Plants sense the quality, quantity, and duration of light signals and
use them to optimise their growth and development. These signals are
perceived by special light receptors of which the phytochrome pigment
system is one of the most important for photo-morphogenetic responses.
Using special diodes that emit monochromatic light, we studied the
effect of red (R), far-red (FR) and R+FR combinations on hypocotyl
elongation of latitudinal ecotypes of Betula pendula .
Continuous R and FR inhibited hypocotyl elongation equally, but
inhibition was higher when seedlings were irradiated by continuous
R+FR. In all cases, inhibition increased with increasing irradiance,
from 0.75 μmol m-2 s-1 to 76 μmol m-2 s-1. Moreover,
seedlings treated by R or R+FR synthesised more anthocyanins than those
exposed to FR. Accumulation of anthocynins increased with increasing
irradiance up to about 19 μmol m-2 s-1