Photo-selective shade nets substantially benefit ornamental plant production by mitigating excessive radiation, enhancing light diffusion, and promoting adequate ventilation. These nets establish favorable microclimates that optimize water utilization, thereby reducing plant water demand through physiological and environmental adjustments. Shade nets of different colors vary notably in their spectral distribution and light transmission characteristics, directly impacting plant morphology, physiology, and development. This study aimed to evaluate how different colored photo-selective shade nets influence physiological, morphological, and floral characteristics, as well as water usage, in Zinnia elegans ‘Cherry Queen’. We used four distinct shade net colors: blue, red, white, and black with 30% shade factor as treatments. The 107 cm x 61 cm shade structure was prepared using the PVC pipes with different colored shade nets wrapped around it. Seeds of zinnia were sown in a commercial substrate, Metro-Mix® 820, and kept on a misting bench. Following germination, the plugs were transplanted in a 3.6 L pot filled with the same commercial substrate and kept under four distinct color shade nets. Substrate moisture content was consistently maintained at 35% volumetric water content using an automated irrigation system using capacitance-based soil moisture sensor, ECH20 10HS from Meter Group. Black shade nets transmitted the least radiation across all wavelengths. Blue shade nets increased transmission in blue and green wavelengths while reducing red and far-red light transmission. Red shade nets enhanced red and far-red wavelength transmission, whereas white nets provided the highest overall radiation across all wavelengths. Morphologically, plants grown under red and white shade nets exhibited similar growth and floral characteristics to those under blue nets, and all showed improved growth compared to plants under black nets. Physiological responses, including photosynthetic assimilation rate, stomatal conductance, chlorophyll fluorescence (Fv/Fm), Soil Plant Analysis Development (SPAD), Normalized Difference Vegetation Index (NDVI), and anthocyanin content measured via leaf spectrometry remained similar across all treatments. Water use per plant was highest under white shade nets, significantly exceeding usage under black nets but comparable to blue and red nets. Growers may prefer red or white shade nets for optimal growth and water efficiency, blue for balanced spectral quality, or black for reduced radiation needs.
