Photosynthesis in non-foliar tissues: implications for yield

Photosynthesis is currently a focus for crop improvement, however the majority of this work has taken place and been assessed in leaves, whilst limited consideration has been given to the contribution that other green tissues make to whole plant carbon assimilation. The major focus of this review is to evaluate the impact of non-foliar photosynthesis on carbon use efficiency and total assimilation. Here we appraise and summarise past and current literature on the substantial contribution of different photosynthetically active organs and tissues to productivity in a variety of different plant types, with an emphasis on fruit and cereal crops. Previous studies provide evidence that non-leaf photosynthesis could be an unexploited potential target for crop improvement. We also briefly examine the role of stomata in non-foliar tissues and their role in gas exchange, maintenance of optimal temperatures and thus photosynthesis. In the final section, we discuss possible opportunities to manipulate these processes and provide evidence that wheat plants genetically manipulated to increase leaf photosynthesis, also displayed higher rates of ear assimilation, which translated to increased grain yield. By understanding these processes, we can start to provide insights into manipulating non-foliar photosynthesis and stomatal behaviour to identify novel targets for exploitation for on-going breeding programmes.