4. Plant Organs
– Organs composed of
one or more tissues.
– Three major types:
– Flowers and fruits
evolved from stems and
5. Function of Plant Organs
LEAVES – Function
ROOTS – Function
ROOTS “the hidden half”
Functions of roots:
Absorption of water & dissolved
Storage (surplus sugars, starch)
7. Structure of Roots
Longitudinal section of roots
Zone of cell division
Zone of cell elongation
Zone of maturation
Cross section of root
Vascular bundle (Stele)
contains xylem and phloem
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)
Support leaves and fruits.
Conduct water and sugars
11. STEM STRUCTURES
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
13. Function of Stems
Support leaves, flowers, fruits.
Transport of water (xylem) and products of
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.
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
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
Cladophylls - stems modified for photosynthesis
(e.g. cacti, asparagus).
Most leaves are thin and flat
An adaptation that helps them capture sunlight for
Although this structure may be typical, it is certainly not
Leaves are extremely variable.
This variability represents adaptations to environmental
20. Leaves structure
Blade - Flat
Petiole - stalk that
blade to stem, and
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)
B. Upper epidermis
C. Palisade layer
D. Spongy Layer
E. Lower epidermis
22. Leaves functions
Carry out photosynthesis in order to make glucose.
Composed of epidermal, vascular and ground tissue.
A flower is the reproductive organ of angiosperms.
Flowering plants reproduce by pollination.
A fruit is defined as a ripened ovary that contains
The function of a fruit is to hold and protect the seeds.
Each kernel of corn on a cob is actually an
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.