Question

In the laboratory, Nicotiana plants are raised by embryo culture, microspore culture, protoplast culture and endosperm culture. What is the ploidy level respectively?
A) n, n, n, 3n
B) 2n, n, 2n, 3n
C) 2n, 2n, 3n, 3n
D) n, 2n, 3n, 2n

Answer 1

The culture of spores is a novel way of reprogramming single cells in plants, which transforms the microspore, the haploid male gametophyte by means of special treatment of the stress, into an embryo. The ‘in vitro’ growth of isolated mature or immature endosperm from the seed at the proper stage on an adequate culture medium to obtain triploid plantlets is endospermic culture.

Complete answer: In reality, the protoplast culture has produced Nicotiana plants. It is tetraploid (4n) because it is formed by the process of protoplasmic fusion or somatic hybridisation. As it comprises half the number of chromosomes, the haploid plant of Nicotiana is obtained from the pollen or microspore culture. The embryo and protoplast culture lift the diploid Nicotiana plant as somatic cells are used in this process. The triple fusion of two polar nuclei and one male nucleus is produced by the endosperm and is therefore triploid. Triploid plants are formed by the endosperm (triploid) culture. The endosperm plays an important role in promoting the embryonic growth by providing nutrients, protecting the embryo and regulating embryo growth by serving as a mechanical barrier during the production and germination of seeds.
Hence, the correct answer is option B.

Note: A plant culture technique is a process in which immature pollen is developed in a liquid medium or on solid media to divide and grow into tissues (either callus or embryonic tissues). Anthers containing pollen are removed from a flower and placed into a culture medium.