1. Lecture (3)
Plant growth & developmentPlant growth & development
Dr/ Bardees Mohammad Ahmad MickkyDr/ Bardees Mohammad Ahmad Mickky
Lecturer of Plant Physiology
Botany Department, Faculty of Science
Mansoura University
1
2. IntroductionIntroduction
Metabolism - Growth - Development
GrowthGrowth
Definition of Growth
Growth Curve
Types of Growth
Phases of Growth
DevelopmentDevelopment
Definition of Development
Differentiation - De-differentiation - Re-differentiation
Developmental Transition in Plants
2
Main topics in lecture (3):Main topics in lecture (3):
3. Metabolism was previously defined as
a summary of all biochemical reactions
occurring within a living cell
or
a summary of all biological reactions
occurring within a living organism
We have also learned that metabolic processes may be
anabolic, i.e. synthetic activities with a net build up
catabolic, i.e. degrading activities with a net break down
3
MetabolismMetabolism -- GrowthGrowth -- DevelopmentDevelopment
4. Anabolic and catabolic activities are
not only the reverse of each other,
but they are also interlinked
(e.g., photosynthesis & respiration)
Moreover, anabolic and catabolic activities
occur in a programmed fashion under definite control
with a certain balance according to the cell demand
Under normal conditions and before senescence,
anabolism should occur in excess of catabolism;
and when this occurs, growth results
4
5. So, growth is an outcome of metabolism
More precisely, what is the philosophy of metabolism?
in other words,
why do biochemical reactions occur within the living cell?
or,
why do biological reactions occur within the living organism?
The answer is simply; to keep it alive
And it here refers to the cell and subsequently to the organism
5
6. But definitely the cell or the organism will not be still alive forever,
it will live for a time that we scientifically call the life cycle
During the life cycle, the organism should NOT remain as the same
with the similar shape, form, structure,
mass, size weight or number of cells.
Instead, certain changes will occur;
and such changes should be positive in both
quantitative (increase) and qualitative (enhancement) levels
So, growth and development are the outcomes of metabolism
6
7. Growth is a gradual permanent irreversible
increase in the plant dry weight
due to the increase in both:
cell number via cell division
and
cell size via cell enlargement.
7
Definition of GrowthDefinition of Growth
8. Growth curve is an S-shaped or sigmoid curve
obtained when we plot growth against time.
This curve mainly shows 4 phases of growth:-
1- initial slow growth (lag phase)
2- rapid period of growth (log / exponential phase)
3- another slow period (diminishing phase)
4- finally growth stops (stationary / steady phase).
8
Growth CurveGrowth Curve
10. (1) Primary and secondary growth:
The increase in plant length due to the activity of
apical meristems (shoot & root tips)
is a vertical type of growth known as primary growth.
The increase in plant diameter due to the activity of secondary
meristems (lateral & intercalary meristems) is a horizontal type
of growth known as secondary growth.
10
Types of GrowthTypes of Growth
11. (2) Limited and unlimited growth:
Plant stem and root usually grow continuously
from early germination stages to plant death.
This type of growth is called unlimited or indeterminate growth.
However, leaves, flowers and fruits
stop growing after attaining certain size.
This type of growth is called limited or determinate growth.
11
12. (3) Vegetative and reproductive growth:
The earlier growth of plant producing
leaves, stems and branches without flowers
is called vegetative growth.
After the vegetative phase of plant growth, plant produces
flowers which are the reproductive part of the plant.
This is called reproductive growth.
12
13. (4) Annual, biennial and perennial growth:
Annual plants complete their life cycle from germination through
flowering and seed production to death in a single year or less.
e.g., cereals and legumes.
Biennial plants complete their life cycle in two years.
e.g., onion and carrot.
Perennial plants live many years, and often die not from old age
but from an infection or some environmental trauma.
e.g., shrubs and trees.
13
14. The period of growth can be generally divided into 3 phases:
1- Phase of cell division (Formation phase)
2- Phase of cell enlargement (Elongation phase)
3- Phase of cell differentiation (Maturation phase)
14
Phases of growthPhases of growth
15. 11-- Formation phaseFormation phase
The meristematic cells of shoot and root apex
divide repeatedly and rapidly
to add new cells to plant length.
These cells are characterized by:
dense protoplasm
large nucleus
thin primary cell wall
15
16. 22-- Elongation phaseElongation phase
The new cells formed through cell division
begin to increase in size due to:
increased vacuolation (vacuole increase in size)
cell wall growth (new deposition + stretching)
33-- Maturation phaseMaturation phase
The cells assume certain forms
based on their function to form the various plant tissues.
