Responses of seed germination and protocorm formation to light intensity and temperature in epiphytic and terrestrial Liparis (Orchidaceae)

Abstract

Epiphytes begin their life history with seed germination on trees and live on the trees throughout the lives. In contrast, the seeds of terrestrial plants germinate on the ground. To clarify differences in early life history between epiphytes and terrestrial species, we compared the responses of in vitro asymbiotic seed germination and protocorm formation to various light intensities and temperatures between the epiphyte Liparis fujisanensis and two closely related terrestrial species, Liparis koreojaponica and Liparis kumokiri (Orchidaceae). Epiphytic germination was higher at low temperature and under high light intensity than that of the terrestrial species. Protocorms were formed only in the dark in the three species. Field measurements of temperature and photosynthetically active radiation in six natural habitats of the species from 2005 to 2006 showed that the habitats of the epiphyte were exposed to higher light intensities than those of the terrestrial species. The high germination capability of epiphyte seeds in wider ranges of light intensity and temperature may be beneficial to its seedling growth in the early growing season in exposed aboveground habitats.