Unit 3: Aseptic culture establishment - Practice Quiz

1 What is an explant in plant tissue culture?

2 Which of the following is commonly used as an explant source?

3 Why are young, actively growing tissues preferred as explants?

4 Which meristematic region is preferred for obtaining virus-free plants?

5 Before excising an explant, the plant material should ideally be:

6 What is the main purpose of surface sterilization of explants?

7 Which of the following is a commonly used surface sterilant for explants?

8 Mercuric chloride () is used in surface sterilization as a:

9 Which alcohol concentration is commonly used for a quick surface sterilization dip of explants?

10 After treating explants with a chemical sterilant, they should be:

11 A few drops of Tween-20 are sometimes added during surface sterilization to act as a:

12 What does the term aseptic mean in tissue culture?

13 Aseptic inoculation of explants is usually carried out in a:

14 Which device in a laminar air flow chamber traps microorganisms and dust from incoming air?

15 Instruments like forceps and scalpels used for inoculation are usually sterilized by:

16 The UV light in a laminar air flow cabinet is switched on before work to:

17 Culture media and glassware are commonly sterilized using an:

18 The standard autoclaving condition for sterilizing culture media is approximately:

19 Which precaution helps prevent contamination during aseptic inoculation?

20 If a culture becomes cloudy with bacterial or fungal growth soon after inoculation, it indicates:

21 A researcher wants to establish a shoot culture with the least contamination and highest regeneration potential. Which explant source is generally most suitable?

22 Why are explants often collected from the innermost or newly emerged tissues of a plant rather than surface-exposed older parts?

23 Before surface sterilization, explants are often washed under running tap water for 15–30 minutes. What is the primary purpose of this step?

24 A lab receives field-grown explants that are heavily contaminated. Which pretreatment would most improve subsequent sterilization success?

25 Why is the size of an explant an important consideration during preparation?

26 A student uses 0.1% mercuric chloride for 10 minutes on a delicate leaf explant and finds all tissue dead. What is the most likely correction?

27 Sodium hypochlorite solutions used for surface sterilization are usually prepared fresh. Why?

28 A few drops of Tween-20 are added to a surface sterilant solution. What role does it play?

29 After treating explants with a chemical sterilant, several rinses with sterile distilled water are performed. What is the main reason?

30 Ethanol (70%) is often used as a brief pre-treatment before the main sterilant. Why is 70% preferred over 100% ethanol?

31 During aseptic inoculation, the neck of the culture vessel is passed through the flame briefly. What does this accomplish?

32 A laminar airflow cabinet is used for inoculation. Which feature primarily maintains the sterile working zone?

33 Instruments like forceps and scalpels are dipped in ethanol and flamed between each explant transfer. Why between each transfer?

34 Flamed forceps are allowed to cool before touching an explant. What problem does cooling prevent?

35 For seeds with a very hard, resistant coat, a longer sterilant exposure is often tolerated compared to soft leaf tissue. Why?

36 A culture batch shows fungal growth after 3 days, while another shows slow-spreading turbidity after 2 weeks. What is the most likely source of the early fungal contamination?

37 When both HgCl₂ and NaOCl are options, why might a lab still choose NaOCl for routine sterilization despite HgCl₂ being highly effective?

38 Aseptic inoculation should be performed with the vessel opened for the shortest time possible. What is the underlying reason?

39 After surface sterilization, the cut ends of an explant that contacted the sterilant are often trimmed away before placing on medium. Why?

40 A researcher selects explants from a virus-indexed, disease-free mother plant. What advantage does this provide over random field collection?

41 A researcher surface-sterilizes leaf explants using HgCl for 10 minutes but observes tissue browning and death, though contamination is fully controlled. What is the most likely cause and correction?

42 Two explant sources from the same plant—shoot tips and mature stem segments—are cultured identically. Shoot tips show high regeneration and low contamination, while stem segments show poor regeneration and high contamination. Which single factor best explains BOTH outcomes?

43 During surface sterilization, a lab adds a few drops of Tween-20 to the sodium hypochlorite solution. What is the primary rationale, and what edge-case risk does over-addition create?

44 A commercial NaOCl bleach is labeled available chlorine. To prepare of a working sterilant, what volume of stock and water are needed?

45 Persistent contamination appears 7–10 days after inoculation as cloudy halos around explants, despite rigorous surface sterilization. What is the most probable source and mitigation?

46 A protocol requires 'etiolated' donor material for improved explant response. Why does etiolation (growing in darkness) benefit explant preparation?

47 After HgCl treatment, why must explants be rinsed with sterile distilled water at least 3–4 times, and what happens if rinsing is inadequate?

48 A lab must sterilize delicate flower petals AND woody nodal segments in the same session. Which strategy best balances efficacy and tissue survival?

49 In a laminar airflow cabinet, HEPA filtration provides clean air, yet an inoculation still shows bacterial contamination traced to technique. Which practice most likely failed?

50 A regeneration protocol yields callus but no shoots from stem explants, while identical medium gives shoots from leaf explants. Assuming hormones are constant, what explant-related factor is most decisive?

51 Ethanol () is often used as a pre-sterilant dip before hypochlorite. Why is preferred over ethanol for this purpose?

52 To minimize phenolic oxidation (browning) during explant preparation of a recalcitrant woody species, which combination of measures is most effective?

53 A seed batch shows internal fungal contamination that survives standard surface sterilization. What advanced approach best addresses seed-borne internal pathogens?

54 Given equal killing efficacy, which sterilant sequence generally offers the BEST balance of contamination control and explant survival for moderately hardy tissue?

55 Why does the physiological age and season of collection of the donor explant significantly affect in-vitro establishment success?

56 An operator observes that even a well-maintained laminar flow hood shows contamination when the pre-filter is clogged. What is the mechanistic explanation?

57 For clonal fidelity in micropropagation, which explant choice minimizes somaclonal variation risk during establishment?

58 A protocol lists sterilization as ' HgCl, 3 min' but a technician tries ', 6 min' to 'be safe.' Contamination drops to zero but survival collapses. What principle was violated?

59 During aseptic inoculation, instruments are dipped in ethanol and flamed between transfers. What is the critical safety-and-sterility rule often overlooked?

60 A recalcitrant explant browns and dies within 48 hours despite low contamination. Sequential subculturing to fresh medium every 1–2 days improves survival. What is the mechanistic basis?