Transcript Intro to Hort

Introduction to
Plant Science
The Importance of Plants
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Without plants, life on earth could not exist
Plants are the primary source of food for
humans and animals
The Importance of Plants cont.
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Plants also:
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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
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Most plants are made
up of four basic parts:
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Leaves
Stems
Roots
Flowers (these later
become fruit or seeds)
Leaves
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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!
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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
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Leaves are arranged in
many different patterns
and positions:
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Alternate
Opposite
Whorled
Simple
Pinnate
Bi-Pinnate
Palmate
Leaves on the Outside
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Parts:
- Petiole
- Midrib
- Blade
- Margin
- Vein
Tip
Margin
Midrib
Leaf Parts cont.
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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
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Leaves have specialized cells that perform
very important, very specific tasks.
Leaf Cells
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Epidermis - skin of the leaf
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Single layer of cells
Leaf Cells cont.
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Chloroplasts
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Food making cells
Chlorophyll - green color
Photosynthesis
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Process by which chloroplasts make food
The oxygen created is used directly by people and
animals
Without O2 there would be no burning, rusting, or
rotting
Photosynthesis
LIGHT
6H2O + 6CO2 ----------> C6H12O6+ 6O2
CHLOROPHYLL
Six molecules of water
plus six molecules of
carbon dioxide, in the
presence of light and
chlorophyll, produce one
molecule of sugar plus
six molecules of oxygen
Plant Food
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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
Respiration
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Plants breathe 24/7
They consume O2 and
release CO2
Roots, stems, and leaves
all need O2 to grow
Plants produce more O2
during photosynthesis
than they consume
while breathing
Stems
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Stems have 2 main
functions:
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The movement of
materials
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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
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Flowers and fruit or seeds
Stems cont.
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Stems are also used for:
Food storage
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Reproductive methods
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Irish Potato
Stem cuttings or grafting
Green stems
manufacture food just
like leaves
Stems on the Outside
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Lenticels
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Breathing pores
Stems on the Outside cont.
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Bud scale scars
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Indicate where a terminal
bud has been located
The distance between
two scars represents one
year of growth
Leaf scars
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Show where leaves were
attached
Unique Stems
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Irish Potato & Gladiolus
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Very different stems
Stems are used for food storage and plant
reproduction
Stems on the Inside
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In all stems:
Water and
minerals travel up
the XYLEM
 Manufactured
food travels down
the PHLOEM
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Dicots
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Dicots (2 cotyledons) 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!
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Sap = new xylem
Heartwood = old, inactive xylem
Tree bark = old, inactive phloem
Monocots
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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)
Monocots vs. Dicots
What do we do with Stems?
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Food
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Asparagus
Irish Potato
Celery
Building Materials
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Wood
Roots
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Usually underground – not visible
Functions:
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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
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Very similar to a stem
Older roots of shrubs &
trees have:
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Phloem on the outside
(old phloem is bark)
Cambium layer
Xylem (wood) on the
inside
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Phloem
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Carries manufactured food down to the root for food
storage
Xylem
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Carries water and minerals up to the stem
Roots on the Outside
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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
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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
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Cash crops
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Carrots
Beets
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Sugar Beets - Sugar
Radishes
Sweet Potatoes
Root Propagation
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Plants with tuberous
roots:
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Dahlia
Peony
Sweet Potato
Are propagated by
separating the root
clump or by rooting
spouts from the root
Types of Root Systems
Fibrous Root System vs. Tap Root System
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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.
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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
Flowers, Fruits, & Seeds
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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
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Fruits and seeds are eaten, collected, and
spread out by animals and people
This reproduces the plant
Seeds
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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
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Flowers differ in shape, size, and color, but all
have relatively the same parts
Flower Parts cont.
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Seeds are the most common way plants
reproduce in nature
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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 selffruitful, or can pollinate itself
Flower Parts cont.
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4 main parts
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Sepals
Petals
Stamens
Pistil
The Sepals
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Green, leaf
like parts of
the flower that
cover and
protect the
flower bud
before it is
open
Petals
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Are actually leaves
Generally the most striking part of the flower
Bright colors are used to attract insects for
pollination
The Stamens
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Male reproductive part
Each stamen consists of:
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Filament
Anther – contains the pollen (male sex cell)
The Pistil
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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
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3 main parts:
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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
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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
Fertilization
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After an insect deposits pollen, fertilization
begins!
The pollen grain
sprouts and sends
a long stalk (pollen
tube) down
the style to the
ovary
Fertilization cont.
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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
Pollen
Incomplete Flower
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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!
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Many plants are grown only for their flowers
Floriculture industry in a multimillion dollar
business!!!