BRIDGE COURSE PROGRAM
Vikasana – Bridge Cource 2012
INTRODUCTION:
Plant begins
g
its life from a single
g
celled zygote after fertilization. It follows
p
manyy successive events to form a complex
body, having root, stem, leaves flower. The
plant p
parts are controlled and
formation of p
maintained by developmental processes.
growth and the differentiation are the
The g
two important process for development.
Growth
y The fundamental characteristic of living g
being.
y It’s a metabolic process – anabolic and catabolic.
y It requires energy.
y Process is a INTUSUSSEPTION‐
P
i INTUSUSSEPTION increasing i
i the protoplasm of a plant body.
Definition of Growth
Growth is an irreversible, permanent, increase in size volume or mass of an organ or its part or an in size, volume or mass of an organ or its part or an individual cell.
Growth results:
y Increasing dry weight.
y Takes place in certain parts‐
Takes place in certain parts root and shoot apex.
root and shoot apex
y Increase in length‐ Meristematic cells at apex.
y Girth/diameter increase due to secondary meristem.
PLANT PARTS‐SHOWING GROWTH
How growth takes place?
g
p
y Division of Meristematic cells.
y Mitotic cellular division.
Mitotic cellular division
y Cell increase in number. y Length increase by root and shoot apex.
GROWTH
UNLIMITED
GROWTH
LIMITED
GROWTH
UNLIMITED GROWTH
y Indeterminate type Ex: Root and shoot system
y Continuous growth.
y Seed germination to death.
y Capacity of cell division is restricted to locations.
p
y
y New cells are added.
y Apical meristems
p
causing primary growth.
gp
yg
y Lateral meristems‐ vascular and cork‐cambium, causing secondary growth in dicot
g
yg
and gymnosperms.
LIMITED GROWTH
y Determinate type
Ex: Leaves, Flowers, Fruits.
y Stop growing after gaining St i ft i i certain size.
Plant also exhibits two kinds of growth:
Plant also exhibits two kinds of growth:
Vegetative growth:‐ Begins from the seed germination. Plant body having, stem, leaves and branches.
Reproductive growth:‐
p
g
Begins after vegetative g
g
growth‐ produce ends in seed flowers, production.
How to measure growth?
g
1.
2.
3.
4.
5.
At cellular level, growth is an increase in amount of protoplasm. It is measured by different means:
Increase in dry/fresh weight.
Increase in length.
Increase in area.
I
Increase in volume.
i l
Increase in cell number.
PHASES OF GROWTH
Root and the shoot apex region are studied to
understand the phases of growth. Period of growth
can be divided into Three phases.
phases
1
1.
Meristematic phase: region of cell division.
phase: region of cell division
2.
Elongation phase: region of cell elongation.
33.
Maturation phase: region of differentiation.
p
g
Root apex showing growth regions
MERISTEMATIC PHASE
y Cells are rich in protoplasm.
y Nucleus is large and prominent.
y Cell walls are primary in nature.
y Cell wall is thin and contains cellulose.
C ll ll i thi d t i ll l
y Plasmodesmata are more in number.
ELONGATION PHASE:
y It is present next to Meristematic region.
y Vacuoles are large in size.
y Enlarged cells.
y Results in new cell wall deposition.
Resu ts
e ce
a depos t o .
MATURATION PHASE:
y The region is present away from the apex.
y It is close to the elongation region.
y Cell reach maximum size.
y Wall thickenings takes place.
W ll thi k i t k l
y Protoplasmic modification occurs.
y Different cell types‐ parenchyma, collenchyma, sclerenchyma, xylem and phloem.
GROWTH RATE
Increase in growth per unit time is I
i th it ti i the growth rate. It may be arithmetic or geometrical.
geometrical
In arithmetic growth, only one d
daughter cell continues to divide and others h ll i
di id d h differentiates and matures.
In geometrical growth, growth increases rapidly, daughter cells continue mitotic divisions. All the cells divide.
SIGMOID CURVE/GROWTH CURVE
When we plot growth against
time, a sigmoid curve or S‐ curve, is
obtained. It is the common character of all
living organisms in nature.
Initial growth is slow and is in lag phase
(lagging
phase).
(l i
h ) Cells
C ll divide‐
di id increases
i
rapidly‐ follows exponential rate‐
logarithmic phase.
phase The daughter cells
undergo mitotic division‐ they retain the
dividing
d
v d g ab
ability‐
ty co
continue
t ue tthee d
division.
vso .
Growth slows down (diminishing)
leading to a stationary phase. We get a
typical sigmoid curve, similar in tissues
and cells of a plant.
