Leaveshave many functions

1. Leaves are the photosynthetic organ of a plant; usually they are composed of 2 parts: the blade and petiole.

2. Leaves are the main site of evaporation of water from the plant.

3. Gas exchange carbon dioxide for photosynthesis and oxygen from photosynthesis and for respiration are usually exchanged through the leaves.

Parts of a Typical Leaf

Function of Leaf Tissues• Cuticle – waxy covering prevents water loss• Upper and Lower Epidermis - Protection• Palisade Mesophyll Cells – main photosynthetic tissue• Bundle Sheath Cells - give some rigidity and

protection to the enclosed vascular tissue. • Xylem – transports water• Phloem – transports sugars• Spongy Mesophyll Cells – create spaces for gas

exchange• Guard Cells – regulate the flow of water• Stomata – openings in the leaf, exchange of gases• Vein (Vascular bundle)– transportation• Sclerenchyma – strength and support

Most of the photosynthesis takes place in the palisade cells… in the chloroplasts.

Stomata -are the "pores" in leaves

(and stems) through which CO2 is taken in and O2 is released during photosynthesis.

Plants control when stomata are open or closed and the width of the opening (formed by two guard cells that expand and contract to open and close the space between them).

Leaf Types

Leaf Margins

Leaf Arrangements

Flowers are the reproductive structures of the plant.

- Attract pollinators, and protects the reproductive structures

- Protects young flower

base of the flower -

Site where the eggs are produced -

 The Male Reproductive Structures are called the Stamens.

They consist of two parts:

• The anther -- a small case in which the pollen grains form

• The filament -- a slender stem that supports the anther

 The Female Reproductive Structure is called the Pistil.

It consists of three parts:• The stigma -- the pollen

grains stick to this small sticky pad

• The style -- the pollen grains grow down through this stem-like cylinder

• The ovary -- this is where the young seeds (eggs) wait for the chromosomes in the pollen (sperm), and where they grow into mature seeds…. Which contain the embryos.

also called a Carpel

Pollinationis the transfer of pollen from the male part of the

plant to the female part of the plant.

Insect Pollination

The pollen is transferred to the stigma by an insect.

Water Pollination orchids are usually water-pollinated plants.

The pollen is transferred

(washed) to the stigma by water

(rain).

Wind Pollinationconifers are usually wind-pollinated plants.

The pollen is transferred (blown) to the stigma by wind.

Self-PollinationPollen from plant A pollinates plant A… the offspring now is composed of the DNA from only one parent.

Self-pollination ensures genetic continuity….. every generation is genetically identical.

Cross-Pollination

Pollen from plant B is transferred to plant A… the offspring now is composed of the

DNA of both parents. Cross-

pollination creates diversity.

Germinationa plant starts to grow…. Germination is

triggered by Cytokinin.

Gymnosperms (cone-bearing plants)

Gymnosperms reproduce using

cones• The Female cone is

called the “Seed” cone… it contains the eggs (which become seeds after fertilization)

• The Male cone is called the “Pollen” cone… the pollen contains the sperm cells.

Double Fertilizationeach pollen grain contains two sperm cells….. One sperm cell fertilizes the egg (2n - which becomes the embryo), the other fertilizes the polar

nuclei. (3n – which eventually becomes the endosperm)

Seeds- Store and digest foods

- Attachment point to Ovule

- Opening for sperm tube

- Protection

Embryonic root -

Embryonic leaves - Epicotyl

Hypocotyl - Embryonic Stem

Monocot and Dicot SeedsMonocots have one cotyledon (seed leaf), Dicots have two cotyledons (seed leaves)

Fruita mature plant ovary that encloses a seed, or seeds, and provides

nourishment and protection

Pericarp

Floral Tube

Mesocarp

Seed

Exocarp

Endocarp

Fruita mature plant ovary that encloses a seed, or seeds, and provides

nourishment and protection