Plant nutrition

Question 1

What is the definition of photosynthesis

Answer 1

The process by which plants manufacture carbohydrates from raw materials using energy from light

Question 2

In photosynthesis, how is light energy absorbed

Answer 2

It is absorbed by the green pigment chlorophyll

Question 3

(word and symbol) equation for photosynthesis

Answer 3

Carbon dioxide + Water –> Glucose + Oxygen

6CO₂ + 6H₂O –> C₆H₁₂O₆ + 6O₂

Question 4

What can glucose, made in photosynthesis be used for?

Answer 4

Making starch - by linking glucose molecules together, energy source stored inside plant cells

Making cellulose - By linking many glucose molecules together in many different ways, cellulose is used to make plant cell walls

Making sucrose - used to transport carbohydrates from one part of a plsnt to another

Making lipids - by rearranging the carbon, hydrogen and oxygen atoms; lipids can be stored as an energy source

Making amino acids - by rearranging the carbon, hydrogen and oxygen atoms and adding nitrogen; used to make proteins which are used to build cells, for active transport and enzymes

Question 5

Describe a test to test if a plant is photosynthesing

Answer 5

1. ) Place leaf in boiling water - destroys waxy cuticle and breaks open cell membranes
2. ) Place the leaf in hot alchahol - this dissolves the chloropyll from the leaf
3. ) Dip the now colourless leaf, brittle leaf into water to soften it
4. ) Add iodine solution - for a positive test, iodine will turn blue black in the presence of starch

Question 6

How to investigate if chlrophyll is needed for photosynthesis

Answer 6

Test a variegated leaf for starch

The green parts containing chlorophyll turn blue-black (positive test)

The white parts which lack chlorophyll will not change the colour of starch

Question 7

Describe a test to show that light is needed for photsynthesis to occur

Answer 7

Partly cover a leaf with a piece of black paper and stand the plant in the light for a day

After this time period, test the whole plant for starch

Only the uncovered side will turn blue-black

Question 8

Describe a test to show that carbon dioxide is neccessary for photosynthesis

Answer 8

Place one part of the plant in soda lime (absorbs CO₂) and the other part without soda lime

Only the part without soda lime will turn blue-black in the presence of iodine

Question 9

What is a “control” in experiments

Answer 9

A control is something you can compare your result to

For example, in the black paper experiement, you compare the parts of the leaf which had and didn’t have light

Question 10

Describe a test to test how variables affects photosynthesis

Answer 10

Use an aquatic plant in water as oxygen is given off as bubbles; the more bubbles = the more photsynthesis/ unit time

A gas syringe is used to measure the volume of oxygen produced

an example - to measure how conc. of CO₂ affects photosynthesis add sodium hydrogencarbonate to water that surrounds the plant, this decomposes in the water to give CO₂

Question 11

Define “limiting factor”

Answer 11

Something present in the environment in such short supply that it restricts life processes

Question 12

In the day

How does rate of photosynthesis compare to rate of respiration

Answer 12

Rate of photsynthesis is greater

Question 13

In the dark which plant processes take place

Answer 13

ONLY respiration

Question 14

What test can you use to investigate the effect of gas exchange in an aquatic plant

Answer 14

Use hydrocarbonate indicator

Turns yellow in large amounts of CO₂

Turns red or purple in little to no carbon dioxide