Course Outcome 4.1
Plant Organ
System and Function
SPECIFIC OBJECTIVES:
At the end of the lesson, the student is expected to:
• Be familiarized with the structures and functions of the plant
organ systems
• Differentiate the structure and function of the four types of plant
tissues
• Compare and contrast the plant cell types: parenchyma,
sclerenchyma, and collenchyma
• Explain the mechanism of plant growth and development
• Describe the structure, function, and types of plant organs
4.1 Review on the Classification Systems
Taxonomic classification systems are constantly being
accommodate discovery of new species and their characteristics.
I.
II.
updated
to
Linnaeus
a. 2 Kingdoms
b. Based on physical similarities
c. Uses only biologists’ observations and knowledge of organisms
Modern
a. 5 or 6 kingdoms
i. Five Kingdom System – older system; include Animalia, Plantae,
Protista, Fungi, and Monera (all prokaryotic species)
ii. Six Kingdom System – also referred to as the 3 Domain System
1. Domain Bacteria – Kingdom Eubacteria (peptidoglycan in
cell walls and prokaryotic)
2. Domain Archaea – Kingdom Archaeabacteria (no
peptidoglycan in cell walls and prokaryotic organisms that
live in extreme environments)
3. Domain Eukarya – Kingdoms Animalia, Plantae, Fungi,
and Protista
b. Based on physical similarities AND genetic similarities
c. Uses observations, knowledge of organisms, molecular clocks, and
other genetic techniques
4.2 Kingdom Plantae
▪ Cell wall
▪ Autotroph (photosynthesis)
Plant Organ System
▪
▪
▪
2
Multicellular
Angiosperms (flowering plants)
 ~90% plants
 Produce seeds within a fruit
 Key adaptations: flowers & fruits
Plants are composed of cells which contain:
 Cell wall
 Central vacuole
 Chloroplasts
Definition 4.2 .1 Autotrophs
An organism that can produce its own food using light, water, carbon
dioxide, or other chemicals. Because autotrophs produce their own food, they are
sometimes called producers.
4.3 Plant Organ System
Plants have 2 major organ system:
I.
Shoot system
a. Above ground parts
b. Stems, leaves, and reproductive parts
II. Root system
a. Usually underground
b. roots
4.3.1 Plant Tissues
There are four types of tissues in plants:
1. Dermal tissue
a. Also called the epidermis
b. Single layer, closely packed cells that cover entire plant
c. Protect against water loss & invasion by pathogens
d. Cuticle: waxy layer
e. Structures:
i. Stomata - Opening in leaf tissue; Help control water
loss from plant
ii. Guard Cells - Controls the opening/closing of
stomata
iii. Trichomes - Hairlike projections on stem and leaf;
Reduces evaporation of water from plant
2. Vascular tissue
a. Main function is to transport water and food throughout
plant
Two types of vascular tissue:
i. Xylem - Transports water from roots to plant;
Composed of tracheids; Tubular cells tapered at
each end
ii. Phloem - Transports sugars to all parts of the
plant; Made up of tubular cells joined end to end
3
Plant Organ System
▪
2 Cell Types: sieve tubes, companion cells
3. Ground tissue
a. In charge of photosynthesis,
storage, and secretion
b. Found throughout plant
c. Anything that isn’t dermal or
vascular
d. Function:
storage,
photosynthesis, support
e. Pith: inside vascular tissue
f. Cortex: outside vascular
tissue
4. Meristematic tissue
a. Produces most of a plant’s
new cells
b. Located in regions of
actively dividing cells
4.3.2 Plant Cells
There are various types of plant cells which include: parenchyma cells, sclerenchyma
cells, collenchyma cells, xylem cells, and phloem cells.
1. Parenchyma cells are the major cells of plants. They make up plant leaves and
are responsible for the plants’ metabolism and food production. These cells are
typically more flexible than others because they are thinner.
2. Sclerenchyma cells are very hard due to thick cell wall and therefore give the
plant support. They usually exists in the plant roots and do not live past
maturity.
3. Collenchyma cells are also hard but not as hard as sclerenchyma cells due to
the uneven thickness of the cell wall. They also provide plants with support but
normally when the plant is young. They grow and stretch as the plant grows.
4. Xylem cells are also known as water conducting cells. They are hard cells that
bring water up to the leaves. They do not live past maturity but their cell wall
remains to allow water to flow freely through the plant.
5. Phloem cells are a system of cells that transports sugar produced by the
leaves throughout the plant. These cells live past maturity.
4
Plant Organ System
Tissue
Main Components
Main Functions
Simple Tissues
Parenchyma
Parenchyma cells
Photosynthesis, storage,
secretion, tissue repair
Collenchyma
Collenchyma cells
Pliable structural support
Sclerenchyma
Fibers or sclereids
Structural Support
Complex Tissues
Epidermis (dermal)
Periderm (dermal)
Xylem (vascular)
Phloem (vascular)
Epidermal cells and their
secretions
Cork cambium; cork cells;
parenchyma
Tracheids; vessel elements;
parenchyma cells;
sclerenchyma cells
Sieve elements, parenchyma
cells; sclerenchyma cells
Secretion of cuticle; protection;
control of gas exchange and
water loss
Forms protective cover on older
stems, roots
Water-conducting tubes;
structural support
Sugar-counducting tubes and
their supporting cells
4.4 Plant Growth
Types of Flowering Plants:
▪ Annuals – 1 year life cycle
▪ Biennials – 2 years
▪ Perennials – continuous life cycle for many years
Definition 4.4
Meristem
This refers to perpetually embryonic tissues with cells that divide for plant
growth. In plants, parts that are sites of active cell division are the apical
meristem and lateral meristems.
