Biology - Plant Structure

tissue

a group of similar cells that work together to carry out a specific function

types of plant tissue

Dermal:

• function: protection and reduction of water loss

• location: a single layer of cells called the epidermis covers the outside of a plant. Waxy cuticle that covers the root and leaves on the epidermis reduces water loss

Ground:

• function: photosynthesis in the palisade layer of the leaf, support, food storage

• location: between vascular and dermal tissue

Vascular:

• function: transport; xylem transports water and phloem transports food

• xylem and phloem are located in the vascular bundles of root stems and leaves

Meristematic:

• made up of cells which divide by mitosis

• meristems are found in the root and shoot tip (apical meristems)

plants are divided into…

an overground shoot system and an underground root system

node & internode

node - a point on a stem from which a leaf emerges/where the leaf is attached

internode - distance between two nodes

a plant has these structures…

• apical bud (at tip of the stem)

• flower

• stem

• fruit

• internode

• auxillary bud; lateral or side bud

• leaf

• node; point on the stem where the leaf is attached

cotyledon & two types

a seed leaf within the seed of a plant

dicot = two seed leaves

monocot = one seed leaf

dicot diagram: testa, plumule, radicle, cotyledons

germinate

seed is growing into a young plant

functions of the root

1. anchors the plant

2. absorbs water (osmosis) and minerals (active transport and diffusion)

3. transports water and minerals to shoot

4. stores food in ground tissue

types of roots

Tap root:

• main long root

• grows from radicle

• lateral roots grow

• e.g. carrot

• typical of dicot plant

Fibrous root

• formed when the radicle dies

• many equal sized roots

• e.g. grass

• typical of monocot plant

Adventitious root:

• roots that don’t grow from the radicle

• e.g. onion

zones of a root

• protection zone: root cap protects the root as it pushes through the soil

• meristematic zone: produces new cells by mitosis & increases the length of the plant; found at root and shoot tips

• elongation zone: cells grow and increase by size via elongation - auxin causes the cells to grow longer

• differentiation zone: cells develop into dermal, ground and vascular tissue

functions of a stem

1. supports the aerial parts

2. transports water and minerals from roots

3. transports food made in leaves

4. photosynthesis

5. may store food

lenticel

opening on the stem of a plant and is used for gas exchange

compounds that leave the plant through lenticels are CO2 & H2O

parts of a winter twig

• node

• internode (distance between 2 nodes = one year)

• terminal/apical bud

• lenticel

• lateral bud

• leaf scar

• girdle scar

herbaceous vs woody plants

herbaceous plant don’t contain wood and woody plants do

vascular bundles in monocot and dicot stem

• dicot = ring

• monocot = scattered

leaf venation

parallel = monocots such as grasses

netted = dicots such as roses

functions of a leaf

1. photosynthesis

2. transpiration (the loss of water vapour from a leaf through the stomoata

3. gas exchange via stomata

4. food storage

control of transpiration

waxy cuticle & action of the stomata

this is bc it doesn’t want to lose too much water

stomata: description, role, control

desc.:

• openings on the leaf surface (lower epidermis)

• they are surrounded by guards cells, that control the opening and closing of the stomata

role:

• regulates gas exchange

• control water loss from a plant

guard cells:

• when they are turgid, the stomata are open

• when they are flaccid, the stomata are closed

control:

• CO2 concentration in the leaf controls the opening and closing of the stomata

• high co2 = stomata close

• low co2 = stomata open

*undersurface of leaf contains guard cells, stomata, dermal cells

vascular tissue: xylem

xylem tracheids:

• long tapered cells w/ tapered ends

• have end walls

• thinner than xylem vessels

• pits allow transfer of water from cell to cell

• lignin in wall for strength and mechanical support

• dead tissue, so no cytoplasm

xylem vessels:

• tubular structures

• end walls break down to form a continuous tube

• pits transport water sideways

• lignin in cell walls from strength and mechanical support

• dead tissue, so no cytoplasm

function and location of xylem

functions:

• transports water and dissolved minerals upwards

• gives mechanical support to plants

location of xylem:

• found in vascular bundles

adaptations of xylem

1. cells are hollow and narrow, so more space for water and dissolved substances to be transported

2. pits allow transfer of water from one tracheid/vessel to another

3. lignin gives support and stops the xylem from collapsing

vascular tissue: phloem

composition:

• phloem is composed of sieve tubes and companion cells

• sieve tubes are long tubular structures

• end walls develop pores are called sieve plates

• sieve tube elements have accompanying companion cells which are living

function:

• phloem transports food from leaves to rest of the plant (food moves upwards and downwards)

location:

• phloem found in vascular bundles

adaptations of phloem

1. sieve plates allow food to pass from cell to cell

2. cells are tubular and hollow so food can pass through. they are hollow because cytoplasm is pushed to the side

monocot vs dicot

monocot:

• one seed leaf

• scattered vascular bundles

• parallel leaf venation

• flower parts in multiples of three

• usually herbaceous

• fibrous roots

dicot:

• two seed leaf

• vascular bundles in ring

• netted leaf venation

• flowers parts in multiples of two and five

• woody or herbaceous

• tap roots

to prepare and examine a transverse section of a dicot stem

1.Cut a number of short lengths of wet stem between nodes using a mounted blade.

2. Place on a board and cut thin transparent slices using the mounted blade.

3.Cut at a 90°angle away from your body.

4. Use your fingers or a carrot as support while cutting.

5. Place the cut sections in a petri dish of water (Prevents drying out).

6. Remove the thinnest section from the water and place it on a microscope slide in a drop of water.

7. Add a coverslip using a mounted needle at a 45° angle to prevent air bubbles.

8. Examine under the microscope at low, medium and high power.

9. Draw a labelled diagram.

10. A geranium is a suitable plant for this experiment.