Photosynthesis — is it limiting to biomass production?

While it is recognized that photosynthesis is the ultimate source of biomass production in plants, little attempt has been made to exploit the considerable knowledge of the light and dark reactions of the process to increase the production of biomass. The question therefore arises as to whether photosynthesis limits production. One of the major problems in assessing the conversion efficiency of solar energy to biomass has been the use of techniques which inevitably underestimate this efficiency. Nevertheless, short-term measurements of production suggest that conversion efficiencies are close to the theoretical photochemical efficiency of photosynthesis (3.5–4%). C4 plants are ultimately more productive than C3 plants as they are able to concentrate CO2 inside the leaf and so eliminate photorespiration. It is suggested that improved adaptation of the photosynthetic process to sub- and supra-optimal conditions and more effective exploitation of leaf area index for increased light interception will lead to increased biomass production rather than any attempts to improve the efficiency of the process per se.