plant cells

What are the 2 systmes of plants?

What are the 2 systmes of plants?

Shoot and root system

Shoot system (above-ground system of plants)

, the site of photosynthesis, transport of sugars, and the site of reproductive organs

Root system (the below-ground system)

anchors the plant in the soil

is responsible for the absorption and conduction of water and minerals,

storage of excess sugars (starch)

shoot system organs

the root, lateral roots and the root hairs

root system organs

the root, lateral roots and the root hairs.

What are the two tissues of plant organs

Meristematic and permanent tissues

Meristematic tissues

responsible for an increase in the plant stem and root and can undergo cell division and divide for the life of the plant.

Permanent tissues

have the ability to no longer divide

three tissues of permanent tissues

dermal, ground, vascular

dermal tissue

protects plants and minimises waterloss

ground tissue

functions in photosynthesis, storage, support, has 3 simple tissues (collenchyma, parenchyma, schlerenchyma)

collenchyma

main supporting tissue of stems

parenchyma

site for photosynthesis

schlerechyma

strength and rigidity

vascular tissue

plant tissue composed of xylem and phloem

xylem (passive transport) (up)

transports water and minerals throughout a plant and provides a plant with support

phloem (active transport) (up and down)

transports sugars and organic compounds like hormones throughout a plant

xylem features

Has more than one type of cell. thickened cell wall to add structure and support

translocation of sugars (phloem)

Sugar is produced by photosynthesis in the mesophyll cells of leaves. It moves into the phloem by active transport through membrane proteins or by simple diffusion through plasmodesmata. It moves down the phloem to the roots, under pressure created by osmosis. This is the pressure flow model of how phloem works. Unlike xylem, phloem cells (called sieve tube members) are living cells, but have no nucleus (to make space for the passage of sugars). They are accompanied by smaller companion cells, which do have a nucleus, and control the activities of themselves and the sieve tube cells.

The flow of water through the xylem from the roots to the leaf, against gravity

transpiration stream

Evaporation (Water Loss)

Water is lost from the leaves of the plant when it is converted into vapour (evaporation) and diffuses from the stomata

• Some of the light energy absorbed by leaves is converted into heat, which evaporates water within the spongy mesophyll

• This vapour diffuses out of the leaf via stomata, creating a negative pressure gradient within the leaf

• This negative pressure creates a tension force in leaf cell walls which draws water from the xylem (transpiration pull)

• The water is pulled from the xylem under tension due to the adhesive attraction between water and the leaf cell walls

soil

Source of water for terrestrial plant is water in the soil.

Soil has solid mineral particles, in dry conditions space= filled with air

Rain= with water

What are root hairs?

Extensions of cells of the epidermal tissue that forms the outer cellular covering of the root

Why are root hairs important?

they increase the surface area, allowing for the uptake of water and nutrients from the surrounding soil.

How do root hairs work

water entres root hairs by osmosis,

From root hair cells, water moves to xylem where its transported as a fluid

what happens to the remainder of water absorbed by roots?

Transpiration

What influences loss of water?

Tempreature- as temperatures increase, the rate of evaporation of water increases

Light intensity: light stimulates the opening of the leaf pores (stomata)

Humidity: the greater the content of water vapor in the air, the lower the rate, such that at 100 per cent humidity in the air, net water loss by transpiration stops

Transpiration

Excess water evapourated from stomata

Stomata

The sites of carbon dioxide uptake and prevention of water in a plant

Where are the stomatas located in?

Tiny pores on the surface of leaves and stems of plants

Structure of stomatas

Surrounding by two guard cells.

How does the structure of stomatas work?

The inner wall of guard cell is thicker, in sunlight, photosynthsis is occuring, guard cells take up water and swell, restults in the opening of stomata

What happens in the dark

Carbon dioxide is not needed, so the guard cells lose water and shrink, water loss is prevented

Transpiration stream (xylem)

The flow of water and dissolved nutrients through the xylem from the root to the leaf

Cohesion

Force of attraction between two particles of the same substances (between two water molecules)

How does cohesion work

water molecules are dragged up the xylem, towards leaves

Adhesion

force of attraction between two particles of different substances (water molecules and xylem wall

How does Adhesion work?

The water vessels are attracted to the small walls of the small xylem vessels

Root pressure

osmotic pressure in the roots creates a minor “push” effect.

Transpiration pull-

The negative pressure that is created in the xylem vessels when water evaporates from the leaves through the stomata

Capillary action

narrowness of vessles, attraction of water to the cellulose fibres and the cohesivness of water molecules all assist water movement

Name and defintion of transport xylem process

Transpiration, The movement of water and dissolved ions from the roots the leaves that rises through te xylem of the plant

Name and defintion of transport phloem process

translocation, the movement of sugars and other substances like amino acids around a plant

Drirection of flow of xylem

Water moves the stem and roots moves upwards or is pulled into leaves

Drirection of flow of Phloem

Any direction- up or down the plant

Major cell type of xylem

Xylem vessels and trachieds, both dead

Major sell type of phloem

phloem sieve tube cells

companion cells both living

Features of major cell types of xylem

Dead cells, long cynlindrical shape, spiral secondary thickening of lingth, hallow, vessels are open ened. Have pits in the side

Features of major cell types of phloem

PST cells: living, cylindrical in shape, no nucleus, end cell walls are perforated - called sieve plates

First step of transpiration

Energy from the sun allows the stomata to open

water then evaporates from the leaves through the stomata and creates negative pressure that pulls water up the roots through the xylem vessels

2

The adhesion between water molecules and the xylem walls helps to keep the water column intact and prevent it from breaking apart

3

The cohesion between water molecules helps to maintain the continuous flow of water through the xylem, creating a transpiration stream that carries water and nutrients throughout the plant

Stomata role

regulation of water balance and gas exchange of plants

why is transpiration stream important

For plant growth and survival, as it provides water and nutrients to the leaves

factors that influence transpiration stream

tempreature, humidity, wind, light and soil mositure

Sieve tube (phloem)

Long thin cells connected end to end to form a continous tube

perforated end walls called sieve plates (allow for the transport of materials between cells

companion cells (phloem)

smaller cells

connected to the sieve tube elements by plasmometabolic

Add support to the sieve tube elements help regulate their function

Tracheids (xylem)

long thin cells tapered at the ends and have pits in their walls

Allow water to move from one cell to another

Vessels (xylem)

short, wider

Have perforations in their walls that allow water to move freely between cells

how to maintain water balance

Stomata on the underside of the leaf reduce water loss, as it reduces exposure to the sun.

Rolled leaves reduce airflow over the stomata, reducing water loss.