Production of amylase in germinating cereal grains

Question 1

What is the role of gibberellin during germination?

Answer 1

It’s secreted by the embryo. Then it diffuses to the aleurone layer of the endosperm to stimulate the production of amylase.
Amylase hydrolyses starch to maltose.

Question 2

How is the effect of gibberellin concentration on amylase production investigated?

Answer 2

1. Dilute gibberellin to produce several concentrations
2. Cut seeds in half, use only the half with the endosperm
3. Dip in sodium hypochlorite solution and wash with water
4. Place seeds in each gibberellin solution and leave
5. Place seeds in a Petri dish and starch agar, leave for 12-48 hours
6. Pour potassium iodide onto the plates and measure the clear zone

Question 3

What does the zone of inhibition indicate? Specific to this practical, not bacterial cultures.

Answer 3

It indicates that starch has been hydrolyzed by amylase (so not stained). The larger the zone of inhibition, the higher the amylase concentration.

Question 4

Why are the seeds placed in sodium hydrochloride solution?

Answer 4

To sterilize them.

Question 5

What is the effect of gibberellin concentration on amylase production?

Answer 5

Increased gibberellin concentration increases area of the clear zone. This indicates an increased production of amylase and more starch hydrolyzed.

Question 6

What are some sources of error in this practical?

Answer 6

The existing gibberellin and amylase content of the seeds may be different.

Question 7

What are some controlled variables in this practical?

Answer 7

Time allowed to soak in gibberellin
Time left on starch agar plate
Source/age of seeds