Plant organs include roots, stems, and leaves which are composed of tissues and serve specific functions. Roots function to anchor plants, absorb water and minerals, store food, and conduct fluids. Stems provide support, transport water and nutrients, and can store food. Leaves capture sunlight for photosynthesis. Flowers evolve from stems and leaves and produce fruits containing seeds.

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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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