NCERT Solutions for Class 11 Biology Chapter 12 - Mineral Nutrition

Answer:

All the elements present in a plant need not be essential for its survival but only few elements are found to be essential for growth and metabolism. Such essential elements are specific to plants and are not replaceable by another element. These are directly involved in the nutrition of the plant. There are some elements such as Zn, Mo, B etc. are non-essential and present in traces. They take part in some metabolic reactions but are not essential for survival.

Answer:

It is important for the studies of physiological role and deficiency symptoms of specific mineral element involving hydroponics.

Answer:

Macronutrients. An element such as potassium, nitrogen, calcium essential in large quantities for plant growth is termed macronutrient. They are generally present in plant tissues in concentrations of at least 10 m-mol kg^–1 of dry matter. Examples Carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, silicon and iron. Micronutrients or trace elements, are needed in very small amounts (equal to or less than 10 m-mol kg^–1 of dry matter). These include iron, manganese, copper, molybdenum, zinc, boron, chlorine and nickel. Beneficial nutrients. They are required by higher plants in large quantities. Examples are sodium, silicon, cobalt and selenium. Toxic element. Any mineral ion that reduces the dry weight of tissues by about 10% is called a toxic element. Example—excess of Manganese causes the development of brown spots in plants. Essential elements. Such elements without whom the physiological functions of plants are affected are called essential elements. These include calcium, hydrogen, oxygen etc.

Answer:

The names of five different deficiency symptoms are :

1. Chlorosis. It is the loss of chlorophyll leading to yellowing of leaves. It is caused by the deficiency of elements N, K, Mg, S, Fe, Mn, Zn and Mo.
2. Necrosis. It is the death of tissue particularly leaf tissue and appears due to the deficiency of Ca, Mg, Cu, K.
3. Inhibition of cell division which affects the general growth of the plant and elongation of parts like roots is caused because of the deficiency of N, K, S, Mo.
4. Some elements like N, S, M delay flowering if their concentrations in the plant are low.
5. Stunted growth occurs due to deficiency of N, P, Ca.

Answer:

In such a case in order to find out the real cause of the symptom, one has to study all the symptoms developed in all the various parts of the plant and compare them with the available standard tables. To observe the real deficient mineral element, a series of experiments are done in which the roots of the plants are inmersed in nutrient solutions and wherein and an element was added/removed or given in varied concentration, a mineral solution suitable for the plant growth is obtained. By this method, essential element is identified and its deficiency symptoms can be discovered.

Answer:

The parts of the plants that show the deficiency symptoms depend on the mobility of the element in the plants. Where elements are actively mobilised within the plants and exported to young developing tissues, the deficiency symptoms tend to appear first in the older tissues. For example, the deficiency symptoms of nitrogen, potassium and magnesium are visible first in the senescent leaves. In the older leaves, biomolecules containing these elements are broken down, making these elements available for mobilising to younger leaves.
The deficiency symptoms tend to appear first in the young tissues whenever the elements are relatively immobile and are not transported out of the mature organs, for example, elements like sulphur and calcium are a part of the structural component of the cell and hence are not easily modified.

Answer:

The process of intake of nutrients from the soil is called absorption. Plants absorb minerals from the soil through the roots by two ways—(a) Passive absorption and (b) Active absorption.
(a) Passive absorption. It is simple process of diffusion of ions from higher concentration to lower concentration into root cells.
(b) Active absorption. The uptake of mineral ions against concentration gradient is called active absorption. Such a movement of ions is carried out with the expenditure of energy (ATP). Carriers are involved in active mineral absorption.
Carrier+ion$\to$Carrier ion complex$\to$Carrier ion enters inner space.

Answer:

The most important condition necessary for fixation of atmospheric nitrogen by Rhizobium is that it should occur in a symbiotic relationship with the roots of leguminous plants like alfalfa, sweet clover, sweet pea, lentils, peas, beans etc. Although Rhizobium also occurs as free living but can carry out fixation of atmospheric nitrogen fixation as a symbiont.

Answer:

1. True. Boron deficiency leads to death of root and shoot tips, loss of apical dominance etc.
2. False. Every element that is present in the plant may not be required by the plant.
3. False. Nitrogen as a nutrient is high mobile element.
4. True.