and LOPUSHINSKY, W. 1989. Pure culture response of ectomycorrhizal fungi to imposed water stress. Can. J. Bot. 67: 29-39. The ability of ectomycorrhizal fungal isolates to tolerate imposed water stress in pure culture was examined in 55 isolates of 18 species. Water potential treatments, adjusted with polyethylene glycol, were applied to Petri dish units. These units allowed colony diameter measurements of fungi grown on liquid media. Delayed growth initiation and inhibition OF growth rate occurred with increasing water stress. For 87% of the isolates, growth rate was inhibited by the initial water potential treatment applied, leaving only seven isolates where growth increased with initial water potential treatments. No growth was evident under the imposed stress treatments For isolates of Lnccaria bicolor, Lnccaria laccatel, and Lnctarius corztroversus; growth occurred only in the control. Drought tolerant species, demonstrated by an ability to grow at a water potential of -3 MPa, included Boletus edulis, Cerrococcun~ geophilurn, Rhizopogotz vinicolor, and five out of eight Sllillus species. Species intolerant of -1 MPa included Hebelorna crustuliniforme, Lnccaria bicolor, Lnccnrin laccata, and Suillus caerulescer~s. Fungal drought tolerance was poorly correlated with estimates of annual precipitation for collection locations. Estimates of drought tolerance seems to depend more on fungal classification than on annual precipitation at the site of collection. Reisolation of Lnccaria bicolor increased growth mte and water stress tolerance when compared with the same fungus prior to reisolation.COLEMAN, M. D., BLEDSOE, C. S., et LOPUSHINSKY, W. 1989. Pure culture response of ectomycorrhizal fungi to imposed water stress. Can. J. Bot. 67 : 29-39. Les auteurs ont examine, en culture pure, 55 isolats de champignons ectomycorhiziens appartenant h 18 espkces, la capacitC h tolCrer un stress hydrique impose. Les traitements faisant appel au polykthylkne glycol ont Ct C appliques en Petri. Cette mtthode permet de mesurer la croissance en diamktre de colonies de champignon croissant en milieu liquide. Avec une augmentation du stress hydrique, on observe un retard dans le debut de la croissance ainsi qu'une diminution du taux de croissance. Chez 87% des isolats, il y a une inhibition du taux de croissance avec le potentiel hydrique initial, ce qui ne laisse que 7 isolats oh ce mPme traitement conduit h une augmentation de croissance. Avec les isolats de Lnccaria bicolor, L.uccaric~ lclccata et Lnctarius corltroversrls aucune croissance ne peut Ptre observCe en pr6sence du stress hydrique impose: il n'y a de croissance que chez les temoins. On retrouve une tolCrance h la skcheresse, telle que demontree par la capacitC h croitre en presence d'un potentiel hydrique de -3 MPa, chez Boletus ecllllis, Cer~ococcurn geophilutn, Rhizopogor~ vinicolor et chez cinq espkces de Suillus sur huit. Les espkces incapables de toltrer -1 MPa incluent Hebelorna cr~~st~~lir~iforrne, Lnccaricl bicolor, Lnccaria laccata et Suilllts caerulescens. ...

Application. In standard (4-week) tests of root growth potential (RGP) of western conifers, root media temperature should be maintained at 20 "C for most species, and possibly higher (23-25 "C) for low-elevation sources of ponderosa pine. A high root media temperature (30 "C) should be avoided with Douglas-fir, Pacific silver fir, noble fir and possibly other true firs because root growth in these species is inhibited by high root temperature.Abstract. Root growth in seedling transplants of Douglas-fir (Pseudotsuga menziesii (Mirb.) France), Pacific silver fir (Abies amabilis@ougl.) Forbes), noble fir (Abies procera Rehd.), lodgepole pine (Pinus contorta Dougl. ex Loud.) and ponderosa pine (Pinus ponderosa Doug. ex Laws.) began when soil temperature exceeded 5 "C. Root growth increased rapidly after 10 "C and attained maximum values at 20 "C. At 30 T, no root growth occurred in the firs; in the pines, root growth was 30 to 39% of maximum. Maximum shoot growth also occurred at 20°C. In ponderosa pine, height growth of seedlings from a high-elevation source was unaffected by cold soil, but in low-elevation seedlings it was reduced. Budburst in Douglas-fir and the pines was delayed up to 11 days by cold soil, whereas in silver fir and noble fir, it was only slightly delayed. Prior to new root growth in ponderosa pine, xylem pressure potentials and stomatal conductances during the afternoon indicated reduced stomatal opening at all soil temperatures, whereas 23 days later, stomata were open to a greater degree when temperatures exceeded 10 "C.

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Mycorrhizal and nonmycorrhizal container-grown Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) seedlings were outplanted on dry, burned-over sites in eastern Washington. Prior inoculation of seedlings did not significantly increase survival or height growth, but biomass increment during the first growing season was substantially reduced. New roots of all seedlings became colonized by native mycorrhizal fungi within 5 months after planting.