NCERT Solutions for Class 11 Biology Chapter 12 Mineral Nutrition

Ans : Plants tend to absorb different kinds of nutrients from soil. However, a nutrient is inessential for a plant if it is not involved in the plant's physiology and metabolism. For example, plants growing near radioactive sites tend to accumulate radioactive metals. Similarly, gold and selenium get accumulated in plants growing near mining sites. However, this does not mean that radioactive metals, gold, or selenium are essential nutrients for the survival of these plants. 

Ans : Hydroponics is the art of growing plants in a nutrient solution in the absence of soil. Since the plant roots are exposed to a limited amount of the solution, there are chances that the concentrations of oxygen and other minerals in the plant roots would reduce. Therefore, in studies involving mineral nutrition using hydroponics, purification of water and nutrient salts is essential so as to maintain an optimum growth of the plants. 

Ans : Macronutrients: They are the nutrients required by Plants in large amounts. They are present in plant tissues in amounts more than 10 m mole/kg 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/kg 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. 

Ans : The five main deficiency symptoms arising in plants are: 
Chlorosis
 
Necrosis
 
Inhibition of cell division
 
Delayed flowering 
 Stunted plant growth 
Chlorosis or loss of chlorophyll leads to the yellowing of leaves. It is caused by the deficiencies of nitrogen, potassium, magnesium, sulphur, 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, sulphur, and molybdenum. Stunted plant growth is a result of the deficiencies of copper and sulphur. 

Ans : In plants, the deficiency of a nutrient can cause multiple symptoms. For example, the deficiency of nitrogen causes chlorosis and delayed flowering. 
In a similar way, the deficiency of a nutrient can cause the same symptom as that caused by the deficiency of another nutrient. For example, necrosis is caused by the deficiency of calcium, magnesium, copper, and potassium. Another point to be considered is that different plants respond in different ways to the deficiency of the same nutrient. Hence, to identify the nutrient deficient in a plant, all the symptoms developed in its different parts must be studied and compared with the available standard tables.