Macronutrients: They are the nutrients required by plants in large amounts. They are present in plant tissues in amounts of more than 10 m mole ${\mathrm{kg}}^{-1}$ of dry matter. Examples include hydrogen, oxygen, and nitrogen.

Micronutrients: They are also called trace elements and are present in plant bodies in very small amounts, i.e., amounts less than 10 m mole ${\mathrm{kg}}^{-1}$ of dry matter. Examples include cobalt, manganese, zinc, etc.

Beneficial nutrients: They are plant nutrients that may not be essential, but are beneficial to plants. Sodium, silicon, cobalt and selenium are beneficial to higher plants.

Toxic elements: Micronutrients are required by plants in small quantities. An excess of these nutrients may induce toxicity in plants. For example, when manganese is present in large amounts, it induces deficiencies of iron, magnesium, and calcium by interfering
with their metabolism.

Essential elements: These elements are absolutely necessary for plant growth and reproduction. The requirement of these elements is specific and non-replaceable. They are further classified as macro and micro-nutrients.

4. Name at least five different deficiency symptoms in plants. Describe them and correlate them with the concerned mineral deficiency.

NEETprep answer: The five main deficiency symptoms arising in plants are:

$\to$ Chlorosis
$\to$ Necrosis
$\to$ Inhibition of cell division
$\to$ Delayed flowering
$\to$ Stunted plant growth

Chlorosis or loss of chlorophyll leads to the yellowing of leaves. It is caused by the
deficiencies of nitrogen, potassium, magnesium, sulfur, iron, manganese, zinc, and molybdenum.

Necrosis is the death of plant tissues as a result of the deficiencies of calcium, magnesium, copper, and potassium.

Inhibition of cell division is caused by the deficiencies of nitrogen, potassium, sulphur, and molybdenum.

Delayed flowering is caused by the deficiencies of nitrogen, sulfur, and molybdenum. Stunted plant growth is a result of the deficiencies of copper and sulfur.