Growth regulators in plants can promote growth or inhibit it - Leaving Cert Biology - Question 8 - 2008

An example of a growth regulator that inhibits growth is abscisic acid. This hormone inhibits seed germination and promotes the closure of stomata during times of drought, thereby reducing water loss.

In my investigation, I used bean plants (Phaseolus vulgaris). These plants are commonly used in experiments due to their rapid growth and easy cultivation.

The investigation was carried out using the following steps:

1. I prepared two separate groups of bean plants: one group was treated with a specific concentration of auxin, while the other served as the control group without any treatment.
2. I used different concentrations of auxin (e.g., 10 mg/L and 50 mg/L) to observe the effect on growth.
3. Each group had five replicates to ensure consistency and reliability of results.
4. I measured the height of the plants every three days over a period of two weeks, recording the growth in a chart for analysis.

A vital safety precaution I took during the investigation was to wear protective gloves and goggles while handling the growth regulators to avoid any skin or eye contact, as these substances can be harmful.

The results indicated that the bean plants treated with auxin showed a significant increase in growth compared to the control group. Specifically, the plants treated with 50 mg/L of auxin grew an average of 15 cm, while the control group only grew 8 cm. Additionally, the group treated with 10 mg/L displayed intermediate growth, averaging 12 cm.