Effects of seed size of Japanese red pine Pinus densiflora on colonization of pine seedlings by ectomycorrhizal Basidiomycete Suillus granulatus and initial growth of seedlings

Abstract

Effects of seed size of Japanese red pine (Pinus densiflora Sieb. et Zucc.) on the colonization by ectomycorrhizal Basidiomycete Suillus granulatus (L.: Fr.) O. Kuntze and initial growth of the pine seedlings were examined. Pine seedlings at 1 month of age were infected with S. granulatus and were grown for 3 months at 23.5℃ under fluorescent light. The relationships among the parameters related to the seed size, growth of seedlings and mycorrhizal colonization were investigated. There was a significantly positive correlation between the fresh weight of seeds and some growth parameters of the seedlings and between mycorrhizal colonization and the parameters related to root growth. In contrast, a significantly negative correlation was observed between mycorrhizal colonization and the height of the seedlings. There was no significant correlation between the fresh weight of seeds and mycorrhizal colonization. These results indicate that the seed size promoted the growth of seedlings at early stages after germination, and that mycorrhizal colonization may suppress the above-ground development of seedlings. Although the seed size does not affect the mycorrhizal colonization directly, the positive and negative correlations of the seed size with the parameters for the initial growth of the seedlings and mycorrhizal colonization suggest the presence of indirect effects of the seed size on the growth of pine seedlings and development of mycorrhizas at the early stages after germination and infection with mycorrhizal fungi.