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2. Plant Organs
Organs: tissues that act together
to serve a specific function.
Dermal
Vascular Leaves
Ground
Dermal
Vascular Stems
Ground
Dermal
Vascular Roots
Ground

3. Plant Organs

4. Plant Organs
– Organs composed of
one or more tissues.
– Three major types:
• Roots
• Stems
• leaves
– Flowers and fruits
evolved from stems and
leaves

5. Function of Plant Organs
LEAVES – Function
 Photosynthesis
STEMS –Function
 Suppor
 Transport.
ROOTS – Function
 Anchorage
 Absorption
 Storage
 Conduction

6. ROOT
 ROOTS “the hidden half”
 Functions of roots:
 Anchorage
 Absorption of water & dissolved
minerals
 Storage (surplus sugars, starch)
 Conduction water/nutrients

7. Structure of Roots
Longitudinal section of roots
 Root cap
 Zone of cell division
 Zone of cell elongation
 Zone of maturation
Cross section of root
 Vascular bundle (Stele)
contains xylem and phloem
 Cortex
 Epidermis
 Root hairs
 Absorb water and minerals

8. Types of Roots
– Fibrous, multibranched roots (e.g. lettuce)
– Dominant tap root
• Tap roots used to absorb water deep in soil
• Some tap roots used to store carbohydrates (e.g. carrots)
– Adventitious roots
• root-like structures arising from stems or leaves
• e.g. prop roots (corn) and holdfasts
– Tuberous roots
• Swollen structure on fibrous root used to store
carbohydrates (e.g. sweet potato)

9. Types of Roots
Fibrous roots Tap root
Adventitious roots Tuberous roots

10. STEMS
 Above-ground organs.
(usually)
 Support leaves and fruits.
 Conduct water and sugars
throughout plant.

11. STEM STRUCTURES
 Stem Structure
 Nodes: location of leaves on stem
 Internodes: stem between leaves
 Buds: undeveloped leaves or flowers
– Terminal (apical)
– axillary (lateral)
– Apical dominance is growth inhibition caused by
apical bud

13. Function of Stems
 Support leaves, flowers, fruits.
 Transport of water (xylem) and products of
photosynthesis (phloem).
 Storage of carbohydrates
 Tubers - swollen underground stems that store
carbohydrates (e.g. potato).
 Corm - swollen base of stem covered in papery leaves.
 Bulb - cluster of fleshy leaves attached to short, thick
stem with basal roots (e.g. onion).
 Bulbils - tiny bulbs arising in leaf axils.
 Rhizome - horizontal stem below ground that
produces roots and shoots at each node.

14. Stems
 Stems used only for asexual reproduction.
 Stolon (or runner) - horizontal stem that arises from
leaf axel and runs above ground (e.g. spider plant)
 When tip of solon hits ground a new plant forms

15. Types of Stems
Types of modified stems
 Spur - stem with short internodes growing from a larger
branch of woody plant.
 Waterspout - stem that arises from latent buds in
branches of woody plants.
 Sucker - stem arising from root tissue, often from cut
woody plant.

16. Types of Stems
Types of modified stems
 Tendrils - twining stems used to secure climbing plants
to vertical surfaces (e.g. peas, grapes).
 Prickles - tiny, pointed projections of epidermis tissues
of stems (e.g. blackberry).
 Thorns - long, pointed projections produced in leaf axils
(e.g. Hawthorn).
 Cladophylls - stems modified for photosynthesis
(e.g. cacti, asparagus).

17. Types of modified stems

18. Types of modified stems

19. LEAVES
 Most leaves are thin and flat
 An adaptation that helps them capture sunlight for
photosynthesis.
 Although this structure may be typical, it is certainly not
universal.
 Leaves are extremely variable.
 This variability represents adaptations to environmental
conditions.

20. Leaves structure
Leaf parts
 Blade - Flat
expanded area
 Petiole - stalk that
connects leaf
blade to stem, and
transports
materials
 Pair of stipules

21. Leaf epidermis
 Is transparent – so that sun light can go through.
 Waxy cuticle protects against drying out
 Lower epidermis: stomata with guard cells – for gas
exchange (CO2, H2O in; O2 out)
A. Cuticle
B. Upper epidermis
C. Palisade layer
D. Spongy Layer
E. Lower epidermis

22. Leaves functions
Leaves
 Carry out photosynthesis in order to make glucose.
 Composed of epidermal, vascular and ground tissue.

23. Flower
 A flower is the reproductive organ of angiosperms.
 Flowering plants reproduce by pollination.

24. Flower To Fruit

25. Fruits
 A fruit is defined as a ripened ovary that contains
angiosperm seeds.
 The function of a fruit is to hold and protect the seeds.
 Each kernel of corn on a cob is actually an
individual fruit
 In peaches, the fruits are soft and fleshy and
contain a single, stony seed.
 Legumes like beans and peas produce a fruit called
a pod that contains many seeds.

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