This Chapter deals with plant growth and development and dormancy of seed and buds

1. Plant Growth and development

2. Plant growth and development
• “Growth” and “development” are sometimes used
interchangeably in conversation, but in a botanical
sense they describe separate events in the
organization of the mature plant body.
• Growth is the irreversible change in size of cells
and plant organs due to both cell division and
cell enlargement.
• Enlargement necessitates a change in the elasticity
of the cell walls together with an increase in the
size and water content of the vacuole.

4. • Growth can be:
I. Determinate: When an organ or part or whole
organism reaches a certain size and then stops
growing.
II. Indeterminate: When cells continue to divide
indefinitely.
• Plants in general have indeterminate growth.
The pattern of plant growth can be represented by a
typical growth curve called sigmoid curve or ‘S’
shaped curve.
Growth is slow at first (lag phase), then gains speed
(log phase or exponential phase) and eventually
slows down and come to halt (Stationary or
Senescence phase or Plateau Phase).

9. Growth pattern of Tomato

10. Type of growth curves in fruit crops:
1. Sigmoid/ Single sigmoid curve – Fruit undergoes slow
enlargement at the early (a) and last stages of growth (c),
while growth is considerably faster during the middle
development stage (b). Ex: Apple, pear, pineapple, banana,
avocado, almond, strawberry, loquat, date palm, papaya,
mango and lemon

11. 2. Double sigmoid curve – Three stages are
seen
a. Ovary, nucellus and integuments of the seed
grow rapidly, but the embryo and
endosperm grow little.
b. Embryo and endosperm grow rapidly, but
the ovary does not increase much in size,
sclerification of the pit also begins and
embryo achieve full size by the end and the
amount of endosperm material increases
greatly.
c. A new surge of ovary growth begins and
continues to fruit ripening
Ex: Peach, plum, apricot, ber, raspberries, fig,
blackberry, blueberry, cherry, pecanut,
persimmon, guava, grapes, olives, etc.

12. 3. Triple sigmoid curve – Five stages are
seen
a. Initial rapid growth, seeds reaching full
size (0-9 weeks)
b. Slow growth, seeds hardens and start to
colour, first very large respiratory response
to ethylene (9-12 weeks)
c. Rapid growth, seeds become dark brown,
response to ethylene increases (12-17 weeks)
d. Very little growth, seeds dark brown,
softening starts, soluble solids starts to
increases, respiratory response to ethylene
rises to a maximum and then decreases (17-
21 weeks)
e. A smaller but significant growth increase
to approximately final size. The fruit
matures, the seeds becoming very dark
brown and free in the tissues.
• Ex: Kiwi fruit.

14. • Development is the progression from earlier to
later stages in maturation, e.g. a fertilized
egg develops into a mature tree.
• It is the process whereby tissues, organs, and
whole plants are produced.
• It involves: growth, morphogenesis (the acquisition
of form and structure), and differentiation.
• The interactions of the environment and the
genetic instructions inherited by the cells
determine how the plant develops.
• This process involves the synthesis of many organic
compounds like protein, cellulose and nucleic
acids.

15. Difference between Growth and Development
S.N Growth Development
1. The increase in cell size and number
that take place during the life history of
an oraganism
The progressive change in size, shape
and function during the life of an
organism by which its genetic potentials
(genotype)are translated into functioning
mature systems (Phenotypes)
2. The increase in size and mass over a
period of time
The transform of an organism into a
more complex form in function and
organization wise
3. A part of development Includes growth, morphogenesis and
differentiation
4. Quantitative Quantitative and qualitative
5. Occurs at the cellular level Occurs at the organizational level
6. Brings changes in the size, shape, form
and structure of the body.
Brings the changes in the organization
and function
7. Stops at maturation Continues throughout the life
8. Can be measured directly A subjective interpretation

17. Seed and bud dormancy
• Seed : Seed is defined as a mature
fertilized ovule containing an
embryo embedded in a an energy
rich endosperm and surrounded
by a protective coat.
• Dormancy: It is the state in which
viable seeds fail to germinate even
under the conditions of moisture,
temperature and oxygen
favourable for vegetative growth.

19. Significance of dormancy
In temperate climates, dormancy of buds
helps the plant to tide over the severe colds
which may be injurious for vegetative and
reproductive growth.
In tropical region, the dormancy of seeds
resulting from their impermeable seed coats
ensures moisture content to remain intact
which ensures good chance of survival.
Dormancy of seeds helps in storing the seeds
for the following season.

23. Types of Seed dormancy
1. Imposed dormancy( Quiescence Dormancy):
 Seed germination need favourable environmental conditions like
sufficient water, proper temperature etc.
 In absence of such conditions seed does not germinate or become
dormant.
or
 The dormancy due caused due to unfavourable environmental
condition is called imposed dormancy.
 This type of dormancy is known as imposed dormancy.
2. Innate (Deep dormancy):
 Sometimes seed is unable to germinate due to the structural,
chemical or physiological properties of seed itself, this
phenomenon is called innate dormancy.
3. Complex types of dormancy:
 These are caused by several different mechanisms which make
germination difficult or hinder it altogether.

