Allelopathy is a kind of interaction between plants in which the inhibitory effect on growth and germination can play an important role during the struggle for existence in interspecific competition. The species (or clone of one species) with a higher allelopathic potential might win the competition and place themselves in a better biosocial position for growth. Also, the clones with a lower allelopathic potential might be useful in agroforestry, e.g. as trees useful for shading the crops. The allelopathic potential of Scots pine (Pinus sylvestris L.), the tree species with a wide range of distribution in Europe and of great economic importance, was estimated in this study. To this end, needles from trees growing in a clonal seed orchard were collected and used as a material to obtain water leachates. The leachates were diluted to 25 and 50% and used in allelopathy tests. The differences between potentials of leachates from Scots pine clones to inhibit germination and growth of the test plant (Sinapis alba L. cv. Borowska) were assessed. All leachates significantly affected the germination and hypocotyl length in comparison to the control, also, there were significant differences between allelopathic effects of leachates from different clones. The clones 1702 and 1703 were characterized as highly allelopathic, with the potential confirmed in two independent allelopathic tests. The clones 355 and 2209 were characterized as clones with a moderate allopathic potential. Also, leachates derived from needles collected from the upper part of the crown exerted a significantly stronger influence on the germination of the test plant than the leachates derived from the lower part of the crown. The possibility of selecting clones with the known allelopathic potential for the successful use in forestry was discussed.

Keywords: allelopathic potential, clones, germination, hypocotyl length, leachates, Scots pine, Pinus sylvestris, test plant, Sinapis alba