physiology

2.  Phytochrome is a photoreceptor, a pigment
that plants use to detect light .
 sensitive to light in the red and far-red
region of the visible spectrum.
 pigment has a regulatory role.
 ubiquitous

3.  It exist in two different forms;
 the Pr form;
 absorbs at a peak of 660nm.
 blue form it absorbs red light and
converted into Pfr form.
 Pfr form;
 absorbs at a peak of 730nm.
 absorbs far-red light and converted into Pr
form.

5.  Family of proteins with a small covalently
bound pigment molecule.
 Occur as a dimer of two identical
polpeptides.
 Each polypeptide has a prosthetic group
called chromophore.
 The pigment is chromophore (linear
tetrapyrole)

7.  The phytochrome pigment was dicovered by
sterling hendricks and harry borthwick in the
agriculture research centre in maryland
during a period from the late 1940s to the
early 1960s.

8.  They regulate the germination of seed and
synthesis of chlorophyll.
 the elongation of seedling.
 timing of flowering in adult plants.

9.  Concern with nuclear gene encoding for
mRNAs of chloroplast proteins.
 Two proteins have been investigated;
 The small subunit of Rubisco.
 The light harvesting chlorophyll binding
protein (LHCP).

11.  The corresponding gene for these proteins
are rbcS (Rubiso small)
and cab (chlorophyll a/b).