Basalt Granite Peat-vermlcullte 



Soil Parent Material 



Figure 2 — Average number of mycorrhizal root 

 tips per 1 0-cm sample or roots from 96 ponde- 

 rosa pine and Douglas-fir seedlings grown in 

 the greenhouse for 30 days (Greenhouse ex- 

 periment 1). Seedlings were root dipped in 

 a vermiculite slurry or were not dipped before 

 being potted in one of three soils. 



200i 



Ponderosa pine Douglas-fir 



Figure 3 — Average number of roots longer 

 than 1 .5 cm from 96 ponderosa pine and Dou- 

 glas-fir seedlings grown in the greenhouse for 

 30 days (greenhouse experiment 1 ). Seed- 

 lings were root dipped in a vermiculite slurry or 

 were not dipped before being potted in one of 

 three soils. 



soil supported the shortest mean root length and 

 the most short roots. Plant water potential was low- 

 est on the basaltic soil and was highest on the peat- 

 vermiculite-sandy loam soil. The granitic soil was 

 more favorable for mycorrhizal root tips, but the soil 

 type influenced leader growth very little (table 3). 



The second greenhouse experiment showed no con- 

 clusive difference in root growth between nondipped 



seedlings, vermiculite, and the weak vermiculite 

 slurry (table 4). However, figure 5 shows that root 

 growth fell as seedlings were dipped in progressively 

 thicker slurry. Likewise, nondipped seedlings pro- 

 duced more mycorrhizal root tips than the 2x vermicu- 

 hte slurry (table 4). The thicker vermiculite slurry 

 treatments also caused lower plant water potential 

 and poorer leader growth. 



Table 3 — Summary data 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 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 





Mycorrhizaf 







Leader^ 



water 



Roots^-' 



of roots 



of roots 



of all 



Roots 



root tips per 



Treatment 



Seedlings 



growth 



potential 



>1.5 cm 



>1.5 cm 



>1.5 cm 



new roots 



<1.5 cm 



10-cm sample 





No. 



cm 



MPa 



No. 





cm 







-No. 



Species 





















Ponderosa pine 



48 



6.2 a 



-0.34 a 



84 a 



361 a 



3.6 



720 a 



696 



79 a 



Douglas-fir 



48 



5b 



-1.61 b 



39 b 



147 b 



3.6 



443 b 



593 



56b 



Soil type 





















Basaltic soil 



32 



5.7 



-1 .04 a 



31 a 



107 a 



3.5 b 



374 a 



534 a 



59 a 



Granitic soil 



32 



5.6 



-0.97 b 



32 a 



89 a 



2.8 a 



470 b 



761 b 



94 b 



Peat-vermiculite 



32 



5.6 



-0.91 b 



123 b 



567 b 



4.5 c 



902 c 



639 ab 



51 a 



Root dip 





















Dipped 



48 



5.7 



-0.96 



53 a 



217 a 



3.6 



490 a 



544 a 



68 



Not dipped 



48 



5.5 



-0.99 



71 b 



291 b 



3.6 



674 b 



745 b 



67 



Overall mean 



96 



5.6 



-0.97 



62 



254 



3.6 



582 



644 



68 



'Analysis of variance showed a likely interaction between soil type and root-dip treatment. 

 ^Analysis of variance showed a likely interaction between species and soil types. 

 ^Analysis of variance showed a likely interaction between species and root-dip treatment. 



5 



