PBL PRESENTATIONLECTURER : DR. HASIMAH ALIMON
WHAT IS PLANT GROWTH?
Plant growth is the process by which a
plant increases in the number ,size and
length of leaves, stems, roots and
tubers.
WHAT IS PLANT DEVELOPMENT?
Plant development by which plant
structures originate
and mature as a plant grows.
TYPE OF PLANT GROWTH AND DEVELOPMENT
LEAVESLEAVES
TUBERTUBERSS
ROOTSROOTS
STEMSSTEMS
LEAVESLEAVESLEAVESLEAVES
WHAT ARE THE FUNCTIONS OF LEAVES?
Absorb sunlight to manufacture plant sugars through a process called photosynthesis.
The cuticle is part of the epidermis. It produces a waxy layer called cutin, which
protects the leaf from dehydration and disease.
Special epidermal cells called guard cells regulate the passage of water, oxygen, and carbon dioxide into and out of the leaf through tiny openings called stomata.
The Growth and Development of Leaves
The first leaves to develop are the unifoliolate
leaves.
Two of these single leaves appear directly
opposite one another above the cotyledons.
All subsequent leaves are
trifoliolates
comprised of
3 leaflets.
THE GROWTH AND DEVELOPMENT OF RICE LEAVES
A leaf primordium is differentiated
from a little below the shoot apical
meristem (SAM).
As it develops, it elongates and
forms a cone-shaped structure
around the SAM.
Soon after, smaller veins start to
form on both sides of its base, and
later in between larger veins.
When the primordium has grown to about
8 mm, a cavity develops at its base.
The auricles and the ligule will be
differentiated from this location, which will
be differentiated into the collar.
The collar separates the blade and the
sheath.
After the cavity has formed, the meristem
that is responsible for elongation is
activated and the blade starts to elongate.
Now the blade has grown to its full size,
and its cells have stopped dividing, the
blade is ready to emerge.
As the blade emerges, it unrolls from
its tip down to the base.
As it unrolls, cells in the blade expand
to reach a larger size.
This is why an older leaf is wider and longer
that a newly emerged leaf not because it
has more cells, but because its cells have
grown larger.
As soon as the blade starts to expand, the
leaf sheath starts to elongate.
The sheath completes its elongation when
the blade has fully expanded.
ROOTSROOTS
WHAT ARE THE FUNCTIONS OF ROOT
Anchor the plant in the soil.
Store food.
Absorb water and mineral salts
from the soil.
Form a passage way for water and dissolved
substances from the root into the stem and
also for foods from the stem down into the
root.
The Growth and Development of Root
Early root growth is one of the functions
of the apical meristem located near the
tip of the root.
The meristem cells more or less
continuously divide, producing more
meristem, root cap cells and
undifferentiated root cells.
The latter become the primary tissues of
the root, first undergoing elongation, a
process that pushes the root tip forward in
the growing medium.
Gradually these cells differentiate and
mature into specialized cells of the root
tissues.
Growth from apical meristems is known as
primary growth, which encompasses all
elongation.
Secondary growth encompasses all growth in
diameter, a major component of woody plant
tissues and many nonwoody plants.
For example, storage roots of sweet potato have
secondary growth but are not woody.
Secondary growth occurs at the lateral
meristems, namely the vascular cambium and
cork cambium.
THE GROWTH AND DEVELOPMENT OF SOYBEN ROOT
As soybean seed takes on the water
and swells, the radical is the first
part of embryo to penetrate the
seed coat .
It develops rapidly into a root which
must become firmly anchored for
seedling to develop enough
leverage to force its way to the soil
surface.
Lateral roots are formed soon after the radical or primary root begins to elongate.
Root hair appear on the primary root within 4 or 5 days after germination and on the lateral roots soon after they are formed .
These hair are the main absorbing surface of the root system.
They are very small nearly invisible without a lens and might be extensions of single epidermal cells.
They are actively growing part of the root just behind the growing point.
What condition did root grow?
Roots will generally grow in any direction
where the correct environment of air,
mineral nutrients and water exists to
meet the plant's needs.
Roots will not grow in dry soil.
At germination, roots grow downward
due to gravitropism.
What are the functions of stem ?
serves as mechanical support for leaves and buds.
Water and food storage.
Reproduction
Photosynthesis
New growth
Types of growth and development in stem Primary stem growth :-
o begins at the tip of the terminal bud in the area called the apical meristem.
o The cell divisions on the apical meristem are responsible for the stem's growth in length.