DIFFERENTIATION:
In three phases of cell growth, cell divides,
enlarges and differentiates. In division and
enlargement
l
t phases,
h
cell
ll increases
i
i size
in
i but
b t later
l t
differentiates and matures to perform a definite
function. This maturityy is the differentiation. Cell
wall and protoplasm undergo changes and stop the
division.
C ll l i h Cell loosing the protoplasmÆ
l
Æ in tracheary
i h
elements of xylem.
Cell gaining rigidityÆ elastic, lignin depositionÆ
elastic lignin depositionÆ
sclerenchyma.
DE
DE‐ DIFFERENTIATION
It’s the process where living, differentiated
cells regain the capacity
cells,
capacit of cell division.
di ision It is
responsible for secondary growth. The
parenchyma cells are known for de‐
de
differentiation.
E I
Ex: Inter fascicular cambium and cork cambium.
f i l bi d k bi
RE‐ DIFFERENTIATION
Meristematic cells or tissues are able to divide
and produce the cells that once again loose the
capacity to divide but matures. They do specific
function after maturity and become a permanent
tissue, the process is re‐ differentiation.
E T
Ex: Tumour
cells and callus in tissue culture.
ll d ll i ti
lt
Differentiation in plant is open, because
y Cells of the same meristem have different
y
structures at maturity.
y Structure at maturity is determined by
location of the cell‐ cells away from apical
meristem develop as root cap in root apex.
apex
y Cell pushed to periphery mature as ll
h d
h
epidermis
DEVELOPMENT
y Sum total of growth and differentiation.
y It includes all changes in life cycle.
y Starts from germination to senescence.
g
Plasmatic growth
Meristematic
Differentiation
cell
Expansion
S
Senescence
DEATH
Maturation
M t
Mature
cellll
PLASTICITY
Development of a plant is influenced by
ENVIRONMENT.. They show different kinds
ENVIRONMENT
of structures OR follow different pathways
in response to environment
environment.. This ability is
called PLASTICITY.
PLASTICITY.
Examples‐Coriander leaves –shapes
,Young
leaves
have
less
dissected
Y
l
h
l
di
t d but
b t
mature leaves show more dissected.
Heterophylly in water plant Limnophylla
heterophylla.
heterophylla Leaves inside water shows
dissected leaves ,leaves above the water level
shows undissected leaves.
Growth,, differentiation and development
p
are related events in a plant.
Development
D
l
t iis a sum ttotal
t l off growth
th and
d
differentiation .
Both are under the control of external and
internal factors.
y EXTERNAL FACTORS ‐EXTRINSIC FACTORS.
y INTERNAL FACTORS ‐INTRINSIC FACTORS.
y GENETICAL CAUSES.
y INTERCELLULAR FACTORS‐ CHEMICALS ,called GROWTH REGULATERS
PLANT GROWTH REGULATERS
™They are also called PHYTOHORMONES.
™They are simple chemicals.
™They produce in small quantity.
™Promote growth or inhibit growth
P
t th i hibit th
™Produce in certain parts of the plants.
™They are transported to the site of action.
ACCIDENTAL INVENTION OF GROWTH REGULATERS
Charles Darwin and his son Francis Darwin
observed grass coleoptiles tips moving g
p
p
g
towards light.
F.W.Went continued the experiments in coleoptiles of oat and isolated the AUXIN.
E.Kurosawa reported an active substance from a fungus Gibberella fujikuroi causing Bakane
di
disease
(f li h dli di
(foolish seedling disease)
)
Skoog and Miller discovered action of coconut milk
promoting Callus formation in tissue culture.
Cousin confirmed the ripening of stored unripened Bananas influenced by ripened
Oranges.
GENERAL CHARACTERS OF PHYTOHORMONES
y Phytohormones may promote the growth or iinhibit the growth.
hibi h h
y Growth promoters involved in cell division, cell enlargement tropic movements flowering enlargement, tropic movements, flowering, fruiting, seed formation, root formation.
,g
y
ex: auxins, gibberellins and cytokinins.
y Growth inhibiters involved in dormancy, abscission wound response and stress.
ex: ethylene and abscisic acid
AUXINS (auxein= to grow)
y Isolated from human urine.
y Chemically Indole‐
y
33‐ Acetic acid and other natural and synthetic compounds. y Produced at growing root and shoot tips.
g
g
p
y Move to the region of action.
y Indole Acetic acid and Indole Butyric acid isolated from plants.
y Naphthalene Acetic acid and 2, 4, D are synthetic auxins.
Functions and applications of Auxins:
Functions y Initiate rooting in tissue culture. Æ
y Promote flowering.
