Effects of Different Light Emitting Diodes on Growth and Quality of Lettuce

Xiaoxue FAN，Bo SONG，Hai XU，Longzheng CHEN*，Zhigang XU，Xihan YUAN

1.Institute of Vegetable Crops，Jiangsu Academy of Agricultural Sciences，Nanjing 210014，China；

2.College of Agronomy，Nanjing Agricultural University，Nanjing 210095，China

Effects of Different Light Emitting Diodes on Growth and Quality of Lettuce

Xiaoxue FAN1，Bo SONG1，Hai XU1，Longzheng CHEN1*，Zhigang XU2，Xihan YUAN1

1.Institute of Vegetable Crops，Jiangsu Academy of Agricultural Sciences，Nanjing 210014，China；

2.College of Agronomy，Nanjing Agricultural University，Nanjing 210095，China

The study investigated the effects on growth and quality of lettuce under six light treatments：yellow LED（Y），green LED（G），red LED（R），blue LED（B）and the red plus blue light（R∶B=3∶1）by dysprosium lamp as control（CK）.The re-sults showed that：under combination of red light and blue light，the fresh weight and dry weight were the largest，and the second was blue light treatment.Com-pared with the control，blue light and red plus blue light significantly enhanced the contents of soluble sugar，soluble protein，free amino acid and vitamin C.The study also showed that，red plus blue light significantly improved activity of nitrate reduc-tase and glutamine synthetase in lettuce leaves，which reduced the contents of ni-trate and nitrite and improved the safety effectively.

Light emitting diode（LED）；Light quality；Lettuce；Growth；Quality；Safety

L ight quality is an important envi-ronment factor that influences many aspects of plant growth and development，such as biomass，plantheight，leafarea and plant shape［1-3］.It was found in the research-es of a variety of crops including cow-pea seedlings，rice and seedlings of Chinese toon that blue light was bene-ficial to the accumulation of soluble protein［4-7］.Improving the proportion of blue light also can promote the nitro-gen metabolism of tobacco，improving the contents of total nitrogen，protein and amino acid［8］.Red light can pro-mote the metabolism of carbohydrates in plants，improving the content of car bohydrates［9-10］.Meanwhile，red light also can inhibit the transport process of photosynthate，facilitating the accu-mulation of starch in plant leaves［11］.

In recent years，novel energy-saving high-efficiency lightemitting diode （LED）has become a hotspot of research.Compared with conventional light sources，LED has the advantages of cold light source，low energy con-sumption，fixed light wavelength，high conversion rate，etc.In practical pro-duction，light density and light quality（red/blue light ratio or red/far-red light ratio）of LED light sources can be reg-ulated.Configuring light spectrum ac-curately according to the requirements by crops using LED light sources can promote high-yield high-quality envi-ronment-friendly crop production with high efficiency［12-13］.In addition，apply-ing LED light sources can solve the problem of impure light quality，result-ing in improved reliability of experi-ment results.In this paper，the effects of yellow light（Y），green light（G），red light（R），blue light（B）and red plus blue light（R∶B=3∶1）generated by LEDs on the growth and quality of lettuce were studied，aiming at understanding the effect of light quality on growth and various quality of lettuce and providing theoretical basis for application of LED light sources in protected cultivation of lettuce.

Materials and Methods

Experiment design

The experiment was carried out at the LED plant light source research center of Nanjing Agricultural Universi-ty in October of 2011，and the experi-ment material was lettuce（Lactvca sativa L.）.Seeds were subjected to soaking for accelerating germination and sown into aperture disks filled with turf，vermiculite and perlite（volume ratio at 3∶1∶1）under following environ-ment conditions：natural light，temper-ature of（20±2）℃，photoperiod of 12 h/d1 and relative humidity of about 80%.When the second true leaf was completely spread，lettuce seedlings with accordant morphologies and growth vigor were transplanted onto polyurethane foam seedling blocks in water planting boxes under LED light sources with 5 different light spectral energy distribution and dysprosium lamps as the control.The five LED treatments were blue light（B），red light（R），green light（G），yellow light（Y）and red plus blue light（R∶B=3∶1）with a light intensity of 100 μmol/（m2·s）.Oxy-gen was supplied into nutrient solution with inflator pumps，the nutrient solu-tion was replaced every 7 d once.The nutrient solution was prepared accord-ing to garden-type nutrientsolution formula，and the microelement formula adopted Aron formula.Each treatment was provided with 15 individual plants with three repetitions under the pho-toperiod of 12 h/d.After 20 d，random sampling was carried out to determine various indicators.Three individual plants were selected from each treat-ment randomly，and each indicator was determined thrice.

