Root induction on in vitro adventitious Pinus monticola Dougl. shoots from mature embryos was improved after 8 weeks co-cultivation with Agrobacterium rhizogenes Conn. strain A4 or the pRi transconjugant strain R1000 as compared to controls, and to naphthaleneacetic acid and indoleacetic acid treatments. An improvement in the number and quality of roots induced was observed on co-cultivated shoots as well as co-cultivated Pinus banksiana Lamb and Larix laricina (DuRoi) K. Koch de-rooted seedlings. Changes in substrate nutrient solution did not influence rooting as much as the presence of Agrobacterium in the rhizosphere. Rooting of cuttings from 3-year-old P. monticola trees was improved in two different seedlots with A. rhizogenes A4 strain.

The relative ability of sibling monokaryotic and reconstituted dikaryotic cultures of Laccaria bicolor (Maire) Orton to colonize short roots of Pinus banksiana Lamb. was studied using two different methods at 4, 8, and 12 months after isolation. Monokaryotic isolates varied in their ability to form ectomycorrhizae. Some lost the ability to colonize rootlets. Dikaryons formed soon after isolation from compatible mating type pairs were vigorous colonizers. A dikaryon formed after 12 months by pairing two competitive monokaryons formed abundant mycorrhizae. However, dikaryons formed after 12 months by using less competitive monokaryons showed a sharply reduced symbiotic ability. The isolation of one apparently nonmycorrhizal monokaryon is reported.

A rapid field method to evaluate the competitive performance of selected ectomycorrhizal isolates is presented. Ectomycorrhizal jack pine seedlings and noninoculated controls produced in growth pouches were outplanted in diverse stations 1 month after inoculation. Photographs taken prior to outplanting and at the time of excavation permitted comparative observations of mycorrhizal development along each lateral root of individual seedlings. Nonmycorrhizal control seedlings showed 0, 20, 20, and 76% mycorrhizal development at the sterilized denuded, unsterilized denuded, burned, and undisturbed jack pine stand stations, respectively. To evaluate the postplanting performance of each isolate tested, an index of colonization and an index of competition were established. Laccaria bicolor was the best colonizer at all stations except the undisturbed jack pine stand, where Rhizopogon rubescens was the best colonizer and also the most competitive. Pisolithus tinctorius was not competitive with the indigenous mycota at the burned or the undisturbed jack pine stand stations.

The holdings of eight collections of fungi have been examined for organisms isolated from wood and/or trees. Further selection of these fungi has been made according to their reported ability to produce volatile, biologically active metabolites. It is emphasized that the isolates in the collections do not necessarily produce such metabolites. The list of fungi fulfilling these conditions is slightly augmented by reports we have found in the literature, where the fungi concerned have not yet been deposited. The biochemistry of these compounds is considered with particular emphasis on their biosynthesis including that by Homo sapiens. The physiological and toxicological activity of these metabolites is reviewed especially with reference to their potential role in the complex symbioses existent in, for example, a tree. The review concludes with a discussion of areas of botany deserving increased attention in the hope that this will stimulate further work. The statements in the review are based on 173 references.