Module - Plant Growth and Reproduction

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3 main types of tissues in plants

A) VASCULAR TISSUE
Carries water and nutrients throughout the plant.

Two types of vascular tissue

1. Xylem
Carries water from roots to other parts of plant.

2. Phloem
Carries sugars from the leaves to other parts of plant.

These two types of tissue make up the veins of a leaf. It is surrounded by a bundle sheath.

B. Dermal Tissue

The word dermal means "of the skin".
Dermal tissue forms the skin of a plant, covering all parts of the roots, stems, and leaves.

Epidermis
The outer protective tissue.
Has a waxy cuticle that waterproofs the plant.
This helps prevent too much water from being evaporated.
Also has STOMATA ( stomates )in the epidermis.
Usually found on the underside of a leaf.
These are pores in the epidermis.
They allow carbon dioxide to enter a leaf.
Allows water vapor and oxygen gas out of the leaves.
Guard cells surround the stomata.
These open and close depending on the environmental conditions and needs of the plant.
The evaporation of water through the stomata is called TRANSPIRATION.

C. Ground Tissue

Consists of all the "stuff" inside the dermal tissues and around the vascular tissue.

Mesophyll
The ground tissue sandwiched between the upper and lower epidermis.
Includes the palisade layer and spongy layer.

Palisade layer (parenchyma)
Occurs directly below the upper epidermis.
This is where most photosynthesis occurs.
They are shaped like columns and are packed tightly together, increasing the exposure to sunlight.

Spongy layer ( parenchyma )

Found between the palisade and the lower epidermis.
It consists of irregular shaped cells surrounded by many air spaces.
These allow oxygen and carbon dioxide to diffuse into and out of the leaf.

ROOTS
The first root of a seed is called a primary root.

In some plants, this primary root grows downward and becomes the largest root of the plant.
This type of root is called a TAPROOT.

The taproot penetrates the soil deeper, but doesn't hold the plant quite as secure as other root systems.

The tap root is the entire food source of the plant.

Examples:
Carrot
Beet
Radish
Turnip

In other types of plants, the primary root doesn't grow as large and so numerous small roots develop and remain at the top of the soil.
This is called a fibrous root system.
This type of root system holds plants more securely in soil.

Purposes of roots
1. Anchors plant in soil.
2. Absorbs water and minerals. Root hairs are often found in young roots to increase the surface area for the plant to absorb water and minerals.
3. Storage for food produced during photosynthesis.

Longitudinal section of root

1. Root hairs
2. Zone of differentiation
Cells develop into specific tissues
Epidermis, xylem, phloem, etc…

3. Zone of elongation
All growth of the root in terms of length occurs here.

4. Root tip
Is covered by a root cap.
Slimy - lubricates cells so root can move easily through soil.


STEMS

Some stems grow only along the surface of the soil.
Example: Strawberry

Cacti have green fleshy stems that can hold water as well as carry on photosynthesis.

Stems we eat
Sugar cane
Asparagus
Stalk of broccoli

Stems change with the seasons

We will look at a winter stem:

1. Foliage leaf scars:
Marks the position of the previous season's leaves.

2. Axillary ( lateral ) buds
Buds found on side of stem
Protected by scales
May produce a lateral branch

3. Terminal bud

The tip of each dormant stem.
Has a protective covering of scales
This is where next year's growth will begin

4. Bud scale scars
Encircles the stem
This is where the previous terminal bud was.

The amount of growth between seasons can be determined by measuring the distance between sets of bud scale scars and terminal buds.


Plants produce their own food in the form of: Glucose

Equation: sunlight + water + carbon dioxide ---->>>> oxygen + glucose
( sunlight + H₂O + CO₂ ---->>> O₂ + C₆H₁₂O₆ )

Which organelle is responsible for photosynthesis occurring?
the chloroplast

Why do leaves appear green?

The pigment chlorophyll absorbs all the colors of light except for green. Green is reflected back.

The 2 most effective colors of light for photosynthesis is: Blue and red

There are 2 main types of chlorophyll:

A) chlorophyll a
A dark green/blue color

B) chlorophyll b
A yellow green color - sometimes called pea green.

All other pigment colors are called accessory pigments.

Carotenes: Oranges and yellows
Xanthophyll: Reds and browns
Lutein: gray
Anthocyanins:blues and purples

Growth in plants

The growth of all plant parts consists of 2 basic processes:
1. Cell division: Process of producing two cells from a single cell.
This takes place in a tissue called a meristem.

2. Cell Elongation: Cells divide to increase the length in the plant.

Meristems: Regions of plant tissue capable of growing into new plant parts.
Found in the tips of both roots and shoots.

Types of hormones ( plant growth regulator )

Cytokinin
Produced in root tips.
Stimulates cell division.
Stimulates lateral bud growth.
Used commercially to prolong life of cut flowers.

Auxin
Produced in tips of stems.
Promotes stem elongation.
Inhibits lateral bud growth.

How do we get a plant to stop growing upward and instead grow outward?
Before the spring causes the buds to appear on the plant, cut off the terminal buds from the stems and branches. This will get rid of the auxin hormone in the stems, and will then allow the lateral buds to grow outward.

Gibberellins
Stimulates rapid growth in length and size of the plant.


Types of plants
Angiosperms - these are flowering plants.
Gymnosperms - Plants do not produce flowers.
Example are the conifers.

Flower Anatomy: see illustration.






The Perfect Flower: Has both male and female reproductive parts

Imperfect Flowers: Flowers that have just male parts or female parts, but not both in the same flower.
EXAMPLES: Corn and Begonia


Pollination and Pollinators

Pollination: Process by which pollen is placed on the stigma.
May be carried by animals or wind.

Pollination by bats
Attracted to flowers that are white or dull in color.
Flowers are big and strong.
Flowers hang upside down.
Lots of nectar.
. Strong, musky smell to flower.

Pollination by bees
Attracted to flowers are big and bright ( usually yellow or blue).
Some have landing platform.
Many flowers have stripes or dots called honey guides.

Pollination by hummingbirds
Hummingbirds have good eyesight but poor sense of smell.
Prefer flowers that are red and without a smell.
Hover feeders.
Petals must be out of the way.

Pollination by butterflies
Butterflies have good vision and weak sense of smell.
Attracted to bright colors ( including red ) and odorless flowers.
Flowers must have landing platform.
Flower has tube of suitable length for tongue.

Monocots vs. Dicots

Monocots

Some characteristics:
Flowers and stamens occur in 3 or multiples of 3.
Veins in leaves are parallel.
One cotyledon ( seed leaf )
Vascular bundles are scattered in cross section of a stem.

Dicots

Characteristics:
Flowers and stamens occurs in 4’s or fives.
Veins are in netted fashion.
Two cotyledons.
Vascular bundles are in a ring in a cross section of stem.


Blooming cycle in plants

Why do some flowers bloom in spring and others in the fall?
this has to do with the length of night.

3 categories of plants:

1. Short day plants

These require long nights and short days.
Requires 12 or more hours of darkness.
Poinsettia & chrysanthemum

2. Long day plants

Requires short nights and long days.
Needs less than 10 - 12 hours of darkness.
Carnation
Snapdragon

3. Day neutral plants

Amount of darkness has no effect on flowering.
Coleus
African Violets