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Structure of the flowering plant
MONOCOTS AND DICOTS
Plants have two main systems:
1. Shoot System
2. Root System
Shoot system:
• The shoot system consists of stem,
branches, petioles, buds, leaves,
flowers, seeds and fruits
Functions include:
•Photosynthesis
•Support
•Transport
•Sexual reproduction
•Food storage
•Gas exchange
Stem:
• Stem functions mainly in support and transport - but can function in
photosynthesis (if it is herbaceous). The stem also functions in growth.
The stem is divided into nodes and internodes.
• Nodes are regions where branching occurs.
• Internodes are where no branching occurs.
Stems also have lenticels.
Lenticels are small pores on a stem that function in gas
exchange.
Transverse sectional structure of stem in monocots:
Transverse sectional structure of the stem in dicots:
Leaf
• Thin organ with a large surface area.
• Organ that makes food.
• Contains the green pigment, chlorophyll.
• The outer dermal layer secretes a waxy cuticle
to prevent excess water loss.
• Organ that also functions in transpiration.
Leaf venation: two types
Parallel:
• The veins run parallel, the entire length of the leaf; e.g. grass, tulip, daffodil.
• Most monocot plants have parallel venation.
Net/Reticulate:
• The veins spread out from a central vein called the midrib
• Most dicot plants have net or reticulate venation.
Internal leaf structure:
• The leaf contains many internal air spaces that gives greater surface
area for gas exchange.
• The cells that make up the internal area contain many chloroplasts
that carry out photosynthesis.
• The lower dermal layer has many pores, called stomata.
• Stomatal opening and closing is controlled by guard cells.
Flower arrangement between monocots and
dicots
• Monocots have flower parts arranged in multiples of three.
• Dicots have flower parts arranged in multiples of four or five.
Bud
Bud: undeveloped shoot
There are three types of bud:
• Axillary bud: Grow side branches
• Apical bud: Increase stem length
• Adventitious bud: present in an unusual
area of the plant - such as the stem,
branch, root or even leaf.
Root system:
A network of underground branches that have various functions:
• Anchorage
• Absorbing water and minerals
• Transport of absorbed water and minerals to the shoot
system
• Storage of food
• Support
Types of root system:
Tap root system
One main root growing downwards with
small secondary roots; e.g. carrot,
dandelion.
Fibrous root system
Main roots of equal size; e.g. grass.
Adventitious root system
Roots that grow in unusual places such as the stem or branches; e.g.
bayan tree, ivy.
Root structure:
There are four zones of a young
root.
• Zone of protection: consists of a root cap, enabling the
root to push its way through the ground.
• Meristematic zone: consists of meristematic tissue that
divides rapidly by mitosis, creating new root tissue.
• Zone of elongation: area of the root affected by growth
regulators, where the cells increase in size.
• Zone of differentiation: area of the root where
unspecialised cells start to become specialised,
becoming ground, dermal and vascular tissues.
The transverse structure of a root
Tissues in flowering plant
1. Dermal
2. Ground
3. Vascular
1. Dermal Tissue
• Consists of the outer layer of the plant
• Function: Absorb water and minerals
2. Ground Tissue
• Area between the Dermal and the Vascular Tissue
• Function: Food Storage
3. Vascular tissue
The vascular system in a plant is composed of two types of tissue:
xylem and phloem.
Xylem
• Composed of two types of cell: TRACHEIDS AND VESSELS
• A dead tissue - there is no cytoplasm and no nuclei
• Contains lignin that gives the tissue high strength.
• Transports water and dissolved minerals upwards.
Xylem:
Xylem:
Phloem:
• A living tissue.
• Transports food (in the form of sucrose) upwards and downwards, depending
on where food is needed.
• Composed of COMPANION CELLS AND PHLOEM SIEVE TUBES.
• Nucleus controls activities of both companion and sieve tube cell
Types of flowering plants
• MONOCOT OR DICOT