S06 - Session O4 - Plant performance of horticultural crops in diffuse light environments.

Authors: David Vuillermet *, Alexandre Burlet, Oscar Stapel

Studies show 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 tunnels and greenhouses. Diffuse light was obtained by using screens, paints and coverings 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, young plants, salads) and in the summer/autumn/winter season (tomato, salads, spinach, chrysanthemum, cyclamen). We observed that diffuse light coverings resulted in a more homogenous light distribution in comparison to transparent coverings. We also observed a strong correlation between increase in Hortiscatter and decrease in hemispherical light transmission. Plants cultivated in diffuse light conditions generally show less fluctuating leaf temperatures and in some cultures even lower leaf temperatures. However, results in terms of plant growth, plant development and yield are for some plant species less clear. The differences between crops cultivated in diffuse light environments and those cultivated in direct light environments is dependent on the light transmission, plant species cultivated, specific sunlight conditions and the exposure time under diffuse light.