barriers for root growth in experiment B, the sieved soil was placed in 30 by 30 by 4 cm 

 root boxes in the greenhouse. Thirty stratified and sterilized ponderosa pine seeds 

 were planted in each box. Three replicates were set up for each of the four leachates, 

 the Hoagland's solution, and the distilled water control. Each root box was initially 

 watered with 200 ml of the appropriate test solution followed by 100 ml every other day. 



The seedlings were allowed to germinate and grow for 35 days, then all but the 

 largest 10 seedlings were removed from each root box. Germination was checked daily 

 until the thinning. The remaining 10 seedlings were allowed to grow an additional 29 

 days at which time the soil was washed away from the roots and the seedlings collected. 

 The root lengths, stem lengths, number of laterals over 1.0 cm, and biomass of the 

 roots and crowns were measured for each treatment. 



The one-way analysis of variance and Newman-Keuls tests were performed for 

 statistical analysis. 



Results and Discussion 



In both experiments A and B, there was no significant difference in germination be- 

 tween any of the plant leachates and the distilled water control (table 5) . However, 

 the seeds watered with the Hoagland's solution in experiment B had a significantly lower 

 germination than the seeds watered with the four plant solutions and the control. These 

 data show that under these conditions, none of the leachates contained phytotoxins 

 that inhibited the germination of pine seeds. The reason for low germination in the 

 Hoagland's treatment is uncertain. 



In experiment A there was no significant difference in total seedling weight and 

 shoot weight between the treatments. There was, however, a significant difference in 

 root weights for duff and bark compared to the control. The reduced root weights of 

 the duff treatment resulted in a shoot/root ratio that was significantly larger than 

 all other treatments and the control. 



In experiment B there was no significant difference in total seedling weight, 

 root and shoot weight, or shoot/root ratios between the plant leachate treatments and 

 the distilled water control. The Hoagland's solution was significantly lower in root 

 weight than the other solutions, which again resulted in a very large shoot/root ratio. 



In experiment B the entire seedlings were extracted from the root boxes, the roots 

 and crown lengths were measured, and the number of lateral roots greater than 1.0 cm 

 were counted. The taproots of seedlings grown in the Hoagland's solution were equal in 

 length with the taproots from seedlings grown in the other solutions (table 5) , but the 

 Hoagland's seedlings had a reduced number of lateral roots. A reduction in the number 

 of laterals resulted in reduced root weights for the Hoagland's treatment but is proba- 

 bly not representative of a disadvantaged seedling under these growing conditions. A 

 similar situation could have existed in experiment A reducing the root weights of seed- 

 lings watered with duff and bark leachates. Neither bark nor duff leachates reduced 

 root growth in experiment B. 



Although this experiment produced no evidence of a germination inhibitor, the 

 experimental design did not eliminate all mechanisms of inhibition associated with 

 leachates. Plant compounds may have to accumulate in the soils over a period of time 

 to reach active concentrations. In this experiment, the soils were not watered with 

 plant leachate until the seeds were sown, and the germination was quite rapid. There- 

 fore, there may not have been sufficient time for the inhibitor to accumulate to the 

 point where it could have affected germination. It is also possible that compounds in 

 the leachates are broken down or rearranged to produce the inhibitor and there may not 

 have been sufficient time for the breakdown product to reach inhibitory concentrations. 

 Therefore, this experiment did not disprove these two mechanisms. 



11 



