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NCERT solution for Class 12 Chapter 12 Mineral Nutrition
Question 1: ‘All elements that are present in a plant need not be essential to its survival’. Comment.
Answer: An element should fulfill certain criteria to be categorized as essential element. Otherwise, it cannot be considered as essential elements. Out of the numerous elements present in plants, only 17 are considered as essential elements.
Question 2: Why is purification of water and nutrient salts so important in studies involving mineral nutrition using hydroponics.
Answer: Purification of water and nutrient salt is important to rule out other influencing factors. Use of pure nutrients and water will help in obtaining accurate scientific results.
Question 3: Explain with examples: macronutrients, micronutrients, beneficial nutrients, toxic elements and essential elements.
Answer: Macronutrients: Elements which are present in large amounts in plant tissues are called macronutrients. They are in excess of 10 mmole per kg of dry matter. Carbon, hydrogen, oxygen, nitrogen, phosphorous, sulphur, potassium, calcium and magnesium are the macronutrients.
Micronutrients: Elements which are present in small amounts, i.e. less than 10 mmole per kg of dry matter are called micronutrients. Iron, manganese, copper, molybdenum, zinc, copper, boron, chlorine and nickel are the micronutrients.
Beneficial Elements: Apart from the 17 essential elements, many other elements are required by plants. For example; sodium, silicon, cobalt and selenium are required by higher plants. These are called beneficial elements.
Toxic Elements: If a mineral ion concentration in tissues reaches to a level that it reduces the dry weight of tissues by about 10%, the mineral then becomes toxic. This shows that any element can become toxic if it crosses a certain threshold in plants.
Question 4: Name at least five different deficiency symptoms in plants. Describe them and correlate them with the concerned mineral deficiency.
Answer: Following are the five deficiency symptoms and related minerals:
a. Yellowing of lower leaves: Magnesium deficiency
b. Pale green leaves: Nitrogen deficiency
c. Purple leaf tints with bronze or brown leaf edges: Potassium deficiency
d. Reddish purple undersides of leaves: Phosphorous deficiency
e. White deposits on leaves: Carbon dioxide deficiency
Question 5: If a plant shows a symptom which could develop due to deficiency of more than one nutrient, how would you find out experimentally, the real deficient mineral element?
Answer: For this, we need to tabulate all the available symptoms in different parts of the plant. Then the symptoms are compared with the symptom table; to arrive at a conclusion about the deficiency of a specific element.
Question 6: Why is that in certain plants deficiency symptoms appear first in younger parts of the plant while in others they do so in mature organs?
Answer: Appearance of deficiency also depends on the mobility of the element in the plant. Some elements are actively mobilized in plants and are exported to young developing tissues. Deficiency of such elements first appears in the older tissues.
Questions will be updated soon....
Plant mineral nutrition is the study of the chemical elements and compounds necessary for plant growth, survival, and reproduction. Plants require macronutrients such as nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur, and micronutrients such as iron, boron, manganese, zinc, and copper, for normal growth and development. The availability and uptake of these essential elements depend on the soil conditions, plant species, and other factors. A deficiency of any one element can cause stunted growth or death of the plant. Proper fertilization and soil management can help ensure plants receive the essential minerals they need. Additionally, chemical fertilizers or organic materials can be used to supplement soil nutrients and improve plant health.
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