Growth responses of soybean (Glycine max L.) seedlings as affected by monochromic or mixture radiation provided by light-emitting diode

Proceedings, 6th IFAC Conference on Bio-Robotics Proceedings, 6th IFAC Conference on Bio-Robotics Proceedings, IFAC Conference on Bio-Robotics Available online at www.sciencedirect.com Beijing, China,6th July 13-15, 2018 Proceedings, IFAC Conference on Beijing, China,6th July 13-15, 2018 Proceedings, 6th IFAC Conference on Bio-Robotics Bio-Robotics Beijing, July 13-15, 2018 Beijing, China, China,6th July 13-15, 2018 Proceedings, IFAC Conference on Bio-Robotics Beijing, China, July 13-15, 2018 Beijing, China, July 13-15, 2018

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IFAC PapersOnLine 51-17 (2018) 770–777

Growth responses of soybean (Glycine max L.) seedlings as affected by monochromic Growth responses of soybean (Glycine max L.) seedlings as affected by monochromic Growth responses of soybean (Glycine max L.) seedlings as affected by monochromic Growth responses of soybean (Glycine max L.) seedlings as affected by monochromic or mixture radiation provided by light-emitting diode or mixture radiation provided by light-emitting diode Growth responses of soybean (Glycine max L.) seedlings as affected by monochromic or mixture radiation provided by light-emitting diode or mixture radiation provided by light-emitting diode or mixture radiation provided by light-emitting diode Zhiyu Ma1, Hai Nian2,3, Shaoming Luo1, Qibin Ma2,3,

