Open Access

Photosynthesis is the primary determinant of biomass with more than 90% of biomass (on a dry weight basis) derived directly from photosynthetic products. There is compelling evidence from free air CO2 enrichment experiments (FACE) that increasing photosynthesis does increase crop yields provided that other constraints do not become limiting (Ainsworth & Long, 2005). The maximum theoretical efficiency with which the sun's energy can be captured as crop biomass is 4.5 to 6%, although it seldom exceeds 2% and averages less than 1%. Improving this conversion efficiency is an important area of research, with the potential to significantly increase crop yields. The processes underlying photosynthesis are highly conserved in different species and thus progress that is made in a model species should equally apply to crop species (Parry et al., 2011; 2013; Carmo Silva et al., 2014). One of the reasons for low photosynthetic efficiency (e.g. of rice and wheat) is that the primary carboxylating enzyme, ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), is slow and also catalyses a competing reaction with O2 rather than CO2. Much research has focused on overcoming the limitations of Rubisco either through mining natural diversity (Driever et al 2014) or by genetic engineering (Lin et al 2014a; 2014b), and has included attempts to increase the flux of CO2 to the site of utilisation by Rubisco. Significant progress has also been made toward promoting a plentiful supply of the CO2 acceptor molecule and Rubisco co-substrate, ribulose-1,5-bisphosphate (RuBP), through altered expression of rate-limiting enzymes required for its continuous regeneration.

Global Wheat Program

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INT3193

INT1511