Effects of Light Intensity on the Growth

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Nov 4, 2016 - medicinal-ingredient yields, Epimedium was exposed to five levels of light intensity until harvest time. Leaf dry biomass under L4 was the highest among different light ..... Sufficient water was provided for plants once every four days .... in ligustrum vulgare leaves under contrasting sunlight irradiance.

molecules Article

Effects of Light Intensity on the Growth, Photosynthetic Characteristics, and Flavonoid Content of Epimedium pseudowushanense B.L.Guo Junqian Pan and Baolin Guo * Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100193, China; [email protected] * Correspondence: [email protected]; Tel.: +86-139-1146-9895; Fax: +86-105-783-3172 Academic Editor: Derek J. McPhee Received: 7 October 2016; Accepted: 2 November 2016; Published: 4 November 2016

Abstract: Epimedium pseudowushanense B.L.Guo is used in traditional medicine as an aphrodisiac and to strengthen muscles and bones. Several recent reports have shown that flavonoids from Epimedium also significantly affect the treatment of breast cancer, liver cancer, and leukemia. However, few studies have examined the medicinal-ingredient yield of Epimedium, a light-demanding shade herb, under different light intensities. To investigate the effects of light intensity on medicinal-ingredient yields, Epimedium was exposed to five levels of light intensity until harvest time. Leaf dry biomass under L4 was the highest among different light treatments. L4 was also associated with the highest net photosynthetic rate. Quantification of epimedin A, epimedin B, epimedin C, and icariin showed that L3 produced the highest amount of epimedin C, and that flavonoid content responded to light levels differently. Results indicated that L3 and L4 were the optimal light levels for medicinal-ingredient yield. Keywords: Epimedium pseudowushanense B.L.Guo; light intensity growth; photosynthetic characteristics; flavonoid content; medicinal-ingredient yield

1. Introduction Epimedii Folium, commonly called Yinyanghuo, is an important perennial shade herb in traditional Chinese medicine. Epimedium belongs to the Berberidaceae family and is widely used as an aphrodisiac and to strengthen muscles and bones. Epimedium leaves contain high amounts of flavonoid glycosides, such as epimedin A, epimedin B, epimedin C, and icariin [1,2]. Recent reports have shown that flavonoids from Epimedium significantly affect the treatment of breast cancer, liver cancer, and leukemia [3–5]. The recognition of the health benefits of Epimedium has increased its market demand. However, its resource recycling rate is low and environmentally dependent. Furthermore, its natural sources are endangered, further increasing prices. Commercial culture can address resource constraints of Epimedium. E. pseudowushanense B.L.Guo is an important resource of Epimedii Folium and is the first Epimedium species introduced and cultivated in Guizhou Province, China. Light is an important environmental factor influencing plant growth, development, and secondary metabolism [6]. Under high light conditions, certain plant species, such as bayberry trees, do not grow because light irradiance decreases photosynthetic rates [7]. Therefore, all plants have their own optimal light intensity ranges for growth. Light intensity that is too high or too low impacts morphology, photosynthetic physiology, and secondary metabolite production. These characteristics are closely related to medicinal plant productivity. For example, Ma and others [8] reported that Camptotheca acuminata grown under 75% irradiance had significantly greater height, net photosynthetic rate (Pn), stomatal conductance (gs), total aboveground biomass, and chlorophyll fluorescence than plants grown under 100% (1500 ± 30 µmol·m−2 ·s−1 ), 50%, and 25% irradiance. Molecules 2016, 21, 1475; doi:10.3390/molecules21111475

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Molecules 21, 1475of different flavonoids varies according to the structure and specific flavonoids 2 ofare 12 The2016, function

