Allelopathic potential of Japanese red pine (Pinus densiflora Sieb. et Zucc.) needles and its litter

摘要

The Japanese red pine forms sparse forest floors, where herbaceous plants do not grow well, hence, the allelopathic potential of aqueous methanol extracts of its needles and litter was investigated to understand the pine allelopathy. Aqueous methanolextract of Japanese red pine needles and litter inhibited the germination of ryegrass and was concentration dependent. The aqueous methanol extracts of red pine needles and litter also inhibited the growth of hypocotyls and roots of cress, lettuce and alfalfa, and growth of coleoptiles and roots of timothy, crabgrass, barnyard grass and ryegrass. The extract inhibition was concentration dependent. Although there were variations in the sensitivity against the extracts among test plant species, both litter and needle extracts were more active on hypocotyls than on roots of dicotyledonous test plants (cress, lettuce and alfalfa), and more active on roots than on coleoptiles of monocotyledonous test plants (timothy, crabgrass and barnyard grass) except ryegrass against the litter extracts. These results suggested that pine needles and litter may possess allelopathic potential and contain allelopathic substances. The inhibitory activity of pine litter was 16 - 33% (comparing the concentrations required for50% growth inhibition) and 56 - 70% (comparing average inhibition values) of the needle extracts. Thus pine litter had higher inhibitory potential, which may contribute to form sparse forest floors due to the growth inhibition of herbaceous plants.