A student investigated the effects of indoleacetic acid (IAA) on the growth of oat seedlings - AQA - A-Level Biology - Question 3 - 2019 - Paper 2
Question 3
A student investigated the effects of indoleacetic acid (IAA) on the growth of oat seedlings.
The student:
- removed the shoot tip from each seedling and cut out ... show full transcript
Worked Solution & Example Answer:A student investigated the effects of indoleacetic acid (IAA) on the growth of oat seedlings - AQA - A-Level Biology - Question 3 - 2019 - Paper 2
Step 1
Explain why the student removed the shoot tip from each seedling.
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The shoot tip produces indoleacetic acid (IAA), which is a plant hormone that regulates growth. Removing it allows the student to observe the effects of varying IAA concentrations on shoot elongation.
Step 2
Explain why the student added glucose solution to each Petri dish.
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Glucose serves as an energy source for the seedlings, providing ATP for respiration and growth, ensuring that any observed effects on growth are due to IAA and not energy deficiency.
Step 3
Explain why the lids were kept on the Petri dishes.
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Keeping the lids on prevents evaporation of the IAA solution and glucose solution, which maintains consistent concentrations throughout the experiment and avoids contamination.
Step 4
Describe and explain the results shown in Table 1 and suggest how the results might have differed if lengths of root had been used.
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The results indicate that as the concentration of IAA increases, the mean change in length of the shoot also increases. This suggests that higher IAA concentrations enhance growth. If lengths of root had been used, the results might differ due to different responses of root cells to IAA, as roots typically have varying sensitivities and might elongate or even inhibit growth at high concentrations.
Step 5
Complete Table 2 with the volumes of stock IAA solution and distilled water required to produce 40 cm³ of 10 ppm (parts per million) IAA solution.
97%
117 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
To prepare a 10 ppm solution, the student would need 4 cm³ of stock IAA solution and 36 cm³ of distilled water, allowing accurate dilution.
