SEED DORMANCY BREAKING AND GERMINATION OF POKEWEED AND LAMB’S EAR: TWO INVASIVE PLANTS

Abstract

We investigated seed dormancy breaking techniques and some environmental factors affecting on seed germination of Pokeweed (Phytolacca americana L.) and Lamb’s Ear (Stachys byzantina K. Koch) in a series of laboratory and green house experiments. The seed dormancy breaking treatments were consisted Gibberellic acid (GA₃), mechanical scarification and leaching duration. Environmental factors were included salt and drought stresses, pH and planting depth. The greater stimulatory effect on germination was observed at low concentrations of GA₃, while seed germination of both Pokeweed and Lamb’s Ear was reduced with high concentrations of GA₃. With decreasing of water potential germination significantly reduced. Seed germination was inversely related to salt concentration. But, Lamb’s Ear germinated in solutions with relatively high salinity.  The Pokeweed seeds germination was greatly reduced at pH lower and higher than 7. Lamb’s Ear seed germination was completely inhibited at pH lesser than 7. The maximum germination percentage of Pokeweed (62%) occurred at planting depth 5 cm after 30 days. Germination percentage of Lamb’s Ear increased in comparison to the control as leaching duration enhanced. But it was declined as leached for 96 hours. The seedling emergence decreased with increasing of planting depth in both plants.