Improving adventitious rooting in Kalanchoe blossfeldiana cuttings using sole source targeted LED lighting spectra

Adventitious root development, an auxin mediated process, is critical for clonal propagation of ornamental crops such as Kalanchoe blossfeldiana. Understanding and manipulating auxin transport as it relates to adventitious rooting can lead to improved rooting success and faster production cycles. Auxin dynamics are known to be heavily influenced by light (direction and quality); as such, it stands to reason that manipulations of the spectral environment (i.e., light quality) may influence auxin dynamics, thereby affecting adventitious root formation. Kalanchoe blossfeldiana was used to study the influence of light quality on adventitious root formation and development. Cuttings were grown in a series of nine controlled environment chambers outfitted with tunable LED light fixtures. Cuttings of a vigorous rooting cultivar ('Ann') were planted in a peat-based substrate and grown under an 18-h photoperiod with a photosynthetic photon flux density of 300 µmol m^‑2 s^‑1. Three red: blue light ratios were evaluated: 1) 90R:10B; 2) 70R: 30B; and 3) 15R: 85B. Preliminary result for cultivar 'Ann' showed no significant differences in rooting under the three light regimes. On-going work will examine auxin dynamics at the point of excision to determine if the quality of light is regulating auxin transport.