SAFETY: Always wear safety goggles when working with chemicals. Wash your hands between handling each plant, and at the end of each lab session.

MATERIALS:

Safety goggles
5 flasks (150 mL)
Wax pencil
100 mL graduated cylinder
300 mL of water
10 mL of isopropyl alcohol
*5 bean seedlings
Scalpel
Cotton
**105 mL of indoleacetic acid solution (IAA),

PREPARATION OF SOLUTIONS AND SEEDLINGS:

*Start your bean seedlings in small individual pots. Make sure you start more than you will need, so you will have enough good seedlings. When the seedlings are tall enough that you will have the leaves, and plenty of stem, sticking out above the top of the flasks, you are ready to begin.

Indole-3-acetic Acid crystals are unstable. Store 2-3 weeks under refrigeration. Discard the crystals if they turn brown or have a fecal smell. You can purchase it from a science supply company, or check with your local nursery

**To prepare a 1 : 10,000 solution, (one part per ten thousand), dissolve 1 gram of IAA powder in 10 mL of isopropyl alcohol, dilute that solution to 1,000 mL with distilled water, and then dilute 100 mL of that solution to 1,000 mL with distilled water.

***To prepare a 1 : 1,000,000 solution, (one part per million), dilute 10 mL of the 1 : 10,000 solution to 1,000 mL with distilled water.

PROCEDURE:

1. Using a wax pencil, label the flasks as follows:

2. Place 100 mL of distilled water in the flasks for test plants 1, 2, and 3. Place 100 mL of the 1 : 10,000 IAA in the flask for test plant 4. Place 100 mL of the 1 : 1,000,000 IAA in the flask for test plant 5.

Throughout this lab, you will be handling the seedlings daily, so handle them very gently.

3. Using a scalpel, carefully cut the stems of five bean seedlings near soil level. Also remove the cotyledons from each plant.

4. Place one plant in each of the five flasks. Make sure the stems are submerged in the liquid. Pack cotton at the top of each flask to keep the plants upright.

5. Using a small paintbrush, coat the leaves of test plant 1 with distilled water. Using a different paintbrush, coat the leaves of test plant 2 with the 1 : 10,000 IAA solution. Using a third paintbrush, coat the leaves of test plant 3 with the 1 : 1,000,000 IAA solution. Repeat each day for 10 days.

6. Set the flasks in a place where the plants will receive the same light. Observe the plants daily for the 10 days. Record the number of roots that appear, on data table 1.

7. Every day after roots appear, carefully remove each plant from the flask, and measure the length (from stem to root tip) of three typical roots in (mm). Measure the same three roots each day. Carefully replace each plant in its original flask. Find the average length of the roots for each plant, and record this average in data table 2.

DATA TABLE 1: Number of roots.
	NUMBER OF ROOTS
Test Plant	Day 1	Day 2	Day 3	Day 4	Day 5	Day 6	Day 7	Day 8	Day 9	Day 10
1 (control)
2 (leaves)
3 (leaves)
4 (stem)
5 (stem)

DATA TABLE 2: Average root length (from 3 roots).
	AVERAGE ROOT LENGTH (mm)
Test Plant	Day 1	Day 2	Day 3	Day 4	Day 5	Day 6	Day 7	Day 8	Day 9	Day 10
1 (control)
2 (leaves)
3 (leaves)
4 (stem)
5 (stem)

GRAPHING:

QUESTIONS:

Using your data in graph form, answer the following:

Q1. Does IAA concentration affect root growth? ______________

Explain your answer.

Q2. Which method of applying IAA was the best? ______________

What criteria did you use in deciding which was the best method?

Q3. What would happen if you increased the IAA concentration for the leaf application method (test plants 2 and 3)?

What would happen if you decreased it?

Q4. What would happen if you increased the IAA concentration for the stem application method (test plants 4 and 5)?

What would happen if you decreased it?

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