PHOTOSYNTHESIS & CROP SYSTEMS BIOLOGY
Xinyou's research addresses topical questions in, and to narrow knowledge gaps between, crop science and plant biology. Various analytical and computational models have been developed not only for predictions but more for generating hypotheses amenable to experimental testing. Such combined experimental and modelling research, often having interdisciplinary features, has covered photosynthesis, photothermal response of flowering, genotype-to-phenotype relationships, and crop productivity and resource use efficiency in the context of climate change. These activities, defining the Centre's "Crop Photosynthesis" and "Crop Systems Biology" themes, have resulted in two books (see the picture above), and more than 120 refereed journal papers and 30 invited speeches in international symposia.
- Inspired by the work of Prof. Graham Farquhar, Xinyou extended the electron transport limited part of the FvCB (Farquhar-von Caemmerer-Berry) photosynthesis model. The extended model is the generalised form for both NADPH- and ATP-determined formulae of the FvCB model. Combined with routine biophysical and gas-exchange measurements, the generalised model can be used to quantify the fraction of alternative electron pathways. The most striking difference between C3 and C4 photosynthesis lies in the fraction for cyclic electron transport and its associated inter-photosystem excitation partitioning (see his papers in Plant, Cell & Environ 2004, 2006, 2012).
- Dynamics of any growth process generally follows a sigmoid pattern. Classical growth functions (Logistic, Gompertz, ...) have an asymptotic parameter as the maximum weight of growth. These equations do not suit for describing a determinate growth process. Xinyou developed a new class of equations for the determinate growth. The equations have few parameters (which all have clear biological meanings), and allow for symmetric and any asymmetric sigmoid patterns. (see Annals of Botany 2003. 91: 361-371 with erratum in 91:753, 2003)
- The original work by Xinyou in exploring the complementarities of crop modelling and genetic mapping enables a better prediction of genotype-by-environment interactions. Built upon this experience, his PhD student Junfei Gu mapped, for the first time, biochemical parameters of the FvCB model, using rice introgression lines (J Exp Bot 2012. 63: 5137-5153). The identified genetic variation in these parameters was found, via computational analysis, to be scaled up for improvement of rice crop yield (Plant, Cell & Environ 2014. 37: 22-34). This suggests that mining natural variation in leaf photosynthesis via conventional breeding can provide an obvious route to improve photosynthesis.
- Given the growing scarcity of available fresh water for global rice production, it is important to investigate the feasibility of growing rice like dryland crops. In collaboration with IRRI, Xinyou's PhD student Niteen Kadam compared contrasting rice with wheat genotypes for a number of morphological, anatomical and physiological characteristics. Opposite water use strategies of wheat and rice (see Plant Physiol 2015. 167: 1389-1401) suggest that developing wheat-alike rice genotypes is probably a long-shot challenge.