Growth and Photosynthetic Performance of African Violet in Response to Light Quality and Phytohormones

Light is an essential source of energy for photosynthesis, which regulates plant growth and morphology. Although vertical farms are vastly practiced for crop production, their potentials for flower production are recently recognized owing to its efficient use of area in a season-independent way. This study examined the effects of light quality and phytohormones application on growth, morphology, and photosynthesis of African violet (Saintpaulia ionantha L.) leaf cuttings. Therefore, gibberellic acid (GA3), zeatin (ZEA), and water (control) were applied on plants that were exposed to red (R), red-blue (R:B), and red-blue-far-red (R:B:F) lights. Results showed highest growth (above-ground biomass fresh and dry weight, root fresh weight, plant fresh and dry weight, number of leaves, and plant leaf area) were recorded in GA3-treated plants that were exposed to RB and RBF lights. Adding FR light caused petiole elongation, which may not be commercially valuable. The highest inflorescence achieved under RBF light, while the lowest inflorescence occurred under R light, furthermore GA3 negatively affected inflorescence. Chlorophyll fluorescence analysis revealed that monochromatic R light reduced photosynthetic capacity, while multichromatic RB and RBF lights and phytohormone application enhanced photosynthetic functionality. Phytohormones under multichromatic lights increased leaf pigmentations. Compact plants with high flowering was achieved in ZEA-treated plants that were exposed to RB light, which adds to their marketable value. In conclusion, multichromatic RB and RBF light spectra combined with ZEA and GA3 application improved growth, photosynthetic capacity, and pigment contents in African violet, making it an ideal choice for indoor farming.