Skip to content
← Theoretical 2

Q31 - Auxin, Cytokinin and Density Effects on Bud Formation in the Moss Physcomitrella

Theoretical 2 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Plant Hormones

When protonemata of the moss Physcomitrella patens were cultured without exchanging the culture medium, some cells formed buds that grew into gametophores. The medium contained no plant hormones originally, but auxin and cytokinin were detected in the medium after culturing protonemata. When protonemata were instead cultured with continuous medium exchange (keeping the medium fresh), bud formation was examined with and without added auxin/cytokinin (Table 1): wild type with no exchange forms buds; wild type with exchange and no hormones added does not; wild type with exchange plus auxin only does not; wild type with exchange plus cytokinin only does not; wild type with exchange plus both auxin and cytokinin does form buds. Mutant x (which does not form buds under natural, no-exchange conditions) with no exchange and no hormones does not form buds; with no exchange plus auxin added, still does not form buds; with no exchange plus cytokinin added, does form buds.

Figure 1. Figure 1.

Figure 2. Figure 2.

Using the information and data, determine which of the statements are true or which are false.

A, B, C fill-in. Choose the most appropriate answer set to fill in the blanks: The wild-type protonemata secrete (A). Auxin sensitivity is (B) in mutant x. Protonemata are more likely to form buds when their growing density is (C).
← Previous: Q30 Next: Q32 →

Question reproduced from IBO 2020, Theoretical Exam 2, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)