1 2,3 1 2,3 Zhiyu Ma ,, Hai Nian Luo Ma 2,3 1 2,3 2,3, Shaoming 1, Qibin 2,3, Zhiyu Ma111Yanbo Nian Shaoming Luo Qibin Ma 2,3,, 2,3 1,,2,3* 2,3,, Zhiyu ,, Hai Hai Shaoming Luo Qibin Ma ，Yinghui Mu Cheng 2,3 2,3* Zhiyu Ma Ma1Yanbo Hai Nian Nian , Shaoming Luo , Qibin Ma , ，Yinghui Mu Cheng 2,3 2,3* 2,3 1 ，Yinghui Mu Cheng Zhiyu Ma Yanbo , Hai Nian Shaoming Luo Qibin Ma2,3, 510225, 2,3 2,3* ，Yinghui Mu,2,3* Yanbo Cheng, 2,3 1.Zhongkai University of Agriculture and Engineering, Guangzhou ，Yinghui Mu Yanbo Cheng 1.Zhongkai University of Agriculture and Engineering, Guangzhou 510225, 1.Zhongkai University of Agriculture and 510225, ，Yinghui Mu2,3* Guangzhou Yanbo Cheng2,3 1.Zhongkai University ofUniversity, Agriculture and Engineering, Engineering, Guangzhou 510225, 2.South China Agricultural College of Agriculture, Guangzhou 510642, 1.Zhongkai University of Agriculture and Engineering, Guangzhou 510225, 2.South China Agricultural University, College of Agriculture, Guangzhou 510642, 2.South China Agricultural University, College of Agriculture, Agriculture, Guangzhou 510642,China 1.Zhongkai University of Agriculture and Engineering, Guangzhou 510225, 2.South China Agricultural University, College of Guangzhou 510642, 3.Guangdong Sub-center of National Soybean Improvement Center, Guangzhou 510642, 2.South China Agricultural University, College of Agriculture, Guangzhou 510642,China 3.Guangdong Sub-center of National Soybean Improvement Center, Guangzhou 510642, 3.Guangdong Sub-center of National National SoybeanCollege Improvement Center, Guangzhou Guangzhou 510642, China 2.South China Agricultural University, of Agriculture, Guangzhou 510642,China 3.Guangdong Sub-center of Soybean Improvement Center, 510642, 3.Guangdong Sub-center of National Soybean Improvement Center, Guangzhou 510642, China 3.Guangdong Sub-center of National Soybean Improvement Center, Guangzhou 510642, China Abstract: The light emitting diodes (LEDs), as a source of monochromic light, has been widely used in the field field of of agriculture agriculture Abstract: The The light light emitting emitting diodes diodes (LEDs), (LEDs), as as aa source source of of monochromic monochromic light, light, has has been been widely widely used used in in the the Abstract: field of agriculture agriculture Abstract: The light emitting diodes (LEDs), as a source of monochromic light, has been widely used in the field of and horticulture. We conducted a pot experiment to investigate the effect of LEDs (W, B, R1:B1:W1, R3:B1, R5:B1, R6:B1 and and Abstract: The light emitting diodes (LEDs), as a source of monochromic light, has been widely used in the field of agriculture and horticulture. horticulture. We We conducted conducted aa pot pot experiment experiment to to investigate investigate the the effect effect of of LEDs LEDs (W, (W, B, B, R1:B1:W1, R1:B1:W1, R3:B1, R3:B1, R5:B1, R5:B1, R6:B1 R6:B1 and and Abstract: The light emitting diodes (LEDs), as a source of monochromic light, has been widely used in the field of agriculture and horticulture. We conducted a pot experiment to investigate the effect of LEDs (W, B, R1:B1:W1, R3:B1, R5:B1, R6:B1 and R) on growth and photosynthesis of soybean (Glycine max L. viz. Huachun 6 (HC6), Huaxia 3 (HX3) and Guixiadou 2 (GXD2)) andon horticulture. conducted a of potsoybean experiment to investigate theHuachun effect of 6LEDs (W,Huaxia B, R1:B1:W1, R3:B1, R5:B1, 2R6:B1 and R) growth and andWe photosynthesis (Glycine max L. L. viz. viz. (HC6), (HX3) and and Guixiadou (GXD2)) R) on growth photosynthesis of soybean (Glycine max Huachun 6LEDs (HC6), Huaxia 33 (HX3) (HX3) Guixiadou 2R6:B1 (GXD2)) andon horticulture. We conducted potsoybean experiment to investigate thephotosynthetic effect of 6 (W,Huaxia B, of R1:B1:W1, R3:B1, R5:B1, and R) growth photosynthesis of (Glycine max viz. Huachun 3 and Guixiadou 2 seedlings. Theand agronomic traits, aphysiological physiological characteristics and capacity soybean seedlings were determined. determined. R) on growth and photosynthesis of soybean (Glycine max L. L. and viz. Huachun 6 (HC6), (HC6), Huaxia 3 (HX3)seedlings and Guixiadou 2 (GXD2)) (GXD2)) seedlings. The agronomic traits, characteristics photosynthetic capacity of soybean were seedlings. The agronomic traits, physiological characteristics and photosynthetic capacity of soybean seedlings were determined. R) on growth and photosynthesis of soybean (Glycine max L. viz. Huachun 6 (HC6), Huaxia 3 (HX3) and Guixiadou 2 (GXD2)) seedlings. The agronomic traits, physiological characteristics and photosynthetic capacity of soybean seedlings were determined. The result showed that root growth, photosynthetic pigment, plant height, stem diameter, hypocotyl length, epicotyl length, root seedlings. agronomic traits, physiological characteristics capacity of soybeanlength, seedlings were determined. The result result The showed that root root growth, photosynthetic pigment, and plantphotosynthetic height, stem stem diameter, diameter, hypocotyl epicotyl length, root root The showed that growth, photosynthetic pigment, plant height, hypocotyl length, epicotyl length, seedlings. traits, physiological characteristics and capacity soybean seedlings were dry weight weight andagronomic shoot dry weight were significantly affected with with light treatment. Pn was was of much higher and the the root determined. growth was The result showed that root growth, photosynthetic pigment, plant height, stem hypocotyl length, epicotyl length, The result The showed thatdry root growth, photosynthetic pigment, plantphotosynthetic height, stem diameter, diameter, hypocotyl length, epicotyl length, root root dry and shoot weight were significantly affected light treatment. Pn much higher and root growth was dry weight and shoot dry weight were significantly affected with light treatment. Pn was much higher and the root growth was The result showed that root growth, photosynthetic pigment, plant height, stem diameter, hypocotyl length, epicotyl length, root dry weight and shoot dry weight were significantly affected with light treatment. Pn was much higher and the root growth was much better under red/blue mixed light (R5:B1) than the other treatment. Photosynthetic pigment of each cultivar was different dry weight shoot dry weight with light treatment. Pn was pigment much higher andcultivar the rootwas growth was much betterand under red/blue mixedwere lightsignificantly (R5:B1) than thanaffected the other other treatment. Photosynthetic of each each different much better under red/blue mixed light (R5:B1) the treatment. Photosynthetic of different dry weight and shoot dry This weight were significantly affected with light and treatment. Pn was pigment much higher andcultivar theseedling rootwas growth much better under red/blue mixed light (R5:B1) the treatment. Photosynthetic pigment of cultivar was different under various treatments. study demonstrates that theother root growth photosynthetic capacity of each soybean couldwas be much better under red/blue mixed light (R5:B1) than than the other treatment. Photosynthetic pigment of each cultivar was different under various treatments. This study demonstrates that the root growth and photosynthetic capacity of soybean seedling could be under various treatments. This study demonstrates that the root and photosynthetic capacity of soybean seedling could be much better under red/blue mixed light (R5:B1) than treatment. Photosynthetic pigment of cultivar was different under various treatments. This study demonstrates thatthe theother root growth growth and photosynthetic capacityand of each soybean seedling could be regulated by light treatments. Therefore, it is important the effectiveness of light quality for growth morphogenesis of soybean under various treatments. This study demonstrates that the root growth and photosynthetic capacity of soybean seedling could be regulated by by light light treatments. treatments. Therefore, Therefore, it it is is important important the the effectiveness effectiveness of of light light quality quality for for growth growth and and morphogenesis morphogenesis of of soybean soybean regulated under various treatments. ThisTherefore, study demonstrates that the the effectiveness root growth and photosynthetic capacityand of morphogenesis soybean seedling be regulated by treatments. it of quality of soybean seedling. regulated by light light treatments. Therefore, it is is important important the effectiveness of light light quality for for growth growth and morphogenesis of could soybean seedling. seedling. regulated by light treatments. Therefore, it is important the effectiveness of light quality for growth and morphogenesis of soybean seedling. Keywords: Light quality; Agronomic traits; Physiological characteristic; Root traits; Photosynthetic parameters seedling. Keywords: Light quality; Agronomic Agronomic traits; Physiological characteristic; Root traits; traits; Photosynthetic parameters © 2018, IFAC (International Federationtraits; of Automatic Control) Hosting by Elsevier Ltd. Photosynthetic All rights reserved. Keywords: Light quality; Physiological characteristic; Root parameters seedling. Keywords: Keywords: Light Light quality; quality; Agronomic Agronomic traits; traits; Physiological Physiological characteristic; characteristic; Root Root traits; traits; Photosynthetic Photosynthetic parameters parameters Keywords: Light quality; Agronomic traits; Physiological characteristic; Root traits; Photosynthetic (Imaptiens walleriana), and parameters petunia (Petunia hybrid) 1. INTRODUCTION hybrid) (Imaptiens walleriana), and (Petunia 1. INTRODUCTION INTRODUCTION (Imaptiens walleriana), and petunia petunia (Petunia hybrid) 1. (Imaptiens walleriana), and petunia (Petunia hybrid) (Wollaeger and Runkle, 2014), cymbidium (Tanaka et 1. INTRODUCTION (Imaptiens walleriana), and petunia (Petunia hybrid) (Wollaeger and Runkle, 2014), cymbidium (Tanaka et al., al., INTRODUCTION Light is the energy1.source for photosynthesis. But major light 1998), (Wollaeger and Runkle, 2014), cymbidium (Tanaka et al., (Imaptiens walleriana), and petunia (Petunia hybrid) (Wollaeger and Runkle, 2014), cymbidium (Tanaka et lettuce (Johkan et al., 2010), rice (Ohashi-Kaneko Light is is the the energy energy1.source source for photosynthesis. photosynthesis. But But major major light light (Wollaeger INTRODUCTION Runkle, 2014), (Tanaka etet al., 1998), lettuce lettuceand (Johkan et al., al., 2010),cymbidium rice (Ohashi-Kaneko (Ohashi-Kaneko et