Nils Fries

Basidiospore germination in some mycorrhiza-forming hymenomycetes

Basidiospores from five randomly selected species of mycorrhiza-forming Hymenomycetes, viz. Laccaria laccata, Amanita muscaria, Lactarius helvus, Paxillus involutus, and Leccinum scabrum, did not germinate on any agar media tested (except for very few and irregular germinations in A. muscaria), nor did an addition of activated charcoal or a living Rhodotorula glutinis colony induce spore germination. However, with these two supplements together on the same agar plate slight germination occurred in all five species. In P. involutus percentage germination was further increased by a volatile factor produced by the mycelium of P. involutus. In L. scabrum a non-volatile substance exuded from its own mycelium strongly promoted germ vesicle and germ tube formation in the presence of activated charcoal. In both of these mycelial germination-inducing factors a certain specificity was indicated.

Abietic acid, and activator of basidiospore germination in ectomycorrhizal species of the genus Suillus (Boletaceae)

Abstract Germination of basidiospores from four ectomycorrhizaforming Suillus species (S. granulatus, S. grevillei, S. luteus, and S. variegatus) was induced by exposing the spores to extracts or exudates from roots of Scotch pine (Pinus sylvestris L.). An active compound was contained in the lipophilic phase obtained by extraction of pine roots with chloroform/methanol. It was isolated and identified as abietic acid, a diterpene resin acid. With S. granulatus, the bioassay species, abietic acid caused germination at concentrations down to 10−7 M.

INCOMPATIBILITY SYSTEMS, CULTURAL FEATURES AND SPECIES CIRCUMSCRIPTIONS IN THE ECTOMYCORRHIZAL GENUS LACCARIA (AGARICALES)

Data from sexual incompatibility and cultural studies were used to further elucidate the biology and taxonomy of species of Laccaria. Six intersterility groups, representing five species, were recorded in 47 Swedish collections by pairing tests among monosporous isolates. In the secondarily homothallic L. altaica the pairings were made with monokaryotic mycelia produced by dedikaryotization. Laccaria altaica, L. amethystina, L. bicolor, and L. proxima each comprised one intersterility group, while members of two groups were referable to L. laccata sensu stricto. Intrastock pairing tests with three species showed a bifactorial (tetrapolar) incompatibility system. In only three of 11 cases analyzed, however, were all four mating type factors found. Each of the species could be further characterized by their growth rate, cultural morphology, and early growth pattern of the primary mycelium. Nutritional tests showed no differences in vitamin requirements for the five species studied. However, L. bicolor responded differently to some complex additives.

SPORE GERMINATION, HOMING REACTION, AND INTERSTERILITY GROUPS IN LACCARIA LACCATA (AGARICALES)

Spore germination was induced in 29 of 30 collections from different basidiocarps of Laccaria laccata by placing the spores on a charcoal-dusted agar medium containing 0.2% peptone, on the surface of which a mycelium of L. laccata was growing. Preserved at 4 C the spores maintained their viability for 2 to 3 months; at -18 C they were viable for about 4 months. Growing hyphae of L. laccata showed a typical homing response towards germinating spores, the eventual conjunction between the hyphal tip cell and the spore leading either to a lethal or to a non-lethal reaction. Mating tests with single-spore mycelia from different stocks, i.e., from spores derived from different basidiocarps, showed that the 14 tested stocks represented four intersterile groups. A method inducing basidiospore germination of Laccaria laccata (Scop.: Fr.) Bk. & Br. under controlled conditions has been described (Fries, 1977). The method was based on two principles: the removal, by means of activated charcoal, of inhibitory substances in the agar medium, and the introduction of a germination-inducing colony of Rhodotorula glutinis (Fres.) Harrison among the spores placed on that medium. However, when the method was tested on a large number of spore collections of L. laccata s.lat. germination was in most cases poor or absent. This implied an unfortunate limitation of the possibilities to obtain monosporous isolates from different strains of this fungus for physiological and genetic investigations. Since L. laccata in many respects is more suitable than most other mycorrhizal fungi for in vitro studies, renewed experiments seemed justified to improve the germination-inducing method. The results of these experiments are reported in the present paper. Recognition reactions in this fungus similar to those earlier described for several species of Leccinum (Boletales) (Fries, 1981) were also discovered. Since spore germination permitted isolation of monosporous mycelia some observations could also be made on incompatibility patterns in L. laccata.

