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Introduction to Horticulture. Importance of Plants Plant Parts & Their Functions. The Importance of Plants. Without plants, life on earth could not exist Plants are the primary source of food for humans and animals. The Importance of Plants cont. Plants also: Provide oxygen Provide shade

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introduction to horticulture

Introduction to Horticulture

Importance of Plants

Plant Parts & Their Functions

the importance of plants
The Importance of Plants

Without plants, life on earth could not exist

Plants are the primary source of food for humans and animals

the importance of plants cont
The Importance of Plants cont.

Plants also:

Provide oxygen

Provide shade

Supply us with medicines

Renew the air

Slow down the wind

Hold soil in place

Are a home for wildlife

Furnish building materials and fuel

parts of the plant
Parts of the Plant

Most plants are made up of four basic parts:




Flowers (these later become fruit or seeds)


Usually underground – not visible


Anchor the plant and hold it upright*

Absorb water and minerals from the soil & conduct them to the stem*

Store large quantities of plant food*

Propagate or reproduce in some plants

* = essential to all plants

roots on the inside
Roots on the Inside

Very similar to a stem

Older roots of shrubs & trees have:

Phloem on the outside (old phloem is bark)

Cambium layer

Xylem (wood) on the inside


Carries manufactured food down to the root for food storage


Carries water and minerals up to the stem

roots on the outside
Roots on the Outside

Different from a stem

On a stem, the

terminal bud

initiates growth

On a root,

the root cap

initiates growth

Root cap continuously makes new cells that protect the root as it pushes into the soil

root external structure
Root External Structure

Behind the root cap are root hairs

Root hairs become side roots that branch out as the root grows older

Absorb moisture and minerals which are conducted up to the larger roots and the stem

roots as crops
Roots as Crops

Cash crops




Sweet Potatoes

root propagation
Root Propagation

Plants with tuberous roots:



Sweet Potato

Are propagated by separating the root clump or by rooting spouts from the root

types of root systems
Types of Root Systems

Fibrous Root System vs. Tap Root System


Stems have 2 main functions:

The movement of materials

Movement of water and minerals from roots up towards the leaves

Movement of manufactured food from the leaves down to the roots

Support of the leaves and reproductive structures

Flowers and fruit or seeds

stems cont
Stems cont.

Stems are also used for:

Food storage

Irish Potato

Reproductive methods

Stem cuttings or grafting

Green stems manufacture food just like leaves

stems on the outside
Stems on the Outside


Breathing pores

stems on the outside cont
Stems on the Outside cont.

Bud scale scars

Indicate where a terminal bud has been located

The distance between two scars represents one year of growth

Leaf scars

Show where leaves were attached

unique stems
Unique Stems

Irish Potato & Gladiolus

Very different stems

Stems are used for food storage and plant reproduction

stems on the inside
Stems on the Inside

In all stems:

Water and minerals travel up the XYLEM

Manufactured food travels down the PHLOEM


Dicots (2 cotyledons - seed leafs) the xylem and phloem are separated by the cambium

The cambium produces new cells

Grow continually because the cambium builds new xylem and phloem cells

Trees are a perfect example!

Sap = new xylem

Heartwood = old, inactive xylem

Tree bark = old, inactive phloem


One cotyledon (seed leaf)

Grasses, corn

No outside cambium

Vascular bundles that contain xylem & phloem

Cells don’t increase in number, they grow in size (won’t keep growing like a tree)

what do we do with stems
What do we do with Stems?



Irish Potato


Building Materials


Which root system is easier to transplant? Fibrous roots or tap roots?

Answer: Fibrous roots

Why? Because when plants are dug up out of the ground, a greater % of the fibrous roots system is saved.

If a root loses to many root hairs while being transplanted, the plant will die.

Larger roots only conduct & store water, nutrients, and food

Root hairs absorb moisture from the ground


Are the food factory of the plant

They produce all of the food that is used by the plant and stored for later use by the plant or by animals

leaves come in all shapes and sizes
Leaves Come in All Shapes and Sizes!

Needles are actually very narrow leaves

The thorns on a cactus are leaves

Some leaves are flat

Other leaves, like onion leaves, are cylindrical

The shape and size of leaves helps to identify plants

leaf arrangement
Leaf Arrangement

Leaves are arranged in many different patterns and positions:





Leaf Composition






leaves on the outside
Leaves on the Outside


- Petiole - Blade - Vein

- Midrib - Margin




leaf parts cont
Leaf Parts cont.