involved for instance in limiting exogenous microbial growth, helping generate new fruits or leaves, providing light protection, andflavonoids enhancingvaries antioxidant defense [9,10]. Qualitative and quantitative The function of different according to the structure and specific flavonoids composition of flavonoids varies under different environments [9]. Changes in light intensity may are involved for instance in limiting exogenous microbial growth, helping generate new fruits influence because the flavonoid hydroxyl groups on the[9,10]. A and Qualitative B rings varyand in or leaves, flavonoid providingcontent light protection, and enhancing antioxidant defense number and position. Several studies have shown that high light irradiance promotes the quantitative composition of flavonoids varies under different environments [9]. Changes in light biosynthesis flavonoids, such as dihydroxy B-ring-substituted flavonoids (luteolin and intensity mayofinfluence flavonoid content because the flavonoid hydroxyl groups on the7-OA and B quercetin 3-O-glycosides) but does not influence the biosynthesis of monohydroxy B-ring-substituted rings vary in number and position. Several studies have shown that high light irradiance promotes flavonoids (pigenin 7-O- and kaempferol 3-O-glycosides) [11–14]. Pacheco and others [15] 7-Oreported the biosynthesis of flavonoids, such as dihydroxy B-ring-substituted flavonoids (luteolin and that Piper aduncum grown under 50% natural light irradiance had higher total flavonoid concentration quercetin 3-O-glycosides) but does not influence the biosynthesis of monohydroxy B-ring-substituted than those (pigenin grown under 100% natural irradiance. Based [11–14]. on thesePacheco reports and and others the harvest time of flavonoids 7-O- and kaempferol 3-O-glycosides) [15] reported E. pseudowushanense, the present study exposed Epimedium to five different light intensities for that Piper aduncum grown under 50% natural light irradiance had higher total flavonoid concentration 60 days. than those grown under 100% natural irradiance. Based on these reports and the harvest time of In the natural environment, E. pseudowushanense grows in woodlands, scrub, and forest E. pseudowushanense, the present study exposed Epimedium to five different light intensities for 60edges. days. In commercial culture, E. pseudowushanense seedlings are usually shade-grown by a simulated wild In the natural environment, E. pseudowushanense grows in woodlands, scrub, and forest edges. cultivation method. However, our understanding of are the usually photosynthesis and flavonoid content of In commercial culture, E. pseudowushanense seedlings shade-grown by a simulated wild E. pseudowushanense under shade management is limited. This study aims to determine the optimal cultivation method. However, our understanding of the photosynthesis and flavonoid content of light conditions for commercial Epimedium production. This study alsoaims aimstotodetermine investigate flavonoid E. pseudowushanense under shade management is limited. This study the optimal accumulation different light intensities improve propagation and light conditionsinforEpimedium commercialunder Epimedium production. This studytoalso aims to its investigate flavonoid cultivation. The results of the present study may contribute to the scientific culture and management accumulation in Epimedium under different light intensities to improve its propagation and cultivation. of as present well asstudy provide reference to forthe other Epimedium We anticipate that our TheEpimedium, results of the maya contribute scientific culturespecies. and management of Epimedium, results will improve our understanding of the changes in photosynthetic parameters and as well as provide a reference for other Epimedium species. We anticipate that our results will improve concentrations of secondary metabolites in Epimedium under different light treatments. Our results our understanding of the changes in photosynthetic parameters and concentrations of secondary will providein aEpimedium sound theoretical foundation for the standardized cultivation this theoretical important metabolites under different light treatments. Our results will provide aofsound medicinal plant. foundation for the standardized cultivation of this important medicinal plant. 2. 2. Results Results 2.1. Effects of Light Intensity on Plant Growth Clear external differences were observed among plants grown under 60 days of different light intensities. Compared Compared with with high high light light intensities intensities (L3, (L3, L4, L4, and and L5), L5), leaf areas were higher under low light intensities intensities (L1 (L1and andL2). L2).L2 L2resulted resultedininthe thehighest highestleaf leaf area. Light intensity had different effects area. Light intensity had different effects on onpseudowushanense E. pseudowushanense growth: L3,and L4,L5 and L5 resulted in number higher number of branches. On the E. growth: L3, L4, resulted in higher of branches. On the contrary, contrary, and L2in resulted higher SPAD water The content. The of number of branches under L3, L1 and L2L1 resulted higher in SPAD and waterand content. number branches under L3, L4, and L4, and L5 were(p156.3% (p187.5% < 0.05),(p187.5% < 0.05), and(p203.1% < 0.05)respectively, higher, respectively, than L5 were 156.3% < 0.05), < 0.05),(pand 203.1% < 0.05)(phigher, than of plants of plants grown SPADunder values L1were and L2 were < 0.05) and(p54.3% (p higher, < 0.05) grown under L1.under SPADL1. values L1under and L2 53.1% (p53.1% < 0.05)(pand 54.3% < 0.05) higher, respectively, than ingrown plants under grownL5. under L5.content Water content responded similarly. The highest respectively, than in plants Water responded similarly. The highest values valuesobserved were observed inunder plantsL1 under the were lowest inunder plantsL5 under L5 (Figure 1). were in plants and L1 theand lowest inwere plants (Figure 1).

Figure 1. Cont.

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Figure 1.1.Morphological Morphological parameters E. pseudowushanense light intensities. Figure parameters of E.ofpseudowushanense under under differentdifferent light intensities. The data The data are expressed as mean ± SD. Different letters indicate significant differences between light 1. Morphological of E.indicate pseudowushanense different lightlight intensities. areFigure expressed as mean ± SD.parameters Different letters significant under differences between intensity intensity treatments n = ±30. The data are< expressed as mean SD. Different letters indicate significant differences between light treatments (p 0.05);(p n 0.05). observed under L4. No differences were observed treatments(p(p> 0.05). > 0.05). were observed under L4.significant No significant differences were observedbetween between other other treatments Compared with L1, intercellular CO 2 concentration (Ci) decreased by 33.1% (p < 0.05), 34.3% Compared with L1, L1, intercellular CO2CO concentration (Ci) decreased by 33.1% (p < 0.05), < 0.05), Compared with intercellular 2 concentration (Ci) decreased by 33.1% (p

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