Phytochrome and internode elongation in Chenopodium polyspermum L. the light fluence rate during the day and the end-of-day effect.

The elongation of the fourth internode of fully green Chenopodium polyspermum L. is strongly stimulated by far-red light (FR) given at the end of the day. The end-of-day effect is more important when the plants had been cultivated for several days with a main light period of 140 Wm(-2) than with a main light period of 85 Wm(-2). There exists a quantitative relationship between the FR end-of-day effect mediated by phytochrome and the value of the light fluence during the day.