•
•
Primary growth
o growth at tips of roots & buds of shoots
o Occurs in apical meristem
o Cause increasing length
Secondary Growth
o Growth thickens shoots and roots therefore increasing diameter of plant
o Occurs in lateral meristem
▪ Vascular cambium: produces secondary xylem (wood)
▪ Cork cambium: produces tough covering that replaces epidermis
❖ Bark - all tissues outside vascular cambium
5
Plant Organ System
Cortex
Epidermis
Vascular
cylinder
Root Anatomy
Key
Root hair
Dermal
Ground
Vascular
Zone of Maturation: primary growth
becomes functionally mature
Zone of Elongation:
cells elongate; push root
tip ahead
Zone of Cell Division: apical
meristem; new cells produced (mitosis)
Apical
meristem
Root cap: protects meristem
as it pushes through soil
Root
cap
100
µm
Primary Growth of Roots
Shoot apical meristem - dome of
dividing cells at tip of terminal bud;
divide and elongate
Primary Growth of Shoots
Plant Organ System
6
4.5 Plant Organs
4.5.1 Roots
▪ Anchor, absorb nutrients, contain vascular
tissue to transport materials
▪ Can be short or long, thick or thin
▪ Have root hairs
o Tiny extensions
o Increase surface area of root
▪ Types of Root System:
o Taproot
❖ One thick, vertical root
❖ Many lateral branch roots
❖ Firmly anchors
❖ Stores food
o Fibrous root
❖ Mat of thin roots spread just
below surface
❖ Shallow
❖ Increased surface area
Modified roots
4.5.1 Stems
▪ Support leaves and flowers, contains vascular
tissue to transport materials
▪ Arrangement of vascular tissue:
o Monocots: Xylem and phloem
scattered throughout stem
o Dicots: Xylem and phloem in a
circle that form a ring
▪ Terminal
/
apical
bud:
growth
concentrated at top end of stem
o Secretes hormone to prevent
growth of axillary buds; growth
directed upward, toward light
▪ Axillary buds – located in between leaf
and stem; forms branches (lateral shoots)
Pinching/pruning
–
removing
terminal bud
▪ Stems are sometimes modified to store
food and (or) water.
o Plants that store large amounts of
water in their stems or leaves are
called succulents
Remarks:
The flowering plants have been divided into two major groups, or classes,: the Dicots
(Magnoliopsida) and the Monocots (Liliopsida)
7
Plant Organ System
4.5.1.1 Variations in a Stems
▪ Stolons – stems that branch from the main stem of the plant and grow
horizontally along the surface or under it.
▪ Bulbs – short section of underground stem encased by overlapping layers of
thickened, modified leaves called scales.
▪ Corms – short, thickened underground stem that stores nutrients for times of
unfavorable growth conditions. Ex: taro / arrowroot
▪ Rhizomes – fleshy stems that typically grow under the soil and parallel to its
surface.
▪ Stem tubers – thick, fleshy storage structures that form on stolons or rhizomes
of some plants
▪ Cladodes – flattened, photosynthetic stems that store water.
4.5.2 Leaves
▪ Primary function: Photosynthesis
▪ Leaves are the solar energy and CO2 collectors of plants.
▪ Some leaves joined directly to stem
▪ In some leaves, a stalk called a petiole joins the leaf blade to the stem
▪ Simple leaf - blade that is not divided
▪ Compound leaf - blade divided into leaflets
4.5.2.1 Leaf Anatomy
▪
▪
▪
Epidermis of underside interrupted by stomata (pores), flanked by guard cells
(open/close stomata)
Mesophyll: ground tissue between upper/lower epidermis
Parenchyma: sites of photosynthesis
Definition 4.5.2
Transpiration
Loss of water through the stomata.
8
Plant Organ System
▪
▪
Phyllotaxy – arrangement of leaves on
a stem
o Opposite
o Alternate
o Whorled
o Basal
Leaf venation - Patterns of veins in
the leaves
o Parallel
o Pinnate
o Palmate
4.6 Plant Development
Angiosperms have 3 unique Features:
1. Flowers
2. Fruits
3. Double Fertilization (by 2 sperm)
▪ Some plants are self-pollinated
▪ Cross-pollinated plants:
o Self-incompatibility: plant rejects own pollen
or closely related plant
o Maximize genetic variation
The development of a plant embryo
Definition 4.6
Pollination
Transfer of pollen from anther to stigma
Plant Organ System
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4.6.1 Fruit
▪ Egg cell → plant embryo
▪ Ovules inside ovary → seeds
▪ Ripe ovary → fruit
▪ Fruit protects enclosed seed(s)
▪ Aids in dispersal by water, wind, or animals
Types of Fruit
4.6.2 Seeds
Mature seed → dormancy (resting)
o Low metabolic rate
o Growth & development suspended
o Resumes growth when environmental conditions suitable for germination
▪ Dispersal
o By wind
o By water
o By animals
▪ Germination
o Seed take up water (imbibition) → trigger metabolic changes to begin
growth
o Root develops → shoot emerges → leaves expand & turn green
(photosynthesis)
o Very hazardous for plants due to vulnerability