbance of the already developed floral diversity. Assessing the impact of certain abiotic conditions on this species may identify the expected areas to be colonized by its seed propagation. Germination of tree of heaven were tested for germination at constant temperatures of 25, 30, 40°C, and at room temperature varying from 25-30°C coupled with total darkness. Seeds were sown in Petri dishes (0.8% agar water) for 6 days of incubation. The kinetic of germination was determined according to five closely related parameters viz. final germination percentage (FGP), mean germination time (MGT), coefficient of velocity of germination (CVG), time to 50% germination (T50) and seedling length (SL). For the saline condition, the seeds underwent various NaCl concentrations from 0, 50, 100 or 200 mM. For each treatment, there were four replicates with 50 seeds incubated in a plastic container between two layers of moist sand at 15% of the appropriate treatment and then placed in a culture chamber at 27°C (± 2°C) for 30-day period. The effect of temperature was not significant on the MGT, CVG and T50. However, it was significant (p< 0.0001) on FGP and SL. The maximum germination of 94% was obtained at a temperature of 30°C and the lowest FGP of 40% was obtained at 25°C. For the salinity effect, the FGP of 75% in the control was much higher compared to the seeds treated at 50 mM NaCl with only 17.2% of FGP.  Germination was completely inhibited from 100 mM NaCl. A. altissima can be classified as sensitive to salt stress during seed germination and seedling emergence. The salinity effect then joined the temperature to monitor nature's A. altissima seed propagation.