C3, C4 and CAM plants Original Scenario-Based Practice

Questions

1. 1.

   In an enclosed arid biodome on a lunar research station, botanists monitor an engineered cultivar designed to minimize transpirational water loss while surviving intense daytime heat. Physiological telemetry reveals that the plant opens its stomata exclusively during the cold nighttime cycle to capture atmospheric carbon dioxide into a four-carbon organic acid that accumulates within large central vacuoles. During the blazing diurnal illumination cycle, its stomata seal tightly while carbon dioxide is enzymatically liberated from these vacuolar reserves to drive the Calvin cycle. Based on these physiological findings, which statement accurately characterizes the metabolic strategy employed by this engineered crop?

   • A) It uses classical C3 carbon fixation, relying on bundle-sheath chloroplasts to avoid photorespiration throughout the night.
   • B) It executes standard C4 photosynthesis by spatially separating initial carbon capture in mesophyll cells from the Calvin cycle in vascular bundle sheath cells.
   • C) It prevents photorespiration by utilizing RuBisCO as the primary nocturnal carboxylase, converting carbon dioxide directly into glyceraldehyde 3-phosphate.
   • D) It relies on Crassulacean acid metabolism (CAM), temporally separating nocturnal carbon capture by PEP carboxylase from diurnal Calvin cycle activity.

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