Light spectral energy distribution

The LED light source system was developed autonomously by the LED plant light source research center of Nanjing Agricultural University，and dysprosium lamps was used as the control.The light spectral energy dis-tribution was shown in Table 1.

Indicator determination and meth-ods

Three individual plants were se-lected from each treatment randomly for the determination of plant height，and fresh weights were weighed with an electronic scales；deactivation of enzymes was carried out in a dryer for 15 min，and the plants were dried to constantweights at80 ℃ to be weighed.Soluble sugar contents were determined according to anthrone colorimetric method［14］；free amino acid contents were determined according to ninhydrin method［14］；soluble protein contents were determined according to CBB G-250 staining method［14］；ni-trate nitrogen contents were deter-mined according to sulfuric acid-sali-cylic acid method［14］；nitrate reductase activity was determined according to in vitro method［14］；nitrite contents were determined according to the method by QIN［15］；and glutamine synthetase activity was determined according to the method by YIN［16］.

Data analysis

All data was processed with Excel 2003，statistics was performed with SPSS 17.0，and variance analysis adopted Duncan's multiple compari-son method.The lowercase letters a，b，c，d and e in the tables represented significant difference of various treat-ments at 0.05 level.

Table 1 Major technique parameters of different light spectral energy distribution under LED

Table 2 Effects of different light quality on morphologies and biomass of lettuce seedlings

Results and Analysis

Effects of different light quality on morphologies and biomass of let-tuce seedlings

As shown in Table 1，in compari-son with the control，the fresh weight and dry weight of individual lettuce plant were the largest under red plus blue light，which were improved by 55.6%and 62.5%，respectively；the next was the blue light treatment，which improved the fresh weight and dry weight of individual lettuce plant by 37.7%and 25%，respectively；and the red light treatment improved the fresh weight and dry weight of individual let-tuce plant by 14.8%and 12.5%，re-spectively.However，yellow LED and Green LED remarkably reduced the fresh weight and dry weight of individu-al lettuce plant.The above results indi-cated that red light，blue light and red plus blue light had positive effect on plants.

Compared with CK，yellow LED，green LED and red LED obviously in-creased the plant height of lettuce；blue LED significantly suppressed the plant height of lettuce；and red plus blue light was not significantly different with CK.

Effects of different light quality on quality of lettuce seedlings

In Table 3，light quality could ob-viously affect the quality of lettuce.the soluble sugar content under the treat-ment by red light was remarkably high-er than those under other treatments，and increased by 24.1%compared with the control，red plus blue light and blue light increased the soluble sugar content by 21.5%and 14.3%com-pared with the control，respectively，while under the treatment by yellow light and green light，the soluble sugar content decreased notably.blue light，red plus blue light and red light result-ed in the soluble protein contents in-creased remarkably，which were high-er than that of the control by 25.2%，5.9%and 4.7%，respectively，while the treatments of yellow light and green light lowered the soluble protein con-tent.Blue light and red plus blue light also led to remarkably improved amino acid contents in lettuce，which were higher than that of the control by 43.4%and 32.8%，while other treat-ments were not significantly different with the control.The vitamin C con-tents in lettuce under blue light and red plus blue light were higher，and in-creased by 29.4%and 17.6%com-pared with that of the control，while un-der the treatments of red light，yellow light and green light，the content de-creased remarkably.

As shown in Table 4，the nitrate content was higher under green light and yellow light，there was no differ-ence between red light and blue light，while red plus blue light resulted in an obviously decreased nitrate content，which was lower than the control by 43.2%.The nitrite content had a trend accorded with that of the nitrate con-tent，and red plus blue light also result-ed in a lowest nitrite content.By the research on the activities of key en-zymes in nitrate metabolism，the activ-ity of nitrate reductase was the highest under red plus blue light，which in-creased by 3 times compared with the control，and blue light and red light al-so improved the activity by 1.5 and 1.75 times，respectively.Meanwhile， the red plus blue light also obviously improved the activity of glutamine syn-thetase by 66.7%compared with the control.It was thus clear that visible red light，blue light and red plus blue light could improve the activities of metabolic enzymes to lower nitrate content in lettuce，and red plus blue light had an optimal light effect.

