The correct combination is (1) A, B and C. Statements A, B and C are true, while D is false because in somatic embryogenesis the heart stage appears before the torpedo stage, not after.

Statement-by-statement analysis

A. Friable callus provides the inoculum to form cell-suspension cultures – TRUE

• Friable callus consists of loosely associated, easily crumbling cells; this texture allows small cell aggregates to disperse readily into liquid medium, making friable callus the preferred inoculum for establishing cell-suspension cultures.

• Compact callus, in contrast, does not break up easily and is inefficient for suspension culture initiation.

B. Habituation refers to callus losing the requirement of auxin and/or cytokinin during long-term culture – TRUE

• In long-term subculture, some callus lines become “habituated,” meaning they grow and divide without the exogenous auxin and/or cytokinin they originally required.

• This hormone independence is a classic definition of habituation in plant tissue culture, so statement B is correct.

C. Cellulase and pectinase enzymes are usually used for generating protoplast cultures – TRUE

• Protoplast isolation relies on enzymatic digestion of the cell wall using cellulase to hydrolyze cellulose and pectinase to degrade the middle lamella, often applied sequentially or together.

• These two enzymes are explicitly cited as the main components of protoplast isolation mixtures, so statement C is correct.

D. During somatic embryo development, torpedo stage embryo is formed before heart stage embryo – FALSE

• In dicot somatic embryogenesis, embryos pass through the same sequence as zygotic embryos: globular → heart → torpedo → cotyledonary stages.

• Therefore, the heart stage precedes the torpedo stage; the statement that torpedo is formed before heart reverses the order and is incorrect.

Option-wise explanation

• (1) A, B and C – Correct, because all three statements accurately describe friable callus, habituation and protoplast enzyme use.

• (2) A, B and D – Incorrect, includes D, which wrongly orders heart and torpedo stages.

• (3) A, C and D – Incorrect for the same reason: D is false.

• (4) B, C and D – Also incorrect, as again D is wrong despite B and C being true.

SEO‑oriented introduction (for article use)

In plant tissue culture, friable callus is essential for starting cell-suspension cultures, habituation describes hormone-independent callus growth after long-term subculture, and cellulase plus pectinase are standard enzymes for protoplast isolation. Somatic embryos, however, always develop in the sequence globular, heart, torpedo and cotyledonary, so any statement placing the torpedo stage before the heart stage is biologically incorrect.