Promote flowering
Æ
Applications
stem cuttings propagation.
i
In pineapples.
y Prevent early drop of leaf and fruit.
P
l d f l f d f i
y Promote older leaves and fruits to fall off.
y Apical dominance.
y Induce parthenocarpy. ÆTomatoes.
ÆKilling of dicot
ÆKilli
f di t
weeds in plantations of l t ti
f coconut, areca‐
nut etc.
t t
y Prevents xylem differentiation.
y Herbicides.
H bi id
GIBBERELLINS
y Extracted from Gibberella fujikuroi‐ a fungus.
y There are more than 100 gibberellins. Denoted as There are more than 100 gibberellins Denoted as GA1, GA2 , etc.
y GA3 was the first gibberellins to discover and study.
y All gibberellins are acidic in nature.
All ibb lli idi i FUNCTIONS AND APPLICATIONS OF GIBBERELLINS
y
increase the length of plant axis
(e o gat o o g ape sta .)
(elongation of grape stalk.)
y
elongation and proper shape.
elongation and proper shape
(apple and other fruits)
y delay senescence. prevent early fall.
(All fruit plants‐ to retain them in tree)
y promotes bolting.
(Beet root cabbage etc)
(Beet root, cabbage etc)
y Stem increase in length.
S
i
i l
h
(sugar cane)
CYTOKININS
y Effect specifically on cytokinesis.
y Discovered as kinetin ,not naturally occurring.
y Coconut milk and corn kernel contain as zeatin.
y Synthesized in root and shoot apex and S th i d i t d h t d young fruits.
Effects and applications
y Cell division promoting activity
y Help to produce new leaves, chloroplast.
hl
l
y Lateral growth and adventitious shoot g
formation.
y Help to overcome apical dominance
y Delay leaf senescence
ETHYLENE.
Growth inhibitor
Growth inhibitor
y Gaseous hormone, produced in senescing ,p
g
tissues and ripening fruits.
y Increases respiratory rate fruit
Increases respiratory rate fruit.
y Influence the swelling of plant axis.
y Promotes senescence.
P
y Formation of abscission layer in leaves and flowers.
y Increases respiration rate‐ripening.
APPLICATION OF ETHYLENE
y Break seed dormancy and bud dormancy.
y Initiates seed germination‐Groundnut, p
g
tubers.
sprouting of Potato
y Promote internodes and petiole elongation
Rice plants of deepwater cultivation
g
y Promote root growth –root hair formation.
y Initiates flowering ‐Pineapple.
Initiates flowering Pineapple.
y Flower induce –Mango.
Flower induce –Mango
y Ethephon
Eth h a fruit ripener
f it i
–Tomato, Apple, T
t A l Cherry, female flower production in cucumbers.
cucumbers
ABSCISSIC ACID‐growth inhibitor.
y Regulates abscission and dormancy.
y Inhibits seed germination y Stimulate closing of stomata.
y Increases tolerance of plants to stress –
I
t l
f l t t t
STRESS HORMONE.
y Induces dormancy‐seed development and d
d
dd l
d
maturation.
y Withstand desiccation.
PHOTOPERIODISM.
Light influence.
Li ht i fl
y Flowering responses to relative length of g p
g
LIGHT and DARK period in 24 HOUR cycle –PHOTOPERIODISM.
y CRITICAL PERIOD‐for flowering.
y MORE – long day plants.
g yp
y LESS‐short day plants.
y NEUTRAL day neutral plants not affected by U R day eut a p a ts ot a ected by
light exposure.
Above
flowering
Critical
photo
period
Below no
flowering
LDP
Oat,rye,beetroot
,pea
Above no
flowering Flowering
after
vegetative
Below
y
maturity
flo ering
flowering
SDP
Tobacco, coffee,
chrysanthemum
DNP
Tomato,
sunflower,
cucumber
EXAMPLES FOR LDP
OAT AND RYE
BEET ROOT
PEA PLANT
EXAMPLES FOR SDP
COFFEE
TOBACCO
CHRYSANTHEMUM
EXAMPLES FOR DNP
TOMATO
SUNFLOWER
VERNALISATION
Low temperature treatment for flowering for a p
period.2 kinds of varieties winter and spring –
p g
barley ,rye.
Spring varieties –planted in spring –flower and grain production in SPRING
Winter varieties –planted in autumn‐flower in spring harvested in summer.
Biennial plants –Monocarpic‐need a cold temperature treatment for flowering.Ex,:Beet
f fl
i
root, Cabbage ,Carrot THANK YOU
AND
ALL THE BEST