Influences of thermoperiod and salinity on Tamarix gracilis seed germination

In order to reveal the seed germination characteristics of Tamarix gracilis in the Turpan Desert Botanical Garden, Xinjiang, seeds of the species were germinated in incubators with 4 photoperiods and 10 NaCl salinities. Experiments were conducted to determine the effects of thermoperiod and NaCl on seed germination. The results showed that 1) seeds can germinate quickly and reach a high germination percentage in a range of temperatures, from 5 ℃/15 ℃ to 25 ℃/35 ℃ in dark/light = 12 h/12 h. The higher the temperature, the faster the germination. 2) The higher the NaCl salinity, the lower the percentage of germination. Germination was not affected by NaCl at concentrations below 0.4 mol·L-1, while germination at higher concentrations (0.6, 0.8, 1.0, and 1.2 mol·L-1) were significantly lower than that of the control. 3) After transferring to distilled water, un-germinated seeds incubated in NaCl showed a low germination recovery rate. Low germination recovery (2.1%34.5%) was noted at concentrations of 0.61.2 mol·L-1. No germination recovery was noted when NaCl concentration was more than 1.2 mol·L-1. This shows that 1.2 mol·L-1 NaCl is the largest concentration of salt tolerance of T. gracilis.