Q8 - CAM-like Nocturnal Carbon Fixation in the Amphibious Plant Isoetes howelli

Theoretical 1 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

Calvin Cycle, Photorespiration & C4/CAM Biochemistry

Isoetes howelli is an amphibious plant that can live in both aerial and submerged conditions. In a completely submerged condition in shallow fresh water, Isoetes howelli shows characteristic metabolism; CO2 is fixed to malate in a certain time period and released in another period to be used in photosynthetic carbon assimilation. This metabolism is not seen in the aerial condition. There shall be a strong photosynthetic competition in daytime between Isoetes howelli and other photosynthetic organisms. Indicate whether each of the following statements is true or false

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

A. The malate concentration in the leaves is the highest just before sunrise.

B. The characteristic metabolism is adaptive because it reduces water loss.

C. This species has characteristic bundle sheath cells with well-developed chloroplasts.

D. In the submerged condition to which this species is adapted, it is more difficult to use CO2 in daytime than in nighttime.

← Previous: Q7 Next: Q9 →

Question reproduced from IBO 2020, Theoretical Exam 1, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)