Download Unit 8

Intro to Horticulture
Parts of the plant and their
functions
Environmental Science
Functions of leaves
.
1. Critical for photosynthesis
(the process by which plants
produce their food).
2. Aid in the process of
transpiration which is
necessary in order for
plants to cool themselves.
3. Leaves can store some food which
can later be transferred to other areas of
the plant.
4. Sometimes, leaves
can be used in asexual or
vegetative propagation.
External Leaf Structures

Leaves are consist of
petiole and blade
– Blade is comprised of
veins and a midrib

The veins of the leaf
form its structural
framework
.
Internal Leaf
Structures

Epidermis
– Cuticle
 Waxy substance covers the leaves and stems
 Waterproof layer that keeps water in plants
Principal Tissues of
the Leaf

Epidermis (cont)
– Stomata
 Openings in the epidermis mainly located on
underside of leaves
 Exchange of gases
•Guard Cells
•Two cells located on each side of
stomata
•Open and closes stomata
Chloroplast
More in cells located in the center of the
leaf
 The chloroplast contains chlorophyll which
gives the plants the green color
 Manufactures food for the plant though
Photosynthesis
 Beginning of the food chain for most living
things

Photosynthesis
CARBON DIOXIDE + WATER + LIGHT ENERGY = GLUCOSE + OXYGEN
Food manufactured by this process goes down to the roots thought the
stem. It is either used by the plant or stored as a starch, sugar, or
protein
Respiration
Plants respire 24 hours/day just as
animals
 In this process they consume carbon
dioxide and give off oxygen

What is the purpose of the stems?

Two main Functions
– The movement of materials- water, minerals,
food
– Support the leaves and reproductive
structures

Can be used for food storage
– Ex. Irish potato
What are the types of stems?
1) Woody Stem: trees, shrubs,
perennials
2) Grass Stem: hollow or filled
3) Herbaceous Stem: like wood
but softer (clover, alfalfa)
4) Modified Stem:
Types of Modified Stems
Bulbs: (onion)
 Tubers: (potato)
 Stolons: above ground runner
(strawberry)
 Rhizomes: below ground runners (field
bindweed or creeping jenny)

What is the Terminal Bud?
Terminal bud tries to make
plant grow taller or longer
 if we remove terminal bud,
the plant will be shorter and
thicker

– Can you think of why we
would want to do this??
– What kind of plants could we
do this on??
Internal Stem Structure

What does the Xylem Carry
– Water and minerals travel up

What about the Phloem
– Manufactured food travels down the
plant

What does the Cambium do?
– Separates the xylem and the phloem
– Thin, green, actively growing tissue
located between the bark and the wood
of a plant
Monocot vs. Dicot

Dicot stem may continue to increase in diameter
because the cambium builds new phloem cells
on the outside and new xylem cells on the inside
– Ex. Trees

Monocot have vascular bundles which contain
both xylem and phloem and no cambium
– This would make it more limited in size
 Ex. corn
Why should we care?

The stems of some
plants we use as food
– Irish potato and
asparagus

Others are used in
building materials
– Lumber from the tree
trunks
Roots

Roots function
– Anchor the plant and hold it upright
– Absorb water and minerals from the soil and
conduct them to the stem
– Store large quantities of plant food
– Propagate or reproduce some plants
Fibrous root vs. tap root

Fibrous root system
– Much easier to transplant
– More spread out

Tap root system
– Longer fewer roots
– End of root contains many root hairs
Functions of Fruit:
1. Protect the seeds inside
the ripened ovule (fruit).
2. Provide nutrients to the soil and
to a newly germinated seedling.
3. Aid in the dissemination/spreading
of seed by providing food for animals.
Animals eat the fruit and seeds. After the
fruit is digested, the seeds pass out in the
animal’s feces at another location.
4. Some plants have dry, dehiscent fruits
which split open to disseminate seeds.
What is the purpose of seeds
To continue the plant process
 There are two types

– Monocots
– dicots
Monocot and dicot