부산대학교 도서관

Astragalus membranaceus, Adenophora triphylla, and Codonopsis lanceolata are three important medicinal plants in traditional oriental medicine, used for treatment of disorders and diseases including inflammation, tumor, and obesity. With an increase in demand for crude drugs and a decrease in wild resources, methods of commercial production of plug seedlings and phytochemicals are needed. It has been widely proven that light, temperature, and carbon dioxide (CO2) have great effects on growth and development of plants. However, the research is still insufficient on suitable cultivation conditions for high quality plug seedlings, and on how those factors influence the quality of plug seedlings of medicinal plants. In this thesis, in order to establish optimal production protocols for high-quality seedlings of A. membranaceus, A. triphylla, and C. lanceolata, the growth, development, and physiological characteristics of plug seedlings were investigated from an individual to a molecular level.In the experiment of supplemental light source, plug seedlings were cultivated in a greenhouse under supplemental light intensity of 120 μmol•m-2•s-1 photosynthetic photon flux density (PPFD) provided by either high pressure sodium (HPS), metal halide (MH), far-red (FR), white LED (red: green: blue = 2:4:3, LED-w), or mixed (red: green: blue = 4:1:4) LED (LED-mix). The LED-mix, with a higher percentage of red and blue light, significantly increased stem diameter, biomass, specific leaf weight, root: shoot ratio, chlorophyll content, and stomata density. The LED-mix also promoted accumulation of soluble sugar, starch, total phenols, and flavonoids. Moreover, the expression of photosynthetic proteins and genes in plug seedlings was also enhanced by LED-mix. In addition, the LED-mix alleviated the oxidative damages by improving enzymatic and non-enzymatic antioxidant systems. Collectively, these results suggest that the LED-mix was the optimal supplemental light source for the production of highest quality plug seedlings of A. triphylla and C. lanceolata.In the experiment of supplemental lighting duration, uniform plug seedlings were cultured under 12, 16, or 20 hours of duration with the same supplemental light intensity of 100 μmol•m-2•s-1 PPFD. The supplemental lighting for 16 h greatly enhanced the quality of plug seedlings with highest biomass, stem diameter, and Dickson’ quality index. Moreover, primary and secondary metabolites including soluble sugar, starch, total phenols and flavonoids were increased by 16 h of lighting as compared to 12 or 20 h. Importantly, an overlong lighting (20 h) had a negative effect on leaf health with visible damages and lower vegetation indexes. In addition, supplemental lighting for 16 h had a beneficial effect on photosynthesis by increasing the chlorophyll content, quantum yield, and stomatal conductance. Therefore, the results strongly indicated that 16 h is an optimal supplemental lighting duration for growth and development of plug seedlings of A. membranaceus and C. lanceolata.In the shading experiment, plug seedlings were grown in a glasshouse with 0, 35 or 55% shading of the sunlight during the day time. An increase in a shading level contributed to degradation of seedling quality with curving, thin shoots and less roots with incomplete root ball formation. Moreover, shoot and root biomass, stem diameter, specific leaf weight, ratio of shoot biomass to shoot length, ratio of root biomass to root length, and ratio of root biomass to shoot biomass were lower in the 35 and 55% shading than those in the not shaded treatment. However, lengths of the shoot, epicotyl, hypocotyl, and internode in the 55% shading were significantly greater than those in the 0% shading, implying that shading accelerated the height growth of seedlings. In conclusion, plug seedlings of A. membranaceus and C. lanceolata needed to be grown under not shaded conditions for quality enhancement.In the experiment of average daily temperature, plug seedlings grown under three day/night temperature regimes, 20/20, 25/15, and 20/15°C. The 25/15°C significantly upgraded the quality of plug seedlings by increasing shoot and root dry weights, stem diameter, and root: shoot ratio. Moreover, the contents of soluble sugar, starch, total phenols, and flavonoids were enhanced in the 25/15°C as compared with those in the other treatments. Furthermore, a lower hydrogen peroxide content and decreased activities of antioxidant enzymes were observed in plug seedlings of A. membranaceus and A. triphylla grown