Table 1 — Root growth of lodgepole pine trees during a 31 -day growth period (growth chamber experiment 1). Significance is 

 indicated by N.S. (not significant) or * (significant at a = 0.05) 







Mean 



Mean 



Est. mean, 





Mean 









length of 



number of 



total length 



number of 



Mean 







new roots 



new roots 



of roots 



new roots 



leader 



Treatment 



Seedlings 



>1.5 cm 



>1 .5 cm 



>1.5 cm 



0.2 to 1 .5 cm 



elongation 





No. 



cm 



No. 



cm 





No. 



cm 



Dipped 



15 



4.5 N.S. 



37* 



161 * 





97 N.S. 



8.7 N.S. 



Not dipped 



15 



4.9 



72 



354 





94 



9.4 



Table 2 — Summary data from 48 lodgepole pine seedlings grown in the growth chamber for 30 days (growth chamber experiment 2). Seedlings 



were either root dipped in a vermiculite slurry or were not dipped before being potted in one of four soil types. Mean values in each 



group followed by the same letter or by no letter are not significantly different (a = 0.05) 















Total 



Mean 



Total 











Plant 



length 



length 



length 





Mycorrhizal 





Leader 



water 



Roots of roots 



of roots 



of all 



Roots 



root tips per 



Treatment Seedlings growth 



potential 



>1.5cm >1.5cm 



>1.5 cm 



new roots 



<1 .5 cm 



10-cm sample 





No. cm 



MPa 



No. 



cm 







-No. 



Soil type 

















Basalt 



12 5.8 



-0.20 



55 275 b 



5.3 b 



654 



757 



74 



Granite 



12 5.7 



-0.19 



42 172 a 



4 a 



551 



758 



87 



Limestone 



12 5.8 



-0.24 



51 292 b 



5.9 b 



717 



649 



83 



Peat-vermiculite 



12 6 



-0.24 



62 385 c 



6.2 b 



674 



579 



114 



Root dip 

















Dipped 



24 5.4 



-0.25 



48 25^ a 



5.2 



549 a 



596 a 



76 



Not dipped 



24 6.1 



-0.19 



57 31 1 b 



5.4 



749 b 



876 b 



102 



Overall mean 



48 5.8 



-0.22 



53 281 



5.3 



649 



736 



89 



ponderosa pine but did not affect Douglas-fir (fig. 1). 

 Dipped seedlings bore more mycorrhizal root tips than 

 nondipped seedUngs, except on granitic soU where the 

 result was just the opposite (fig. 2). The vermiculite 

 slxirry had no effect on plant water potential (table 3). 



Root growth was better for ponderosa pine than for 

 Douglas-fir seedlings on the peat-vermiculite-sandy 

 loam soil. Root growth differed little between the 

 species on the basaltic and granitic soils (fig. 3). Al- 

 though the average long root length was the same for 

 both species, ponderosa pine had a greater total root 

 length because it had more long roots than Douglas-fir. 

 Ponderosa pine also produced more mycorrhizal root 

 tips. The number of roots shorter than 1.5 cm dif- 

 fered little between species. Ponderosa pine showed 

 greater leader growth and higher plant water poten- 

 tial than Douglas-fir seedlings (table 3). 



More new roots (longer than 1.5 cm) were produced 

 in the peat-vermiculite-sandy loam soil (table 3). Fig- 

 ures 3 and 4 show that peat-vermiculite-sandy loam 

 soil was much better for pine root growth, but did not 

 greatly improve Douglas-fir root growth. The granitic 



120 



Dipped 

 Not dipped 



Ponderosa pine 



Douglas-fir 



Figure 1 — Average number of roots 

 greater than 1 .5 cm from 96 ponderosa 

 pine and Douglas-fir seedlings grown in 

 the greenhouse for 30 days (greenhouse 

 experiment 1). Seedlings were root 

 dipped in a vermiculite slurry or were not 

 dipped before being potted in one of three 

 soils. 



4 



