Variety of plant cells

There are 2 types of vascular (transport) tissue found throughout the plant.

Xylem tissue consists of

1. Xylem vessels

Xylem vessels are dead.

They are long hollow tubes allowing water to easily move up through the plant.

They are strengthened by rings or spirals of lignin. This helps to support the plant.

2. Tracheids

Tracheids are also dead.

They are hollow spindle shaped cells whose ends overlap with neighbours. They have lignified walls which make them ideally suite for support.

Phloem tissue is the second type of vascular tissue.

All phloem tissue is alive.

There are 2 types of cells.

1. Cells belonging to a sieve tube.

The end walls of these cells are perforated to allow cytoplasm to move from one cell to another carrying food. These perforated end walls are called sieve plates.

2. Companion cells

The companion cells contain a nucleus which controls the sieve tube.

The first plant organ which is being examined is the root.

The root has several tissues including xylem and phloem.

The epidermis has some of its cells elongated to provide root hairs.

This provides a large surface area for absorption of water.

The epidermis cell are box like which allow cells to fit together.

This is needed for protection.

Another plant organ is the stem. This also contains xylem, phloem and epidermis.

The final organ examined is the leaf.

If a cross section of the leaf is taken, it is seen that the leaf consists of several tissues.

There are 2 types of cell in mesophyll tissue.

The palisade mesophyll cells have chloroplasts present. They also have columnar shape which provides a maximum surface area for absorption of light.

This is where most photosynthesis takes place.

The spongy mesophyll cells have a round shape which allows moist air to be present between cells of the tissue. These cells also have chloroplasts.

More photosynthesis takes place here. In addition the moist air spaces llow carbon dioxide to reach the cells.

There are 2 types of epidermal tissue.

The first type is the upper epidermis tissue. These cells are all identical to each other. They fit closely together for protection although they allow light to pass through to reach the mesophyll.

The second type of epidermal tissue is the lower epidermis.

There are 2 types of lower epidermis tissue. The epidermal cells are irregular shape allowing the cells to fit together into a strong layer. This provides protection.

The guard cells surround the stomata. The guard cells are sausage shaped with a thick inner cell wall facing stoma..There are chloroplasts present

The guard cells control gas exchange by changing shape and opening or closing stomata.

What to do.

1. Collect diagram sheet.

2. Copy and complete the following table.

Cell type Specialised features

How structure suits function

Cell type Specialised Features How structure suits function

Xylem vessels

Tracheids

Phloem

Spongy Mesophyll

Guard Cells

Palisade Mesophyll

Hollow tubes which are lignified and dead

Allows water transport and gives stem support

Hollow spindle shaped lignified cells

Gives stem extra supportAllows cytoplasm to move carrying food

Contains large nucleus

Allows control of itself and sieve cell

Round shape and chloroplasts

Produces air spaces for gas diffusion and can do secondary photosynthesis

Columnar and packed with chloroplasts

Produces a tightly packed layer of photosynthetic cells

Sausage shaped with thicker inner wall

Allows stomata to open and close for gas exchange

Companion cells

Epidermal cells

Root Hair Cells

Perforated end walls and no nucleus

Sieve cells

Box or irregular shape that fit tightly together

Produce a strong protective “coat”

Long extension into the soil

Produces a large surface area for water absorption