Specific Leaf Area and Photosynthesis of Apple Trees Under a Dynamic Agrivoltaic System

Abstract

It has been assumed that crops cultivated in agrivoltaics (AV) systems can produce enough carbohydrates through the process of photosynthesis because they are expose to an excess of light. However, many studies have shown increases in specific leaf area (SLA) under shading that can be associated to reductions in the photosynthetic capacity of leaves. This study aimed to evaluate the impact of severe and fluctuating AV shading on apple leaf morphophysiological characteristics (SLA and photosynthesis). 10-year-old ’Golden Delicious’ apple trees grown in a dynamic AV system were monitored over three consecutive seasons (2019 to 2021) along with a control without panels. From February 2019 until July 2021, the photovoltaic modules rotated to maximise tree shading (15 hours of shading per day in summer). From July 2021 onwards, a lighter shading strategy was tested (5.8 hours of shading per day in summer). SLA at several dates was always higher for trees in the AV system (bigger individual leaf area but thinner leaves). SLA was not modified when light availability was increased late in the season. Light response curves indicated a lower saturation point for leaves grown in the AV system and a linear negative relationship was found between SLA and maximal photosynthetic capacity. To avoid leaf morphology modifications due to shade acclimatation, we propose to avoid severe shading during leaf development. We expect this study will provide a better understanding on how to modulate the light microclimate at specific times of the season in dynamic AV systems.