Petiole - leaf stalk

Blade - the larger, usually flat part of the leaf

Midrib - large central vein from which all other leaf veins extend

Veins - form the structural framework

Margins - edges of plant leaves

leaves on the inside
Leaves on the Inside

Leaves have specialized cells that perform very important, very specific tasks.

leaf cells
Leaf Cells

Epidermis - skin of the leaf

Single layer of cells

Chief function: protect the leaf from loosing too much moisture

Guard Cells - open and close a small space or pore on the underside of a leaf called a stoma to allow the leaf to breathe (exchange O2 for CO2) and transpire (or give off moisture)

leaf cells cont
Leaf Cells cont.


Food making cells

Chlorophyll - green color


Process by which chloroplasts make food

The oxygen created is used directly by people and animals

Without oxygen there would be no burning, rusting, or rotting

6h 2 o 6co 2 c 6 h 12 o 6 6o 2
6H2O + 6CO2 ----------> C6H12O6+ 6O2



Six molecules of water plus six molecules of carbon dioxide in the presence of light produce one molecule of sugar plus six molecules of oxygen

plant food
Plant Food

Food made in the leaves moves down the stem to the roots

It is then used by the plant or stored in the roots or stem as sugar, starch, or protein

The plant is also used as food for people and animals

The leaves are usually the most nutritious part


Plants always breathe

They consume oxygen and release carbon dioxide

Roots, stems, and leaves all need oxygen to grow

Plants produce more oxygen during photosynthesis than they consume while breathing

flowers fruits seeds
Flowers, Fruits, & Seeds

Flowers are pretty & contain nectar in order to attract insects

These insects fertilize the flower by pollination

Pollination begins fruit and seed formation

fruits seeds
Fruits & Seeds

Fruits and seeds are eaten, collected, and spread out by animals and people

This reproduces the plant


Seeds have special devices to ensure propagation

Some seeds are sticky (thistles), some float in the wind (dandelions), others can survive stomach acid (cherry pits)

flower parts
Flower Parts

Flowers differ in shape, size, and color, but all have relatively the same parts

flower parts cont
Flower Parts cont.

Seeds are the most common way plants reproduce in nature

Sexual process involving male and female parents

A complete flower has both male and female parts

Only one parent is needed if a plant is self-fruitful, or can pollinate itself

flower parts cont1
Flower Parts cont.

4 main parts





the sepals
The Sepals

Green, leaf like parts of the flower that cover and protect the flower bud before it is open


Are actually leaves

Generally the most striking part of the flower

Bright colors are used to attract insects for pollination

the stamens
The Stamens

Male reproductive part

Each stamen consists of:


Anther – contains the pollen (male sex cell)

the pistil
The Pistil

Located in the center

of the flower

Female part

Produces female sex cells (eggs or ovules)

If fertilized, the eggs become seeds

parts of the pistil
Parts of the Pistil

3 main parts:

Stigma – sticky, catches the pollen

Style – tube that leads to the ovary

Ovary – eggs develop here, after fertilization the ovary grows to become a fruit or seed coat

flower construction
Flower Construction

Insects looking for nectar have to climb over the anther and brush pollen on their legs

As they climb towards the center looking for food, they deposit pollen on the stigma


After an insect deposits pollen, fertilization begins!

The pollen grain

sprouts and sends

a long stalk (pollen

tube) down

the style to the


fertilization cont
Fertilization cont.

The pollen sperm cell can then fertilize the female egg cells and seeds begin to develop

The ovary enlarges into a seed coat or fruit

incomplete flower
Incomplete Flower

Has ONLY male parts or female parts

Male flower – sepals, petals & stamens but no pistil

Female flower – sepals, petals, & pistil, but no stamens

Examples: Kiwi, Ginkgo

flowers are important
Flowers are Important!

Many plants are grown only for their flowers

Floriculture industry in a multimillion dollar business!!!

what is a fruit
What is a fruit?

A ripened flower ovary

Botanically, fruits = vegetables & vegetables = fruits

In most plants, a fruit is formed following fertilization of the ovules

They contain seeds

what about seedless fruit
What about seedless fruit?

Seedless fruit -- fruit that form without pollination or fertilization

These fruit are called PARTHENOCARPIC

Examples: Banana, navel orange

When the fruit ripens, the ovary wall thickens.

This is called the pericarp

The pericarp has three sections:

The endocarp

The mesocarp

The exocarp

types of fruits
Types of Fruits

Aggregate fruits

Multiple fruits

Simple fruits