Photoselective particle films influence physiology and growth of citrus

Particle films impact pest management and crop physiology by redistributing light within the canopy. Although most commercial particle film products have nonselective reflectance, recent studies found positive effects of a red-dyed particle film on pest suppression and growth in citrus. To better understand the impacts of photo-selective particle films on tree physiology and growth, we implemented a series of trials in citrus. Photoselective particle films of white (undyed), red, blue, purple, and green color were developed using photostable dyes. The experiment was repeated three times. In Trials 1 and 2 treatment rates were the same quantity of kaolin per treatment. However, because different photoselective films provided differences in shading, in Trial 3 the kaolin rates were adjusted to result in the same incident radiation to the leaves. We measured gas exchange and leaf temperatures midmorning and midday on multiple dates. All particle film treatments reduced leaf temperature (similar to 4-8 degrees C). Depending on environmental conditions, some particle films increased net CO2 assimilation or stomatal conductance especially white and red. Trees growing under red and white films resulted in higher total dry weights compared to the other colored films, and red films had the highest mean in all three trials. Photoselective particle films impacted both quantity and quality of incident radiation. The red-dyed kaolin film resulted in the best growth and physiological responses in citrus. These products represent an easily deployable technology to manipulate the light environment of crops in the field.