Effect of Different Levels of Temperature and Drought Stress on Germination Characteristics of Roman Nettle (Urtica pilulifera)

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.