in the 25/15°C. Additively, 25/15°C significantly increased the chlorophyll content, quantum yield, and stomatal conductance in C. lanceolata. Therefore, the results suggested that the 25/15°C day/night temperature is the most suitable temperature regime for the growth and physiological development of plug seedlings of A. membranaceus, A. triphylla, and C. lanceolata.In the experiment of night temperature, uniform plug seedlings were cultivated in three environment-controlled chambers with day/night temperature of 25/10, 25/15 or 25/20℃. The night temperature of 15℃ remarkably enhanced the quality of plug seedlings by increasing shoot, root and leaf dry weights, and by promoting stem diameter and Dickson’ quality index. This temperature also stimulated and increased contents of primary and secondary metabolites, including soluble sugar, starch, total phenols and flavonoids. In addition, increase in chlorophyll content and stomatal conductance was found in the night temperature of 15℃, implying that 15℃ was beneficial for photosynthesis. Taken together, the results suggested that 15℃ is an optimal night temperature for growth and development of plug seedlings of A. membranaceus and C. lanceolata.In the experiment of difference between day and night temperatures (DIF), uniform plug seedlings were cultured in three environment-controlled chambers under an average daily temperature of 20°C with negative (-10°C), zero, or positive (+10°C) DIFs. The positive DIF significantly increased biomass of the shoot, root and leaf, stem diameter, and Dickson’ quality index, resulting in an enhancement of seedling quality. Moreover, contents of primary and secondary metabolites, including soluble sugar, starch, total phenols and flavonoids, were obviously increased with an increasing DIF with the maximum found in +10°C DIF. Furthermore, increase in chlorophyll content and stomatal conductance was obtained in the positive DIF, indicating that positive DIF was in favor of photosynthesis. Collectively, the results suggested that a positive DIF (+10℃) is recommendable for enhancing quality of plug seedlings of A. membranaceus and C. lanceolata.In the experiment of CO2 enrichment, uniform plug seedlings were grown in growth chambers at a CO2 level of either 350 (ambient), 700, or 1,050 μmol•mol-1. The elevated CO2 markedly increased the stem diameter, specific leaf weight, and chlorophyll content in all three species. The highest dry weight was found in the 700 and 1,050 µmol•mol-1 CO2 for A. triphylla and C. lanceolata, and A. membranaceus, respectively. The primary and secondary metabolites in A. membranaceus and A. triphylla were also affected by CO2 level, and greatest contents of soluble sugar, starch, protein, total phenols and flavonoids were observed in the 700 µmol•mol-1 CO2. The greatest stomatal density and aperture in A. triphylla were found in the 700 µmol•mol-1 CO2, suggesting the greatest photosynthesis. Therefore, the data suggested that enriched CO2 at 700 µmol•mol-1 is recommendable for growth and development of plug seedlings of A. membranaceus, A. triphylla, and C. lanceolata.In the experiment of CO2 and supplemental light source, uniform plug seedlings were grown in a glasshouse under no (control) or one of the three supplemental light sources [high pressure sodium (HPS), metal halide (MH), or mixed light emitting diode (LED-mix)] combined with one of three levels of CO2 (350, 700, or 1,050 μmol•mol-1). The supplemental light intensity used was 100 μmol•m-2•s-1 PPFD and lighting time (also the CO2 enrichment time) was 10:00 pm-2:00 am every day. The supplemental lighting either with LED, MH, or HPS greatly improved the seedling quality with increased dry weights of the shoot, root and leaf, stem diameter, leaf area, and Dickson’ quality index as compared with the control in both species. An enriched CO2 at 1,050 μmol•mol-1 increased root and leaf dry weights, stem diameter, and DQI as compared to the other two levels. The LED combined with 1,050 μmol•mol-1 CO2 increased content of both soluble sugar and starch. However, an enriched CO2 at 700 μmol•mol-1 was beneficial for accumulation of total phenols and flavonoids. Furthermore, LED combined 700 μmol•mol-1 CO2 increased chlorophyll, quantum yield, and stomata conductance at daytime, while stomatal conductance at nighttime was the greatest under LED with 1,050 μmol•mol-1 CO2. In conclusion, the data suggest that LED combined with 1,050 μmol•mol-1 CO2 is recommended for growth and development of plug seedlings of A. membranaceus and C. lanceolata.