Growth and physiological responses of Panax ginseng seedlings as affected by light intensity and photoperiod

Abstract

The effects of light intensity and photoperiod, and their combination as daily light integrals (DLI) on the growth and physiological traits of Panax ginseng seedlings were investigated to establish a light environment for seedling production. Stratified seeds of Panax ginseng 'Chunpoong' were sown. The seedlings were cultivated for 20 weeks using warm-white LEDs with DLI from 1.44 to 10.94 mol m(-2) d(-1), which are combinations of three light intensities (50, 120, and 190 mu mol m(-2) s(-1)) and three photoperiods (8, 12, and 16 h d(-1)) in a plant factory with artificial lighting (PFAL). As the DLI increased, the shoot length and leaf area were exponentially reduced after shoot development at both nine and 20 weeks of treatments. At nine weeks of treatment, the greater light intensity and longer photoperiod treatments, where the shoot established fastest, the photosynthetic products were translocated to the roots first and the dry weight distribution in the root increased as DLI increased. In the high light intensity and long photoperiod treatments, SPAD value, maximum (F-v/F-m), and minimum (F-v/F-o) quantum efficiency tended to decrease, and the photosynthetic traits were negatively affected over time with leaf senescence. The root growth rate in high light intensity with long photoperiod treatments seemed to lag behind that in low light intensity with short photoperiod treatments. As a result, this study found that a light intensity of 50 mu mol m(-2) s(-1) with a 12 h d(-1) photoperiod (DLI of 2.16 mol m(-2) d(-1)) was a suitable light environment for both shoot and root growth of ginseng seedlings. Further, the shoot establishment should be considered to design a light environment for ginseng seedling production in a PFAL.