16
17. Thus, there are 3 main activities involved in
plant growth and development:
1- Cell division
2- Cell enlargement
3- Cell differentiation
division and enlargementresults primarily from both cellGrowth
while development occurs as the sum of
growth and differentiation
17
Definition of DevelopmentDefinition of Development
18. Differentiation is a process during which
cells undergo structural changes
in their cell wall and protoplasm
to possess distinct morphology
with unique function.
.A differentiated cell can not divide
18
DifferentiationDifferentiation -- DeDe--differentiationdifferentiation -- ReRe--differentiationdifferentiation
19. However, an undividable differentiated cell sometimes
regains the power of division in a process known as
de-differentiation. Now, a de-differentiated cell
can divide to produce new cells.
Again, these newly-produced cells loose the ability to divide
and become a part of permanent tissue. This process is
called re-differentiation.
19
20. Plants undergo several developmental transitions
during their life cycle.
Shoot of higher plants passes through 3 more or less distinct
phases during its post-embryonic development, and these are:
1- Juvenile vegetative phase,
where the plant is not competent to flower
2- Adult vegetative phase,
where the plant can respond to floral inductive signals
3- Reproductive phase,
where the flower is produced to undergo reproduction
20
Developmental Transition in PlantsDevelopmental Transition in Plants
21. Lecture (4)
Plant growth & developmentPlant growth & development
Dr/ Bardees Mohammad Ahmad MickkyDr/ Bardees Mohammad Ahmad Mickky
Lecturer of Plant Physiology
Botany Department, Faculty of Science
Mansoura University
1
22. Vegetative GrowthVegetative Growth
Leaf Growth
Phytohormonal Levels during Leaf Growth
Environmental Effects
Reproductive GrowthReproductive Growth
Flowering
Pollination
Fertilization
Seed Formation & Fruiting
2
Main topics in lecture (4):Main topics in lecture (4):
23. Leaf growth occurs due to the growth of both:
lamina and petiole
This occurs due to the increase in
cell number via cell division
and
cell size via cell expansion.
3
Leaf GrowthLeaf Growth
24. 4
Phytohormonal Levels during Leaf GrowthPhytohormonal Levels during Leaf Growth
Phytohormones
Growth Activators Growth Inhibitors
Auxins
Cytokinins
Gibberellins
ABA
Ethylene
Jasmonate & related
High Levels
During
Leaf Growth
High Levels
During
Leaf Growth
25. Leaf growth is affected by different environmental factors
such as:
5
Environmental EffectsEnvironmental Effects
Temperature
Light
Water
Minerals
Pests & Diseases
26. Reproductive growth begins with the formation of flower
in a process known as flowering.
Flowering is highly affected by:
1- Light
( photoperiodism: response to light / dark ratio = day / night ratio)
2- Temperature
(vernalization: need for cold temperature)
6
FloweringFlowering
27. Photoperiodism is the response of plants to
day/night or light/dark ratio.
The response of plants to day/night ratio may be:
seed germination, vegetative growth or flowering.
Flowering is the first photoperiodic response to be discovered
and the most studied response.
7
28. 8
Some plant species need low day/night ratio to flower,
so they bloom in winter and are called
short day plants (e.g., soybean).
Other plant species need high day/night ratio to flower,
so they bloom in summer and are called
long day plants (e.g., spinach).
The last type of plant species flower
regardless of day/night ratio,
and they are called day neutral plants (e.g., tomato).
29. 9
Vernalization is the artificial exposure of
plants (or seeds) to low temperatures
in order to stimulate flowering.
For example; winter wheat would not flower
without a period of chilling (vernalization).
30. Pollination is the transfer of the male pollen grain from flower
stamen to the female ovule in the flower carpel.
This transfer process may happen with the aid of:
10
PollinationPollination
Wind
Insects
Animals
Human
32. Flowers may have
only male or female organs (called imperfect flowers)
or both together (called perfect flowers).
These terms should not be confused with
those that describe the plant as whole.
The individual plant may produce
either male or female flowers (called dioecious plant )
or produce both (called monoecious plant ).
In monoecious species,
individual plant may have imperfect or perfect flowers.
12
33. Only after pollination,
when the pollen has landed on the stigma of a suitable flower,
the pollen grain on the stigma grows a tiny tube,
all the way down the style to the ovary.
This pollen tube carries a male gamete
to meet a female gamete in an ovule.
In a process called fertilization,
the two gametes join and their chromosomes combine,
to form a fertilized ovule called a zygote.
13
FertilizationFertilization
34. 14
Seed Formation & FruitingSeed Formation & Fruiting
The fertilized ovule goes on to form a seed,
which contains a food store and an embryo.
The ovary develops into a fruit to protect the seed.
That embryo will later grow into a new plant
after the processes of
germination, growth and development.
