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 LEAVES TUBERS ROOTS STEMS
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
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.
The figure on the left is a cross section of a young rice shoot showing a rolled-up leaf blade being enclosed by an older leaf sheath. The figure on the right demonstrates the location of the sheath "1" and the young blade "2".
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.
WHAT ARE THE FUNCTIONS OF ROOT
Anchor the plant in the soil.
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.
Types of growth and development in stem
Primary stem growth :-
begins at the tip of the terminal bud in the area called the apical meristem.
The cell divisions on the apical meristem are responsible for the stem's growth in length.
Secondary stem growth :-
Also known as secondary thickening or lateral growth arises from secondary meristems.
Secondary xylem and secondary phloem are formed.
Stems are tend to thickening.
Cambium is developed at the outer part of the stem.
More stronger than primary stem.
Shoot (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:
Crowns ( strawberries)
Spurs (apple, cherry trees)
Stolons ( strawberry runners)
Specialized below-ground stems
Tunicate - thin, papery covering; protection to the bulb from damaging and drying during digged out from the soil.
Nontunicate – do not have papery cover.
What are the functions of tubers?
Types of growth and development in tubers
are formed from the thickening of rhizomes or stolons.
Exp:- potato tubers are developed from thickened stolons or known as propagation.
Enlargement of modified lateral roots and budding.
Types of tubers:
There are 2 types of tubers:
MECHANISM OF GROWTH
MECHANISM OF GROWTH
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 GROWTH
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 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.
Abscisic Acid (ABA)
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
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.
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.
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,
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.
Promotes stomatal closure during drought stress.
Promotes seed dormancy and inhibit early germination.
Promotes leaf senescence and desiccation tolerence .
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).