Mineral ions and plant growth sim
Grow four bean seedlings in water culture (complete solution, no nitrate, no magnesium, distilled water), wait 4 days at a time, drag the ruler from jar to jar to record each shoot's height and the colour of its oldest leaves, and graph the growth.
Plant nutrition: mineral ions. Nitrate ions for amino acids and proteins (deficiency: stunted growth, yellow older leaves) and magnesium ions for chlorophyll (deficiency: chlorosis, yellowing between the veins) · covers the IGCSE, GCSE topic
What the sim shows
Mineral ions and plant growth. Four glass culture jars each hold a young bean seedling in a cork lid, held up by a plug of cotton wool, with its roots in a culture solution: jar 1 a complete culture solution with every mineral ion a plant needs (the control), jar 2 the same with no nitrate, jar 3 the same with no magnesium, and jar 4 distilled water with no mineral ions at all. A foil sleeve keeps light out of each solution, so algae cannot grow in it. Press Wait 4 days, drag the ruler to each jar and read the shoot height from the cotton wool to the shoot tip in the close-up, and look at the oldest leaves. Plants take up mineral ions from the water around their roots. Nitrate ions are needed to make amino acids, and so proteins, for growth: without nitrate a plant is stunted and its older leaves turn yellow. Magnesium ions are needed to make chlorophyll: without magnesium the leaves turn yellow between the veins (chlorosis), older leaves first, so they absorb less light, photosynthesise less and the plant grows more slowly. For the first days all four live on the stores in their seeds, so they look alike. Simplified on purpose: every number is illustrative (≈): real seedlings vary, and the growth follows a smooth model curve rather than real day-to-day changes; the four seedlings start exactly alike, 20 mm tall, and each seed's food and mineral store is the same; the light, temperature and air are the same for every jar, and the solutions never run low or need topping up; growth with an ion missing is a fixed share of growth in the complete solution: about a fifth with no nitrate, three fifths with no magnesium; only the oldest leaves' colour is recorded, as green, pale green or yellow; real yellowing comes on gradually and is a judgement; only nitrate and magnesium are left out on their own; other ions (such as phosphate and potassium) are missing only from the distilled water; the roots are hidden in the foil and are not measured; the bench apparatus is drawn to scale, and the close-up is not to scale.
- Lit: the ruler, its zero level with the cotton wool
- Close-up: the ruler at the shoot tip, and the oldest leaf
- Foil sleeve: keeps light out of the solution
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