Effect of thidiazuron and monochromatic light on shoot development in vitro culture of Polygonum cuspidatum Sieb et Zucc

Abstract

Polygonum cuspidatum Sieb. et Zucc, a medicinal plant, contains many phenolic compounds such as resveratrol. It has antioxidant, antibacterial, anti-cancer, HIV, and neuron protective properties. In this study, stem segments having an auxiliary bud were cultured in vitro on MS medium supplemented with TDZ at 0.1 mg/L for obtaining the highest number of shoots (8–9 shoots/cluster after eight weeks). The bud shoots were originated from the differentiation in the periphery of the lateral meristem. After eight weeks, the shoots cultured under the monochromatic light showed that the plant height, fresh and dry weight was higher than those grown under the fluorescent light at the same intensity of 50 µmol photon/m²/sec. Blue LED reduced the number of shoots/cluster, and respiration intensity of the inoculum compared to the red LED or fluorescent light conditions. However, after eight weeks, the total sugar and phenolic content in leaves and stems, as well as the resveratrol content of shoots under blue light, were always higher than under red LED or fluorescent light. Moreover, when samples were exposed under the one-week blue light condition at a double intensity (100 µmol photon/m²/sec), the shoot clusters growing under blue LED also had a remarkably high total phenolic content and significantly high resveratrol levels compared to the two other treatments. The roles of endogenous growth regulators in shoot clusters under different lighting conditions were also analyzed and discussed.