IGCSE Biology - 6.2 Plant Nutrition - Mineral Deficiencies
IGCSE Biology - 6.2 Plant Nutrition - Mineral Requirements
This page details the symptoms of nitrate and magnesium ion deficiencies in plants, as required for the Cambridge IGCSE Biology 0610 syllabus.
Nitrate Deficiency
Symptoms of Nitrate Deficiency
Nitrate (NO3-) is an essential nutrient for plant growth, primarily involved in the synthesis of amino acids, proteins, and nucleic acids. Deficiency leads to a range of symptoms:
Overall Yellowing (Chlorosis): Older leaves are affected first, resulting in a general yellowing of the foliage.
Necrosis: Yellow areas can progress to brown or black necrotic (dead) patches, particularly on older leaves.
Stunted Growth: The plant will exhibit reduced overall growth and may appear smaller than healthy plants.
Pale Green Colour: The yellowing is often a pale, washed-out green rather than a deep, healthy green.
Reduced Yield: In crops, nitrate deficiency significantly reduces yield.
Diagram
Suggested diagram: A plant showing yellowing of older leaves, with necrotic patches developing. Label the affected leaves.
Magnesium Deficiency
Symptoms of Magnesium Deficiency
Magnesium (Mg2+) is a central component of the chlorophyll molecule and is crucial for photosynthesis. Deficiency manifests as:
Interveinal Chlorosis: The most characteristic symptom is yellowing between the veins of the leaves, while the veins themselves remain green. This is because magnesium is mobile within the plant, and the plant prioritizes supplying it to actively growing tissues.
Necrosis: Yellow areas can develop into brown or black necrotic spots, often starting between the veins.
Leaf Margin Necrosis: The edges of the leaves may also show necrosis.
Reduced Leaf Size: New leaves may be smaller than normal.
Distorted Growth: In severe cases, growth can be distorted.
Table - Comparing Deficiencies
Nutrient
Primary Symptoms
Location of Symptoms
Effect on Growth
Nitrate (NO3-)
Overall Yellowing (Chlorosis), Necrosis
Older leaves first, progressing upwards
Stunted growth, reduced yield
Magnesium (Mg2+)
Interveinal Chlorosis, Necrosis
Between the veins of leaves, often starting on older leaves
Reduced leaf size, distorted growth
Understanding these deficiency symptoms is crucial for diagnosing plant nutrient problems and implementing appropriate solutions.