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.

In a plant with nitrate ion deficiency, several distinct symptoms will be apparent. The most noticeable is chlorosis, which is the yellowing of the leaves, particularly the older, lower leaves. This occurs because nitrate is a crucial component of chlorophyll, the pigment responsible for photosynthesis. Without sufficient nitrate, the plant cannot produce enough chlorophyll, leading to a reduction in its green colour.

Furthermore, the stunted growth associated with nitrate deficiency is also a key symptom. Nitrate is essential for the synthesis of amino acids, which are the building blocks of proteins. Reduced protein synthesis directly impacts growth and development. The plant will also exhibit a general weakening, making it more susceptible to disease and environmental stresses. Finally, the veins in the leaves may remain green for a short time as the plant attempts to transport the limited available nitrate, but the overall effect is a pale, yellowing appearance.

Underlying Reason: Nitrate is vital for the production of amino acids and chlorophyll. These are essential for protein synthesis and photosynthesis respectively. A deficiency in nitrate directly limits these processes, resulting in reduced growth, chlorosis, and overall plant weakness.

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.