Nitrate ions (NO₃^-) are essential for protein synthesis in plants. They are a key component in the formation of amino acids, which are the building blocks of proteins.

• Nitrate ions are converted into ammonia (NH₃) and then into amino acids through a series of enzymatic reactions.
• Amino acids are then linked together to form proteins.
• Proteins are vital for a wide range of functions in plants, including enzyme production, structural support, and transport of substances.

Without sufficient nitrate, protein synthesis is limited, leading to stunted growth and reduced overall plant development.

Both nitrate and magnesium deficiencies result in stunted growth and reduced plant vigour. However, the specific symptoms differ. Nitrate deficiency primarily manifests as general chlorosis starting in the older leaves, while magnesium deficiency is characterized by interveinal chlorosis, where the areas between the veins turn yellow while the veins remain green. The progression of symptoms also differs; nitrate deficiency affects the entire leaf, while magnesium deficiency typically starts in the older leaves and progresses inwards.

Here's a table summarizing the key differences:

A plant deficient in magnesium ion will display distinct symptoms, primarily affecting the older leaves first. The most characteristic symptom is interveinal chlorosis. This means the areas between the veins of the leaves will turn yellow, while the veins themselves remain green. This is because magnesium is a central atom in the chlorophyll molecule. A lack of magnesium prevents the formation of functional chlorophyll in the affected areas.

As the deficiency progresses, the yellowing will spread, eventually affecting the entire leaf, leading to necrosis (tissue death) in the affected areas. The leaf margins may also become distorted or curled. Growth will be stunted, and the plant may appear generally weak and pale. The deficiency typically affects the lower leaves first due to the mobility of magnesium within the plant.

Underlying Reason: Magnesium is a key component of the chlorophyll molecule. Without sufficient magnesium, chlorophyll synthesis is impaired, leading to interveinal chlorosis and ultimately necrosis. Magnesium is also involved in the activation of enzymes required for photosynthesis, further contributing to the reduced photosynthetic capacity of the plant.