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C4 grass evolution

The C4 pathway is a fuel injection system for photosynthesis that increases the rate of leaf sugar production in hot climates.  Our research investigates when, how and why C4 photosynthesis evolved.
  1. Which genes are required for C4 photosynthesis and how did they evolve?
  2. What environmental factors drove the evolution of C4 photosynthesis?
  3. How does C4 photosynthesis interact with other physiological processes, and influence the ecology of plants?
  4. To what extent can the ecology of C4 plants be explained by their evolutionary history?
  5. What factors drove the assembly of C4 grassy biomes?

The African grass Alloteropsis semialata is unique among plants in having C3 and C4 variants. With Pascal-Antoine Christin and Erika Edwards at Brown University, we are beginning to understand the evolution of C4 photosynthesis in this species.

With Brad Ripley at Rhodes University we have discovered that the C4 type does not develop winter frost protection and loses its photosynthetic advantage over the C3 during drought events. However, its higher photosynthetic efficiency is linked to greater storage and seed production, and more rapid recovery after fire.

Recently, we have broadened this work to consider multiple evolutionary lineages of C4 grasses. Recent work with Lawren Sack at UCLA looked at the interaction of C4 photosynthesis with plant hydraulics, showing that the pathway allows stomata to stay open longer in a drying soil. We are currently up-scaling our experiments to investigate the controls on growth in hundreds of species.