Unit 4: In vitro propagation - Practice Quiz

1 What is callus in the context of plant tissue culture?

2 The piece of plant tissue used to initiate a tissue culture is called an:

3 Which combination of plant growth regulators is commonly used to induce callus formation?

4 Which of the following is a widely used basal medium for callus culture?

5 Before inoculation, explants are surface sterilized mainly to:

6 Which chemical is commonly used for surface sterilization of explants?

7 The ability of a plant cell to develop into a whole plant is known as:

8 Callus induction is usually carried out under which lighting condition?

9 Which agent is added to solidify the culture medium for callus growth?

10 The typical temperature maintained for callus culture incubation is approximately:

11 Which of the following can be used as an explant for callus induction?

12 Which carbon source is most commonly added to callus culture media?

13 Which auxin is frequently used to promote callus formation?

14 Callus induction and subculturing are performed inside a:

15 Transferring callus to fresh medium at regular intervals is called:

16 The pH of a typical plant tissue culture medium is usually adjusted to about:

17 Which method is used to sterilize the culture medium before use?

18 A high auxin-to-cytokinin ratio in the medium generally favors:

19 Which of the following best describes the texture of a typical callus?

20 The tissue culture technique of growing cells on artificial medium under sterile conditions is broadly termed:

21 A researcher inoculates a leaf explant on MS medium but observes no callus formation even after 4 weeks. Which modification is most likely to induce callus?

22 Why is surface sterilization of explants with sodium hypochlorite or mercuric chloride essential before callus induction?

23 An explant containing more actively dividing meristematic cells generally shows a higher callus induction rate. Which explant would therefore be expected to callus most readily?

24 During callus culture, the appearance of a brown coloration around the explant is most commonly caused by which phenomenon?

25 A student wants to prepare of MS medium with a sucrose concentration of . How much sucrose should be added?

26 Which combination of plant growth regulators is typically used to promote unorganized callus proliferation rather than shoot or root organogenesis?

27 When preparing callus from a stem explant, why is the explant usually cut into small segments of a few millimetres rather than left as a large piece?

28 The proper orientation of a leaf explant on solid medium for callus induction is usually with the:

29 Which of the following best explains why callus formation depends on the totipotency of plant cells?

30 A callus culture is regularly transferred to fresh medium every 3–4 weeks. This subculturing is primarily done to:

31 Before autoclaving, the pH of MS medium for callus culture is typically adjusted to approximately:

32 Callus obtained from monocot explants such as cereals is often initiated from which explant because of its high regenerative capacity?

33 Why must all callus induction procedures be carried out inside a laminar air flow cabinet?

34 A friable (loose, crumbly) callus is generally more desirable than a compact callus for establishing suspension cultures because:

35 If a callus culture repeatedly turns necrotic soon after transfer, which practical step is most appropriate to try first?

36 Which factor of the donor plant most strongly influences the success of callus induction from its explant?

37 In a callus induction experiment, an explant is placed on medium containing 2,4-D. To prepare of this medium, how much 2,4-D is required?

38 Why are freshly cut edges of an explant, rather than the intact central surface, usually the first regions to produce callus?

39 Many callus cultures are initially incubated in darkness rather than light primarily because:

40 Agar is included in solid callus induction medium mainly to:

41 A researcher observes that a leaf explant produces abundant callus on the abaxial surface but almost none on the adaxial surface when placed on the same medium. Which factor most directly explains this differential callusing response?

42 Two explants of the same species are cultured: one with high endogenous auxin and one with low. To obtain comparable callus, the low-auxin explant needs a higher exogenous auxin dose. What principle governs the effective callusing response?

43 A hypocotyl explant browns rapidly and fails to form callus within 3 days of inoculation. Which intervention most directly addresses the underlying cause?

44 When comparing callus induction from a mature stem node versus a shoot apical meristem of the same plant, which statement is most accurate regarding genetic and morphogenic behaviour?

45 An immature embryo explant on 2,4-D readily forms embryogenic callus, whereas a mature leaf on the same medium forms only non-embryogenic friable callus. What best explains the difference in competence?

46 A protocol calls for 2,4-D. A stock is prepared at . To make of medium, what volume of stock is required?

47 During surface sterilization of a field-collected root explant, callus cultures repeatedly show endophytic bacterial contamination appearing only after 7-10 days. Which strategy is most appropriate?

48 A callus that was initially white and friable turns compact, green, and nodular after several subcultures. What does this transition most likely indicate?

49 Explants from a woody species leach large amounts of phenolics, blackening the medium. Beyond antioxidants, which combined approach best minimizes this problem at inoculation?

50 A researcher wants to maximize the fraction of explant cells contributing to callus. Which explant preparation choice best increases the wounded-surface-to-volume ratio?

51 Two media differ only in gelling agent concentration: vs agar. The explant on higher agar shows reduced callus growth. What is the most likely physiological cause?

52 For a species where anther explants are used to produce haploid callus, which precaution is essential to ensure the callus is gametophytic rather than somatic in origin?

53 A callus induction experiment yields the following percentages on four auxin:cytokinin (mg/L) ratios: = 90%, = 40%, = 10%, = 5%. What does this trend indicate about callus induction requirements in this system?

54 An investigator notices that callus derived from older, differentiated cotyledon tissue is slow-growing and hard to maintain, while callus from the same species' seedling root grows vigorously. Which concept best explains this?

55 A protocol requires the medium pH to be set to before autoclaving. If the analyst sets pH to after autoclaving instead, what problem is most likely?

56 In callus induction from a monocot such as rice, immature embryos and mature seed-derived scutellum are common explants, while leaf blades respond poorly. What is the primary reason mature monocot leaf explants callus poorly?

57 A student prepares of MS medium and needs sucrose plus agar. If they accidentally use agar for the whole liter, what outcome is expected?

58 When establishing callus from a highly heterozygous perennial, why might a technician prefer nodal or internodal segments over random callus for downstream micropropagation despite slower callusing?

59 A callus culture initiated in light is friable and non-morphogenic, whereas the identical explant in darkness gives compact callus that later regenerates shoots. Which factor most plausibly accounts for the light-dependent difference?

60 An explant of dermal-rich tissue yields callus only from cut edges, not the intact epidermis. What does this observation reveal about the cellular origin of callus?