SUMMARYThe ability of two shrubby alders to form ectomycorrhizae with known species of fungus was investigated. Frankia-'moc\i\aX.ed seedlings oi Alnus crispa and Alnus rugosa were raised in growth pouches and inoculated with a pure culture inoculum of potential ectomycorrhizal fungi. Ten of the 46 species of fungi used formed ectomycorrhizae with both Alnus species. Only Alpova diplophloeus showed a well distributed Hartig net; others had a net only proximally, while others had none. These patterns are discussed in terms of more or less rapid Hartig net development. "The Hartig net was always confined to the epidermal layer of the root, never completely surrounding it. This situation appears to predominate in the Angiosperms. Colonization of young actinorhizae by Alpova diplophloeus led to the formation of ectomycorrhizal structures.

Development of the Laccariabicolor (Maire) Orton basidiome in association with container-grown Pinusstrobus L. seedlings was influenced by photosynthetic photon flux densities (PPFD). Three growth patterns were observed. At a PPFD of 330 μmol•m−2•s−1, basidiome growth was rapid, and complete development was achieved after 16 days. At a very low PPFD (20 μmol•m−2•s−1), the basidiome development ceased, although some residual growth was observed for a few days. At an intermediate PPFD (50 and 90 μmol•m−2•s−1), basidiome growth was less rapid than that observed at 330 μmol•m−2•s−1. Significant differences in the net photosynthesis of the host plant resulted in corresponding changes in basidiome biomass. The effect of basidiome removal on the photosynthetic response of the host plant was evaluated at three stages of basidiome development (2- to 4-, 6- to 8-, and 10- to 15-mm pileus diameter). At each developmental stage, removal of the basidiome induced a very rapid decrease in both net photosynthesis and stomatal conductance of the host plant. This decrease in net photosynthesis indicates that the growth and development of the basidiome are dependent on the host plant's current rate of net photosynthesis.

Dkprrr~ernerl~ des Scier~c~e,~~fi~resti~r-e.s, Frrc.~rltk rle For-ester-ie et Gkorlksie. Urlivc~r.sit6 Lrrvril, Qu6bec (Qlrk.), Crrrl~rlri GI K 7P4 Rcccivcd Octobcr 22, I984 GODBOUT, C., and J . A. FORTIN. 1985. Synthcsizcd cctomycorrhizac of aspcn: fungal gcnus lcvcl of structural charactcrization. Can. J . Bot. 63: 252-262. Thc ability of Po/)~rlrr.s trern~rloirle.~ Michx. to form cctomycorrhizac with idcntificd spccics of fungi was invcstigatcd using a pouch techniquc. Twcnty-ninc out of 54 fungus spccics formcd cctomycorrhizac on aspcn sccdlings. Aspcn sccms to display littlc spccificity for cctomycorrhizal fungi. Only cpidcrmal Hartig ncts wcrc obscrvcd in thc synthcsizcd cctomycorrhizac and pcricpidcrmal oncs wcrc frcqucntly cncountcrcd. Structural and morphological chnractcristics of cctomycorrhizac arc prcscntcd by gcnus of mycorrhizal fungi. This grouping of characters by gcnus sccnis possiblc indcpcndcntly of thc host plant. Thc classification of cctomycorrhizac is vicwcd in a ncw way in which structural typcs would bc taxononlically rclatcd to thc gcnus of thc fungal symbiont.Gor,oour, C., ct J. A. FOKTIN. 1985. Synthcsizcd cctomycorrhizac of aspcn: fungal gcnus lcvcl of structural characterization. Can. J . Bot. 63: 252-262. La capacitC dc Poplrlrrs frernrrloirle.~ Michx. B forn~cr dcs cctomycorhizcs avcc dcs cspkccs dCtcrmindcs dc champignons a Ct C cxplorCc au moycn dc la tcchniquc du sachct dc croissancc. Sur 54 cspkccs dc charnpignons cssnyCs, 29 ont form6 dcs cctomycorhizcs sur dcs plantulcs. LC pcuplicr faux-trcmblc scmblc affichcr pcu dc spCcificitC vis-$-vis Ics champignons cctomycorhizicns. Chcz Ics cctomycorhizcs obtcnucs. Ic rdscau dc Hartig a toujours CtC Cpitlcrmiquc ct dc nombrcux rCscaux pCriCpidcrmiqucs furcnt obscrvCs. Lcs caractCristiqucs structuralcs ct morphologiqucs dcs cctomycorhizcs ont CtC rcgroupCcs ct dCcritcs par gcnrc dc champignons cctomycorhizicns. Ccttc fa~on dc rcgroupcr Ics caractkrcs scmblc possiblc sans tcnir comptc dc la plantc-hbtc. La classification dcs cctomycorhizcs cst cnvigagCc dans unc nouvcllc optiquc sclon laqucllc Ics typcs structuraux scraicnt taxonomiqucmcnt rclids au gcnrc du champignon symbiotiquc.

No abstract

No abstract