Recognition reactions between basidiospores and hyphae in Leccinum

Two or possibly three recognition reactions between basidiospores and vegetative hyphae are described in Leccinum (Boletaceae, Homobasidiomycetes). The first, the inductor reaction, leads to the germination of basidiospores. It is mediated by a substance exuded from the hyphae, which induces the basidiospores to form a germ vesicle. This inductor reaction is specific for groups of species of which two have so far been found in Leccinum, one consisting of two and the other of four species. In the second recognition reaction, the homing reaction, a substance exuded from the spore vesicle induces nearby hyphae to grow towards the vesicle. This reaction is not species- or species-group-specific. It leads to contact between the hyphal tip and the spore vesicle and is probably followed by fusion between the cytoplasms of the two cells. The outcome of this fusion is lethal or non-lethal depending on which species are involved. This suggests the operation of a third recognition mechanism, which seems to be species-specific.

Spore germination inHebeloma stimulated by living plant roots

Basidiospores from 14 strains ofHebeloma (Agaricales) representing 5 groups of mycorrhiza-forming species were tested for germination on a nutrient agar medium. Germination occurred in 13 strains but never exceeded 0.1%. A 10-fold increase or more in germination percentage was obtained in 4 out of 7 tested spore collections only by placing the growing root of a pine seedling among the spores on the agar medium.

Sexual incompatibility in Suillus luteus and S. granulatus

Intrastock pairings of homokaryons from one North American and four Swedish spore collections of Suillus luteus showed in all cases a bipolar sexual incompatibility. The heterokaryons produced were easily recognized as such by a morphology, cytology and growth rate which differed from that of the homokaryons. All five stocks were inter-compatible, which shows the conspecificity of the Swedish and the American strains. Analogous tests were made with homokaryons of S. granulatus comprising four American and three Swedish strains. Only in one of the Swedish strains did the pairings give rise to a heterokaryotic mycelium morphologically different from the homokaryons. Cytological evidence and the presence of clamps in most of these heterokaryons confirmed the conclusion that S. granulatus is also bipolar. No mating reactions were seen in the pairings with American homokaryons of S. granulatus . Generally, the American isolates gave the impression of species taxonomically different from the Swedish ones.

Variations in the content of phosphorus, nucleic acids and adenine in the leaves of some deciduous trees during the autumn

SummaryThe content of acid soluble, lipid-bound and nucleic-acid phosphorus was determined in leaves collected from 9 species of deciduous trees (Acer platanoides, Tilia platyphylla, Carpinus betulus, Prunus padus, Fagus silvatica f. atropurpurea, Quercus petraea, Sorbus intermedia, Sorbus Aria, andBetula pubescens) during the autumn. The movement of phosphorus back to the branches and the stem from the leaves was demonstrated in some cases, (this was particularly noticeable in the case ofT.p., S.i. andS.A.). At the same time a transformation of organically bound to inorganic phosphorus occurred in all species. Even in the falling leaves, however, there always remained a certain percentage of nucleic acid P and lipid-P.In 6 species (A.p., T.p., C.b., P.p., F.s., andA.p.) the changes in the content of adenine were also studied, the adenine being determined microbiologically. Before leaf fall a decrease to c. 50% of the original amount was noted.An approximate calculation has been made of the a mounts of nucleic acids and adenine received by the soil in decidance forests from the fallen leaves each autumn.

Growth of ectomycorrhizal fungi stimulated by lipids from a pine root exudate

SummaryThe content of fatty acids was analysed in an exudate from roots of pine seedlings grown axenically in vermiculite with a synthetic nutrient medium. The dominating fatty acdis were fewer in the exudate than in the roots. Unsaturated fatty acids were predominant. The total lipid fraction of the exudate promoted mycelial growth in two of the three ectomycorrhizal fungi tested.

The influence of amino acids on growth and lateral root formation in cotyledon-less pea seedlings

Es wurde die Einwirkung von 22 Aminosäuren in verschiedenen Konzentrationen auf Wachstum und Entwicklung junger, in steriler Agar-Kultur gezüchteter Erbsenkeimlinge studiert. In höheren Konzentrationen (≧10 µMol je Kultur) wirkten die meisten Aminosäuren hemmend auf das Wachstum, was sich besonders an der Wurzel zeigte. Eine Sonderstellung nahm dabei Oxyprolin ein, das schon bei einer Konzentration von etwa 0,3 µMol je Kultur eine deutliche Hemmung verursachte. Diese wurde nur teilweise durch Prolin aufgehoben. Die durch Entfernung der Kotyledonen bedingte akropetale Verschiebung des «durchschnittlichen Insertionspunktes» (=AIP) der Seitenwurzeln konnte durch Hefeextrakt oder Arginin gewissermaßen rückgängig gemacht werden.