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Q32 - Zinc and Iron Interactions in Arabidopsis Micronutrient Toxicity

Theoretical 1 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Mineral Nutrition & Nutrient Uptake

Zinc (Zn) and iron (Fe) are both micronutrients for plants. Plants obtain Zn and Fe ions from soil through the root system, and transport them to the shoot. Plant culture media usually contains low concentrations of these micronutrients. Half-strength MS medium, a typical plant culture medium, contains 15 uM Zn2+ and 50 uM Fe2+. Although micronutrients are essential for plant growth, at excess concentrations they inhibit plant growth. To examine the inhibitory effects of excess micronutrients, Arabidopsis thaliana plants were grown on half- strength MS media, supplemented with additional Zn2+ and/or Fe2+. Plants that had been grown on half-strength MS media, supplemented with additional Zn2+ and/or Fe2+ at the indicated concentrations, were pictured from above (a), measured for the dry weight of the shoot (b), and analyzed for the Zn contents in the shoot and root (c).

Effects of additional Zn and Fe ions on plant growth Plants that had been grown on half-strength MS media, supplemented with additional Zn2+and/or Fe2+at the indicated concentrations, were pictured from above (a), measured for the dry weight of the shoot (b), and Effects of additional Zn and Fe ions on plant growth Plants that had been grown on half-strength MS media, supplemented with additional Zn2+and/or Fe2+at the indicated concentrations, were pictured from above (a), measured for the dry weight of the shoot (b), and

Using the information and data, determine which of the statements are true or which are false.

A. Zn accumulation in the shoot shows a stronger correlation to growth defects than the correlation shown by Zn accumulation in the root.
B. The growth defect caused by excess Zn2+ in the culture medium is mitigated by the addition of Fe2+.
C. High concentrations of Fe2+ in the culture medium suppresses Zn2+ uptake by the root.
D. Total Zn amount in the shoot is not affected by the addition of Fe2+ in the medium.
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Question reproduced from IBO 2020, Theoretical Exam 1, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)