Bio CA1

What plants need to grow healthy

Sunlight, water, oxygen

Carbon dioxide

Mineral ions

What plants respond to

Their environmental conditions and change in their surroundings

What the response is called

Stimulus

Three types of stilmuli that plants respond to

Phototropism ,sun

Hydrotropism, water

Gravitropism , gravity

What is a tropism

Any response to a stimulus

Movement towards stimulus

Positive tropism

movement away from stimulus

Negative tropism

Unidirectional/ unilateral

Light from one direction

Uniform

Light that shines evenly from all directions

What hormones control

Growth , flowering,fruit ripening

Auxins

Plant growth hormones which control the growth of shoots and roots

How auxin works?

1. Auxin is produced in the tip of growing shoots and roots

2. Auxin diffuses down to the region where cell division occurs

3. Auxin stimulates the cells in the region to elongate ( more auxin equals faster elongation)

1. If light shines equally all around the tip , auxin will be spread evenly throughout the cells leading the shoot to elongate at the same rate and straight up

1. If light shines from one side the auxin will diffuse to the darker side making the cells on the shaded side elongate and grow faster than from cells in the other side

The higher concentration of auxins of the darker side

More growth by causing more cell elongation

Which causes shoot to bend and grow faster towards the light

Why is important for plants to respond at light

• It must receive the maximum amount of sunlight for photosynthesis. Therefore more glucose is made which is used to release more energy for respiration, this energy is used for greater growth

• Reproduce pollination

When tips are removed

No auxin is made so there is no growth

When tips are covered

Auxin diffuses to all the parts of the stem , causing the cells to elongate equally and upwards

tips are illuminated (gain light ) from one side only

Auxin diffuses and accumulates in the shaded side causing the shaded side to grow more . Seeding bend towards light

Negative geotropism happens in

Shots ,lower side grows faster shoot grows upwards

Positive geotropism

Roots, lower side grow slower , root grows down towards gravity

Why is important for a plant to respond to gravity

absorbs water and mineral ions

Ensures that roots grows deep enough to anchor the plant

Ensures plants grow tall enough to reach light => photosynthesis

Maximising chances for pollination

Clinostat

Machines that rotates ( cancels gravity ) so seeding grow horizontally

Why is auxin not considered a hormone

It’s transported in phoelm not plasma

is produced on tips not from organs

Auxin has different effect on roots and shoot

Stem

Positive phototropism, grows towards light , get maximum light for photosynthesis

Negative geotropism ,grows away from gravity , more chances to find light

Root

Negative phototropism, grows away from light , less chance of drying out (collects water )

Positive geotropism, grows towards gravity , more chances to find minerals

Diffusion

The net movement of particles from a region to high concentration to a region of low concentration (passive transport ,does not require energy )

Diffusion is affected by

Temperature

Concentration gradient

Surface area

Distance

Size of particles

Higher the temperature

More kinetic energy

Faster molecule movement

More collisions

Rate of diffusion is higher

Greater the difference in concentration

Faster movement will occur

More random collisions

Bigger the cell or structure is

Smaller the surface area to volume ratio ,which slows the rate of diffusion

Larger the surface area to volume ratio

Faster rate of diffusion

Smaller distance

Faster transport

Larger particles..

Cannot pass through without assistance

Calculating rate

Change/ time

Osmosis

The net movement of water molecules from an area of high water potential to an area of low water potential through a semi permeable membrane

Concentrated solution

Larger mass of solute dissolved in a given volume => lower water potential

Dilute solution

Smaller mass of solute dissolved in a given volume of solvent => higher water potential

How to answer osmosis question

State where high and low water potential are

State the direction of movement of WATER MOLECULES

Say OSMOSIS

say the movement happens across a SELECTIVELY PERMEABLE MEMBRANE

State what happens to the cell INCREASE IN VOLUME/ BURST

Isotonic solution

Equal water concentration, no net movement flaccid

Hypertonic solution

Higher concentration of ions (concentrated) plasmolyzed

Hypotonic

Has lower concentration ( dilute) turgid

Active transport

Movement of particles across the cell membrane by carrier proteins from low to high concentration, using energy from respiration

Concentration gradient (high to low ) is the opposite to

Active transport (low to high concentration)

% change =

Final - starting mass / starting x 100

Surface area

6(l x w)

Volume

L x w x h

Surface area to volume ratio

sa / v