Plants and photosynthesis

What is the word equation for photosynthesis

Water + carbon dioxide —sunlight—> glucose + oxygen

What absorbs light energy in the leaf

Chlorophyll in the chloroplasts

Which is the by product of photosynthesis- oxygen or glucose

Oxygen

What are the uses of glucose in a plant

Transformed into cellulose, proteins and oils / stored as starch / Used in respiration to release energy

What 3 factors affect photosynthesis

Temperature / Light intensity / Carbon dioxide

When temperature increases the rate of photosynthesis…. ,because…

Increases to an optimum then decreases because photosynthesis is controlled by enzymes and their activity increases until they denature.

When light intensity increases, the rate of photosynthesis… until…

Increases until lack of another factor e.g. Carbon Dioxide limits any further increase.

When Carbon Dioxide increases, the rate of photosynthesis… until…

Increases until lack of another factor e.g. light intensity limits any further increase.

How is the rate of photosynthesis measured when investigating the affect of temperature?

Recording the volume of oxygen produced in different temperatures

How is the rate of photosynthesis measured when investigating the effect light intensity?

By moving a plant closer to a light source and recording the O2 produced

How is the rate of photosynthesis measured when investigating the effect of carbon dioxide?

Enclose the leaf in a transparent bag/jar with sodium hydroxide this chemical absorbs CO2.

What are the stomata

Made of guard cells and can open and close to allow gas exchange in the day and prevent water loss at night

How do we test a leaf for starch?

Leaves kept in the dark for 24 hrs are destarched. They can the be used to investigate photosynthesis in different conditions. If a plant has been photosynthesising its leaf will contain starch.

The test:

1. Boil the leaf to kill it

2. Decolorise using ethanol

3. Wash to soften

4. Test with iodine- a blue/black colour shows the presence of starch.

A nitrate deficiency causes plants to have

Poor growth

A potassium deficiency causes plants to have

Yellowing of leaves

A phosphate deficiency causes plants to have

Poor root growth

Water is used in…

Photosynthesis, transport of minerals and provides support by filling the cell vacuoles.

Cell vacuoles keep cells… and prevents…

turgid and prevents cells becoming flaccid and wilting

Water from the xylem evaporates into…/ Some water vapour is lost from the… in …

Air spaces / stomata in transpiration

Water can also be used for…

Photosynthesis

What is transpiration

The loss of water vapour by evaporation from the leaves of plants

What 4 factors affect the rate of transpiration

Temperature / humidity / wind speed / light intensity

What does the phloem do

Transport of sucrose in all directions - translocation

What happens to sucrose when it leaves the phloem

It can be converted to starch or glucose

How does sucrose get into the phloem

Neighbouring cells, companion cells, contain many mitochondria to actively transport it into the phloem

Where does sucrose come from

Glucose produced in photosynthesis

Xylem vessels are vessels are adapted to allow water to move easily from the… to…

Roots to the leaves

Does the xylem carry water up or down the plant

Up the plant only

What is transpirational pull

Water diffuses out of the leaves via the stomata then more water is pulled up to fill the space

Minerals are actively transported into root hair cells which allows water to be drawn by…

Osmosis into the root cells then to the xylem

The active transport needed to transport minerals into root hair cells means that the cells are actively ___ requiring lots of ___

Respiring / oxygen

What is glucose used for

Respiration -release energy / cellulose- cell walls / starch- storage / amino acids - build plant proteins / lipids- store energy inside seeds.

Excess glucose made by a leaf is stored as..

Starch (one use)

What colour does iodine turn in the presence of starch

Blue/black

What is a control variable

Something you keep the same

What is the function of the waxy cuticle

The waxy layer reduces evaporation from leaf surfaces.

What is the upper epidermis

A thin layer of cells that are transparent to allow light to reach photosynthesising cells.

What is the function of the palisade mesophyll

Top of the leaf, contains many chloroplasts (maximise light absorption)-tightly uniform packed

What is the function of the spongy mesophyll layer

Contains air spaces between cells to allow the movement of gases

What is the function of air spaces

To allow carbon dioxide and oxygen through the leaf

What do guard cells do

They can close to prevent excessive water loss by evaporation in dry conditions.

What does the stomata do

It allows gases to move in and out of the leaf and allows water vapour to diffuse out of the leaves, maintaining the forward movement of water in the xylem.

What is the Formula for transpiration rate

Distance moved/Time taken

How do we estimate transpiration rate using a potometer?