In order to investigate the effect of different levels of temperature and drought stress on seed germination parameters of nettle roman (Urtica pilulifera L.), an experiment was conducted as factorial in a completely randomized design with three replications at the Department of Agronomy, College of Agriculture, University of Guilan, in 2014. Treatments included different temperature levels (5, 10, 15, 20 and 25 °C) and drought stress levels (0 (control), -2, -4,-6 and -8 bars). The results showed that treatments and their interactions had a significant effect on germination percentage (GP), germination rate (GR), root length and root dry weight. The highest GP (88%), GR (1.8 seed/day) and root dry weight (0.06 g) were obtained as the result of the interaction between the temperature of 25°C and no-stress condition. In this study, with an increase in drought stress and a decrease in temperature, GP, GR, root dry weight, root length and shoot length decreased. The impact of drought stress on GR and GP was lower at 20°C, compared with the temperature of 25°C. A decrease in water potential from -4 to -6 bars at 20°C caused a reduction of 50% and 30% in GP and GR, respectively. However, these reductions at 25°C were 75% and 70%, respectively. According to the results, it could be stated that the significant reduction threshold of seed germination parameters was -2 bars.

 
Highlights:

1. The germination characteristics of Roman nettle were studied under drought stress and temperature.
2. In drought stress of -4 bars, germination percentage and germination rate decreased significantly.