al., Light for Light is the energy source for photosynthesis. But major factors affecting plant growth and development are light 1998), (Johkan et 2010), rice et al., Light is affecting the energyplant sourcegrowth for photosynthesis. But major light 2006), 1998), (Johkan et 2010), rice (Ohashi-Kaneko (Wollaeger and Runkle, 2014), cymbidium (Tanaka etet Spinach, Arabidopsis (Zhang, al., as as factors and are 1998), lettuce lettuce (Johkan et al., al., 2010), riceet et al., al., 2006), Spinach, Arabidopsis (Zhang, et(Ohashi-Kaneko al., 2011), 2011), as well well as factorsis affecting affecting plant growth and development development are light 2006), Light the energy source for photosynthesis. But major factors plant growth and are intensity, light quality and photoperiod. Generally, traditional Spinach, Arabidopsis (Zhang, et al., 2011), as well as 1998), lettuce (Johkan et al., 2010), rice (Ohashi-Kaneko et al., factors affecting plant growth and development development are light light strawberry 2006), Spinach, Arabidopsis (Zhang, et al., 2011), as well as (Nhut et al., 2003). intensity, light quality and photoperiod. Generally, traditional 2006), Spinach, Arabidopsis (Zhang, et al., 2011), as well as strawberry (Nhut et al., 2003). intensity, light quality and photoperiod. Generally, traditional factors affecting plantand growth and development are light intensity, light quality photoperiod. Generally, traditional artificial light sources, such as incandescent, fluorescent, and 2006), strawberry (Nhut et al., 2003). Spinach, Arabidopsis et al., 2011), as well as intensity, lightsources, quality and Generally, traditional strawberry (Nhut et 2003). artificial light light suchphotoperiod. as incandescent, incandescent, fluorescent, and However, strawberry (Nhutstudies et al., al., showed 2003).(Zhang, artificial sources, such as fluorescent, and more that the essential intensity, light quality and photoperiod. Generally, traditional artificial light sources, such as incandescent, fluorescent, and halogen lamps, were used to study the light intensity, light However, more studies showed that the essential light light qualities qualities (Nhut et al., 2003). artificial light sources, suchto as study incandescent, fluorescent, and strawberry halogen lamps, were used the light intensity, light However, more studies showed that the essential light qualities halogen lamps, were used to study the light intensity, light However, more studies showed that the essential light qualities of plant growth is discontinuous, blue and red light are artificialorlamps, light sources, such incandescent, and However, quality photoperiod, which are the the composite spectrumlight halogen were to study light intensity, more studies showed thatblue the essential of plant plant growth growth is discontinuous, discontinuous, and red red light lightqualities are the the halogen lamps, were used used toasare study the lightfluorescent, intensity, light quality or photoperiod, which the composite spectrum and of is blue and light are the quality or photoperiod, which are the composite spectrum and However, more studies showed that the essential light qualities of plant growth is discontinuous, blue and red light are the essential light for normal growth and development of halogen to wavelength. study light quality or photoperiod, which are the composite spectrum and very difficult to were get aused single Theintensity, light-emitting plant growth discontinuous, and red lightofareplant the essential light for foris normal normal growth blue and development development plant quality orlamps, photoperiod, which are the the composite spectrumlight and of very difficult to get a single wavelength. The light-emitting essential light growth and of plant very difficult to get aa single wavelength. The essential light for growth and development of 2007; plant plant discontinuous, andLee red et light the (Heo et al., Kurepin et 2007; al., quality or photoperiod, which are athemonochromatic composite spectrum and of very difficult to getcan single wavelength. The light-emitting light-emitting diode (LED) light provide spectrum essential light2002; foris normal normal growth and development plant (Heo et growth al., 2002; Kurepin et al., al.,blue 2007; Lee et al.,ofare 2007; very get a single wavelength. The light-emitting diodedifficult (LED) to light can provide monochromatic spectrum Shimizu (Heo et al., 2002; Kurepin et al., 2007; Lee et al., 2007; essential light for normal growth and development of plant diode (LED) light can provide aaa monochromatic spectrum (Heo et al., 2002; Kurepin et al., 2007; Lee et al., 2007; et al., 2011; Li et al., 2013; Wollaeger and Runkle, very difficult to get a single wavelength. The light-emitting diode (LED) light can provide monochromatic spectrum light, such as red and blue light, which can use to investigate et et al.,al., 2002; et 2013; al., 2007; Lee etandal.,Runkle, 2007; Shimizu 2011;Kurepin Li et et al., al., Wollaeger diode (LED) lightand can provide a monochromatic spectrum (Heo light, such such as red red blue light, which which can use use to to investigate investigate Shimizu et 2011; Li 2013; Wollaeger (Heo et al.,al., 2002; Kurepin et al., 2007; Lee etand al.,Runkle, 2007; light, as and blue light, can Shimizu et al., 2011; Li et al., 2013; Wollaeger and Runkle, Wollaeger and Runkle, 2015). diode (LED) light can provide a monochromatic spectrum 2014; light, such red and blue light, which can use to investigate the effect ofas light quality on the plant growth and development. Shimizu et al., 2011; Li et al., 2013; Wollaeger and Runkle, 2014; Wollaeger and Runkle, 2015). light, such as red and blue light, which can use to investigate the effect of quality on the plant growth and development. 2014; Wollaeger and Runkle, the effect effect of light light quality onof theLED plant growth and development. Shimizu et al., 2011; Li et al.,2015). 2013; Wollaeger and Runkle, 2014; Wollaeger and Runkle, 2015). light, such red and blue light, which can use development. to investigate Since 1990s, thequality effects light qualities have been LED the of on the plant growth and 2014; light Wollaeger andused Runkle, 2015). the effect ofaslight light quality onof theLED plant growth and development. can be not in Since 1990s, the effects light qualities have been Since 1990s, the effects of LED light qualities have been LED light can be used not only only in plant plant cultivation cultivation under under 2014; Wollaeger andused Runkle, 2015).in the effect of light quality on the plant growth and development. Since 1990s, the effects of LED light qualities have been studied on plant biology. LED is high-efficiency light for plant LED light can be not only plant cultivation under Since 1990s, the effectsLED of LED light qualities have been greenhouse, LED light can be used not only in plant cultivation under but also in crops breeding. In recent, LED light studied on plant biology. is high-efficiency light for plant LED light can be used not only in plant cultivation under greenhouse, but also in crops breeding. In recent, LED light studied on plant biology. LED is high-efficiency light for plant Since 1990s, the effects of energy-saving, LED light qualities have been studied on biology. LED is light for production because of their longer life, high has greenhouse, but also in crops breeding. In recent, LED light studied on plant plant biology. LED is high-efficiency high-efficiency light for plant plant LED light can be used not only in plant cultivation under greenhouse, but also in crops breeding. In recent, LED light been used in a homemade growth room design for low cost production because of their energy-saving, longer life, high greenhouse, but also in crops breeding. In recent, LED light has been used in a homemade growth room design for low cost production because of their energy-saving, longer life, high studied onefficiency, plant biology. LED is high-efficiency lightand forso plant production because of energy-saving, longer life, high luminous andtheir monochromatic spectrum on speed has been used in aaalso homemade growth room design for low cost production because of their energy-saving, longer life, high has been used in homemade growth room design for low cost greenhouse, but in crops breeding. In recent, LED light breeding; it enables 4-6 generations of wheat to be luminous efficiency, and monochromatic spectrum and so on has been used in a homemade growth room design for low cost speed breeding; it enables 4-6 generations of wheat to be luminous efficiency, and monochromatic spectrum and so on productionefficiency, because of energy-saving, longer life,et luminous and monochromatic spectrum and so on (Tennessen et al., 1994; Tanaka et al., 2008; Mitchell al., speed breeding; it enables 4-6 generations of wheat to be luminous efficiency, andtheir monochromatic spectrum and sohigh on grown has been used in a homemade growth room design for low cost speed breeding; it enables 4-6 generations of wheat to be in one year (Watson et al., 2017). Normally, (Tennessen et al., 1994; Tanaka et al., 2008; Mitchell et al., speed breeding; it enables 4-6 generations of wheat to be grown in one year (Watson et al., 2017). Normally, (Tennessen et al., 1994; Tanaka et al., 2008; Mitchell et al., luminous and Tanaka monochromatic spectrum and et so on conventional (Tennessen et al., al., 1994; Tanaka Mitchell et al., 2012). Asefficiency, an important factor et in al., light2008; environment, light grown in (Watson et 2017). Normally, (Tennessen et 1994; Mitchell al., speed ityear enables 4-6 method generations ofsunlight wheat to be grown breeding; in one one year (Watson et al., al.,used 2017). Normally, soybean breeding in 2012). As As an an important factor et in al., light2008; environment, light grown in one year (Watson et al., 2017). Normally, conventional soybean breeding method used sunlight in the the 2012). important factor in light environment, (Tennessen et important al., 1994; regulation Tanaka et function al., 2008; etlight al., field, quality exerts onMitchell plant growth, 2012). As an important factor in light environment, light conventional soybean breeding method used sunlight in the 2012). As an important factor in light environment, light grown in one year (Watson et al., 2017). Normally, conventional soybean breeding method used sunlight in the and only 2-3 generations of soybean can be achieved per quality exerts important regulation function