Secondary stem growth :-o Also known as secondary thickening or lateral growth
arises from secondary meristems.o Secondary xylem and secondary phloem are formed.o Stems are tend to thickening.o Cambium is developed at the outer part of the stem.o More stronger than primary stem.
Stem terminologyShoot (a young stem [1 years old or
less] with leaves)
twig (A young stem [1 year old or less] that is in the dormant winter stage with no leaves.)
branch (A stem that is more than 1 year old, typically with lateral stems radiating from it)
(A woody plant's main stem)trunk
Types of stems:
Specialize above ground stems:o Crowns ( strawberries) o Spurs (apple, cherry trees)o Stolons ( strawberry runners)
Specialized below-ground stems
o Rhizomeo Bulb
Tunicate - thin, papery covering; protection to the bulb from damaging and drying during digged out from the soil.
Nontunicate – do not have papery cover.o Cormo Tuberous stem
What are the functions of tubers? food storage
reproduction
Types of growth and development in tubers
Stem tubers are formed from the thickening of
rhizomes or stolons. Exp:- potato tubers are developed from thickened
stolons or known as propagation.
Root tubersEnlargement of modified lateral roots and
budding.
Types of tubers:
There are 2 types of tubers:
i. Stem tubers
ii. Root tubers
MECHANISM OF GROWTH
Seed germination Photosynthesis Plant hormones
MECHANISM OF GROWTHMECHANISM OF GROWTH
SEED GERMINATION
Germination is the process in which a plant or fungus emerges from a seed or spore and begins growth.
example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm.
of a sporeling from a spore, for example the growth of hyphae from fungal spores, is also germination.
MECHANISM OF GROWTHMECHANISM OF GROWTH
PHOTOSYNTHESIS
a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight.
the process always begins when energy from light is absorbed by proteins called photosynthetic reaction centers that contain chlorophylls.
MECHANISM OF GROWTHMECHANISM OF GROWTH
also known as plant growth regulators (PGRs) or phytohormones,
are chemicals that regulate plant growth. Plant hormones are often not transported
to other parts of the plant and production is not limited to specific locations.
occur in extremely low concentrations Plants lack glands that produce and
secrete hormones, instead each cell is capable of producing hormones.
affect gene expression and transcription levels, cellular division, and growth.
Auxin (IAA)CytokininsGibberellinsBrassinosteroidsAbscisic Acid (ABA)Ethylene
Auxin (IAA)
are class of plant growth substance and morphology (often called phytohormone or plant hormone)
On the molecular level, auxins have an aromatic ring and a carboxylic acid group
Function: Primary site of synthesis in shoot apical
meristem and young leaves. influence cell enlargement, bud formation
and root initiation. in conjunction with cytokinins, they control
the growth of stems, roots, and fruits, and convert stems into flowers.
Stimulate stem elongation and promotes the formation of lateral and adventitious roots.
Regulates development of fruit.
Cytokinins
Synthesized primarily in the roots and transported to other organs.
-promote cell division and organ development, but impede senescence.
influence cell division and shoot formation. Modify apical dominance and promote lateral
bud growth. Promote movement of nutrients into sink
tissues. Stimulate seed germination. Delay leaf senescence.
Gibberellins
Site for production in meristems of apical buds and roots, young leaves and developing seeds.
Stimulates stem elongation, pollen development, pollen tube growth, fruit growth, and seed development and germination.
Regulate sex determination and the transition from juvenile to adult phases.
control cell expansion,
Brassinosteroids
Present in all plant tissue at different intermediates predominate in different organs.
Promotes cell expansion and cell division in shoot, at low concentration promote root growth.
Promote xylem differentiation but inhibit phloem differentiation.
Promote seed germination and pollen tube elongation.
Abscisic Acid (ABA)
Almost all plant cell can synthesize ABA.
Inhibit growth.Promotes stomatal closure during
drought stress.Promotes seed dormancy and inhibit
early germination.Promotes leaf senescence and
desiccation tolerence.
Ethylene
Can be produce by almost all plant parts.
Promotes ripening of many types of fruit, leaf abscission and the triple response in seedlings (inhibition of stem elongation, promotion of lateral expansion and horizontal growth).
Enhances the rate of senescence.Promotes root and root hair formation.
LEAF SENESCENCE
DESICCATION TOLERENCE
LEAF ABSCISSION
THANK
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YOUYOU
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