By comprehensively analysis，compared with the control and other treatments，red plus blue light could better improve the contents of soluble sugar，soluble protein，free amino acid and vitamin C，while remarkably lower nitrate content，thus indicating the best quality of lettuce under the treatment of red plus blue light.

Table 3 Effects of different light quality on quality of lettuce seedlings

Table 4 Effects of different LED light quality on safety of lettuce seedlings

Conclusions and Discus-sion

A lot of researches showed that red light and blue light had an impor-tant regulation effect on protein metabolism of higher plant，and the protein contents in leaves and seeds of a variety of plants under blue lighttreatmentwere higher than those of red light treatment［9，11］.This study found that the contents of solu-ble protein and free amino acid in leaves of lettuce under blue LED treatment were the highest，which was the same as the results of previous studies.Previous studies found that blue light could obviously promote dark respiration ofmitochondrias，and thus provided energy and carbon frameworkfornitrogenmetabolism and protein synthesis［9］；and mean-while，blue light could activate NR，therebyproviding more assimilable carbon so-urces for protein synthe-sis［18-19］.Therefore，blue LED is benefi-cial to synthesis and accumulation of soluble protein and amino acid of lettuce.

Saccharides were the starting matter for organic metabolism，and were the main energysource for maintaining vital movement［20］.Previ-ous studies found that red light im-proved soluble sugar contents in a va-riety of vegetables including tomato，Chinese toon seedlings and Chinese cabbage［7，21-22］；and there were also studies reporting that red plus blue light improved soluble sugar content in rice seedlings［23］.In this study，it was al-so found that the soluble sugar content was the highest in the lettuce under the red light treatment，and the second was the soluble sugar content in the lettuce under the treatment of red plus blue light，which was in accordance with the results by previous studies.

Vitamins are essential for human health.There were researches indicat-ing that blue light could promote the synthesis of vitamin C.Under blue light treatment， pea seedlings， radish sprouts and garlic seedlings have higher vitamin C contents［24-26］.Proper ratio of blue light to red light can effec-tively improve vitamin C content in plants［27］.In the researches on oilseed rape，it was found that vitamin C con-tent in leaves of tissue culture seedlings was the highest at the ratio of 3∶1 of blue light to red light［28］.In this study，we found that the treatments of blue light and red plus blue light resulted in higher vitamin C contents，which was in accordance with previ-ous studies.

Illumination plays an important role in nitrate metabolism in plants，and is one of the main factors deter-mining nitrate content.Nitrate reduc-tase （NR）and glutamine synthetase（GS）are two kinds of key enzymes in the assimilation process of NO3-［18］.Dif-ferentlight quality can obviously change the activities of NR and GS. There were researches indicating that blue light was likely to stimulate NR di-rectly，and meanwhile，red light andphytochrome also could regulate and control NR activity［29-30］.In addition，GS activity can be promoted by NR activity to some extent［31］.The results of this study showed that red plus blue LEDs at a ratio of 3：1 had a positive effect on the regulation and control of NR and GS of lettuce，while the effects by monochromatic red light and blue light were less obvious than red plus blue light，which might be related to the in-teraction of phytochrome with cry-tochrome.Nitrate accumulation in vegetables was caused by frustrated nitrogen metabolism，and its content was in positive correlation with NR and GS activities，which was verified by the results of this study in that the combi-nation of red and blue light improved the activities of nitrate metabolic en-zymes and effectively reduced the ni-trate content in lettuce.

Because the spectral energy dis-tribution of red light and blue light accords with the peak areas of ab-sorption spectrum of chlorophyll，red plus blue light can influence grow and development of plants positively，and proper spectral proportion，which may vary from species to species，can give full play to growth potential of plants［27，32］.

［1］MORTENSEN LM，STROMME E.Ef-fects of light quality on some green-house crops［J］.Sci Hortic，1987，33：27-36.

