Table 2. --The pH and osmotic potential of test solutions obtained by artifioial 

 extraction and natural leaching of ponderosa pine plant materials 





: Experiment A 



: Experiment B 







Osmotic 









: Potential 







Solution 



: pH (Atms . ) 



: Solution : 



pH 



Stemf low-2 

 Stemf low-1 

 Bark 10% 

 Bark 5% 



Green Needle 5% 

 Green Needle 10% 

 Litter 5% 

 Litter 10% 

 Roots 5% 

 Throughfall 

 Roots 10% 

 5x Hoagland 

 Ho ag land 

 Duff 10% 

 Duff 5% 

 Rain 



Control-Distilled H^O 



2.9 

 3.2 

 3.2 

 3.5 

 4.0 

 4.0 

 4.0 

 4.1 

 4.1 

 4.4 

 4.5 

 4.5 

 4.8 

 5.4 

 5.9 

 6.1 

 6.9 



-0.3 

 -0.2 

 ■0.4 



1 



■2.3 



-0.7 



■0.2 

 -0.2 



Bark 10% 

 Stemf low 



Green Needle 10% 

 Green Needle 5% 

 Bark 5% 

 Litter 10% 

 Duff 10% 

 Duff 5% 

 Litter 5% 

 Throughfall 

 Roots 10% 

 Roots 5% 

 Rain 



Control-Distilled HO 

 5x Hoagland 

 Hoagland 



3.5 

 3.6 

 3.8 

 3.9 

 3.9 

 4.1 

 4.3 



4.4 

 4.4 

 4.7 

 4.9 

 5.0 

 5.9 

 7.1 

 7. 1 

 7.3 



^The osmotic potentials were not measured for the 5 percent solutions. Accurate 

 osmotic potentials could not be obtained for the litter and duff 10 percent solutions 



because of suspended particulates, 



In experiment A, green needle 5 percent was the only test solution with a signifi- 

 cantly lower germination than the distilled water control (table 3) . The germination 

 of pine seeds in rainwater was not significantly different from any of the plant ex- 

 tracts. In experiment B, the germination of the control was significantly greater than 

 green needle 10 percent, whereas the rain was greater than duff 5 and 10 percent, roots 

 5 and 10 percent, green needle 5 and 10 percent, bark 10 percent, and stemflow. 



In both experiments A and B, there was a tendency for those solutions with a low 

 pH to also have a low germination, whereas those solutions with a high pH had a high 

 germination. In a side experiment testing the effects of solution pH only, germination 

 was unaffected by pH values, 3.0, 5.0, and 7.0. Seed germination values varied 

 insignificantly from a low of 80.7 percent in the pH 3.0 solution to a high of 84.0 

 percent in the pH 7.0 solution. However, the pH of the solutions in experiments A 

 and B could have changed the toxicity of the solutions if the toxic compounds were 

 sensitive to acid or base. 



It has been well documented that ponderosa pine seeds exhibit the greatest germi- 

 nation when under some water stress. Germination is usually the highest in solutions 

 with an osmotic potential near -3 atmospheres (Larson and Schubert 1969, Djavanshir and 

 Reid 1975, Rietveld 1975). The lowest osmotic potential recorded in experiments A and 

 B was -3.2 atmospheres for the 5x Hoagland's solutions (table 2); consequently, osmotic 

 potential was not responsible for poor germination in these experiments. 



7 



