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(a) (i) What is a tropism? (ii) What is a plant growth regulator? (b) Answer the following in relation to an investigation that you carried out into the effect of the growth regulator IAA on plant tissue - Leaving Cert Biology - Question 9 - 2010
Question 9
(a) (i) What is a tropism? (ii) What is a plant growth regulator? (b) Answer the following in relation to an investigation that you carried out into the ef... show full transcript
Worked Solution & Example Answer:(a) (i) What is a tropism? (ii) What is a plant growth regulator? (b) Answer the following in relation to an investigation that you carried out into the effect of the growth regulator IAA on plant tissue - Leaving Cert Biology - Question 9 - 2010
Step 1
What is a tropism?
Answer
A tropism is the growth response of a plant to a stimulus, which can be either positive or negative. In a positive tropism, the plant grows towards the stimulus, while in a negative tropism, it grows away from the stimulus. Common types of tropisms include phototropism (response to light) and gravitropism (response to gravity).
Step 2
What is a plant growth regulator?
Answer
A plant growth regulator is a substance that influences the growth and development of plants. These regulators can promote or inhibit processes such as cell division, elongation, and differentiation. Examples include auxins, gibberellins, cytokinins, and abscisic acid. IAA (indole-3-acetic acid) is a well-known auxin commonly used in plant growth regulation.
Step 3
Step 4
Describe how you carried out the investigation.
Answer
To carry out the investigation, the tissue segments were placed in a petri dish containing different concentrations of IAA. The segments were left for a minimum of two days to allow for adequate absorption of the growth regulator. After this period, the growth of each segment was measured. A control group was maintained, where tissue segments were placed in distilled water to compare the effects of IAA.
Step 5
Describe the control that you used.
Answer
The control used was a set of plant tissue segments that were treated with distilled water instead of IAA. This control was essential to compare the effects of the growth regulator against the natural growth of the plant tissue without any external influence.
Step 6
Compare the results that you obtained in the experiment and in the control.
Answer
In the experimental group treated with IAA, there was a noticeable increase in growth compared to the control group. The segments that received IAA showed more elongation and possibly more directed growth towards light sources, as expected with positive phototropism. In contrast, the control group showed minimal or no growth enhancement, confirming the effect of IAA as a growth regulator.