Plant performance of horticultural crops in diffuse light environments

Several studies have shown interesting plant responses when plants are exposed to diffuse natural light in greenhouses resulting for example in better tomato yield. The French technical institute of horticulture ASTREDHOR in collaboration with its partner SERAIL has evaluated in a 3-year project named Di'Light the impact of diffuse light on vegetable crops in plastic tunnels and ornamental plants in greenhouses. Diffuse light was obtained by glass and PE film with light diffusing properties. All materials were analyzed for hemispherical light transmission and light diffusion performances. Different plant species were cultivated in the spring/summer seasons (bedding plants, potted plants) and in the summer/autumn/winter season (tomato, salads, spinach, cyclamen). Diffuse covering gives a more homogeneous light distribution in comparison to clear (from 25% Hortiscatter). Ornamental plants cultivated in diffuse light conditions generally show smaller leaf temperature fluctuations, better fresh weight and higher flower abundance. Under Double Layer PE, vegetable yield was improve during the spring and summer (tomatoes) but decrease for the leafy vegetable in winter. The differences between crops cultivated in diffuse light environments and those cultivated in direct light environments is dependent on the covering light transmission, plant species cultivated and specific sunlight conditions.