Growth or defence? Functional trade-offs in changing environments

Rising atmospheric CO2 is increasing carbon availability for plant growth, but species show a variety of CO2 responses. One reason for this may be that plants use photosynthetic carbon for both growth and defence against herbivores. This forces plants to make life history decisions about which process to prioritise. A number of ecologically important plant groups, particularly grasses, have adopted silicon for physical defence and structural support because it is energetically cheaper to acquire than carbon-based alternatives such as lignin. However, grasses have also repeatedly evolved C4 photosynthesis, a physiological mechanism for boosting the efficiency of carbon uptake in hot and CO2-depleted environments. This has created an interesting model system in which to test the relationships between carbon and silicon supply, and their deployment for defence and support. A better understanding of these relationships will improve our predictions about how different species will respond to the ongoing rise in atmospheric CO2.

This project will use an experimental approach, growing C3 and C4 plants under controlled environmental conditions to test a number of interlinked questions. How does C4 photosynthesis change the allocation of carbon and silicon to growth, chemical and physical defences, and structural support? How are those trade-offs influenced by silicon supply and variation in atmospheric CO2 from sub-ambient to elevated levels? How effectively does silicon substitute for carbon, and does this differ in C3 and C4 plants?

The project will suit a motivated student with interests in the impacts of global change on the world’s plants, and a curiosity about the ecological mechanisms involved. The work will use state-of-the-art plant growth facilities and lab analyses to address questions of fundamental ecological interest in a changing climate, giving the student expertise and experience in this important area of contemporary research. The student will work within a diverse and stimulating research environment, being based within a large research grouping at the University of Sheffield, but also spending periods of time at the University of York. In addition to the research training, opportunities are also available to learn about science communication to public audiences, work within policy environments, and collaboration across disciplines.

Informal enquiries about the project, group and department are welcomed. Further information about the supervisors and our research interests can be found here:

Colin http://osbornelab.group.shef.ac.uk
Sue https://www.york.ac.uk/biology/research/plant-biology/sue-hartley/#research

And here are links to our publications:

Colin https://scholar.google.co.uk/citations?user=ZPeZmp0AAAAJ&hl=en
Sue https://scholar.google.co.uk/citations?user=Icb-iNYAAAAJ&hl=en

Recent references in this area:

Atkinson, R.R.L., Mockford, E.J., Bennett, C., Christin, P.-A., Spriggs, E.L., Freckleton, R.P., Thompson, K., Rees, M., Osborne, C.P. (2016) C4 photosynthesis boosts growth through altered physiology, allocation and size. Nature Plants 2, 16038.

Hartley, S.E., DeGabriel, J.L. (2016) The ecology of herbivore-induced silica defences in grasses. Functional Ecology 30, 1311-1322.