Shepherd's purse (Capsella bursa-pastoris) is a problematic weed in citrus orchards and crop fields in northern Iran. In a series of laboratory and greenhouse experiments, we evaluated the effects that treatment with gibberellic acid (GA 3 ) and potassium nitrate (KNO 3 ), as well as environmental factors, including temperature, the duration of pre-chilling (wet and dry), drought stress, salt stress, pH, and sowing depth, have on seed dormancy breaking and germination in C. bursa-pastoris. Treatment with GA 3 strongly stimulated germination of C. bursa-pastoris in conditions of light/ dark and continuous darkness. The germination rate was highest (40.08%) for seeds treated with 400 ppm of GA 3 in the light/dark condition. Treatment with KNO 3 did not significantly influence seed germination. Longer wet pre--chilling promoted germination and was more successful in seed dormancy breaking than was dry pre-chilling. Seed germination occurred at 10-30°C and within a range of pH of 3-11. Drought and salt stress both strongly inhibited germination. Seedling emergence decreased in proportion to sowing depth. The rates of C. bursa-pastoris germination and seedling emergence were highest for seeds on the soil surface.

The effect of wet and dry pre-chilling duration, pH, osmotic stress, salt stress and planting depth on seed germination and seedling emergence of three foxtail species (Setaria glauca, S. verticillata and S. viridis) was investigated in a series of laboratory and greenhouse experiments. Both wet and dry prechilling for 45 days promoted seed germination of S. glauca compared with the control. Pre-chilling was not significantly effective in seed dormancy breaking of S. viridis and S. verticillata. The maximum germination of foxtails (S. verticillata, S. viridis) was obtained when seeds were treated with pH 7 buffer solution. Increasing of osmotic and salt stress decreased seed germination of foxtails. Setaria verticillata seed germination was more tolerant than those of S. glauca and S. viridis to high water stress condition. Setaria glauca and S. verticillata seed germination were more tolerant to high salinity stress than S. viridis. Seedling emergence decreased with increasing the burial depth and no germination observed at 8 cm soil depth. Isto obravnavanje ni imelo značilnega vpliva na prekinitev dormance semen pri zelenem in vretenčastem muhviču. Največja kalitev muhvičev (S. verticillata, S. viridis) je bila dosežena pri semenih, tretiranih s pufersko raztopino s pH 7. Povečanje ozmotskega in solnega stresa je zmanjšalo kalitev vseh vrst muhvičev Semena vretenčastega muhviča so bila bolj odporna na večji sušni stress kot semena zelenega in sivozelenega muhviča. Semena sivozelenega in vretenčastega muhviča so bila bolj odporna na velik slanostni stress kot semena zelenega muhviča. Vznik vseh treh vrst muhvičev se je zmanjševal s povečevanjem globine setve, na globini 8 cm kalitve ni bilo.Ključne besede: ozmotski in solni stress, globina setve, kalitev, Setaria pumila, S. verticillata and S. viridisVajihe AMINI et al.

Setaria glauca (L.) Beauv., Setaria verticillata (L.) P. Beauv., and Setaria viridis (L.) P. Beauv. are summer annuals and problematic weeds of many annual and perennial summer crops and orchards in the north of Iran. There is no information about interspecific variations in responses to environmental factors. In this study, interspecific variations of the Setaria in response to temperature in light/dark and complete darkness regimes, pH, salt and osmotic stress, and seed sowing depth in the laboratory and greenhouse experiments were investigated. The optimum temperature of S. viridis and S. verticillata seed germination was 25/15°C in light/dark regime, while germination of S. glauca at 20°C was the maximum in both light/dark and complete darkness regimes. The maximum germination of the Setaria occurred at pH 7 (41-48 %) and no seed germinated at pH 11. S. verticillata and S. viridis were moderately tolerant to salt and osmotic stress, but S. glauca was more tolerant to higher levels of stress. The maximum seedling emergence occurred when the seeds were planted on the soil surface (88-94 %) and decreased as sowing depth increased. Seedling emergence of S. verticillata and S. viridis reached zero at depths of 6 cm, while 12.11 % of S. glauca seedlings emerged at a depth of 8 cm.