Investigate the effect of IAA growth regulator on plant tissue. Flashcards
What is IAA?
Indole-3-acetic acid (IAA) is a plant growth regulator belonging to the auxin group. It promotes cell elongation, apical dominance, and root development.
What biomolecule would you equate IAA to in an animal?
IAA functions similarly to hormones in animals, as it regulates growth and development.
Name the plant you used in this experiment.
Cress seeds (Lepidium sativum) or radish seeds are commonly used.
State the location in a flowering plant where a growth regulator is secreted.
Growth regulators like auxins (e.g., IAA) are secreted in the meristematic tissues, such as shoot tips (apical meristem), root tips, and young leaves.
Why is a control necessary?
A control ensures that any growth differences are due to IAA and not other environmental factors. The control setup contains no IAA or a neutral solution (e.g., distilled water).
Why are the acetate grids placed in each Petri dish?
Acetate grids allow for accurate measurement of seedling growth by providing a fixed reference for comparison.
How would you make up serial dilutions of IAA?
Serial dilution involves diluting a stock solution in steps to achieve lower concentrations.
Example for IAA dilution (100 ppm stock solution): 1 cm³ of stock + 9 cm³ of distilled water → 10 ppm; 1 cm³ of 10 ppm + 9 cm³ of distilled water → 1 ppm; 1 cm³ of 1 ppm + 9 cm³ of distilled water → 0.1 ppm.
How did you ensure that there was sufficient water for the seeds during the experiment?
Moist filter paper was placed in each Petri dish. The Petri dishes were covered to prevent evaporation and stored in a humid environment.
What is a coleoptile?
A coleoptile is a protective sheath covering the emerging shoot (plumule) in monocotyledonous plants like wheat or maize. It helps guide the shoot towards the light and protects it as it grows through the soil.
Give an example of a growth regulator that promotes and inhibits growth.
Promotes Growth: Auxins (e.g., IAA); Inhibits Growth: Abscisic Acid (ABA).
At what concentration of auxin is there maximum root growth?
Typically at low concentrations (~0.01 – 1 ppm).
At what concentration of auxin is there maximum stem growth?
Typically at moderate concentrations (~10 ppm).
What effect does 10⁴ ppm have on root growth?
Inhibits root growth due to high auxin concentration, which disrupts normal cell division and elongation.
Name A in the diagram below.
Without the diagram, it is likely that A refers to agar or filter paper used as a medium for seed growth.
What is the purpose of A in this experiment?
Provides a surface for seeds to grow on while allowing IAA solutions to be absorbed.
How would you make up solutions of different concentrations from a stock solution of IAA?
Using serial dilution as described in Question 7. A known volume of IAA stock solution is diluted stepwise with distilled water to achieve different concentrations.
