Q14 - C3 and C4 Leaf Anatomy and Climate

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

Calvin Cycle, Photorespiration & C4/CAM Biochemistry

Among plant families, grasses and Chenopodiaceae contain many species using the C4 photosynthesis pathway, and many C4 species have evolved independently from C3 ancestors within these families. The figures show cross-sections of C3 and C4 leaf types from different species. Cross section of leaves from: A, C3 species; B, C4 species; C–D, C3 or C4 species. ch = chlorenchyma; at = aqueous tissue; cb = central vascular bundle; hy = hypodermis; pa = palisade cells or mesophyll cells; kr = Kranz cells or bundle-sheath cells.

Figure 1. Figure 1.

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

A. Evolution of C4 species is favoured in a climate of increasing drought, salinity and heat, but with no change in CO2 level

B. Leaf in Fig. C is from a C3 plant

C. Leaf in Fig. D is from a C3 plant

D. During a period of global CO2 increase, without a concomitant increase in temperature, the global distribution of C4 plants is likely to expand

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Question reproduced from IBO 2015, Theoretical Exam A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)