Optimizing In Vitro Propagation of “Ladania” (Cistus creticus L.) Through Interaction of Light Spectra and Plant Growth Regulators

This study investigates the impact of light conditions on the growth, rooting, and photosynthetic performance of in vitro cultivated Cistus creticus L. explants. Initially, different plant growth regulators were tested for multiple shoot growth [5 and 10 μM 6-Benzylaminopurine (BA), 5 and 10 μM meta-Topolin (mT), and 0.5 and 1 μM melatonin (Mel)] and rooting [5 and 10 μM mT, 0.5 and 1 μM Mel, and 0.5 and 1 μM Indole-3-butyric acid (IBA)]. The media with the best results were Murashige and Skoog (MS) with 5 μM BA or 5 μM mT for shoot formation and 0.5 μM Mel or 1 μM IBA for rooting. Also, the explants were cultured under red (R), blue (B), or white (W) LED lights or fluorescent (FL) lamps. After four weeks, the photosynthetic rate, chlorophyll concentration, fluorescence (Fv/Fm), and shoot/root measurements were recorded. The optimal plant regulator for shoot generation was 5 μM mT under a W LED. For rooting, 1 μM IBA combined with a R LED resulted in 100% rooting, 3.53 roots/explant, and a 1.25 cm root length. The B LED led to the highest photosynthetic rate, while the chlorophyll concentration was highest with 5 μM BA under a FL lamp (CCI = 3.03). During acclimatization, a R LED and 1 μM IBA yielded the highest survival rate (70%). The current findings could reinforce the in vitro cultivation of the species for use in the floriculture industry, as well as for medicinal and other industrial purposes. Growth rooms equipped with automated LED lighting systems could optimize the micro-environment and create suitable climatic conditions to enhance in vitro plant growth.