C3, C4 and CAM plants Original Scenario-Based Download PDF

Questions

1. 1.

   In an enclosed planetary greenhouse subjected to intense daytime heat and severe water rationing, an astrobotanist cultivates an experimental crop lineage named Solis-9. Physiological sensors reveal that Solis-9 opens its stomata exclusively during the cooler nocturnal hours, utilizing PEP carboxylase to fix atmospheric carbon dioxide into malate that accumulates inside large central vacuoles. Throughout the scorching daylight hours, stomata remain firmly sealed while the stored malic acid is decarboxylated internally, delivering a concentrated stream of carbon dioxide to RuBisCO. Which physiological principle correctly classifies Solis-9 and explains its metabolic advantage over standard C3 plants under these harsh conditions?

   • A) It operates via Crassulacean Acid Metabolism (CAM), using temporal separation of carbon fixation to minimize daytime transpirational water loss and suppress photorespiration.
   • B) It operates via the C4 pathway, utilizing bundle-sheath spatial isolation to shield RuBisCO from atmospheric oxygen during peak solar irradiance.
   • C) It operates via an enhanced C3 pathway, relying directly on RuBisCO to trap carbon dioxide during nocturnal darkness before light reactions begin.
   • D) It operates via Crassulacean Acid Metabolism (CAM), relying on spatial separation between mesophyll and bundle-sheath cells to fix carbon into three-carbon sugars at night.