Plant growth and development

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

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