The next advance in field crop productivity will need to come from improving crop photosynthetic efficiency, which could involve genetic manipulation of photosynthesis at the biochemical/leaf level and/or improving distribution of captured resources, such as light, for efficient photosynthesis. However, improvement progress is confounded by uncertainties of consequences arising at crop level due to the scale gap across biological levels of organisation. A gene-to-phenotype modelling approach connecting across scales may present a way forward. The objective of this research is to develop a cross-scale modelling framework that connects a crop model, Agricultural Production System sIMulator (APSIM), with biochemical models of C3 and C4 leaf photosynthesis to enable yield consequences simulations. The modelling framework involves upscaling and integration of the leaf photosynthesis models to daily crop canopy growth using a sun-shade modelling approach and is input into APSIM to drive crop growth and yield while APSIM generates leaf area and canopy nitrogen content to drive the leaf photosynthesis models. Environmental effects, such as temperature, on crop growth and development dynamics are captured in APSIM, while their effects on leaf photosynthesis are being improved. Simulation of consequences on both wheat leaf photosynthesis and crop growth and yield of changing canopy architecture, effecting how light is distributed in the canopy with varying leaf erectness, is presented. This work provides a tool for evaluating and potentially directing photosynthetic manipulation for crop improvement.