defination main difference between the vegetative shoot and reproductive shoot vegetative shoot apex origin of reproductive shoot apex

1. TRANSITION OF VEGETATIVE
SHOOT APEX INTO
REPRODUCTIVE SHOOT APEX
Presented by :- charmi j . Patel
Roll no :- 209
Paper :- CBO 404
M.Sc. Sem - 2
Botany
Department of life sciences , patan .

2. • Contents :
 Definition : Transition
: shoot apex
 Main difference between the vegetative shoot and
reproductive shoot
 Vegetative shoot apex
 Origin of Reproductive shoot apex

3. • Definition :
 Transition :- The process or a period of
changing from one state or condition to another
.
 Shoot apex :- The shoot is the productive center
for a plant. It is the organ system that gives
rise to stems, leaves and flowers. Therefore , the
shoot system is functionally responsible for food
production ( photosynthesis ) and reproduction.
Shoots can be classified as vegetative or floral
(reproductive ).

4. • Main difference between the vegetative
shoot apex and reproductive shoot apex :
 Vegetative shoot apex :- It is usually branched.
Growing points is not used up. Growth is
usually unlimited.
 Reproductive shoot apex :- growing point is
used up in production of floral organs. Growth
is limited.

5. • Vegetative shoot apex :
 The vegetative shoot apices vary in shape, size
and cytohistologic structure, and in their relation
to the lateral organs.
 The shoot apex of pinus and other conifers are
commonly narrow and conical in form. In cycads
and ginkgo they are usually broad and flat.
 The apical meristem of a grass and some other
monocotyledons remains elevated above the
youngest leaf primordium.

6.  There is tunica – corpus organization in the shoot
apex of angiosperms.
 One to five layered tunica have been observed in the
dicotyledons , and one to three layered in the
monocotyledons.
 In angiosperms the number of parallel periclinal
layers in the shoot apex may vary during the
ontogeny of the plant body and under the influence
of seasonal growth changes.
 In the angiosperms the segregation of apical
meristem zones is more definite than in lower
groups.

8.  There are two sets of initials, one above the other,
which give rise to tunica and corpus.
 The number of layers in the tunica may vary even
in an individual plant.

9. • Origin of reproductive shoot apex
:
 In the reproductive state in angiosperms, floral apices
replace the vegetative apices either directly or through
the development of an infloresence.
 The flower, which may occur singly or as part of an
infloresence, is formed during the reproductive phase
of growth.
 It develops from a terminal or lateral vegetative shoot
apex and results in the culmination of meristematic
activity of the particular meristem.
 Thus, the floral apex, like the leaf primordium and
unlike the vegetative shoot apex, shows determinate
growth.

10.  The change to the reproductive stage may be first
detected by the modified growth habit of the shoot.
 When the flowers develop an axillary-branch
inflorescence, there appears an acceleration in
production of axillary buds, which shows one of the
earliest indication of approaching flowering.
 Simultaneously, the nature of foliar organs subtending
the axillary buds also changes. The develop as bracts
more or less distinct from the foliage leaves.

11.  Here during the reproductive stage the axillary buds
appear earlier and grow more vigorously than the
subtending bract primordia.
 The next feature that reveals the beginning of the
reproductive state is the sudden increase in the
elongation of internodes.
 From the viewpoint of histology and cytology the
reproductive meristem differs from the vegetative
meristem in varying degree.

12.  It may have the same quantitative relationship
between the tunica and the corpus as was present in
the vegetative apex, or the number or separate surface
layers may be reduced or increased.
 The most conspicuous change is exhibited in the
distribution of the eumeristematic and the more highly
vacuolated cells.
 In many species the apex of the infloresence or the
flower shows a uniform, small-celled mantle like zone
of one or more layers enclosing a large celled core,
this type of apex may be flatter and wider than the
vegetative one.

13.  It is not necessary that the mantle may
coincide with the tunica, a part of corpus may
be included in it.
 The cells of the central tissue enlarge and
become vacuolate, and the meristematic activity
remains restricted to the mantle zone.
 This activity is concerned only with the
production of floral organs.

16. • References :
 A textbook of Botany
- Anatomy of Angiosperms
- By :- B. P. Pande

17. Thank you