on plant growth, conventional soybean breeding method used sunlight in the field, and only 2-3 generations of soybean can be achieved per quality exerts important regulation function on plant growth, 2012). As an important factor in light environment, light quality exerts important regulation function on plant growth, morphogenesis, photosynthesis and metabolism and so on field, and and onlysoybean 2-3Watson’s generations ofmethod soybean can be be achieved per quality exerts important regulation function on plant growth, conventional breeding used sunlight in per the field, only generations of can achieved year. If method in breeding, it morphogenesis, photosynthesis and metabolism and so field, only 2-3 2-3Watson’s generations of soybean soybean can be achieved morphogenesis, photosynthesis and metabolism and so on on year. and If applied applied method in soybean soybean breeding,per it quality exerts function on plant growth, morphogenesis, photosynthesis metabolism and so (Eskiits, 1992;important Heo et al.,regulation 2002; and Folta and Childers, 2008; Li should year. If applied Watson’s method in soybean breeding, it morphogenesis, photosynthesis and metabolism and so on on field, and only 2-3 generations of soybean can be achieved per year. If applied Watson’s method in soybean breeding, it accelerate the speed of soybean breeding, and shorten (Eskiits, 1992; Heo et al., 2002; Folta and Childers, 2008; Li applied Watson’s in breeding, soybean breeding, it (Eskiits, 1992;Previous Heo et al., al., 2002;indicated Foltametabolism and Childers, 2008; Li– year. shouldIfaccelerate accelerate the speed speed method of soybean soybean and shorten shorten morphogenesis, photosynthesis and and so on (Eskiits, 1992; Heo et 2002; Folta and Childers, 2008; Li et al., 2011). reports that red light (610 should the of breeding, and (Eskiits, 1992;Previous Heo et al., 2002;indicated Folta and Childers, should the of soybean and shorten year. Ifaccelerate applied Watson’s method in breeding, soybean breeding, it However, there few about the et al., al., 2011). 2011). reports that red light light2008; (610Li–– the should accelerate the speed speed soybean breeding, and shorten the period. period. However, there ofwas was few information information about the et Previous reports that red (610 (Eskiits, 1992; Heoplant et al., 2002;indicated Folta and Childers, 2008; et al., 2011). Previous reports indicated that red light (610 720 nm) increased biomass accumulation and stimulate the period. However, there was few information about the should accelerate the speed of soybean breeding, and shorten the period. However, there was few information about the of light quality on the growth of soybean. In this study, et al.,nm) 2011). Previous reports indicated that redand light (610Li– – effect 720 increased plant biomass accumulation stimulate the period. However, there was few about the effect of light light quality on on the growth growth of information soybean. In In this this study, 720 increased biomass accumulation and stimulate et al.,nm) 2011). Previous reports indicated that red(Jeong light (610 720 nm) increased plant biomass accumulation and stimulate development of theplant photosynthetic apparatus et al.,– we effect of quality the of soybean. study, 720 nm) increased biomass accumulation and stimulate period. However, there was few information about the effect of light quality on the growth of soybean. In this study, applied red, blue and different red-blue ratio LED light to development of the theplant photosynthetic apparatus (Jeong (Jeong et al., al., the effect of light quality on the growth of soybean. In this study, we applied red, blue and different red-blue ratio LED light to development of photosynthetic apparatus et 720 nm) increased plant biomass accumulation and suggested stimulate 2012; Wollaeger and Runkle, 2014). Other studies development of photosynthetic apparatus (Jeong et we applied red, blue and different red-blue ratio LED light to development of the the photosynthetic apparatus (Jeong et al., al., observe effect of light quality on the growth of soybean. In this study, we applied red, blue and different red-blue ratio LED light to how the light quality affect the growth of soybean. The 2012; Wollaeger and Runkle, 2014). Other studies suggested we applied red, blue and different red-blue ratio LED light to observe how the light quality affect the growth of soybean. The 2012; Wollaeger and Runkle, 2014). Other studies suggested development the photosynthetic (Jeong et al., we 2012; Wollaeger and Runkle, 2014). apparatus Other studies suggested that blue light of (400 – 500 nm) inhibits cell elongation, stomatal observe how the light quality affect the of 2012; Wollaeger Runkle, 2014). Other studies suggested applied different red-blue ratio LED lightThe to observe howred, the blue lightaand quality affectbasis the growth growth of soybean. soybean. The provide theoretical for breeding of that blue blue light (400 (400and 500 nm) inhibits inhibits cell elongation, stomatal results observe how the light affect the growth of soybean. results will will provide aquality theoretical basis for speed speed breedingThe of that light –– 500 500 nm) cell elongation, stomatal 2012; Wollaeger and Runkle, 2014). Other studies of suggested that blue light – nm) inhibits elongation, stomatal opening, leaf(400 expansion and stemcell expansion plants soybean. results will provide a theoretical basis for speed breeding of that blue light (400 – 500 nm) inhibits cell elongation, stomatal observe how the light quality affect the growth of soybean. The results will provide a theoretical basis for speed breeding of opening, leaf expansion and stem expansion of plants results will provide a theoretical basis for speed breeding of soybean. opening, leaf expansion expansion of plants that blue light – 500Sellaro nm)and inhibits elongation, opening, leaf expansion and stem expansion of plants (Gruszecki et (400 al., 2010; etstem al.,cell 2010). In addition, the results soybean. opening, leaf expansion and stem expansion ofstomatal plants will provide a theoretical basis for speed breeding of (Gruszecki et al., 2010; Sellaro et al., 2010). In addition, the soybean. (Gruszecki et al., al., 2010; Sellaro Sellaro etand al.,root 2010). In addition, addition, the soybean. opening, leaf expansion and stem expansion of plants (Gruszecki et 2010; et al., 2010). In the blue light could promote shoot biomass lettuce MATERIALS (Gruszecki et al., promote 2010; Sellaro etand al.,root 2010). In addition, the 2. soybean. blue light could shoot biomass of lettuce 2. MATERIALS MATERIALS AND AND METHODS METHODS blue light lightetcould could promote shoot and root biomass of lettuce (Gruszecki etal., al.,2010). 2010; Sellaro al.,blue 2010). Inred addition, the 2. (Johkan Therefore, and light are blue promote shoot root biomass of lettuce AND METHODS 2. MATERIALS AND blue lightet could promote shoot etand and root biomass of lettuce (Johkan al., 2010). Therefore, blue and red light are 2. MATERIALS AND METHODS METHODS (Johkan et al., 2010). Therefore, blue and red light are blue lightetconsidered could promote shoot andeffective root and biomass of lettuce (Johkan al., Therefore, blue red light are generally to be the most light irradiation Plant and growth 2. AND METHODS (Johkan al., 2010). 2010). Therefore, blue and red irradiation light are 2.1 generally etconsidered considered to be be the most most effective effective light 2.1MATERIALS Plant materials materials and growth conditions conditions generally to the light irradiation 2.1 Plant materials and growth conditions (Johkan et al., 2010). Therefore, blue and red light are generally considered to be the most effective light irradiation for plant growth. The physiological and morphological effects 2.1 Plant materials and growth conditions generally considered to be the mostand effective light irradiation 2.1 Plant materials and growth conditions for plant growth. The physiological morphological effects for plant growth. The physiological and morphological effects national soybean regional test generally considered be the moststudied effective irradiation for plant growth. The physiological and morphological effects of light quality have been widely in light plants, such as Three 2.1 Plant materials and growth conditions for plant quality growth. The to physiological and morphological effects Three national soybean regional test control control varieties varieties were were of light light have been widely studied in plants, such as Three national soybean regional test control varieties were widely studied in plants, such as of quality have been Three national soybean regional test control varieties were in this experiment. Huachun 6 (HC6) is aa spring and for light plant quality growth.have The physiological and morphological effects widely studied in plants, plants, such as used chrysanthemum (Zheng van studied Labeke, 2017), such tomato of light quality have beenand Three national soybean regional test control varieties were widely in as of been used in this experiment. Huachun 6 (HC6) is spring and chrysanthemum (Zheng and van Labeke, 2017), tomato used in this experiment. Huachun 66 (HC6) is aa3 (HX3) spring and tomato chrysanthemum (Zheng and van Labeke, 2017), planted soybean cultivar, while Huaxia Three national soybean regional test control varieties were used in this experiment. Huachun (HC6) is spring summer of light quality have been widely studied in plants, such as chrysanthemum (Zheng and van Labeke, 2017), tomato (Solanum lycopersicum), salvia (Salvia splendens), impatiens in this experiment. Huachunwhile 6 (HC6) is a3 (HX3) spring and and chrysanthemum (Zheng salvia and van Labeke, 2017),impatiens tomato used summer planted soybean cultivar, Huaxia (Solanum lycopersicum), (Salvia splendens), summer planted soybean cultivar, while Huaxia 3 (HX3) and (Solanum lycopersicum), (Salvia splendens), summer planted soybean Huaxia (HX3) in this experiment. Huachunwhile 6 (HC6) is a3 chrysanthemum (Zheng salvia and van Labeke, 2017),impatiens tomato used (Solanum salvia (Salvia splendens), impatiens summer planted soybean cultivar, cultivar, while Huaxia 3 spring (HX3) and and (Solanum lycopersicum), lycopersicum), salvia (Salvia splendens), impatiens summer planted soybean cultivar, while Huaxia 3 (HX3) and (Solanum lycopersicum), salvia (Salvia splendens), impatiens 2405-8963 © 2018, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

