Read the paragraph and answer the questions:
Plant tissue culture is based on the special property of plant cells to generate a whole plant, called totipotency. The plant part used in tissue culture is called explant. The nutrient medium provides a carbon sources such as sucrose. inorganic salts, vitamins, amino acids and growth regulators like auxins cytokinins etc. Propagation of thousands of plants in very short duration through tissue culture is called micropropagation. Each of these plants will be genetically identical to the original plant i.e., they are somaclones. Another application of tissue culture is to recover virus free plants, from the infected ones. The apical or axillary meristem, which is free of virus, is removed and cultured in-vitro to obtain virus-free plants. Scientists have succeeded in culturing meristems of sugarcane, banana, potato etc. Scientists have isolated single cells from plants and after digesting their cell walls, the protoplasts were isolated. Protoplasts from two different varieties of plants - each having a desirable character - are fused to get hybrid protoplasts. These hybrid protoplasts are called somatic hybrids and the process is called somatic hybridisation. Somatic hybrids are further grown to form a new plant. Protoplast of tomato is fused with that of potato, to form new hybrid plants called Pomato. Pomato unfortunately did not have all the desired combination of the two plants.
In tissue culture, the nutrient medium usually contains ________as a carbon source.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Sucrose
Cells grown in tissue culture cannot make enough food for themselves, so the nutrient medium supplies a carbon source. The passage names it: sucrose, along with inorganic salts, vitamins, amino acids and growth regulators.
Option (1) Sucrose — Correct. Sucrose is the sugar used as the carbon and energy source in the medium.
Option (2) Maltose — Incorrect. Maltose is a sugar formed when starch is digested; it is not the carbon source the medium provides.
Option (3) Carbon dioxide — Incorrect. CO2 is the carbon source of photosynthesis, not of the culture medium.
Option (4) Calcium carbonate — Incorrect. Calcium carbonate is an inorganic salt, not a food the cells can use for energy.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.