［2］ESKINS K.Light-quality effects on Ara-bidopsis development.Red，blue and far-red regulation of owering and mor-phology［J］.Physiol Plant，1992，86：439-444.

［3］ESKINS K，WARNER K，F(xiàn)ELKER F. Light quality during early seedling devel-opment in uences the morphology and bitter taste intensity of mature lettuce（Lactuca sativa）leaves［J］.Plant Physi-ol，1996，147：709-713.

［4］DENG JM（鄧江明），CAI QY（蔡群英），PAN RC（潘瑞熾）.Effect of light quality on the contents of protein and free amino acids in rice seedlings（光質(zhì)對水稻幼苗蛋白質(zhì)、氨基酸含量的影響）［J］. Chinese Bulletin of Botany（植物學(xué)通報(bào)），2000，17（5）：419-423.

［5］GUO YS（郭銀生），GU AS（谷艾素），CUI J（崔瑾）.Effects of light quality on rice seedlings growth and physiological characteristics（光質(zhì)對水稻幼苗生長及生理特性的影響）［J］.Chinese Journal of Applied Ecology（應(yīng)用生態(tài)學(xué)報(bào)），2011，22（6）：1485-1492.

［6］LIN BY（林碧英），ZHANG Y（張瑜），LIN YZ（林義章）.Effects of Light Quality on Photosynthetic Characteristics and Several Physiological and Biochemical Indices of Cowpea Seedings（不同光質(zhì)對豇豆幼苗光合特性和若干生理生化指標(biāo)的影響）［J］.Chinese Journal of Trop-ical Crops（熱帶作物學(xué)報(bào)），2011，32（2）：235-239.

［7］ZHANG LW（張立偉），LIU SQ（劉世琦），ZHANG ZK（張自坤），et al.Dynamic of Different Qualities on Growth of Toona sinensis Seedlings（不同光質(zhì)下香椿苗的生長動(dòng)態(tài)）［J］.Acta Agriculturae Bore-ali-occidentalis Sinica（西北農(nóng)業(yè)學(xué)報(bào)），2010b，19（6）：115-119.

［8］SHI HZ（史宏志），HAN JF（韓錦峰），GUAN CY（管春云），et al.Effects of red and blue light proportion on leaf growth，carbon-nitrogen metabolism and quality in tobacco（紅光和藍(lán)光對煙葉生長碳氮代謝和品質(zhì)的影響）［J］.Acta Agronomi-ca Sinica（作物學(xué)報(bào)），1999，25（2）：215-220.

［9］KOWALLIk W.Blue light effects on res-piration［J］.Annu Rev Plant Physiol，1982，33：51-72.

［10］Li Q，CHIERI K.Effects of supplemen-tal light quality on growth and phyto-chemicals of baby leaf lettuce［J］.Env Exp Bot，2010，67：59-64.

［11］SAEBO A，KREKLING T，APPEL-GREN M.Light quality affects photo-synthesis and leaf anatomy of birch plantlets in vitro［J］.Plant Cell Tiss Org，1995，2：177-185.

［12］WEI LL（魏靈玲），YANG QC（楊其長），LIU SL（劉水麗）.Review on research and developing trends of light-emitting diode in plant factory（LED在植物工廠中的研究現(xiàn)狀與應(yīng)用前景）［J］.Chinese Agricultural Science Bulletin（中國農(nóng)學(xué)通報(bào)），2007，23（11）：408-411.

［13］YANG QC（楊其長），XU ZG（徐志剛），CHEN HD（陳弘達(dá)），et al.Application Principle and Technology Progress in Using Light-Emitting Diode（LED）Light Sources in Modern Agriculture（LED光源在現(xiàn)代農(nóng)業(yè)的應(yīng)用原理與技術(shù)進(jìn)展）［J］.Journal of Agricultural Science and Technology（中國農(nóng)業(yè)科技導(dǎo)報(bào)），2011，13（5）：37-43.

［14］LI HS（李合生），Principles and tech-niques of plant physiological biochem-ical experiment（植物生理生化實(shí)驗(yàn)原理和技術(shù)）［M］.Beijing：Higher Educa-tion Press（北京：高等教育出版社），2000.