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IFAC BIOROBOTICS 2018 Beijing, China, July 13-15, 2018

Zhiyu Ma et al. / IFAC PapersOnLine 51-17 (2018) 770–777

Guixiadou 2 (GXD2) are summer planted soybean cultivar. The seeds were sown in 30 plastic pots (10 cm × 10 cm × 9.5 cm, five seeds per pot), with culture medium, which containing horticultural vermiculite and Canadian sphagnum peat moss (Terra-Lite Agricultural Mix; The Scotts Co., Marysville, Ohio). After sown, the pots were transferred to the growth chamber and arranged with different light treatment. Seven days after sown, three plants were kept per pot to grow better. The condition was a photosynthetic photon flux (PPF) of 180 ± 5 μmol·m-2 s-1 for 12 h, temperature at 25±2°C/19±2°C during day and night and the relative humidity at 60 ±5%.

calipers (Shanghai tool works Co., LTD. Shanghai, China) were used to measure the stem diameter. Fresh leaves were sampled and scanned with a scanner, then analyzed by using the special image processing software (Image–Pro Plus V6.0) to determine the total leaf area. After scanned, the leaves sample was used to analysis photosynthetic chlorophyll, soluble sugar and soluble protein contents. The rest were used to determine the root dry weight and shoot dry weight, . Roots sample was harvested and washed carefully, then scanned with scanner and analyzed with WinRHIZO (Version 2009b, Regent Instruments, Montreal, QC, Canada).

2.2 Lighting system

2.4 Statistical analysis

The seven light sources contained blue (peak = 437 nm)，red (peak = 660 nm) and near infrared (peak = 720 nm) LEDs. The intensities of these three LED types were adjusted to create seven light-quality treatments viz., W, B, R1:B1:W1, R3:B1, R5:B1, R6:B1, R. The spectral curve of eight treatments was measured by a spectroradiometer (FLA5000+, Flight Technology Co., Ltd. China) (Fig. 1). All light treatments were 12 h photoperiod (12 h light /12 h dark), canopy photosynthetic photon flux was set to 180 ± 5 μmol·m-2·s-1. In order to keep the same light intensity, the height of the LED light could be adjusted above the seedlings of soybean.

All data were collected by Microsoft Excel 2013 and analyzed using the SPSS 17.0 (SPSS Inc., Chicago, IL, USA). One-way analysis of variance (ANOVA) was used to test for significant differences among different treatment. Results were expressed as mean ± standard deviations with 5 replications and p values less than 0.05 were considered statistically significant.

3. RESULTS 3.1 Agronomic traits of soybean seedling Plant height, stem diameter, hypocotyl length, epicotyl length, total leaf area and shoot dry weight was significantly affected by light treatment, the interaction of light and cultivar was also substantially affected height, hypocotyl length and epicotyl length, soybean cultivars varied significantly regarding plant height (Fig. 2). Plant height was highest under R treatment and was lower under R1:B1:W1 treatment. It increased with the increasing of red light ratio (Fig 2A). Stem diameter was highest under R6:B1 treatment for GXD2 and HX3, and under R5;B1 for HC6. The lowest stem diameter was detected under R treatment for all cultivars. With the ratio of red light increasing, stem diameter was increased (Fig 2B). Hypocotyl length decreased with the increasing of red light ratio for GXD2, the highest hypocotyl length was investigated under R and W treatment for all cultivars (Fig 2C). Higher epicotyl length was observed for R and R6:B1 treatment, while lower epicotyl length was measured under R1:B1:W1 treatment (Fig 2D). The leaf area was the lowest under R treatment for all cultivars, the highest leaf area under R6:B1 for GXD2 and HC6, and under R5:B1 for HX3 (Fig 2E). The shoot dry weight highest under R3:B1 treatment for GXD2 and HX3, it was higher in W treatment than other R/B mixed light treatment and monochromic light treatment for GXD2 and it was convers for HX3. The highest shoot dry weight was HC6under W treatment but lowest under B treatment (Fig 2F). Soybean seedling agronomic traits were significantly affected by light quality. Compared with B and R/B combined light treatment, plant height, hypocotyl length, epicotyl length and, and it could decrease stem diameter, leaf area and shoot dry weight could be increased by R treatment.

