Explanation:

All codes are correct.
Tissue Culture

• It is the production of new plants from a small piece of plant tissue or cells removed from the growing tips of a plant in a suitable growth medium.
• In this process the growth medium or culture solution is very important as it is used for growing plant tissue because it contains various plant nutrients in the form of ‘jelly’ known as agar and plant hormones which are necessary for the growth of plants.

Applications of Plant Tissue Culture

• To study the respiration and metabolism of plants.
• For the evaluation of organ functions in plants.
• To study the various plant diseases and work out methods-for their elimination.
• Single cell clones are useful for genetic, morphological and pathological studies.
• Embryonic cell suspensions can be used for large scale clonal propagation.
• Somatic embryos from cell suspensions can be stored for long term in germplasm banks.
• In the production of variant clones with new characteristics, a phenomenon referred to as somaclonal variations.
• Production of haploids (cells with a single set of chromosomes) for improving crops.
• Mutant cells can be selected from cultures and used for crop improvement.
• Immature embryos can be cultured in vitro to produce hybrids, a process referred to as embryo rescue.

Hence option 4th is correct.