Question

A few gram seeds were placed in each of the three pots A, B and C containing soil. The soil in Pot A is mixed with some green twigs and leaves. The soil in Pot B is mixed with old cow dung while soil of pot C mixed with urea. Pots are watered regularly. Which of the following will be observed after 10 days?
A. Lot of growth in A
B. Not much growth in B
C. Lot of growth in B but very little growth in C
D. Very little growth in A but lot of B and C

Answer 1

Hint: Minerals found in the soil can enter into the plants by roots. Plants can get their inorganic nutrients from air, soil and water. About 21 elements are essential for normal plant growth and development. An essential element must be absolutely necessary for normal growth and development.

Complete Answer:
- In 1860, German botanist Julius von sachs showed that plants can be grown into maturity by applying nutrients in the absence of soil. This technique is known as hydroponics. So, here we have to add water and nutrients for the growth of plants.
- From discovered 105 elements about 21 elements needed for plant growth. There are also techniques that can detect elements even at a very low concentration.
- Elements essential for plant growth and metabolism are divided into two groups based on their quantitative requirements, namely macronutrients and micronutrients.
1. Micronutrients are needed in very small amounts. They are also known as trace elements. Examples are nickel, chlorine, boron, iron, manganese, copper etc.
2. Macroelements are present in large amounts in plant tissues. Examples are carbon, nitrogen, hydrogen, oxygen, sulphur, phosphorus, calcium, potassium etc.

- Essential elements can perform various functions. They are involved in the metabolic processes in plant cells such as permeability cell membrane, maintenance of osmotic concentration, enzymatic activity, buffering action, electron transport system etc.
- Here, the soil in pot A is mixed with green twigs and leaves, it will take more time to extract elements by decaying leaves and twigs for the growth of seeds compared to pot B and pot C. - And there is only less number of microbes for decomposition. Whereas in pot B and C, soil is highly fertile due to the presence of cow dung and urea. So there will be more elements in free state essential for plant growth. Therefore, pot B and C show high growth and pot A shows less growth of seeds.

Thus, the correct answer is option D.

Additional information: When the supply of an essential element is less, then the plant growth will become retarded. This concentration of essential elements below which plant growth is retarded is known as critical concentration.

Note: Each element has one or more specific structural or functional roles in plants. In the absence of one element, a plant shows certain morphological changes. These changes show the element deficiencies known as deficiency symptoms. These symptoms depend on elements and disappear when deficient elements are provided to the plant.