Journal of Bio-Environment Control, Vol. 30, No. 1:85-93, January (2021) DOI pissn 수경재배양액내탄산정처리

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1 Journal of Bio-Environment Control, Vol. 30, No. 1:85-93, January (2021) DOI pissn 복권정 1 ㆍ노승원 1 ㆍ김영국 2 ㆍ남창수 3 ㆍ진채린 3 ㆍ박종석 4 * 1 충남대학교농업생명과학대학원예학과대학원생, 2 충남대학교공과대학컴퓨터융합학부교수, 3 충남대학교농업생명과학대학원예학과학부생, 4 충남대학교농업생명과학대학원예학과교수 Changes in Growth and Bioactive Compounds of Lettuce According to CO 2 Tablet Treatment in the Nutrient Solution of Hydroponic System Gwonjeong Bok 1, Seungwon Noh 1, Youngkuk Kim 2, Changsu Nam 3, Chaelin Jin 3, and Jongseok Park 4 * 1 Graduate Student, Department of Horticulture Science, College of Agriculture & Life Sciences, Chungnam National University, Deajeon 34134, Korea 2 Professor, Department of Computer Science and Engineering, College of Engineering, Chungnam National University, Deajeon 34134, Korea 3 Under Graduate Student, Department of Horticulture Science, College of Agriculture & Life Sciences, Chungnam National University, Deajeon 34134, Korea 4 Professor, Department of Horticulture Science, College of Agriculture & Life Sciences, Chungnam National University, Deajeon 34134, Korea Abstract. In hydroponic cultivation, in order to investigate the change of lettuce growth and physiologically active substances through CO 2 tablet treatment in nutrient solution, we used a solid carbonated tablets commercially available in the Netherlands. The experiment consisted of 0.5-fold, 1-fold, and 2-fold treatment groups with no treatment as a control. As a result, the atmospheric CO 2 concentration in the chamber after CO 2 tablet treatment showed the highest value at µl L -1 in the 2-fold treatment zone immediately after treatment, and the ph in the nutrient solution decreased the most to ph 6.03 in the 2-fold treatment zone. After that, over time, the CO 2 concentration and ph recovered to the level before treatment. Leaf width and leaf area of lettuce showed the highest values of 17.1cm and cm 2 when treated 2-fold with CO 2 tablet, while fresh weight and dry weight of the above-ground part were highest at g and 3.08 g in 0.5-fold treatment. The root length of lettuce was the longest (28.4 cm) in the control, but there was no significant difference in the fresh weight and the dry weight among the treatments. Apparently, it was observed that the root length of the lettuce was shortened