Bupleurum chinense and Medicago sativa sustain their growth in agrophotovoltaic systems by regulating photosynthetic mechanisms

The three-dimensional nature of agrophotovoltaic systems (APV) accounts for the needs of photovoltaic power generation and agricultural production. The combination can solve conflicts among utilization of resources, ecological protection, and agricultural production to achieve low-carbon economic development. However, the economically respond (crop yield and quality) of different species under the decreased light available system is still unclear. To provide insights, we compared agrophotovoltaic and traditional ecosystems to explore the economic feasibility of planting Bupleurum chinense (B. chinense) and Medicago sativa (M. sativa) from the perspectives of light utilization, photosynthetic responses, and land use. The combined system improved the land equivalent ratio, net income and species quality of B. chinense and M. sativa. Both species showed high plasticity, and maintained growth and development by regulating their morphology and photosynthetic parameters. B. chinense in the APV increased its light use efficiency, photosynthetic rate, and root biomass by increasing its height, electron transfer flux, and up-regulating a photosystem I protein (PsaA). M. sativa in the APV allocated more energy to photochemical reactions to improve photosynthetic capacity. It captured and utilized the limited light by reducing leaf mass per unit area and dark respiration, increasing the chlorophyll content, and down-regulating a photosystem II protein (PsbD). Our results showed the importance of species selection based on morphological and photosynthetic responses and provide insights into the selection of appropriate species, efficient resource utilization, and sustainable economic development based on APV.