［15］QIN SC（秦遂初）.Crop nutrition fertil-ization and diagnosis experiment（作物營養(yǎng)施肥與診斷實(shí)驗(yàn)）［M］.Beijing：A-gricultural Publishing House （北京：農(nóng)業(yè)出版社），1992.

［16］YIN ZX（殷召學(xué)）.Effects of nitrogen，phosphorus and potassium nutrients on the physiological influences nutri-tion quality and key enzymes in nitro-gen metabolism of Chinese chive （氮磷鉀對韭菜生理效應(yīng)、營養(yǎng)品質(zhì)及氮代謝關(guān)鍵酶的影響）［D］.Baoding：Agri-cultural University of Hebei（河北農(nóng)業(yè)大學(xué)），2005.

［17］LI SHAOSHAN（李韶山），PAN RUICHI（潘瑞熾）.Effects of blue light on the growth of rice seedlings（藍(lán)光對水稻幼苗生長效應(yīng)的研究）［J］.Chinese Jour-nal of Rice Science（中國水稻科學(xué)），1994，8（2）：115-118.

［18］CAMPBELL WH.Nitrate reductase biochemistry comes of age［J］.Plant Physiol，1996，111：355-361.

［19］NINNEMANN H.Some aspects of blue light research during last decade［J］. Photochem Photobiol，1995，61：22-31.

［20］TAO Y，STANLEY MB.Effect of light quality on production of extra cellular polysaccharides and growth rate of Porphyridium cruentum ［J］.Biochem Eng J，2004，19：251-258.

［21］PU GAOBIN（蒲高斌），LIU SHIQI（劉世琦），LIU LEI（劉磊），et al.Effects of Dif-ferent Light Qualities on Growth and Physiological Characteristics of Toma-to Seedlings（不同光質(zhì)對番茄幼苗生長和生理特性的影響）［J］.Acta Horticul-turae Sinica（園藝學(xué)報(bào)），2005，32（3）：420-425.

［22］WANG T（王婷），LI WL（李雯琳），GONG FE（鞏芳娥），et al.Effects of different LED light qualities on growth and physiological characteristics of non-heading Chinese cabbageLED （光源不同光質(zhì)對不結(jié)球白菜生長及生理特性的影響）［J］.Journal of Gansu Agri-cultural University（甘肅農(nóng)業(yè)大學(xué)學(xué)報(bào)），2011，46（4）：69-73.

［23］CAI HC（蔡鴻昌），CUI HX（崔海信），CUI JH（崔金輝）.Effects of Different Light Qualities on the Quality of Tomato Plug Seedlings（不同光質(zhì)對番茄穴盤苗質(zhì)量的影響）［J］.Journal of Agricul-tural Science and Technology（中國農(nóng)業(yè)科技導(dǎo)報(bào)），2010，12（3）：114-118.

［24］ZHANG LW（張立偉），LIU SQ（劉世琦），ZHANG ZK（張自坤），et al.Dynamic Effects of Different Light Qualities on Pea Sprouts Quality（不同光質(zhì)對豌豆苗品質(zhì)的動(dòng)態(tài)影響）［J］.Northern Horti-culture（北方園藝），2010a（8）：4-7.

［25］ZHANG LIWEI（張立偉），LIU SHIQI（劉世琦），ZHANG ZIKUN（張自坤），et al. Effects of light qualities on the nutritive quality of radish sprouts（光質(zhì)對蘿卜芽苗菜營養(yǎng)品質(zhì)的影響）［J］.Acta Nutri-menta Sinica（營養(yǎng)學(xué)報(bào)），2010c，32（4）：390-392.

［26］YANG XJ（楊曉?。?，LIU SQ（劉世琦），ZHANG ZK（張自坤），et al.Effects of Different Light Emitting Diode Sources on Nutritional Quality of Garlic Seedling（不同發(fā)光二極管對青蒜苗營養(yǎng)品質(zhì)的影響）［J］.Acta Nutrimenta Sinica（營養(yǎng)學(xué)報(bào)），2010，32（5）：518-520.［27］WEN J（聞婧），WEI LL（魏靈玲），YANG QC（楊其長）.Application of LED in leaf vegetable plant factory（LED在葉菜植物工廠中的應(yīng)用）［J］.Agriculture Engi-neering Technology（農(nóng)業(yè)工程技術(shù)），2009（6）：11-12.