300 R R 6 :B 1

200

R 1 :B 1 : W 1

gh

100

t

R 5 :B 1 R 3 :B 1

Li

R e la tiv e r a d ia tio n ( % )

400

B W

0 400

600

771

800

1000

1200

W a v e le n g th ( n m )

Fig1. The spectral distribution of seven light quality treatments delivered by blue (B; 437 nm) and red (R; 660 nm) LEDs 2.3 Measurements of growth and morphogenesis Three weeks after sown, the photosynthetic rates (Pn), stomatal conductance (Gs) and intercellular carbon dioxide concentration (Ci) in the top fully expanded leaves were measured by using a portable photosynthesis system (LI-6400, LI-COR, Lincoln, Nebraska, USA) with 5 replications. After that, ten plants were randomly selected and harvested to investigate the physical and chemical characters. The stem length and the internode were measured with ruler. The dial

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50

b

b 30

a

ab

a b

cd cd d e

20

b

dd

Stem Diameter (cm)

Plant height (cm)

40

0.3

A

a

b

cd c

cc d

10 0 HC6

bc b

bc b bc

b bc cd d d

Epicotyl length (cm))

Hypocotyl length (cm)

a

a

a

bcd cd

d

bcd cd d d

4 2 0 HC6

HX3

D

a 20

a

bc b

c

ab

cd c d cd

d

d

10

a

b

15

b

cd dd

e

e

5

HX3

GXD2

HC6

HX3

0.3

30 a

aa

a

a

a

Shoot dry weight (g)

a ab a abc bc bc c

F

E

a

Leaf area (cm2)

0.1

0 GXD2

20

HC6

c

25

C

a

10

25

GXD2

B ab b abab a bc

0.2

HX3

12

6

a ab ab ab bc c ab

0.0 GXD2

8

ab ab ab a a b ab

ab ab a ab b b b

15

10 5 0

a

ab 0.2

bb

b

b

a b

ab abc abc bc abc c

a

a b

b ab

b ab

0.1

0.0 GXD2

HC6 W B

HX3 R1:B1:W1

R3:B1

R5:B1

GXD2 R6:B1

HC6

HX3

R

Fig. 2 Effects of light quality on the agronomy traits of soybean seedling The vertical bars indicate the SD (n=5). Means with different letters within each panel are significantly different at the 5% level by Duncan. R3:B1 treatments. Red and blue combined light was benefit to the root growth of soybean seedlings, but high red light ratio could inhibit the root growth.

3.2 Root traits . The root length, surface area root volume and root dry mater weight was increased under red and blue combined light treatments (Table 1). The highest root length was observed under R5:B1 treatment. The highest root surface area and root volume of GXD2 was produced by R1:B1:W1 treatment, those of HC6 and HX3 under R5:B1 yielded. The highest root average diameter of GXD2 and HC6 was under R1:B1:W1 treatments, and that of HX3 under R5:B1 treatment. However, root average diameter of HX3 was increased with increasing of red light ratio. The highest root dry weight of GXD2 was found under B treatment, and that of HC6 and HX3 under

3.3 Photosynthetic parameters Pn was significantly higher under R1:B1:W1, R3:B1 and R5:B1 treatment than the other treatments, and it was highest under R5:B1 treatment for all cultivars (Fig. 3A). Pn was increased with the increasing of red light ratio, but as the redlight ratio continually getting much higher, Pn was conversely decreased. Pn was the lowest under R6:B1 treatment for all soybean cultivars. There was no difference between soybean cultivars.

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Table 1 Effects of light quality on root traits of soybean seedling Soybean

Light quality

Length (cm)

Surface Area (cm2)

GXD2

W B R1:B1:W1 R3:B1 R5:B1 R6:B1 R W B R1:B1:W1 R3:B1 R5:B1 R6:B1 R W B R1:B1:W1 R3:B1 R5:B1 R6:B1 R Light Soybean Soybean*light

217.04±43.08c 231.32±40.54c 355.99±34.27ab 397.50±26.53a 403.04±9.46a 280.39±45.53bc 280.23±20.37bc 324.48±30.43ab 342.67±41.46ab 322.73±47.65ab 387.04±51.68ab 469.51±61.59a 350.02±56.09ab 265.88±53.33b 347.37±42.04ab 274.02±48.26b 347.18±49.02ab 302.32±25.31ab 424.45±40.30a 404.30±42.21a 261.42±11.57b 0.000 0.154 0.240

35.09±6.05d 36.09±6.58d 66.60±7.07a 60.96±4.01abc 63.30±2.86ab 47.21±7.70bcd 43.35±2.31cd 51.79±5.67ab 58.54±6.25ab 65.76±10.01ab 67.24±9.03ab 80.20±11.03a 56.70±7.80ab 44.67±7.27b 55.06±6.79bc 46.03±8.61c 57.14±7.80bc 50.65±4.54bc 78.62±9.29a 69.66±7.44ab 47.15±2.56c 0.000 0.021 0.278

HC6

HX3

ANOVA (P value)

Average diameter (mm) 0.53±0.03b 0.50±0.01b 0.60±0.03a 0.49±0.01b 0.50±0.01b 0.54±0.01b 0.50±0.01b 0.51±0.02b 0.55±0.02b 0.65±0.05a 0.55±0.01ab 0.54±0.02b 0.52±0.03b 0.55±0.05ab 0.50±0.00c 0.53±0.01bc 0.53±0.01c 0.53±0.01bc 0.59±0.03a 0.55±0.01abc 0.57±0.01ab 0.004 0.020 0.010

Root volume (cm3) 0.46±0.07c 0.45±0.09c 1.00±0.13a 0.75±0.05b 0.79±0.06b 0.63±0.11bc 0.54±0.02bc 0.66±0.08b 0.80±0.08ab 1.08±0.20a 0.93±0.13ab 1.09±0.17a 0.73±0.09ab 0.61±0.09b 0.69±0.09b 0.62±0.12b 0.75±0.10b 0.68±0.07b 1.17±0.18a 0.96±0.11ab 0.68±0.05b 0.000 0.005 0.132

Root dry weight (mg) 32.58±1.48a 33.68±3.98a 30.25±2.80ab 30.33±2.30ab 22.95±2.91b 22.85±1.08b 10.45±0.80c 22.80±1.85bc 30.20±3.21b 30.58±2.46b 44.40±3.15a 19.28±1.97c 26.30±2.99bc 24.33±1.13bc 14.20±1.97d 20.65±1.28cd 31.13±2.10b 39.80±3.36a 30.83±3.14b 30.78±1.94b 22.08±1.80c 0.000 0.512 0.000

Values are means ± SD (n=5). Means with different letters are significantly different at the 5% level by Duncan in each column within each soybean cultivar.

