practical investigations into plant hormones

Question 1

outline the procedure you would use to investigate geotropism

Answer 1

• line 3 petri dishes with moist cotton wool
• space out 10 cress seeds on the surface of the wool, press them down into the wool slightly
• put a lid on each dish, wrap the dishes in foil to prevent any light reaching them. leave the dishes where temperature is constant and warm.
• set up the dishes so that they are placed at different angles eg. 90 degrees, 45 degrees 0 degrees.
• leave the seeds for 4 days
• after 4 days unwrap each dish and note the direction of the shoot and root growth of the seedlings. record in a table.

Question 2

what are the controlled variables for investigating geotropsim

Answer 2

• volume of water provided
• mass of cotton wool
• number of seeds
• exposure to light
• temperature
• time allowed for growth
• species of seed

Question 3

outline the procedure to investigate the effect of auxin

Answer 3

• select 30 plants similar in height, age and mass. Count the number of side shoots growing from the same stem
• remove tip of shoot for all plants and apply a paste with auxin to 10 plants, apply a paste without auxin to another 10 plants and leave the other plants as they are.
• allow 6 days for the plants to grow.
• count the number of side shoots that have grown from the main stem

Question 4

what are the control variables for investigating the role of auxin

Answer 4

height, mass and age of plants

species of plants

temperature

light intensity

water

Question 5

outline the procedure to investigate phototropism

Answer 5

• select 9 wheat shoots equal in height, age and mass, plant in same type of soil
• record height of shoot (mm)
• cover the tips of 3 shoots with a foil cap
• leave 3 shoots without a foil cap
• wrap the base of 3 shoots with a foil cap leaving only the tip unexposed.
• set up the shoots in front of a light source, same distance same intensity
• leave shoots to grow for 2 days
• record amount of growth in mm, and the direction of growth in a table.

Question 6

outline the procedure to investigate the effect of giberellins on plant stem elongation

Answer 6

• select 40 plants of similar mass, age and height
• leave 20 to grow, and water the other 20 with a dilute giberellin solution
• leave the plants to grow for 28 days
• measure the length of the stem every 7 days
• calculate the mean stem length