the top three theories of root apical meristem in plants. The theories are: 1. Apical Cell Theory 2. Histogen Theory 3. Korper-Kappe Theory.The root apical meristem, or root apex, is a small region at the tip of a root in which all cells are capable of repeated division and from which all primary root tissues are derived. The root apical meristem is protected as it passes through the soil by an outer region of living parenchyma cells called the root cap.

2. GOVIND GURU TRIBLE
UNIVERSITY,BANSWARA
M.SC.(BOTANY)
2nd SAMASTER

3. 1. Root is the descending or underground part
of the plant axis.
2. Root is usually cylindrical and non-green (lack
chlorophylls), but sometimes green as in
Trapa and Taeniophylum.
3. The growing point of root tip is sub- terminal
and protected by a root cap or calyptra.
4. Unicellular root hairs present just behind the
root caps which increase the absorptive
surface area of roots.
5. Lateral roots are endogenous in origin i.e.
arise from pericycle of the main root.
- Root is usually positively geotropic (grows downward
into the soil) and positively hydrotropic ( grows
towards the source of water) but negatively
phototropic .
- Root does not bear nodes, internodes, leaves or buds
(exceptions are sweet potato, wood apple etc.)

4. TYPES OF ROOTS
ON THE BASIS OF THEIR ORIGIN ROOT
ARE FOLLOWING TYPE –
TAP ROOT - On germination of a seed,
the radicle elongates into primary root
or true root or tap root. In dicot plants,
the tap root is persistent and produces
lateral roots such as secondary’ roots,
tertiary roots etc.
- All lateral roots arise in acropetal
succession i.e. younger roots towards
apex and older roots towards base.
The tap root and its branches
constitute the tap root system.

5. These are the roots that grow from any
part of the plant other than radicle. In
monocot plants, the tap root is short
lived and soon replaced by adventitious
roots. A group of adventitious roots and
their branches constitute adventitious
root system.

6. FIBROUS ROOT
Fibrous roots are composed a large
Numbers of roots nearly equal in size .
This type root system found in the
Grasses.

7. Root apex is sub terminal in position
because of terminal position of root cap.
Root apex is of few types depending on the
mode of origin of cap and relations
between histogens and primary tissue
regions of the root proper.
The following three theories of Root apex
organization are discussed below-
1. Apical CellTheory
2. HistogenTheory
3. Korper-KappeTheory.

8. 1. Apical Cell Theory-
This theory was proposed by Nageli who
drew the attention to the occurrence of
a single apical cell or apical initial that
composes the root meristem.
- The apical initial is tetrahedral in shape
and generates root cap from one side.
-The other three sides donate cells to
form epidermis, cortex and vascular
cylinder.
- Apical cell theory is confined to vascular
cryptogams only as the root apical
meristem of flowering plants does not
have a single apical cell.

9. Hanstein in 1868 advocated the theory.
According to Hanstein root apical meristem
consists of three cell-initiating regions called
histogens. The histogens are called
dermatogen, periblem and plerome that
respectfully form epidermis, cortex and
vascular cylindrical that are present in a
mature root.
2. Histogen Theory-

10. 3. Korper-Kappe Theory (1917)-
The theory says that the cells in the root
apex divide in a pattern called T-divisions.
The cells of this region divide first
horizontally.
The lower daughter cell then divides
longitudinally, i.e. at right angles to the
plane of the first division.
Thus the planes of the two divisions form a
T in a median longitudinal section of the
root. The inner region of the apex is the
korper. In this region the T is inverted, the
second division takes place in the upper
daughter cell.

11. ROOT ORIGINETED
FROM MERISTEM
• Apical
meristem
produces
the cap Cell
divisions at
the apical
meristem
cause the
root to
lengthen
Farther up,
cells
differentiate
and mature.

12. • Developed from the epidermal cells
away from the root tip Increasing the
surface area available for water and
mineral absorption.
• Epidermis functions in the uptake of
water and minerals Large surface area
facilitates uptake.

13. TISSUES OF ROOT
• Root tissues can be regarded
as a series of concentric rings
of different tissues.

14. Epidermis
-Single layer of cells on the exterior of
the root not covered with a cuticle.
-Root is designed for water uptake.
-Cuticle is a barrier to water.
-Comprised of large undifferentiated
cells .
-Functions in the storage of food
reserves (proteins and starches) in root
tissues.
Cortex

15. Endodermis –
Single layer of cells outside
vascular system .Spaces between
the cells are covered with a waxy
layer, called suberin .
Blocks passage of water and
dissolved nutrients into the vascular
system .
Endodermis functions to regulate
the uptake of water and nutrients
into the plant.

16. pericycle

17. •The transport system
1.Phloem –
Living cells comprised of seive tube
elements and companion cells.
2.Cambium –
A meristematic tissue supplying cells
that will develop into vascular
structures.
3.Xylem –
Dead cells with thickened cell walls,
typically larger than phloem cells.

18. -Functions in the transport of water and
mineral nutrients.

19. A LONG LOOK AT THE
ROOT
Where cells elongate and
differentiate Pushes the root tip
throh the soil .
A longitudinal section through
the root (from bottom to top)
shows these various tissues and
how they develop.
1. Elongation zone
2. Maturation zone
Cells develop their final form Root
hairs form, xylem cells thicken and
die.

20. INTERNAL STRYCTURE OF ROOT

21. THE FUNCTIONS OF
ROOT
1.Anchoring of the plant to the
soil.
2.Absorption of water and
nutrients from the soil.
3.Conduction of absorbed
water and nutrients to stem.
4.Storage of food.
5.Vegetative reproduction and
competition with other
plants.