Abstract: With introduced sandy land Mongolian pine (Pinus sylvestris var.mongolica) seeds as test material,this paper studied the effects of polyethylene glycol (PEG)-simulated drought stress on their germination.The results showed that PEG could retard the germination of stressed seeds,and the germination rate,germination index,and germination potential were all decreased with increasing PEG concentration.The seeds treated with 30% PEG (about -1.20 MPa water potential) could not germinate at all throughout the experiment period,suggesting that 30% PEG or -1.20 MPa water potential was the threshold for the germination of Mongolian pine seeds. under 10% PEG stress (about -0.20 MPa water potential),the lengths of radicle and hypocotyl were shorter,illustrating their growth be more sensitive to PEG-simulated drought stress,while the radicle / hypocotyl ratio was increased with increasing PEG concentration,indicating that Mongolian pine seeds had a stronger resistance to drought stress after germination.Drought stress might be a possible cause that inhibited the natural regeneration of Mongolian pine on sandy land.

Key words: Solid organic waste, Composting, Stability, Maturity, Evaluation