Mineral Nutrition Test - 3

Essential elements are those element which are absolutely necessary for supporting normal growth and reproduction of plants, thhe elements are specific in their action and are directly involved in the nutrition of the plant potassium is macroelement, zinc and iron are microelement. Iodine and sodium are essential for animals and are not required by most of the plants however, iodine is found in certain marine algae.

Calcium is an important constituent of middle lamellae in plants, where it is present as calcium pectate. Hence, actively growing regions of calcium like stem tip and root hairs essentially require calcium.

Carbon is one of the macronutrients present in the plants. It is the most abundant element found in plants. Carbon is a constiuent of organic compounds. It is one of the non-mineral element. Carbohydrates like sugars, starches and cellulose are the important organic compounds composed of carbon present in plants.
So, the correct answer is 'Carbon'

Plants can be grown in either soil or water or in both with essential nutrients. But it cannot grow in water or soil deficient in nutrients. 

So, the correct answer is 'water or soil without essential nutrients.'

A trace element is any chemical element that is present in minute amounts in an environment or ecosystem.
Although a plant's primary nutritional needs are mostly met through nitrogen, phosphorus, and potassium (NPK), they also require small amounts of other elements as well.

Plants require seventeen essential mineral elements which can be grouped into two classes based on the amount required- 
Macronutrients (required in large amount) and micronutrient (required in small amounts).
The essential macronutrients are carbon, hydrogen, oxygen, nitrogen, phosphorous, potassium, sulphur, magnesium, calcium and essential micronutrients are iron, molybdenum, boron, chlorine, copper, zinc, nickel and manganese.

A plant cell is characterised by the presence of a cellulosic cell wall outside the cell membrane. The cell wall is dead at maturity. The cell walls of adjacent cells are joined together by the presence of cementing middle lamella. The middle lamella comprises of calcium pectate.

Carbon is obtained by photosynthesis as a gas.