55. Statements given below are either TRUE (T) or FALSE (F). Find the correct combination.
P. Somatic embryo is unipolar in nature
Q. Heterokaryon can be selected using a fluorescence-activated cell sorter (FACS)
R. The term somaclonal variation is coined by Larkin and Scowcroft
S . Differentiation of shoot buds during in vitro culture is known as somatic embryogenesis
(A) P-T, Q-F, R-T, S-F
(B) P-F, Q-T, R-F, S-T
(C) P-T, Q-F, R-F, S-T
(D) P-F, Q-T, R-T, S-F

Plant tissue culture and biotechnology exams often test nuanced concepts like somatic embryogenesis, somaclonal variation, and cell selection techniques. This true/false statement quiz evaluates your grasp of these topics, crucial for students in genetics, plant biology, and molecular biology. Let’s break it down step-by-step, verify each statement, and identify the right option.

Correct Answer: (D) P-F, Q-T, R-T, S-F

Option D accurately reflects the truth values: P is false (somatic embryos are bipolar), Q is true (FACS selects heterokaryons), R is true (Larkin and Scowcroft coined somaclonal variation), and S is false (shoot bud differentiation is organogenesis, not somatic embryogenesis).

Detailed Explanation of Each Statement

P. Somatic embryo is unipolar in nature
False. Somatic embryos, formed during plant tissue culture, develop from somatic (non-reproductive) cells and mimic zygotic embryos. They are bipolar, featuring both a shoot apex (plumule) and root apex (radicle), enabling complete plantlet regeneration. Unipolar structures, like callus-derived shoots, lack this dual polarity. This distinction is key in plant biotechnology for mass propagation.

Q. Heterokaryon can be selected using a fluorescence-activated cell sorter (FACS)
True. Heterokaryons are hybrid cells with nuclei from two different species or genotypes, formed in protoplast fusion experiments. FACS sorts cells based on fluorescence markers (e.g., FITC-labeled antibodies targeting species-specific antigens). It detects dual fluorescence in heterokaryons, separating them from homokaryons efficiently— a standard technique in somatic hybridization for crop improvement.

R. The term somaclonal variation is coined by Larkin and Scowcroft
True. In 1981, Australian researchers Peter J. Larkin and William R. Scowcroft introduced “somaclonal variation” to describe genetic and epigenetic changes in plants regenerated from somatic cell cultures. This phenomenon arises from tissue culture stress, leading to heritable variations useful in breeding but challenging for clonal fidelity.

S. Differentiation of shoot buds during in vitro culture is known as somatic embryogenesis
False. Shoot bud differentiation from callus or explants is organogenesis, a direct pathway forming shoots (often roots follow). Somatic embryogenesis involves embryo-like structures from single cells, progressing through globular, heart-shaped, and torpedo stages. Confusing these leads to errors in regeneration protocols.

Why Other Options Are Incorrect

These errors highlight common pitfalls: mistaking embryo polarity, overlooking FACS utility, forgetting term origins, or mixing embryogenesis with organogenesis.

Mastering these concepts boosts success in exams like CSIR-UGC NET, ICAR, or biotech entrances. For deeper dives, check protocols in journals like Plant Cell Reports.