by CO 2 tablet treatment and a lot of side roots occurred. In addition, there was a growth disorder in which the roots turned black, but it was found that there was no negative effect on the growth of the above-ground part. As a result of analyzing the bioactive compounds of lettuce by CO 2 tablet treatment, chlorogenic acid and quercetin were detected. As a result of quantitative analysis, chlorogenic acid increased by 249% compared to the control in 1-fold treatment, but quercetin decreased by 37%. As a result of comparing the DPPH radical scavenging ability showing antioxidant activity, the control and 0.5-fold treatment showed significantly higher values than the 1-fold and 2-fold treatments. This suggests that carbonated water treatment is effective in increasing the growth and bioactive compounds of hydroponic lettuce. Additional key words : antioxidant activity, chlorogenic acid, DFT, DPPH, HPLC, quercetin 서론 상추 (Lactuca sativa L.) 는국화과에속하는 1년생초본식물로대표적인쌈및샐러드채소로엽채류중배추, 양배추다음으로많이생산되는작물로알려져있으며 (KOSIS, 2019), *Corresponding author: jongseok@cnu.ac.kr Received January 15, 2021; Revised January 25, 2021; Accepted January 25, 2021 비타민 A, B, C 및다량의철분을함유하여경제적가치가높은작물로알려져있다 (Jang 등, 2007). 특히최근에는소비자들의청정채소에대한수요가증가함에따라수경재배상추에대한선호도가높아지고있으며실제식물공장을필두로한우리나라의수경재배면적중상추가차지하는비중이주를이루고있다. 실제수경재배상추는노지재배와비교하여농약및오염물질로부터안전하므로상품성이매우높다 (Ryoo, 2009). 생물환경조절학회지, 제 30 권제 1 호 2021 년 85

2 복권정 노승원 김영국 남창수 진채린 박종석 환경조절이가능한식물생산시스템에서엽채류생산을위한환경과생육에관한연구가활발히진행되고있다. 대표적으로파장별광원에따른생육특성 (Um 등, 2010) 및 LED를이용한엽채류재배 (Lee 등, 2010) 등과같은광조건과양액조성 (Choi 등, 2005;Kang과 Kim, 2007; Kwack 등, 2015) 과관련된연구가주를이루고있으며, 부분적으로양액내마이크로버블 (Park과 Kenji, 2009), 전기자극 (Lee와 Oh, 2020) 등과같은환경스트레스조건이엽채류생육에미치는영향에관한연구들도이루어지고있다. 식물은주변환경요인에의한생육및대사활동에영향을받게되는데이산화탄소는식물의광합성에관여하는효소들의활성을결정하고, 식물체내탄수화물의이동을활성화해영양생장을촉진한다 (Huang 등, 2007). 따라서 CO 2 농도증가는식물의광합성을촉진하며 (Alexandrov과 Oikawa, 2002) 더불어식물세포의팽압을조절하여기공전도도를낮출수있다고보고되었다 (Ainsworth과 Rogers, 2007). 더불어식물체내생리활성물질을함량을변화시키며탄닌과같은페놀류의함량을증가시킨다고알려져있으며 (Akula과 Ravishankar, 2011) 이와같은결과를바탕으로다양한작물에대한제한적인공간에서탄산시비를이용한연구가보고되었다. 착색단고추 (Capsicum annuum L.) 의경우시설재배시탄산가스시비농도와시간이증가함에따라작물의지상부생육이증가하였으며 (Kang 등, 2007), 딸기 (Fragaria ananassa) 의경우탄산시비를통해수확후딸기의경도, 당도, 산도가증가하는결과 (Choi 등, 2017) 가보고되었다. 최근에는다양한탄산시비공급원에관한연구로드라이아이스를이용한대기중 CO 2 농도증가시킨연구 (Paek 등, 2020), 연소식탄산가스발생기를이용하여이산화탄소농도를증가시킨연구 (Lee 등, 2018) 등이보고되었다. Hwang(2012) 의보고에따르면탄산수로 6일간콩나물을재배한결과콩나물의중량, 두께등의생장과비타민 C, isoflabvone과같은유효성분함량이대조구에비해증가하였다. 