5.4.2 Practical Skill: Investigate the Effect of Minerals on Plant Growth

Aim:

To investigate how different mineral ions affect plant growth.

Background Information

Plants require minerals for essential functions:

• Nitrates $(NO₃⁻)$: Needed for the synthesis of proteins, DNA, and chlorophyll.
• Phosphates $(PO₄³⁻)$: Required for the production of ATP, DNA, and cell membranes.
• Potassium $(K⁺)$: Regulates stomatal opening and enzyme activation.
• Magnesium $(Mg²⁺)$: Essential for chlorophyll production and enzyme activity. A deficiency in any of these minerals leads to poor growth and specific symptoms (e.g., yellowing leaves for magnesium deficiency).

Method

1. Preparation:

• Select a suitable plant species (e.g., cress seeds or bean plants).
• Prepare nutrient solutions with varying concentrations of minerals:
• Full solution containing all essential minerals (control).
• Solutions lacking one specific mineral (e.g., no nitrates, no phosphates, etc.).
• Label the solutions clearly.

2. Setup:

• Place equal numbers of seeds or seedlings in separate pots filled with sterile growth medium (e.g., sand or vermiculite).
• Water each pot with the assigned nutrient solution, ensuring consistent volume across treatments.

3. Growth Conditions:

• Place the pots in a controlled environment with equal light intensity, temperature, and humidity.
• Ensure regular watering with the appropriate nutrient solutions.

4. Data Collection:

• Measure plant growth over time (e.g., height, number of leaves, biomass).
• Record observations of physical symptoms such as leaf yellowing, stunted growth, or wilting.

5. Analysis:

• Compare the growth and health of plants across different treatments.
• Use quantitative data (e.g., mean height or biomass) to identify the effect of mineral deficiencies.

Expected Results

• Nitrate Deficiency: Stunted growth and yellow leaves (chlorosis).
• Phosphate Deficiency: Poor root development and purple discolouration of leaves.
• Potassium Deficiency: Yellowing leaf edges and brown spots.
• Magnesium Deficiency: Interveinal chlorosis (yellowing between veins).

Evaluation

• Reliability: Repeat the experiment multiple times and calculate mean values.
• Control Variables: Ensure all plants receive the same light, water, and growth medium conditions.
• Limitations: Growth medium may not fully mimic natural soil conditions, potentially influencing results.