The fifth meeting of scientists working with Frankia and actinorhizal plants was held at Montmorency Forest of Laval University in Quebec from August 6-8, 1984. Results of research presented at the meeting are included in this special volume of Plant and Soil. The understanding of actinorhizal systems continue to increase, though work­ and use shops and discussions at this and similar meetings make it evident that this important subject remains open for fruitful investigation at all levels. Some important 'firsts' were reported at this meeting. The first extensive survey of Frankiae and their host specificity ranges from Asia was presented. This is of significance since Asia is a center of diversity for many actinorhizal host plant genera. A report that proto­ plasts of Frankia have been produced and regenerated for the first time improves the possibility for genetic manipulation of Frankia. It is also important to note the first report herein of successful mass inoculation of actinorhizal plants commercially for stabilization and reclamation of disturbed soils around hydroelectric power projects in Quebec. This heralds the transfer of actinorhizal technology to private and public users. The bacterial genus Frankia is easily recognized both in vivo and in vitro, and isolation of this organism has become routine. But, as yet, there are not sufficient biochemical, morphological, or anatomical criteria for establishing species.

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Studies of an effective strain of Frankia from Allocasuarina lehmanniana of the Casuarinaceae.- In vitro production of specialized reproductive torulose hyphae by Frankia strain ORS 021001 isolated from Casuarina junghuhniana root nodules.- Characterization and infectivity of a spontaneous variant isolated from Frankia sp. WEY 0131391.- Restriction pattern analysis of genomic DNA of Frankia isolates.- Restriction enzyme digestion patterns of Frankia plasmids.- Host range of Frankia endophytes.- Preinfection events in the establishment of Alnus-Frankia symbiosis: Development of a spot inoculation technique.- Effect of juglone on growth in vitro of Frankia isolates and nodulation of Alnus glutinosa in soil.- Nitrogen fixation and respiration by root nodules of Alnus rubra Bong.: Effects of temperature and oxygen concentration.- Effect of spring flooding on endophyte differentiation, nitrogenase activity, root growth and shoot growth in Myrica gale.- Performance of in vitro propagated Alnus glutinosa (L.) Gaertn. clones inoculated with Frankiae.- Variation in response among three Alnus spp. clones to progressive water stress.- In vitro propagation and nodulation by Frankia of actinorhizal Russian Olive (Elaeagnus angustifolia L.).- Inoculation and production of container-grown red alder seedlings.- Seed germination, seedling inoculation and establishment of Alnus spp. in containers in greenhouse trials.- Large scale inoculation of actinorhizal plants with Frankia.- Biomass production by alders on four abandoned agricultural soils in Québec.- Nitrogen cycling in dense plantings of hybrid poplar and black alder.