［28］HUIMIN LI，CANMING TANG，ZHI-GANG XU.Effects of light emitting diodes on growth and morphogenesis ofRapeseed （BrassicanapusL.）plantlets in vitro［J］.Sci Hortic，2013，150：117-121.

［29］LILLO C，APPENROTH KJ.Light reg-ulation of nitrate reductase in higher plants：Which photoreceptors are in-volved［J］.Plant Biol.2001，3：455-465.

［30］SOPORY SK，SHARMA AK.Spectral quality of light，hormones and nitrate assimilation.-In：Abrol Y.P.（Ed.）Ni-trogen in higherplants.Research Studies Press Ltd.，1990：129-157.

［31］LIN QH（林清華），LI CJ（李常鍵），PENG JI（彭進(jìn)），et al.Effect of NaCl stress on glutamate synthase and glutamate de-hydrogenase 0f rice plants（NaCl對水稻谷氨酸合酶和谷氨酸脫氫酶的脅迫作用）［J］.Journal of Wuhan Botanical Research（武漢植物學(xué)研究），2000，18（3）：206-210.

［32］YANG QC（楊其長）.Application and Prospect of Light-Emitting Diode（LED）in Agriculture and Bio-industry（LED在農(nóng)業(yè)與生物產(chǎn)業(yè)的應(yīng)用與前景展望）［J］.Journal of Agricultural Sci-ence and Technology（中國農(nóng)業(yè)科技導(dǎo)報(bào)），2008，10（6）：42-47.

Responsible editor：Yingzhi GUANG

Responsible proofreader：Xiaoyan WU

不同LED光源對生菜生長和品質(zhì)的影響

樊小雪1，宋波1，徐海1，陳龍正1*，徐志剛2，袁希漢1（1.江蘇省農(nóng)業(yè)科學(xué)院蔬菜研究所，江蘇南京 210014；2.南京農(nóng)業(yè)大學(xué)農(nóng)學(xué)院，江蘇南京210095）

［目的］探明光質(zhì)對生菜生長和各項(xiàng)品質(zhì)的影響，為LED光源在生菜設(shè)施栽培上的應(yīng)用提供理論依據(jù)。［方法］以生菜為材料，利用LED精量調(diào)制光源，設(shè)置黃光（Y）、綠光（G）、紅光（R）、藍(lán)光（B）和紅藍(lán)組合光（R∶B=3∶1）5個(gè)LED光處理，以鏑燈白光為對照，探討不同LED光源對生菜生長和品質(zhì)的影響。［結(jié)果］紅藍(lán)組合光下生菜植株鮮樣質(zhì)量和干樣質(zhì)量最大，其次是藍(lán)光處理。與對照相比，藍(lán)光和紅藍(lán)組合光顯著提高了生菜可溶性糖、可溶性蛋白、游離氨基酸和維生素C含量。試驗(yàn)還發(fā)現(xiàn)，紅藍(lán)組合光顯著提高了生菜葉片中硝酸還原酶和谷氨酰胺合成酶活性，從而降低了硝酸鹽和亞硝酸鹽含量，有效提高了其安全品質(zhì)。［結(jié)論］適宜的光譜比例能夠充分發(fā)揮植物的生長潛力。

LED光源；光質(zhì)；生菜；生長；營養(yǎng)品質(zhì)；安全性

農(nóng)業(yè)部公益性行業(yè)（農(nóng)業(yè)）科研專項(xiàng)經(jīng)費(fèi)項(xiàng)目（201403032）；江蘇省自主創(chuàng)新基金項(xiàng)目［CX（13）2004］。

樊小雪（1983-），女，山東淄博人，博士，助理研究員，研究方向?yàn)槭卟擞N與生理生態(tài)，E-mail：fxx600@163.com。*通訊作者，男，博士，副教授，研究方向?yàn)槭卟擞N與分子育種。

2015-07-08

Supported by the Special Fund for Agro-scientific Research in the Public Interest by the Ministry of Agriculture （201403032）and the Jiangsu Province Agricultural Science and Technology Independent Fund Project［CX（13）2004］.

*Corresponding author.E-mail：fxx600@163.com

Received：July 8，2015 Accepted：September 20，2015

修回日期 2015-09-20