RBSE Solutions for Class 11 Biology Chapter 12 Mineral Nutrition

Rajasthan Board RBSE Solutions for Class 11 Biology Chapter 12 Mineral Nutrition Textbook Exercise Questions and Answers.

RBSE Class 11 Biology Solutions Chapter 12 Mineral Nutrition

RBSE Class 11 Biology Mineral Nutrition Textbook Questions and Answers

Question 1. 
‘All elements that are present in a plant need not be essential to its survival.’ Comment.
Answer:
More than sixty elements of the 105 discovered so far are found in different plants. But on the basis of utility only 17 mineral elements considered to be essential. The essential elements can be divide into two classes on the basis of their quantitative requirement:
(a) Macronutrients: These are found in 1 to 10 mg/L concentration of dry matter of plant. e.g., carbon, hydrogen, oxygen, nitrogen, potassium, calcium, magnesium, phosphorus and sulphur.
(b) Micronutrients: These are found in less than 0.1 mg/L concentration of dry matter of plants. e.g., Chlorine, boron, iron, manganese, zinc, copper, nickel and molybdenum.

Question 2. 
Why is purification of water and nutrient salts so important in studies involving mineral nutrition using hydroponics?
Answer:
In impure water there are many minerals dissolved. Generally minerals are also contaminated. If impure water is used in culture medium, then there interuption will be there in investigation of essentiality of elements in hydroponics technique. Therefore pure water and pure nutrient salts should be used for mineral nutrient related studies in hydroponics techniques.

Question 3. 
Explain with examples: macronutrients, micronutrients, beneficial nutrients, toxic elements and essential elements. 
Answer:

1. Macronutrients: The elements which required by plants comparatively in large quantity, are called macronutrients. For example - C, O, H, N, S, P, K/Ca etc.
2. Micronutrients: The elements which are required by plant in small quantity are called micronutrients. For example, Cl, B, Fe, Cu, Zn, Ni, and Mo.
3. Beneficial elements: Besides essential elements, some useful elements are also required for higher plants, they are called beneficial elements.
4. Toxic element: The concentration of a mineral in which can reduces up to 10% in dry weight of tissues, is considered as toxic element. The toxicity level of different nutrient is also different.
5. Essential Elements: There are 17 elements essential to plants. On the basis of their quantity essential elements are grouped in two categories -  macronutrients and micronutrients.

Question 4. 
Name at least five different deficiency symptoms in plants. Describe them and correlate them with the concerned mineral deficiency.
Answer:
The main deficiency symptoms in plants are as follow:

1. Chlorosis: Becoming of leaves into yellow due to loss of chlorophyll is called chlorosis. It is caused due to deficiency of N, K, Mg, S, Fe, Mn, Zn and Mo.
2. Necrosis: To perish of cells and tissues is called necrosis. It is seen on leaves as patches, rot and blight. It is caused due to deficiency of Ca, Mg, Cu and K.
3. Inhibition of Cell division: There, growth of plant is stopped when cell division is checked. It is caused due to absence or deficiency of N, K, S, Mo etc.
4. Delay of Flowering: In some plants flowering is delayed due to deficiency of N, S and Mo.
5. Deformation: The growing points of plant become die due to disorganisation of deformation, decolouration and meristematic tissue. It is caused due to deficiency of boron.

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:
There, symptoms of the deficiency of many elements are arise by the deficiency of any one element. Therefore to identify unsufficient element, the symptoms are studied which appearing on various parts of the plant, and to compare them with available standared table. On deficiency of some element in different plants, the symptoms are also different.

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:
Some morphological changes arise due to deficiency of nutrient elements in plants. These changes show inadequacy. They are different as per different element. The symptoms of inadequacy depends on moveability of nutrient elements. These symptoms first appear on new born parts or old tissues of plants.
In plant, where elements moving actively and are transferred to young growing tissues, there inadequacy symptoms first appear in old tissues. For example, the symptoms of inadequacy of nitrogen, potassium, magnesium etc., are first appear in old leaves. From old leaves, these elements available by degradation of various biomolecules and are moved to new leaves. When elements are not movable and do not transfer from adult organs to other tissues then inadequacy symptoms first appear in new leaves. For example, calcium, sulphur etc., do not transfer easily. To identify deficiency symptoms, the study of symptoms appeared in various parts of the plant is done according to a standard table.

Question 7. 
How are the minerals absorbed by the plants?
Answer:
The mineral absorption by plants roots is done through two paths:
1. Apoplast Pathway: The minerals with water stream from soil reach to xylem through cell walls of root hairs, cortical cells, endodermis, pericycle and xylem parenchyma. Because in xylem path the water has highly negative pressure therefore it reaches to xylem via apoplast. The casparian strips of endodermis does not take part in it.

2. Symplast Pathway: In this system, the cytoplasm of all cells remains inter - connected by plasmodesmata. In symplast movement, the minerals move forward through protoplasm and plasmodesmata. The metabolic energy is required for it. This movement is comparatively slow and found during active mineral absorption.

Question 8. 
What are the conditions necessary for fixation of atmospheric nitrogen by Rhizobium. What is their role in N2 - Fixation?
Answer:
Conditions for Atmospheric Nitrogen Fixation:

1. Nitrogenase enzyme
2. Leghaemoglobin
3. ATP
4. Anaerobic environment.

The roots of leguminous plants have gland like structures, which are called root nodules. The bacteria Rhizobium are found in these root nodules. Many chemical components such as nitrogenase enzyme, leghaemoglobin etc., are also found in these root nodules. Nitrogenase enzyme catalyst the conversion of atmospheric nitrogen to ammonia. For activeness of this enzyme, anaerobic condition is required. Leghaemoglobin scavanges nitrogenase from contact of oxygen. The energy is required for ammonia synthesis. 8 ATP are required to synthesize one molecule of ammonia. The energy requirement is fulfiled by anaerobic respiration in root cells. Ammonia is used in amino acid formation.

Question 9. 
What are the steps involved in formation of a root nodule?
Answer:
Multiple interactions are involved in the formation of root nodules:

1. The Rhizobium bacteria divide and form colonies. These get attached to the root hairs and epidermal cells.
2. The root hairs get curled and are invaded by the bacteria.
3. This invasion is followed by the formation of an infection thread that carries the bacteria into the cortex of the root. The bacteria get modified into rod - shaped bacteroides.
4. As a result, the cells in the cortex and pericycle undergo division, leading to the formation of root nodules.
5. The nodules finally get connected with the vascular tissues of the roots for nutrient exchange.

Question 10. 
Which of the following statements are true? If false, correct them:
(a) Boron deficiency leads to stout axis.
(b) Every mineral element that is present in a cell is needed by the cell.
(c) Nitrogen as a nutrient element, is highly immobile in the plants.
(d) It is very easy to establish the essentiality of micronutrients because they are required only in trace quantities.
Answer:
(a) Statement is true.
(b) Statement is false, out of 110 elements only 60 elements are found in plants out of which, only 17 elements are considered, to be as essential.
(c) Statement is false. Nitrogen is highly moveable nutrient.
(d) Statement is false. It is very hard to know the essentiality of micronutrient elements because they are used in very little amount. Generally, due to impurity in nutrient mineral salts, it is difficult to establish the essentiality of them.