Pollen viability and longevity in Juniperus taxa native to Slovakia.

Pollen viability, dispersion ability and longevity during deep-freezer storage were studied in three Juniperus taxa distributed in Slovakia. All these characteristics of pollen are closely related to the pollination and/or fertilization success of the junipers in nature. Pollen viability varied considerably between the three populations of J. communis and one population of each, J. sibirica and J. communis var. intermedia. Pollen germination rate ranged between 40.75% and 75.06%, and pollen tube length between 30.32 and 40.41 µm. A clear tendency indicates a higher germination rate of J. communis pollen from lower altitudes and reduced germination of J. sibirica and J. communis var. intermedia pollen from higher altitudes. The dispersion potential of the J. communis pollen during its shedding seems relatively low. In 2021, pollen cloud density was diluted at 68.1% at the 4 m distance from the test shrub, in 2022 of 52.1% at the 17 m distance from the pollen source. A deep-freezer storage of juniper pollen in a double-walled polyethylene bag with silica gel was not efficient enough, as indicated by the drop of pollen germination rate of 31.2% in J. communis and of 79.4% in J. sibirica during a 1-year storage period at - 81 °C.