Prickly lettuce is a drought-tolerant weed native to Asia Minor and common in Mediterranean climates. It is a strong competitor with crops for water because of its deep taproot. The purpose of this investigation was to determine the effect of different constant temperatures (3, 5, 7, 10 15, 20, 25, 30, 35, 40 and 45oC) and water stress (water potentials of 0, -2, -4, -6, -8 and 10 bar) on germination of Lactuca serriola at laboratory conditions. Results showed that temperature, osmotic potential and interaction between them had significant effects on germination percentage (GP) and germination rate (GR). The highest and the lowest GP and GR were obtained at 0 and -8 bar water potentials, respectively. Also the maximum and minimum GP were shown at 15-20oC and 30oC, and the maximum and minimum GR were obtained at 20oC and 5oC, respectively. Decreasing of water potential at all temperatures caused a delay in the starting of germination but L. serriola could germinates in a wide temperature ranges (2.8 - 41.5oC) and its optimum temperature for germination rate was between 10.2 to 22.3oC. Its base water potential for germination was between -10.2 to -13.8 bar in different temperatures.

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