(2.18-2.22) Flowering Plants

What is photosynthesis?

It is a biological process whereby light energy is converted into chemical energy.

What are the necessary factors for photosynthesis?

light, carbon dioxide, chlorophyll and water

Simplified process of photosynthesis:

CO2 enters through the stomata

Water rises through stem

Chlorophyll traps energy from sun in leaves

H2 and O2 produced by converting H2O

H2 combines with CO2 to make C6H12O6 and O2

O2 released as a waste product

What is the word equation for photosynthesis?

Carbon dioxide + water ——> oxygen + glucose

What is the balanced chemical equation for photosynthesis?

6CO2 + 6H2O ———> C6H12O6 + 6O2

How do CO2 levels in plants affect photosynthesis?

As CO2 conc. goes up,

as does the rate of photosynthesis

until it is no longer the limiting factor at which point

the rate of photosynthesis plateaus.

How does light intensity in plants affect photosynthesis?

As light intensity rises,

the rate of photosynthesis goes up too.

It plateaus when it is no longer the limiting factor and

something else is stopping the process.

How does temperature in plants affect photosynthesis?

Higher temperature = more thermal energy = more kinetic energy = more collisions of CO2 and H2 = faster reactions = rate of photosynthesis goes up.

Photosynthesis is catalysed by enzymes.

When the temperature goes higher than the optimum,

the enzyme is denatured so the rate of photosynthesis decreases quickly as

the active site changes.

Describe the structure of a leaf, top to bottom?

Waxy cuticle

Upper epidermis

Palisade mesophyll

Spongey mesophyll

Lower epidermis

What is a waxy cuticle?

Protective layer that prevents water loss via evaporation

What is the upper epidermis?

Thin, transparent layer of cells that allow light to enter the palisade layer

What is the palisade mesophyll?

Site of photosynthesis, each cell is packed with chlorophyll

What is the spongey mesophyll?

Site of gas exchange, where the vascular bundle is

What is the lower epidermis?

Layer that contains guard cells and stomata

What is the stomata?

Mouth shaped openings flanked by guard cells to regulate gas exchange and prevent water loss.

What are guard cells?

Cells that flank the opening and closing of stomata by absorbing and losing water.

How does a large surface area make the plant well adapted for photosynthesis?

Increases the ability to absorb more sunlight + Co2 from the underside.

How does leaves being thin make the plant well adapted for photosynthesis?

Easy access for light + CO2

All the reactants are in close proximity so photosynthesis occurs quickly.

How does chlorophyll make the plant well adapted for photosynthesis?

Loads of chloroplasts in palisade layer = loads of chlorophyll in palisade layer = lots of sunlight which is needed for photosynthesis.

How does network of ‘veins’ make the plant well adapted for photosynthesis?

Transports water + nutrients + glucose around the leaf quickly.

What are the minerals that plants need?

nitrate, sulphate, phosphate, magnesium, iron, potassium

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What does nitrate do?

Needed to make amino acids, which are needed to make proteins.

What does sulphate do?

Needed to make proteins.

What does phosphate do?

Needed to make DNA and chemicals involved in respiration.

What does magnesium salt do?

Needed to make chlorophyll.

What does iron salt do?

Not in chlorophyll, but needed to make it.

What does potassium salt do?

Keeps the correct salt balance for leaves.

A lack of nitrate ions leads to…

Stunted growth, yellow leaves.

A lack of sulphate leads to…

poor growth, yellow leaves

A lack of phosphate leads to…

stunted growth- primarily roots, older leaves are darker.

A lack of magnesium leads to…

yellow plant, limited growth.

A lack of iron leads to…

yellow leaves.

A lack of potassium leads to…

older leaves yellow, mottles leaves.