1. UNIVERSITY OF ALLAHABAD
DEPARTMENT OF BOTANY
ASSIGNMENT TOPIC ON – QUIESCENT
CENTRE
Submitted to- Submitted by –
Dr. Satya Narain Sir Anshika yadav
M.Sc Sem 2
2. CONCEPT OF QUIESCENT
CENTER
• A region in the apical meristem of a
root were cell divisions proceeds very
slowly or not at all , but the cells are
capable of resuming meristematic
activity should tissue surrounding
them be damaged.
3. • Clowes (1956,1958) while making
autoradiographic studies of DNA
synthesis in the root tip of Zea ,
discovered a central cup-like region of
cells lying between the root cap and
the active meristematic region.
• Group of inactive cells.
• Present only in monocot roots.
4. Characters
• Less DNA,RNA
• Less protein synthesis
• Light cytoplasm and small nucleus
• Cell division very less
• Fewer mitochondria , and ER
5. Root apex of Allium cepa
Showing quiescent center
6. A quiescent center arises twice in
primary roots –
First during embryogeny and again
during early stages of germination of
seed.
At the time of emergence from the seed
the root is without quiescent center .
In lateral root primordia of Zea mays a
quiescent center also appears twice ,
first while primordium is still embedded
in the cortex and then after emergence
from parent roots.
7. FUNCTIONS
• Act as reservoir of cells.
• The cells of quiescent center become
active whenever the previously active
initials are damaged.
• Thus this center act as a reservoir of
cells relatively resistant to damage
because of inactivity and provides a
permanent source of active initials.
8.
9. Experiment of Clowes
• Roots are exposed to toxic doses of X-
rays ,the meristematic cells stop
synthesizing DNA, and the cells of
quiescent center becomes
meristematic and start synthesizing
DNA .
• REASON - cells of quiescent center are
more resistant to irradiations than
actively dividing cells.
10. Views regarding appearance of
quiescent center
1-Clowes(1972) –
• quiescence is the particular location of
root meristems result from antagonistic
direction of cell growth.
2-Clowes (1978)-
• During embryogenesis the appearance
of the quiescent center coincides with
appearance of root tip.
3-Adam (1989)-
• Suggest the activation of quiescent
center after removal of cap .
11. 4 - Costa and Dolan (2000)-
Hypothesized the origin and
maintenance of quiescent center in
maize root tips.
5 - Kerk and Feldman(1994)-
• High level of auxin bring about
elevated levels of ascorbic acid
oxidase (AAO) and resultant
depletion of abscorbic acid within
quiescent center.
12. CONCLUSION
• Possible causes of appearance of
quiescent center in a growing root may
be antagonistic directions of cell
growth in various parts of meristems
or the presence a rapidly dividing cells
around this region which make it
inactive .
