Source-sink interactions
New research investigates how plant growth is controlled by the supply of carbon from photosynthesis (source strength) verses the demand for carbon in growing tissues (sink strength). This control has important implications for how trees and crops respond to the continuing increase in atmospheric CO2.
Our work so-far in this area has developed theory to explain how source activity, carbon allocation and sink development limit growth. We have applied this theory to investigate source-sink interactions in an experimental system, and to develop a simulation model of plant source-sink interactions.
We are currently developing new research projects to look at the impacts of rising CO2 on savanna trees, the controls on carbon sequestration in temperate woodland species, and the CO2-fertilization of crops. We welcome enquiries from prospective students and postdocs in these areas (see Opportunities).
C4 photosynthesisOver the last fifteen years, our research has used C4 photosynthesis as a study system. The C4 biochemical pathway provides a carbon-concentrating mechanism to improve the efficiency of photosynthesis compared with the ancestral C3 type under hot conditions, and has been widely credited for the ecological success of grasses in transforming 20% of the land surface into savannas.
Our work has advanced understanding of how this evolutionary innovation overcomes environmental limitations, how a greater efficiency of photosynthesis changes the biology of the whole plant, and how the resulting shifts in plant-environment interactions transform ecosystems. The research has been multi-disciplinary and ambitious in scale, taking in global and geological perspectives, establishing general principles by comparing many plant species, and uncovering evolutionary and physiological mechanisms responsible for C4 plant success.
Crop domestication
Since 2005, we have collaborated with archaeologists to work on the origins of agriculture. People first began farming and domesticating crops in multiple independent geographical regions 10,000 years ago. These early events in global agriculture transformed human history, and eventually gave rise to our modern food system where 60% of calorie intake comes from just three crop species.
Our research looks at how agriculture began and how crops were domesticated. To what extent did the characteristics we associate with domesticated crops arise from deliberate breeding, and to what extent did they arise unintentionally from the sowing, management and harvesting of plants? And why, out of all the edible plants exploited by hunter gatherers, did early agriculture become focused on a small number of staple crops? We compare the biology of crop landraces and wild relatives to make inferences about the processes at work during the origins of agriculture, looking at plant productivity, allocation, size and responses to the environmental limitations imposed by atmospheric CO2, soil nutrients and water.