The aim of the research programme is to understand the regulation of photosynthesis in higher plants. Because of the large fluctuations in external environmental conditions and the differing states of development of the whole plant, optimum performance in terms of resource capture and avoidance of stress requires regulation of photosynthesis. A major focus of the research is to discover how plants respond to different levels of sunlight.
The programme can be separated into two major overlapping areas.
- Regulation of light harvesting
- Light utilisation by crop plants
Regulation of light harvesting. We are investigating the mechanisms by which plants are protected from damage by excess excitation energy.
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Under conditions when absorbed irradiation exceeds the capacity for utilisation in photosynthesis a process is induced by which the excess energy is dissipated. This feedback control mechanism is called nonphotochemical quenching (NPQ) – it involves a fundamental switch in the function of the light harvesting assemblies in the chloroplast membranes. As apart of an international collaboration, we wish to determine the molecular mechanism of NPQ. The approach is multidisciplinary, combining biochemical and structural analysis of purified proteins with spectroscopic, physiological and genetic analyses of intact systems. (click here for more information)
Figure 1. The light harvesting complexes of plants. A structural model of an intact Arabidopsis PSII supercomplex obtained by EM (taken from Ruban et al. 2003 Nature) - blue is the trimeric LHCII, and green the monomeric minor antenna complexes. |
Light utilisation by crop plants. Because adaptation and acclimation of plants to light is such an important facet of growth and development, we have sought to explore these processes in relation to crop productivity. We are using the model plant Arabidopsis thaliana to determine the effects of genetic manipulation of the pigment and protein composition of the chloroplast on photoprotection and stress tolerance. Then, we aim to transfer this knowledge to increase the performance of crop plants.
Figure 2. Arabidospsis thaliana ecotype Cvi grown at 100 uM PAR. |
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We have selected two contrasting crops which nevertheless are: a) of crucial economic importance in developing countries; and b) grown in extreme climatic conditions. In one project we have been investigating rice grown under irrigated tropical conditions in South East Asia. This work, which is carried in collaboration with the International Rice Research Institute in the Philippines and the University of Nottingham, has the objective of identifying the factors, which limit the light utilisation by the rice leaf under field conditions. The second project is an investigation of common bean in South America, in collaboration with crop scientists in Chile, Bolivia and Colombia - here, a major limitation to yield arises from abiotic stress (combinations of extreme temperature, drought, poor soils and high solar radiation, including UV). There is enormous genetic variation in the tolerance to these stress factors and we wish to understand the molecular basis of this variation. (click here for more information)
Figure 3. Photosynthesis and crop yield. Indica IR72 growing at IRRI. |