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Plant Nutrition - Mineral requirements

Grade 12A LevelBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Plants require mineral ions for healthy growth and development, absorbed from the soil through root hair cells. The two most critical ions are Nitrates (NO3−NO_3^-) and Magnesium ions (Mg2+Mg^{2+}).

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Nitrates (NO3−NO_3^-) are essential for the synthesis of amino acids, which are polymerized to form proteins. They are also vital components of nucleic acids like DNADNA and RNARNA.

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Magnesium (Mg2+Mg^{2+}) is the central atom in the chlorophyll molecule (C55H72O5N4MgC_{55}H_{72}O_5N_4Mg). Without it, the plant cannot effectively perform photosynthesis.

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Deficiency of Nitrates leads to stunted growth and the yellowing of older leaves (chlorosis), as the plant cannot produce enough proteins for new cells.

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Deficiency of Magnesium causes interveinal chlorosis, where the leaves turn yellow but the veins remain green, leading to reduced glucose production via photosynthesis.

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Mineral ions are often moved into the root hair cells against a concentration gradient via active transport, a process requiring energy in the form of ATPATP (Adenosine Triphosphate).

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Phosphate ions (PO43−PO_4^{3-}) are also required for the production of ATPATP and are a structural component of the phospholipid bilayer in cell membranes.

📐Formulae

C55H72O5N4Mg (Chlorophyll a structure showing the Mg core)C_{55}H_{72}O_5N_4Mg \text{ (Chlorophyll a structure showing the Mg core)}

R−CH(NH2)−COOH (General structure of an amino acid requiring Nitrogen)R-CH(NH_2)-COOH \text{ (General structure of an amino acid requiring Nitrogen)}

6CO2+6H2O→chlorophylllightC6H12O6+6O26CO_2 + 6H_2O \xrightarrow[chlorophyll]{light} C_6H_{12}O_6 + 6O_2

💡Examples

Problem 1:

A farmer notices that his crop leaves are turning yellow between the veins while the veins themselves remain green. Identify the likely mineral deficiency and explain the biological cause.

Solution:

The plant is likely suffering from a deficiency of Magnesium ions (Mg2+Mg^{2+}).

Explanation:

Magnesium is a vital component of the chlorophyll molecule. When Mg2+Mg^{2+} is deficient, the plant cannot synthesize enough chlorophyll, leading to chlorosis. Because chlorophyll is first broken down in the tissues between veins to transport remaining nutrients, those areas turn yellow first.

Problem 2:

Why does a deficiency in Nitrate ions (NO3−NO_3^-) result in stunted growth in plants?

Solution:

Nitrates are required to form amino acids and proteins.

Explanation:

Proteins are necessary for the formation of enzymes and structural components of new cells. Without sufficient NO3−NO_3^-, the rate of protein synthesis decreases, meaning the plant cannot produce the new cells required for primary and secondary growth, resulting in a stunted appearance.

Problem 3:

Explain how the concentration of O2O_2 in the soil affects the uptake of K+K^+ ions.

Solution:

Lower O2O_2 levels lead to decreased uptake of K+K^+ ions.

Explanation:

The uptake of mineral ions like K+K^+ often occurs via active transport. This process requires ATPATP generated through aerobic respiration. Since aerobic respiration requires oxygen (O2O_2), a lack of soil aeration reduces ATPATP production, thereby inhibiting the active transport pumps in the root hair cell membranes.