functions of synergids reproductive biology of angiosperms BSc botany hons

1. By – Kirandeep Kaur
Roll.no - 314
Synergids

2.  The term synergid comes from the
Greek “synergos,” which means
“working together” and was reportedly
coined by Strasburger.
 Synergid cells are two specialized
elongated cells that lie adjacent to the
egg cell in the micropylar end in the
female gametophyte of angiosperms.

3. EM of LS through the egg apparatus of an
unfertilised embryo sac of Tourenia fournieri

4.  Wall around synergids is incomplete.
 There is distinct wall around micropylar one-
third of cell which thins towards chalazal end
and, finally disappears, chalazal one-third of
cell lacks a wall.
 Protoplast of synergid separated from that of
central cell by double membranes.
 Exceptions;
Wall extends all over the synergid cell –
Epidendrum scutella.
May be deposits of cutin in micropylar portion

5.  Polarised cytoplasm.
 Chalazal region – one large or many small
vacuoles.
 Micropylar end-large amount of cytoplam
and prominent nucleus .
• Cytoplasm-
• rich in mitochondria , ER , dictyosomes;
concentrated near FA ,
• shows abundance of lipids , RNA and
protiens ,

6.  Synergid and egg cell show opposite polarity.
 Synergid haustoria – Quinchamalium
chilense
 Inner surface of hautorium has wall
projections involved in absorption and
conduction of nutrients to synergid.
 Synergids - ephemeral.
 One degenerates before or soon after entry
of pollen tube into the embryo sac whereas,
(persistent synergid) other degenerates
shortly after embryo sac received pollen tube
discharge.

7. Filiform apparatus
 The synergid cell wall forms a highly
thickened structure called the filiform
apparatus at the micropylar end.
 Its diffrerntiation from synergid wall described
by Habermann.
 EM revealed, FA is mass of finger-like
projections into the synergid cytoplasm.
 It seems to be formed mainly from substance
transformed from starch grains.

8. Filiform apparatus
 Structurally,
FA has core of tightly packed
microfibrils enclosed by non-fibrillar
sheath.
 It resembles spongy wall of transfer
cells.
 Rich in polysaccharides.
 Forms are variable
( spherical- Torenia / wedge shaped-
Petunia)
 Crepis capillaris – synergids lack

9. Post- pollination changes
 Synergid visited by pollen tube discharge
degenerates (degenrating synergid) faster
than other( persistant synergid)
 Features shown by degenerating synergid-
Large chalazal vacuole disappears.
Nucleus and nucleolus flattened and nuclear
membrane disappeared.
Organelles disorganised.
Crystals appear in cytoplasm.

10. Functions
 Surface area of plasma membrane at
micropylar end increased by FA , and
cytolasm near FA rich in secretory organelles(
ER, dictyosomes, vesicles) – is is suggested
that FA facilitates transport of substances into
and out of synergid.also, plays a role in
directing pollen tube growth to synergid cell.
 One of synergids forms seat for pollen tube
discharge in embryo sac.

11.  JENSEN (1965) -FA may be aiding the
synergid in absorption and transportation of
materials into embryo sac from nucellus . FA
forms path of entry for these substances.
Many scientists suggested that it doesn’t play
role in nutrition
because of presence of cuticle over micropylar
wall of embryo
sac in Jasione.
Current view is, entry of metabolites in embryo
sac is

12. Diagrammatic representation of proposed function of synergid in
absorption , storage and transport of metabolites.