Similar to Pn, Gs was increased with the increasing of red light ratio, it was highest under R1:B1:W1 treatment for GXD2 and HC6, and it decreased when red-light ratio continually getting much higher. For HX6, the highest Gs was found under R5:B1 treatment, but there was no significant difference with R1:B1:W1 or R3:B1 treatment. The lowest Gs was observed under R6:B1 treatment, even lower than W treatment (Fig. 3B).

The highest soluble starch content in GXD2 and HX3 was measured under R6:B1 treatment, that of HC6 under R3:B1 treatment (Fig. 4B). It was increased with the increasing of red light ratio under red-blue combined light treatment. Compared with red or blue light treatment, the soluble starch content in seedlings of three soybean cultivars was increased under the combined light treatment.

The highest Ci was observed under R1:B1:W1 treatment for GXD2 and HC6, and the difference between other treatments was not significant. Ci was highest under R treatment for HX3, but the difference between R and R1:B1:W1 treatment was not significant (Fig. 3C).

Compared with W treatment, the soluble protein content in seedling of HC6 and HX3 was much higher under other treatments . Soluble protein content was increased with the increasing of red light ratio (Fig. 4C). 3.5 Chlorophyll contents

3.4 Photosynthesis products of soybean seedling

As shown in Table 2, the chlorophyll contents in GXD2 was increased under R5:B1 treatment, but that of HC6 and HX3 under R1:B1:W1 treatment. However, the Chla/Chlb and Chl/Car ratio was decreased under R1:B1:W1 and R5:B1 treatment (Table 2). The photosynthetic pigment of each cultivar seedlings was different under various light quality.

The highest soluble sugar content in GXD2 leaves was observed under R3:B1 treatment, which was increased with the increasing of red light ratio. For HC6, the highest soluble sugar content was detected under R6:B1 treatment. The highest soluble sugar content was measured in GXD2 under R3:B1. The sugar content in HX3 was significantly higher under B and R6B1 than other treatments. 774

PN (umol CO2 m-2 s -1 )

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aaa

aa

aaa

b bc

c

bb

b

a

b bb

b

d

GXD2

HC6

(Wollaeger and Runkle, 2015) and cucumber (Hernández and Kubota., 2016). However, there were some converse results in the other studies about marigold (Heo et al., 2002), withania (Lee et al., 2007). So, the effects of red light and blue light on the growth of plant were different according to plant type. Compared with R treatment, the stem diameter was significantly increased with B treatment (Fig 1B). When mixed some red light into blue light, the stem diameter was enhanced with the increase of red light ratio. Compared with monochrome light, stem diameter was increased under red/blue mixed light. Similar results were found in amaranth and tabaco (Chen et al., 2012; Su et al., 2014).

A b

HX3

7.0

a

0.5

0.4 0.3

B

a

0.6

a ab

bc c

b bb c

aa bb

b

Soluble sugar (mg g-1)

Gs (umol CO2 m-2 s -1 )

0.7

d

a ab

bc cd

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5.0

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bb

b

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a bc

A

abab b

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2.0 1.0 GXD2

HC6

HX3

Soluble starch (mg g-1)

GXD2

b b aabb bab

a bab b babb

300

HC6

C ab abc a bcd cde de e

200

a 8.0

bc a

6.0 c 4.0

abab bc bc bc

0

20.0

Soluble protein (mg g-1)

HX3

Fig. 3 Effects of light quality on the photosynthetic characteristics of soybean seedling. Different letters are significantly different at the 5% level by Duncan within each soybean cultivar. 4. DISCUSSION 4.1 Effects of light quality on the growth of soybean seedling

aa bc b c bc

c

2.0 0.0

HC6

B ab cd de

f

100

GXD2

HX3

e

GXD2

.

cc

a

a

10.0

500 Ci (umol CO2 m-2 s -1 )

ab

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0.0

400

a

6.0

HC6

HX3 a

15.0 10.0

ababcab bc bc c

ab bc ab bc bc

a c

C a abc ab bc bc abc c

5.0 0.0

Light is an important non-biological factor for plants growth, and the light quality can regulate plant physiological and morphological reaction (Kurepin et al., 2007; Li et al., 2013; Wollaeger and Runkle, 2015). In present study, the light quality had a good effect on the growth and morphology of soybean seedlings. Compared with the red light, plant height, epicotyl length and hypocotyl length were decreased under the blue light and W1:R1:B1 LED light. This is consistent with previous studies on hypocotyl length (Zhang et al., 2014). Similar effects was also found in wheat (Goins et al., 1997), rice (Guo et al., 2011), impatiens, salvia, petunia and tomato

W

B

GXD2 R1B1W1

HC6 R3B1 R5B1

HX3 R6B1 R

Fig. 4 Effects of light quality on photosynthesis products of soybean seedling. Different letters are significantly different at the 5% level by Duncan within each soybean species. The leaf area was decreased under blue LED light (Fig. 1F). It was similar to the findings in other plant, such as impatiens, salvia and petunia (Ohashi et al., 2007; Wollaeger and Runkle, 2014; Wollaeger and Runkle, 2015), but it was converse to

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Table 2 Effects of light quality on photosynthetic pigment of soybean seedling soybean

Light quality

Chl a（mg g-1）

Chl b（mg g-1）

GXD2

W

1.61±0.18ab 1.48±0.02b 1.55±0.13ab 1.43±0.12b 1.85±0.05a 1.54±0.09ab 1.69±0.09ab 2.07±0.05a 1.10±0.10d 1.56±0.11bc 1.29±0.02cd 0.96±0.25d 1.01±0.15d 1.81±0.15ab 1.69±0.10bc 0.97±0.15d 1.74±0.05ab 1.44±0.05c 1.53±0.08bc 1.62±0.07bc 1.99±0.06a

0.40±0.05a 0.34±0.01a 0.35±0.03a 0.40±0.05a 0.44±0.02a 0.43±0.04a 0.45±0.04a 0.58±0.01a 0.26±0.03b 0.35±0.03b 0.35±0.01b 0.27±0.06b 0.28±0.04b 0.47±0.05a 0.44±0.03abc 0.23±0.04d 0.41±0.01bc 0.38±0.01c 0.39±0.02bc 0.46±0.02ab 0.49±0.02a

2.00±0.23ab 1.82±0.03b 1.90±0.16ab 1.83±0.16b 2.29±0.07a 1.97±0.12ab 2.14±0.13ab 2.66±0.06a 1.36±0.12d 1.91±0.14bc 1.64±0.03cd 1.23±0.31d 1.29±0.19d 2.28±0.20ab 2.13±0.12b 1.20±0.19c 2.15±0.07b 1.82±0.06b 1.92±0.11b 2.08±0.09b 2.47±0.08a

