defination intro-types of bud-factors affecting dormancy

1. BUD DORMANCY

2. CONTENTS
• Defination
• Introduction
• Types of bud
• Factors affecting dormancy

3. DEFINATION
• In botany ,a bud is an undeveloped or
Embryonic shoot and normally occurs in the
axil of a leaf or at the tip of stem.
• Once formed a bud may remain for some
time in condition, or it may form a shoot
immediately.
• Buds may be specialized to develop flowers
or short shoots ,or may have the potential for
general shoot development.

4. INTRODUCTION
• The buds of many woody plants, especially
in temperate or cold climates, are protected
by a covering of modified leaves called
scales.
• Which tightly enclose the more delicate
parts of the bud.
• Many bud scales are covered by a gummy
substance which serves as added protection.

6. • When the bud develops, the scales
enlarge somewhat but usually just drop
off, leaving on the surface of the growing
stem a series of horizontally elongated
scars.
• The minute underdeveloped leaves in
such buds are often excessively hairy.
• In many of the latter, buds are even
more reduced, often consisting of
undifferentited masses of cells in the
axils of leaves.

7. • A terminal bud occurs on the end of a
stem and lateral buds are found on the
side.
• Since buds are formed in the axil of
leaves, there distribution on the stem is
the same as that of leaves.
• in many plants buds appear in
unexpected places these are known as
adventitious buds.

8. TYPES OF BUDS
• Buds are often useful in the
identification of plants, especially for
woody plants in winter when leaves have
fallen.
• Buds may be classified and described
according to different criteria:-location
,status, morphology and function

9. FOR LOCATION:-
• TERMINAL:-When located at the tip of a
stem.
• AXILLARY:-When located in the axil of a
leaf.
• ADVENTITIOUS : When occurring
elsewhere for example on trunk or on
roots.

10. FOR STATUS:-
• ACCESSORY:-For secondary buds formed
besides a principal bud.
• RESTING:-For buds that form at the end of
growth season ,which will lie dormant untill
onset of the next growth season.
• DORMENT OR LATENT:- For buds whose
growth has been delayed for a rather long
time .The term is usable as synonym of
resting.
• PSEUDOTERMINAL:-For an axillary bud taking
over the function of terminal bud.

11. FOR MORPHOLOGY:-
• SALLY OR COVERED:-When scales,
also referred to as perule. Cover and
protect the embryonic parts;
• NAKED:-When not covered by scales.
• HAIRY:-when also protected by
hairs.

12. FOR FUNCTION:-
• VEGETATIVE:- If only containing
vegetative pieces: embryonic shoot
with leaves (a leaf bud is the same)
• REPRODUCTIVE:-If containing
embryonic flower.(a flower bud is
the same).
• MIXED:-If containing both
embryonic leaves and flowers.

13. FACTORS AFFECTING
DORMANCY
• Factors Affecting seed germination :
External and internal factor
• Some of the important factors are:
• External factors such as water, oxygen
and suitable temperature.2 internal
factors such as seed dormancy due to
internal conditions and its relesase.

14. EXTERNAI FACTORS:
• 1 WATER : A Dormant seed is generally
dehydrated and contains hardly 6-15% water
living cells. the active cells, however , require
about 75-95%of water for carrying out their
metabolism.
• Therefore the dormant seed must absorb
external water to become active and show
germination
• water also brings in the dissolved oxygen for
use by the growing embryo.

15. OXYGEN:- oxygen is necessary for
respiration which releases for respiration
which releases needed for growth
• Germinating seeds respire very actively
and need sufficient oxygen.
 SUITABLE TEMPERATURE: Though
germination can take place over a wide range
of temperatur(5-40c), the optimum for most
of the crop plants is around 25-30c.
• The germination in most cases stops at 0c and
45c.

16. • INTERNAL FACTORS
• Seed dormancy due to internal
conditions its release:
• In some plants the embryo is not fully
mature at the time of seed shedding
• Such seed do not germinate till the embryo
attains maturity.
• The freshly shed seed in certain plants may
not have sufficient amounts of growth
hormones required for the growth embryo.

17. • The seeds of almost all plants remain
viable or living for a specific period of
time.
• seeds of lotus have the maximum
viability period of 1000 year.
• Seeds germinate before the ending of
their viability periods.

18. REFERENS
• A Text book of college botany
- S. Sundara rajan

19. THANK YOU