Topic 6 - Plant Structures and their Functions

Photosynthesis

endothermic reaction in plants and algae that uses light energy to react carbon dioxide and water to produce glucose and oxygen

Photosynthesis conversion of energy

Light -> chemical potential

Photosynthesis balanced equation

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Polymer

A long molecule consisting of monomers bonded together.

Monomer

small chemical unit that makes up a polymer

Why should you boil a leaf when testing for starch

Disrupts the cell membrane

Why is hot ethonal used when testing a leaf for starch

Allows iodine solution to penetrate the cell

Why is the leaf boiled when tested a leaf for starch

Softens the cell wall

4 steps to test a leaf for starch

Boil ethonal wash iodine

Why do cells need guard cells

To exchange gases

Why do cells need palisade mesophyll

To do photosynthesis

What occurs in the vascular bundle

Gas exchange

Why does the leaf cell need enough air space

For gas exchange

What happens if the leaf has a thin waxy cuticle

More water loss and desiccation (no moisture)

What happens if there are too many chloroplasts in the upper and lower epidermis

not able to let light in

Layer 1 of a leaf

Waxy cuticle

Waxy cuticle

Impermeable prevents water loss/desiccation

Layer 2 of a leaf

Epidermal layer

Epidermal layer

Transparent

Layer 3 of a leaf

Palisade mesophyll

Palisade mesophyll

Lots of chloroplasts for photosynthesis

Layer 4 of a leaf

Spongey mesophyll

Spongey mesophyll

Round irregular shapes for air space for gas exchange for photosynthesis and respiration

Layer 5 of a leaf

Vascular bundle

Vascular bundle

Xylem transpiration phloem translocation

Layer 6 of a leaf

Guard cells

Guard cell

controls opening of stomata

As light intensity doubles

rate of photosynthesis

As light intensity halves

rate of photosynthesis

As distance doubles

light intensity

As distance halves

light intensity

How are light intensity and distance linked

indirectly proportional

How are light intensity and rate of photosynthesis linked

Directly proportional

How would you measure rate of photosynthesis

Oxygen bubbles

Method for light intensity and rate of photosynthesis experiment

Water and pond weed in a test tube water and sodium hydrogen carbonate beaker measure lamp distance count bubbles Average increase distance

ROP and LI experiment

why is there more CO2

Light intensity =

1/distance²

Distance =

Square root of 1/light intensity

If you half the distance

light intensity

If you double distance

light intensity

What 3 things affect rate of photosynthesis

Temperature light intensity CO2 concentration

What type of reaction is photosynthesis

Enzyme controlled endothermic

Water in a leaf steps (4)

Root hair cells through cell walls Through xylem evaporation

Measuring the rate of transcription experiment method

Move air bubble to the end add leaf to the end of the potometer let acclimate Fan changes wind speed measure cm travelled per min repeat and average

Tropism

A growth response in a particular direction by plants detecting stimuli

If the auxins are evenly distributed

the plants elongates

If the auxins are in the shadows

the plants elongates

In the shoots

auxins

In the roots

auxins

why are the auxins oj the underside of roots/shoots

The top side grows faster and falls downwards

What is the response of auxins

Growth

Light - shoot

Auxins move in direction of stimulus

Light - root

Auxins move away from the stimulus

Gravity - shoot

Auxins move away from the stimulus

Gravity - root

Auxins move in direction of the stimulus

What tropism is upright shoot growing towards light

Positive phototropism

What tropism is horizontal root grows down

Neutral gravitropism

What tropism is root growing away from light

Negative phototropism

Name a gas plant hormone

Ethylene

What does hormone rooting powder do

Auxins cause plant cuttings develop roots quickly so that genetically identical plants can be produced quickly using cuttings

What causes plant cutting to develop roots quickly

Hormone rooting powder

What do gibberellins do (seeds)

promotes seed germination/ controls seed dormancy

What controls seed dormancy

Gibberellins

What do artificial auxins do

Kills plants with broad leaves by making them grow uncontrollably

What does ethene do

Ripens the fruit before it is sold from storage

What ripens fruit

Ethene

What do gibberellins do (no seeds)

Cause some plants to develop without pollination

What causes some plants to have no seeds

Gibberellins

Dry environment stem adaptation

Swollen and round to store water

Dry environment spine adaptation

Instead of leaves to prevent water loss

Dry environment thick waxy cuticle

Prevent evaporation

Dry environment root adaptation

Extensive roots

Dry environment stomata adaptation

Only open at night

Wet environment air pockets adaptation

Air pockets allow oxygen to slow down into the roots

Wet environment roots adaptation

Adventitious roots sprout off underwater stem to take in H2O and O2

Wet environment stem and roots adaptation

Elongated stem and shallow roots for more absorption

Wet environment flowers on the surface adaptation

Collect maximum amount of sunlight

Wet environment long leaves adaptation

Soak up more

Dark environment living near entrances of caves adaptation

Photosynthesis light

Dark environment leaves adaptation

Broad

Cold environment low growing adaptation

Survive wind and cold trap airborne dust to use as a nutrient source

Photosynthesis is a series

of chemical reactions catalysed by enzymes

Why is photosynthesis endothermic

Taking energy from the surroundings

During the day

plants photosynthesise but also

Why do trees adapt to have huge buttress roots

Absorb water and dissolved mineral ions

What is water absorbed by plant roots used for

• carrying dissolved mineral ions

• keeping cells rigid

• cooling the leaves

• photosynthesis

What do the hairs on root hair cells provide

Extensions give large sa

Structure of hairs in root hair cells

Thin cell wall increases flow of stuff into the cell

Diffusion

Particles constantly move randomly

Diffusion in plant roots

Cell walls open

Osmosis

Solvent molecules travel down the concentration gradient through a semi-permeable membrane

Mineral salts are

Naturally occurring ionic compounds

Why do plants need ions

To produce new substances

Active transport in a plant

Against the concentration gradient

Water osmosis in a plant

Very thin root hair cells and tiny tubes join the cytoplasm of cells

Water diffusion in a plant

Through cell wall of root hair cells

Root hair cell semi-permeable membrane

Not permeable to mineral ions

How come the concentration gradient in a plant will not change

Plants uses water

Why does water evaporate on leaves

Keeps them cool encourages flow of water up the stem

What do xylem vessels form

A series of continuous unbroken tubes from root to leaves