0.000 0.004

0.000 0.102

0.000

0.000

B R1:B1:W1 R3:B1 R5:B1 R6:B1 HC6

R W B R1:B1:W1 R3:B1 R5:B1 R6:B1 R

HX3

W B R1:B1:W1 R3:B1 R5:B1 R6:B1 R

ANOVA

Light Soybean Soybean * Light

Chl（mg g-1） Car（mg g-1）

Chl a/Chl b

Chl/Car

0.38±0.01a

4.05±0.05bc 4.36±0.12ab 4.40±0.09a 3.65±0.15d 4.23±0.08ab 3.65±0.11d 3.78±0.09cd 3.57±0.10c 4.36±0.31ab 4.44±0.14a 3.64±0.06bc 3.57±0.45c 3.62±0.08bc 3.84±0.22abc 3.89±0.14abc 4.17±0.28ab 4.28±0.07a 3.82±0.02bc 3.95±0.10ab 3.54±0.03c 4.08±0.05ab

6.96±0.34c 5.99±0.50c 5.95±0.27c 9.71±0.62a 5.79±0.34c 9.70±0.44a 8.42±0.32b 8.04±0.37ab 5.96±0.65bc 5.43±0.14c 8.05±0.30ab 9.05±1.40a 9.29±0.46a 7.80±0.56ab 6.92±0.35b 6.41±0.57bc 5.62±0.13c 8.25±0.13a 5.61±0.20c 8.79±0.11a 6.54±0s.06b

0.007 0.000

0.000 0.001

0.000 0.205

0.000 0.006

0.000

0.000

0.296

0.000

0.31±0.03b 0.28±0.03b 0.31±0.02b 0.18±0.01c 0.40±0.02a 0.19±0.02c 0.27±0.02b 0.32±0.02a 0.26±0.04ab 0.33±0.03a 0.20±0.01bc 0.15±0.04b 0.15±0.02b 0.33±0.04a 0.33±0.03a 0.23±0.05b 0.40±0.02a 0.22±0.01b 0.34±0.02a 0.23±0.01b

Values are means ± SD (n=5). Means with different letters are significantly different at the 5% level by Duncan in each column within each soybean species.

lettuce with the greatest area were grown in the environments with blue light (Kim et al., 2004). The growth of soybean seedling was significantly affected by light quality, the interaction of soybean variety and light quality was significant for plant height, hypocotyl length and epicotyl length (Table 3).

the maximum value appeared at R5:B1 for HX3 and HC6, then at R3:B1 for GXD2 (Table 1). In contrast, red light was more effective for root elongation of cherry rootstock (Iacona and Muleo, 2010). This observation has not only indicated poor growth of root under only red light, but also indicates that the light quality can also regulate root induction. In this study, blue light and mixed light of red and blue was benefited to enhance the root growth of soybean seedlings. The best ratio of R/B mixed light was different for different soybean varieties (Table 1).

Table 3. ANOVA results of light quality on the agronomy characteristic of soybean seedling at 5% level Duncan (p value).

.000 .000

.000 .247

.000 .100

.000 .426

Shoot dry weight .000 .666

Light*Soybean .029

.008

.000

.706

.000

Plant Hypocotyl epicotyl Stem length diameter height length Light Soybean

4.3 Effects of light quality on photosynthesis Light quality is an important factor for photosynthetic pigments, the content of chlorophyll of impatiens under fluorescent light and only red light was relatively high than those grown under the other lighting treatment (Wollaeger and Runkle, 2014; Wollaeger and Runkle, 2015). In present study, the chlorophyll content of three cultivars was the lowest under B treatment. This indicated that the blue light could affect soybean seedlings to synthesize chlorophyll. But the content of chlorophyll of soybean seedlings was relatively higher under W treatment, white LEDs emitted green light, whereas there was no green light under all other light treatments. There were similar results showed that the content of chlorophyll of salvia and petunia under fluorescent light treatment was higher

4.2 Effects of light quality on growth of root. Compared with blue or red LED lights, the root grows stronger under mixed LED light (R+B, W+R+B). The root length, root surface area and root average diameter were increased under the mixed light . this is similar with the results of Zhang et al. (2014). There was significant difference between R/B ratio, 776

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than other treatments, the fluorescent light emitted 54% green light (Wollaeger and Runkle, 2014). The similar results of chlorophyll content were reported between LED light treatments in lettuce, salvia and tomato (Liu et al., 2011; Wollaeger and Runkle, 2015; Wollaeger and Runkle, 2014). However, previous studies had reported that the chlorophyll concentrations in leaves under B light were greater than those under R light (Hogewoning et al., 2010).

improve the growth of soybean seedlings. R5:B1 has a good effect on the seedlings growth of soybean. These are only in seedling growth period of soybean, but the light quality effect during the full growth period of soybean need for further research. REFERENCES

The change of photosynthetic pigment content affects photosynthesis in leaves, causing the change of net photosynthetic rates, stomatal conductance, inter cellulate CO2 concentration and transpiration rate. In this study, chlorophyll content of soybean seedling under W and R treatment were relatively higher than those under R/B mixed light treatment, but Pn was relatively lower under W, B and R treatment. Similarly, the Pn and Gs under mixed light of R and B LEDs was greater than white LED (Song et al., 2009; Zhang et al., 2014). Photosynthetic dysfunction in plants grown under monochromatic red light shows that the stomatal conductance does not respond to light, and the low photon quantum efficiency can be used for CO2 fixation, resulting in a decrease in its net photosynthetic rate (Hogewoning et al., 2010). Compared with W, B and R treatment, Pn was much higher under R/B mixed treatment (except R6:B1), it increased with the increasing of red-light ration. Under R/B mixed light treatment, red-light could improve photosynthesis of soybean seedling, but much higher red-light ration could inhibit photosynthesis of soybean seedlings. The photosynthetic performance of plants treated with appropriate ratio of redblue combined light was significantly better than that of monochromatic light treatment, which was closely related to the increase of specific leaf weight, chlorophyll content, leaf nitrogen content and stomatal conductance of red/blue mixed light treated plants (Hogewoning et al., 2010; Wang et al., 2016; He et al., 2017). Soluble protein and soluble sugar are important indexes of physiological and biochemical. It was found that the soluble sugar content of Pea sprouts and Toona sinensis were highest under red light, but soluble protein under blue light were higher than the other treatments (Zhang et al., 2010a; Zhang et al., 2010b). In this study, the soluble sugar content of soybean seedlings under R/B mixed light was relatively high, while it was relatively low under monochromatic lights and white light. This may be that the photosynthetic rates under R/B mixed light were relatively high and the photosynthetic product consumption increase (Su et al., 2014), higher soluble sugar content increase soluble starch content (Fig 4B). The results showed that the soluble protein of HC6 and GXD2 under red light was higher, but under blue light relatively lower. This result was similar to pea sprouts. Proteins are large molecules and it need more energy during the synthesis of photosynthetic product, and the quantum energy is high during blue wavelength, therefore the blue light can promote the synthesis of protein (Zhang et al., 2010a). 5. CONCLUSION Light quality is an important environmental factor for photosynthesis, and also a controllable environmental factor in facility agriculture. The red/blue mixed light is benefit to 777

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