Improving canopy photosynthesis is a major viable approach to drastically increase crop yields. However, canopy photosynthesis is determined not only by leaf photosynthetic properties, which are further determined by a complex array of energy conversion, electron transfer, and CO₂ fixation processes, but also by highly heterogeneous canopy microclimates inside the canopy. As a result, identifying new options to improve canopy light use efficiency has become a major task for plant biologists and crop breeders.

Recently, Dr. ZHU Xinguang’s lab at Shanghai Institute of Plant Physiology and Ecology of Chinese Academy of Sciences described an in silico approach to rapidly identify new potential options to modify plants for improved canopy photosynthesis. The study was published in Plant, Cell & Environment.

This new in silico approach relied on the success of developing a dynamic systems model of canopy photosynthesis. By using 3D reconstruction, ray tracing algorithm and ordinary differential equations, the model effectively integrates leaf photosynthetic processes, leaf shape and canopy architecture information. It can be used to quantitatively study canopy photosynthetic efficiency and examine the consequences of modifying any properties related to photosynthesis, leaf shape, or canopy architecture on canopy photosynthetic efficiency, and hence can be applied to design crops for optimized canopy photosynthesis.

With this model, researchers demonstrated that decreasing antenna size of photosystem can increase canopy photosynthetic efficiency and nitrogen use efficiency. Decreasing antenna was shown to be able to improve canopy photosynthesis through two mechanisms, i.e. decreasing the loss of energy through heat and increasing the light availability for leaves in the bottom layers of a canopy.

This new finding cast major doubts on the current dogma held in major crop breeders, i.e. greener leaves are equivalent to higher photosynthesis and hence should be selected during breeding. In nature, leaves tend to evolve greater antenna with the possible driving forces including capturing more nitrogen inside leaves, i.e. leaving less for their competitors, and shading other neighboring competitors. The current research focuses on identifying approaches to manipulate antenna size of photosystem to boost crop canopy photosynthesis for greater yields.

The study was funded by the strategic leading project, Ministry of Science and Technology of China, Bill and Melinda Gates Foundation, China National Science Foundation and State Key Laboratory of Hybrid Rice.