RESEARCH SUMMARY 



A series of laboratory and field experiments were conducted to 

 determine if mature ponderosa pines produce a substance (phytotoxin) 

 that inhibits the germination and growth of seedlings directly under 

 the tree crown. 



Neither live nor dead materials collected from ponderosa pines 

 produced either volatile or water-soluble phytotoxins that drastically 

 inhibited germination of seeds or growth of seedlings. 



Seeds overwintering beneath the canopy of mature pines, or 

 planted in soils collected there, showed reduced germination. Exact 

 cause of the reduction was not determined. If weak phytotoxins were 

 responsible, they did not inhibit growth of seedlings that germinated. 



