Light-Emitting Diodes Modify Medicinal Quality of Mown Rabdosia rubescens, with Changes in Growth, Physiology, and Antioxidant Activity, under Drought Stress

Medicinal plants accommodated by understory habitats can easily suffer over-exploitation in the heavy harvest of natural products. It is necessary to develop a sustainable cultural protocol to provide high-quality stocks for efficient regeneration. Drought places stress on medicinal plants during their culture by limiting new sprout growth and reducing the quality of medicinal extracts. Artificial mediating approaches should be considered in a sustainable regime of medicinal plant culture to test the potential tradeoff between resistance to drought and production ability. In this study, Rabdosia rubescens seedlings were raised in three light-emitting diode (LED) spectra from red (71.7% red, 14.6% green, 13.7% blue), green (26.2% red, 17.4% green, 56.4% blue), and blue (17.8% red, 33.7% green, 48.5% blue) lights. Mown seedlings were subjected to a simulated drought event. Drought stressed the seedlings by reducing the growth, dry mass, nitrogen (N) uptake, and oridonin content. Mowing increased the oridonin content but decreased total C and N accumulation and the δ(13)C level. The red light benefitted starch accumulation only under the well-watered condition, and the green light induced an upregulation of δ(13)C but decreased antioxidant activity. Oridonin content was negatively associated with combined δ(13)C and catalase activity. Overall, either mowing or blue light can be recommended for the culture of R. rubescens to increase oridonin content, alleviating some of the negative consequences of drought.