Unit-IV: Seed Germination and Amylase Activity

This unit focuses on practical experiments to understand the physiological triggers behind the early development of a plant embryo into a seedling.

Light is a key environmental factor that influences seed germination in many species by interacting with the phytochrome system.

Objective:

To observe how different light conditions (light vs. dark) affect the percentage and rate of seed germination.

Requirements:

• Viable seeds (e.g., lettuce or pea).
• Petri dishes and filter paper.
• Distilled water.
• Dark box or aluminum foil.

Procedure:

1. Surface sterilize the seeds to prevent fungal growth.
2. Place equal numbers of seeds in two sets of Petri dishes lined with moist filter paper.
3. Expose one set to continuous or periodic light.
4. Place the second set in complete darkness (using a dark box or foil).
5. Maintain constant moisture and temperature for both sets.
6. Count the number of germinated seeds in both sets daily for a week.

Observation and Calculation:

Calculate the germination percentage for each set using the formula:

Germination % = (Number of seeds germinated / Total number of seeds) x 100

Compare the results to determine if the seeds are positively photoblastic (require light), negatively photoblastic (require dark), or non-photoblastic.

During germination, the hormone gibberellin (GA) triggers the production of the enzyme alpha-amylase to break down stored starch into sugars for the embryo.

Objective:

To demonstrate the presence and activity of amylase enzyme in germinating seeds.

Principle:

Starch reacts with iodine to give a blue-black color. If amylase is active, it will hydrolyze starch into maltose, and the blue-black color will not form.

Procedure:

1. Take germinating seeds (e.g., wheat or barley) and grind them to prepare an enzyme extract.
2. Prepare a 1% starch solution.
3. Add a specific volume of the enzyme extract to the starch solution.
4. At regular time intervals (e.g., every 5 minutes), take a small sample of the mixture and add a drop of iodine solution.
5. Record the time taken for the mixture to reach the "achromic point" (where no blue color is formed).

Results:

The disappearance of the starch-iodine reaction over time confirms the induction and activity of amylase during the germination process.