Plant Responses RPA

Question 1

Method for investigating changes in light intensity

Answer 1

1) pour fixed volume of water into 3 different Petri dishes (use measuring cylinder to measure volume) and add equal mass of cotton wool to each (use top pan balance to measure mass)
2) Add 10 mustard seeds to each Petri dish and leave in a warm place for the seeds to germinate. Ensure they all have the same level of sunlight and temperature and if needed water them with the same volume of water each day
3) after 3 days the seeds should have germinated- make sure there is an equal number of seedlings in each Petri dish by removing excess seedlings if some seeds from other Petri dishes haven’t germinated
4) place 1 Petri dish in a dark cupboard, place one Petri dish on a well lit window sill, place one Petri dish in partial light
5) use ruler to measure height of each seedling from all 3 Petri dishes each day for 5 days in a row and record results in table
6) calculate mean height of seedling in each of the 3 Petri dishes for each of the 5 days and compare height for different conditions

Question 2

For changing light intensity, for which condition would you expect the seedlings to be the tallest

Answer 2

Dark cupboard as seedlings grow rapidly upwards to try and reach the sunlight

Question 3

Sources of error

Answer 3

Seedlings in same dish may not receive same exposure to light
Different seedlings may start off at different heights (solve by measuring initial height and then calculating change in height each day)

Question 4

Sources of error

Answer 4

Seedlings in same dish may not receive same exposure to light
Different seedlings may start off at different heights (solve by measuring initial height and then calculating change in height each day)