34. Causes of Seed dormancy
1. Seed coat impermeable to water:
The presence of impermeable testa or hard and
multi-layered seed coat leads to dormancy.
Seeds of certain plants especially leguminosae,
Solanaceae, Malvaceae, Chenopodiaceae etc.
2. Seed coat impermeable to Oxygen
 In few plants belonging to Compositae family,
dormancy of seeds results from the impermeability of
seed coats to oxygen
3. Mechanically resistant seed coats:
The presence of hard seed coat prevents the expansion
of the embryo which results in dormancy of few
plants.

36. 4. Immaturity of embryo:
Seed germinate only after a period of rest
during which the development of the embryo
inside the seed is complete.
Embryo is not matured at the time of
harvesting.
 For maturity of such embryo, rest period is
required.
Example: Caltha palustris

37. 5. Germination inhibitors:
Dormancy of seed also results due to the presence of
certain germination inhibitors (Coumarin, Abscisic
acid, Ferulic acid, Ammonia, Dinitrophenols,
Parascorbic acid, Aldehydes, Aklloids, Fluorides.
Example: Tomato fruit pulp contain- Caffeic and
Ferulic acid which induce dormancy.

38. 6. Chilling ( low ) temperature requirement:
 In certain plants such as Apple, Rose, Peach,
Walnut, Pinus, etc., the seed remain dormant after
harvest in the autumn because they have a very low
temperature or chilling requirement for germination.
Such seeds need chilling temperature (4-7 C for few
weeks.
In nature, the chilling temperature is provided by the
winter temperatures.

40. 7. Light sensitive seeds:
In many species the germination of seed is affected by
light resulting in seed dormancy and these type of seed
are called photoblastic seeds:
i. Positively photoblastic seeds: Seeds germinates only
after they have been exposed to light. E.g. Tobacco ,
tomato
ii. Negatively photoblastic seeds: Seed germination is
inhibited by light. E.g. Garlic, Onion, Pholx, Nemophila
and Silene

41. Control/Methods of breaking of dormancy
1. Scarification:
 The process of rupturing or weakening the seed coats
by mechanical or other means is called Scarification.
It is employed in those cases where the dormancy of
seed is caused due to impermeable seed coats.
It is done mechanically either by thrashing the seed by
machines or by hands (Coriander) or chemically by
treating with strong mineral acids like Conc. H2SO4,
Hydrogen peroxide (H2O2).
2. Application of pressures
Dormancy due to impermeability of testas to water can
be subjected to hydraulic pressure of 2000 atm at 18 ºC
for 5-20 minutes.

45. 3. Low temperature treatments ( Stratification)
In many species, seed dormancy can be overcome if
the seeds are treated in moist medium at low
temperature (0-5 or 4-7 ºC) for sufficient period.
This process is called stratification.
It can be also done by alternating the layers of wet
sphagnum (peat moss) and some suitable materials
and then keeping them at low temperature.
4. Alternating temperature treatment
An alternation of low and high temperature (the
difference of the two being not more than 10ºC or
20 ºC breaks the dormancy in certain plants.

50. 5. Germination stimulating compounds:
Kinetin, Gibberellin, Auxin, Cytokinin, Ethylene,
Potassium Nitrate (KNO3) and Thiourea are
commonly used to induce germination.
6. Removal of inhibitors:
Growth inhibiting chemicals are removed by
repeated washing with water.
7. Treatments with PGRs.
GA3 substitute the cold treatment requirement in
many seeds.
Cytokinin promotes germination of many seeds.

51. 8. Specific light requirement:
Dormancy of photoblastic seeds can be overcome by
light exposure.
Red light promotes germination in lettuce seeds.

53. Bud dormancy:
 A period of temporary suspension of growth in buds
especially during moisture stress and temperature
extremes (during winter) is known as bud dormancy.

56. Types of buds
• Buds are often useful in the identification of plants,
especially for woody plants in winter when the
leaves have fallen.
• Buds may be classified and described according to
different criteria:
Location
Status
Morphology
Function

57. 1. Based on Location
a. Terminal Bud
When located at the tip of a stem
b. Axillary bud
When located in the axil of a leaf
c. Adventitious bud
When occurring elsewhere for example: on
trunk or on roots

58. 2.Based on status
a. Accessory bud:
• For secondary buds formed besides a principal bud.
b. Resting bud:
• For buds that form at the end of growth season
which will lie dormant until the onset of the next
growth season.
c. Dormant or Tolerant:
• For buds whose growth has been delayed for a rather
long time. The term is usable as synonym of resting.
d. Pseudo terminal:
• For an axillary bud taking over the function of
terminal bud.

59. 3. Based on Morphology
a. Scally or Covered:
• When scales also referred to as perule. Cover
and protect the embryonic parts.
b. Naked:
• When not covered by scales.
c. Hairy:
• When also protected by hairs.

60. 4. Based on Function
a. Vegetative bud:
• If only containing vegetative pieces:
embryonic shoot with leaves (a leaf bud is the
same)
b. Reproductive bud:
• If containing embryonic flower (a flower bud
is the same)
c. Mixed:
• If containing both embryonic leaves and
flower

62. Reasons for bud Dormancy

71. References
• https://www.slideshare.net/MahnoorImran14/metho
ds-of-breaking-dormancy-239812464
• https://www.slideshare.net/gohilsanjay3/bud-
dormancy
• https://www.slideshare.net/Vishu1234567/seed-
dormancy-133074445
• https://www.slideshare.net/MaitriThakor/seed-
dormancy-213436624
• Modern plant Physiology-R K Sinha