アカネ科外来草本メリケンムグラ（Diodia virginiana L.）の発芽ならびに生育特性

概要

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A proposal to use Virginia buttonweed- Diodia virginiana L. (Rubiaceae), one of the exotic grass species native to North America, on the reservoir slop in the dam has actively been presented for revegetation in Japan. Therefore, this paper deals with seed germination and growth of young seedling of D. virginiana to evaluate behavior of this species on natural and semi-natural ecosystem for biodiversity conservations. Results obtained were as follows; (1) Seed germination of D. virginiana was shown at 25°C or more, (2) Within a range of 25-35°C, the germination rate increased at higher temperatures, (3) Light or dark conditions did not affect the seed germination, (4) The germination was also observed under 1‰ NaCl solution, (5) Seeds carried out cold stratification (5°C with dark and wet conditions for 90 days) had an increased germination rate, comparing with untreated seed, (6) Young seedling of D. virginiana would possess the high flood-tolerance because the seedlingt had survival rate of 100% after the submergence for 180 days, and (7) The seedling would become an annual in a cold region with sub-zero temperatures and be a perennial in a warm region without the above temperatures although D. virginiana has been described as an annual plant species by a good many reports.