Unit 5: Plant growth regulators - Practice Quiz

1 Which two classes of plant growth regulators are most commonly used to control organogenesis in tissue culture?

2 A high cytokinin to auxin ratio in the culture medium generally promotes which type of organ formation?

3 A high auxin to cytokinin ratio in the culture medium generally promotes which type of organ formation?

4 Which of the following is a commonly used auxin in plant tissue culture?

5 Which of the following is a commonly used cytokinin in plant tissue culture?

6 The classic concept that the auxin-cytokinin ratio controls organ formation was demonstrated by which researchers?

7 The formation of organs such as shoots and roots from cultured plant tissues is called:

8 Which auxin is particularly favoured for inducing rooting in micropropagated shoots?

9 When auxin and cytokinin are supplied in nearly equal (balanced) amounts, the tissue typically forms:

10 The process of producing new shoots from an explant in culture is commonly referred to as:

11 Which plant growth regulator primarily promotes cell division and shoot bud formation?

12 Which plant growth regulator primarily promotes cell elongation and root initiation?

13 Which of the following is a synthetic auxin commonly used to induce callus in tissue culture?

14 For successful in vitro rooting of micropropagated shoots, the medium is usually supplemented with:

15 Kinetin is best classified as which type of plant growth regulator?

16 NAA (Naphthaleneacetic acid) belongs to which class of plant growth regulators?

17 If cultured tissue produces only roots and no shoots, the medium most likely contains:

18 Zeatin is naturally occurring plant growth regulator classified as a:

19 The multiplication of shoots to obtain many plantlets from a single explant is generally achieved by using media rich in:

20 In tissue culture, after shoots are formed and elongated, the next stage before transferring plantlets to soil is:

21 A tissue culture technician wants to induce shoot proliferation from callus. Which auxin-to-cytokinin ratio in the medium would most likely favor this outcome?

22 In vitro rooting of microshoots is typically induced by transferring them to a medium containing which class of regulator?

23 A culture given a very high cytokinin concentration produces numerous shoots that fail to elongate and appear stunted. What is the most likely reason?

24 Which regulator is commonly added to promote shoot elongation after multiplication when shoots remain too short?

25 A researcher uses 2,4-D at high concentration during initiation. Which developmental outcome is most expected?

26 During micropropagation, why are microshoots often transferred to a fresh medium with reduced or no cytokinin before rooting?

27 Which combination is most appropriate for inducing multiple shoots directly from a nodal explant?

28 A student observes that shoots rooted well on auxin-containing medium but the roots are thick, short, and callused at the base. What is the most likely cause?

29 Which of the following best explains why IBA is often preferred over IAA for in vitro rooting?

30 In the Skoog–Miller model of organogenesis, an intermediate auxin-to-cytokinin balance typically results in what?

31 A protocol calls for a two-step rooting: a short pulse on high-auxin medium followed by transfer to auxin-free medium. Why is this done?

32 Which regulator combination would you expect to give the poorest shoot regeneration from callus?

33 A hyperhydric (vitrified), glassy, water-soaked appearance of in vitro shoots is often linked to which regulator condition?

34 For difficult-to-root woody species, which strategy involving regulators is often used?

35 Which observation would indicate that the cytokinin level in a multiplication medium is optimal rather than excessive?

36 Adventitious shoot regeneration directly from a leaf explant (without callus) is best promoted by which condition?

37 TDZ (thidiazuron) is sometimes used in shoot regeneration protocols primarily because it has what type of activity?

38 If shoots are transferred to a rooting medium but no roots form even after weeks, which adjustment is most logical to try first?

39 Which statement correctly describes the general roles of auxin and cytokinin in organogenesis?

40 A plantlet with well-developed shoots but poor roots is unlikely to survive acclimatization. Which culture-stage error most likely caused the poor rooting?

41 In Skoog and Miller's classic model of organogenesis, a callus cultured on a medium with a high auxin-to-cytokinin ratio is most likely to undergo which morphogenic response?

42 A researcher obtains excellent shoot multiplication using BAP but observes severe hyperhydricity (vitrification) in the shoots. Which modification is the most rational first step to reduce hyperhydricity while retaining organogenic response?

43 During in vitro rooting, auxin is often required only for the initial induction phase and can inhibit later root elongation. Which two-step protocol best exploits this biphasic auxin requirement?

44 Why is IBA generally preferred over IAA for in vitro root induction in many species?

45 A callus fails to form shoots even at high cytokinin levels but readily forms roots. The most likely explanation involving endogenous hormones is:

46 TDZ (thidiazuron) is frequently used for shoot regeneration in recalcitrant woody species. A common drawback of using TDZ that must be managed is:

47 In direct organogenesis versus indirect organogenesis, which statement about the PGR regime and somaclonal variation is correct?

48 The synthetic auxin 2,4-D is powerful for callus induction but is usually avoided during shoot regeneration because:

49 A protocol reports shoot regeneration frequency . Out of 48 explants, 36 form shoots, giving what regeneration frequency?

50 Gibberellic acid (GA) is sometimes added after shoot induction. Its most appropriate role in an organogenesis sequence is to:

51 In many microshoots, adding activated charcoal to the rooting medium improves root formation primarily because it:

52 A microshoot line roots poorly even with high IBA. Genetic analysis shows adequate auxin transport. The most plausible physiological cause and remedy is:

53 Which combination correctly matches the PGR-controlled morphogenic outcome according to the auxin:cytokinin (A:C) ratio concept?

54 Ethylene often accumulates in sealed culture vessels during organogenesis. Its typical effect and a common mitigation are:

55 When comparing kinetin, BAP, and zeatin for shoot induction, a key practical reason BAP is most commonly chosen is:

56 A dose-response study shows shoot number rising with BAP up to mg/L, then declining at mg/L with abnormal, stunted shoots. This pattern best illustrates:

57 In monocots (e.g., cereals) that are recalcitrant to organogenesis, 2,4-D is used to induce embryogenic callus, but shoot regeneration requires switching PGRs. The correct rationale is:

58 Some easy-to-root species form roots on PGR-free (basal) medium. The best explanation is:

59 A lab needs to convert mg of a stock to prepare L of medium at mg/L NAA from a mg/mL NAA stock solution. What volume of stock is required?

60 During acclimatization, in vitro rooted plantlets often show poor survival despite good root systems formed under high auxin. A PGR-related contributing factor is: