Mineral Nutrition: Question and Answers for Class 11th biology Chapter 12 (CBSE/ NCERT)
Question: ‘All elements that are present in a plant need not be essential to its survival. Comment.
Ans: The following factors determine whether a nutrient is necessary or not for plant survival out of all those received by plants:
1. The element that supports regular plant growth and reproduction.
2. A substitute element cannot fulfil an element’s criteria.
3. The substance must directly affect plant metabolism.
4. The element is regarded as essential if it meets all of these requirements.
Question: Boron deficiency leads to a stout axis.
Ans: A Micronutrient called boron is present in plants. Its lack causes internal tissues to disintegrate, the death of stem and root apices, and a reduction in flowering and fruiting. The above assertion is true because boron contributes to the production of pectin in the walls, which results in a strong axis.
Question: Every mineral present in the cell is needed by the cell. True/ False
The cell does not need to require every mineral that is there. Only substances directly engaged in plant metabolism cannot be substituted and are necessary for plant growth and reproduction. 17 different elements are necessary for plants to survive.
Question: Nitrogen as a nutrient element is highly immobile in plants. True/ False
Mobile elements move from the old parts of the plants to the fresh, rapidly expanding regions. Nitrogenous substances are involved in the production of proteins. Because it travels as nitrates, nitrogen in plants is very mobile. Magnesium, calcium, zinc, chlorine, and iron are among the other nutrients that are immobile in plants.
Question: It is very easy to establish the essentiality of micronutrients because they are required in trace quantities.
Although they are required in extremely small amounts, micronutrients are necessary for the growth and development of plants. Even though they are only minimally required, the absence of these has an impact on the plants and results in several symptoms and illnesses. Therefore, it is simple to prove that micronutrients are necessary.
Question: Why is the purification of water and nutrient salts so important in studies involving mineral nutrition using hydroponics?
Ans: A technique for raising plants to maturity in a nutrient solution is hydroponics. Since the procedure is artificial and any pollutants in the water or undesirable nutrient salts can interfere with the plant’s growth or development, cleaning the water and nutrient salts is crucial. Additionally, it leads to inaccurate findings in investigations involving mineral nutrients, changing the essentiality or necessary mineral concentration.
Question: Explain with examples: macronutrients, micronutrients, beneficial nutrients, toxic elements and essential elements.
Ans: Macronutrients: The nutrients that are needed in high concentrations of more than 10 mmoles per kilogramme of dry matter are called macronutrients. Carbon, hydrogen, nitrogen, oxygen, sulphur, phosphorus, potassium, calcium, magnesium, and other elements. They are known by the name of Major elements as well. They help in the cells’ osmotic potential development. Even a small bit too much of these won’t make you toxic.
Micronutrients: The nutrients that are needed in small amounts, or less than 10 mmoles per kilogramme of dry matter, are referred to as micronutrients. These include manganese, iron, nickel, molybdenum, chlorine, zinc, copper, and molybdenum. Other names for them are trace elements. They are poisonous even in very small amounts and have no impact on how the osmotic potential of the cell develops.
Beneficial Nutrients: In addition to the 17 elements divided into macro- and micronutrients, there are advantageous elements including silicon, selenium, cobalt, and sodium. The higher plants need them for a variety of functions, including the regulation or compensation of harmful substances.
Toxic Elements: The micronutrients are always needed in smaller amounts, and any small reduction in their amount might cause deficiency symptoms, while an increase in their amount can cause toxicity. Toxicity can result from any reduction in mineral ion concentration that results in tissues losing 10% of their dry weight. Although the degree of toxicity differs amongst plants, it is also difficult to identify. The majority of mineral toxicity prevents other minerals from being absorbed. Example: Chlorosis is brought on by a nitrogen deficiency.
Essential Elements: The substance that must be consumed since the body cannot produce enough of it to meet all of its demands.
They are used
(a) as parts of chemical compounds in plants that relate to energy, such as magnesium and phosphorus.
(b) Enzyme activators or inhibitors, such as magnesium and zinc.
(c) For controlling osmotic potential, such as potassium.
Question: How are the minerals absorbed by the plants?
Ans: There are two distinct phases to the mineral absorption process from the soil solution. The apoplast phase, also known as the passive phase, is the first stage of cell development during which time the ions are rapidly taken up into the free, or “outside space,” where nutrients move but do not enter the cytoplasm. Transmembrane proteins function as selective apertures in ion channels, which is how it happens. The second phase, known as the symplast phase or active phase, is when water moves between the cytoplasm and vacuoles of neighbouring cells and ions are slowly taken up into the inner space while metabolic energy is being used. Ion movement is referred to as flux, with the outward movement of ions being referred to as efflux and inward movement being referred to as influx.
Question: What are the conditions necessary for the fixation of atmospheric nitrogen by Rhizobium? What is their role in N2 -fixation?
Ans: The following conditions must be met for atmospheric nitrogen fixation:
(a) A strong reducing agent
(b) ATP-based energy
(c) An anaerobic environment
(d) An enzyme called nitrogenase
Leguminous plants, such as garden peas, sweet peas, alfalfa, etc., have a symbiotic relationship with the bacteria Rhizobium. The root nodules contain several biological elements, including leghaemoglobin and the enzyme nitrogenase (Mo-Fe protein), which catalyses the production of ammonia from free atmospheric nitrogen. In the nitrogen fixation process, it is the first stable product.
By using the enzyme nitrogenase, the rhizobium transforms the free nitrogen into a useful form, such as ammonia, and it is then benefited by the carbohydrates, proteins, and oxygen of plants that support the bacteria’s growth. To keep the nitrogenase enzyme from being harmed, the leghemoglobin scavenges any free oxygen.
The reaction is : N2 + 8e-+ 8H++ 16ATP→ 2NH3 + H2+ + 16ADP + 16Pi
Question: What are the steps involved in the formation of a root nodule?
Ans: To maintain the symbiotic relationship between Rhizobium and the roots of the leguminous plants, root nodules are formed. Rhizobium is a nitrogen-fixing bacterium that helps in converting atmospheric nitrogen into nitrates, which plants can use for growth. The following are the steps involved in root nodule formation: After coming into touch with the weak root hair, the Rhizobium bacteria begin to spread around it. If the infection is effective, the bacteria next infect the root of the hair, which makes it curl. Bacteria are transported by the infected threads into the inner cortex, where they undergo modification to become rod-shaped bacteroids. It induces the inner cortex and pericycle cells to divide, which results in the creation of nodules. The nodules, which continue from those in the roots, provide the vascular link with the plant.