Biosystematic studies onMaianthemum (Liliaceae-polygonatae)

Abstract

The photosynthetic activity of the foliage of aMaianthemum species, i.e.,M. dilatatum under changing light and temperature regimes in the typical temperate woodland environment was investigated in Ohodaira, Nikko, located at an altitude of ca. 1300 m above sea level, and its adaptive significance was discussed in relation to the ecological life history of this species. It was revealed thatM. dilatatum from the broad-leaved deciduous forest floor displays a very characteristic photosynthetic behaviour which has thus far not been reported for any other forest floor plants.M. dilatatum sprouts at the early spring light phase and efficiently performs photosynthesis under this prevernal light condition; a considerably high saturation light intensity of approximately 20–25 klux results in an unusually high net photosynthetic rate (ca. 30 mgCO₂/dm²/hr) as a forest floor plant. However, in the subsequent period, at the end of June and July, a rather drastic decrease was observed in the photosynthetic rate in response to the reduction of the light intensity on the forest floor.

Also,M. dilatatum showed a broad photosynthetic optimum over a wide thermal range from 10 to 30 C at the prevernal stage. This is another interesting functional characteristic of this temperate woodland herb.