Abstract
Mycorrhiza are symbiotic formations of fungus and roots and are the main organs of nutrient uptake by land plants. The formation of ectomycorrhizae allows trees to dominate the vegetation cover of the boreal zone. Pinus sylvestris L., Picea obovata Ledeb. и Abies sibirica Ledeb. are forest-forming conifers of the Komi Republic. Transmission electron microscopy shows that the fungal sheath of mycorrhiza is most developed in A. sibirica. The Hartig net in all studied trees extends deep into the primary cortex to the endodermis. Glycogen accumulates in the cytoplasm and polyphosphate-containing granules (volutin) in the vacuoles of young fungal cells. Starch accumulates in the cells of primary cortex and central cylinder of young ectomycorrhizae. Reserve substances disappear in the sheath and the Hartig net as the mycorrhiza ages, and starch can remain in the central cylinder. A stable presence of reserve substances was noted at the beginning and in the middle of the growing season. There is an active growth of sucking roots and the formation of ectomycorrhizae during this period in the middle taiga subzone. The occurrence of glycogen and polyphosphate-containing granules in fungal cells is reduced in the autumn period. This is due to a decrease in the intensity of growth processes and the prevalence of physiologically inactive mycorrhizal endings. The starch decrease in the amyloplasts of the primary cortex cells and the central cylinder of ectomycorrhizae is associated with a seasonal decrease in its content in all tree organs, preparation of the plant for the season with low temperatures.