하지만현재까지엽채류수경재배시양액내탄산가스농도증가가상추의생육및품질등에관한연구는보고되지않았다. 본연구는담액수경재배시발포형고체탄산정을배양액에투입하였을때근권부 ph와 EC에대한영향과탄산정처리에의해발생되는이산화탄소가상추의지하부와지하부의생육및생리활성물질함량에미치는영향을살펴보고자수행되었다. 1. 실험재료및재배환경 재료및방법 실험에는적축면상추 (Seonpung Plus+, Kwonnong Seeds Co. Ltd., Cheongjusi, Korea) 를사용하였으며, 종자를 240공암면배지 (Rockwool, Grodan Co. Ltd., The Netherlands) 에파종하여 2일간암조건의챔버에서발아를시킨뒤, 챔버내온도 22 ± 2 C, 습도 70 ± 5%, 형광등광도 230 ± 20µmol m -2 s -1, 광주기 16/8h( 명기 / 암기 ) 조건의완전제어형식물재배실에서 21일간육묘하였다. 육묘 3주차에는본엽이 3~4매가전개되었으며균일한묘를선발하여처리구에따라 semi-dft 수경재배장치 (Gafatech Co. Ltd., Hwaseongsi, Korea) 4대에각각 14주씩총 56주를정식하였다. 정식이완료된수경재배장치를처리구별각챔버로옮겨온도 23 ± 1 C, 습도 70 ± 5%, 고압나트륨등광도 330 ± 20µmol m -2 s -1, 광주기 16/8h ( 명기 / 암기 ) 조건으로같게설정하여재배하였다. 수경재배시양액은 Hoagland 배양액을변형하여 (Table 1) 사용하였고양액내탄산정처리에의한양액의 EC와 ph 변화를고려하여 3일마다양액을새로교체해주어 EC 1.3 ± 2dS m -1, ph 6.5 ± 0.2로유지해주었다. 정식 3주후수확하여생육및항산화물질분석을수행하였다. 2. 양액탄산정처리및양액모니터링 양액내탄산정처리를위해알약형태로제작된고형탄산정 (CO 2 -TABS, No Mercy Supply, The Netherlands) 을이용하였다. 해당제품은알약형태의탄산정으로양액에넣으면탄산기체가양액내에서발포되어 30분이내에전부용해되고탄산가스가서서히기화되는특징을가지고있다. 해당탄 Table 1. Composition of the nutrient solution used in the experiment. Chemical Conc. (mg L -1 ) Chemical Conc. (mg L -1 ) Ca(NO 3) 2 4H 2O H 3BO KNO CuSO 4 5H 2O 0.05 NK 4H 2PO MnSO 4 5H 2O 2.18 MgSO 4 7H 2O Na 2M OO 4 2H 2O 0.02 Fe-EDTA ZnSO 4 7H 2O Journal of Bio-Environment Control, Vol. 30, No. 1, 2021

3 산정 1정의무게는 2g이며사용기준용량은 100L를기준으로사용하게되어있다. 따라서본실험의수경재배장치용량인 18L를고려하여탄산정을분말화한뒤 0.36g의분말을수경재배장치양액에녹인것을 1배처리로기준으로하여사용하였다. 탄산정처리농도에따른상추의생육및품질차이를알아보기위하여무처리를대조구로하여 18L의양액에탄산정 0.18g(0.5배 ), 0.36g(1배 ), 0.72g(2배 ) 을각각처리하였으며, 탄산정처리는탄산의효력을유지하기위해정식후 3일간격으로양액을새로교체할때마다각처리구별기준량의탄산정을새로용해해주었으며양액교체는오후 6시에실시하였다. 탄산정처리에따른챔버내대기중 CO 2 변화및양액내 ph를측정하기위하여 CO 2 Analyzer(Li-820, Licor Co. Ltd., USA) 와 ph meter(hi , Hanna Instruments Co. Ltd., The Netherlands) 를이용하여대기중 CO 2 변화는탄산정처리시작후 24시간동안 30분간격으로챔버내 CO 2 를측정하였으며, 양액내 ph는탄산정처리후 3일간매일측정하였다. 3. 생육분석방법 정식 3주후처리구별로 10주의상추를수확하여생육조사를수행하였다. 버니어캘리퍼스 (SD PRO, Shin Con CO. Ltd., Korea) 를이용하여가장큰잎의엽장, 엽폭, 1cm 2 크기이상의엽수를측정하였으며, 개체별총엽면적을엽면적측정기 (LI-3100, Licor Co. Ltd., USA) 를이용하여측정하였다. 단위면적당엽록소함량비교를위하여 SPAD-502 (Minolta Camera Co. Ltd., Japan) 을이용하여 SPAD 값을측정하였다. 상추의생체중은지상부와지하부로나누어전자저울 (MW-2N, CAS Co. Ltd., Korea) 로측정하였고, 생체중을측정한시료를봉투에담아 80 C로설정된열풍건조기 (HB-501M, Hanbaek Scientific Technology Co. Ltd., Bucheon, Korea) 를이용해 1주일간건조한후전자저울을사용해건물중을측정하였다. 4. 생리활성물질정량분석 탄산정처리에따른상추의생리활성물질및항산화도분석을위하여처리구별상추 3주씩수확한잎을액체질소로급속냉각시켜 -70 C에냉동보관하였다. 냉동된시료는동결건조하여믹서기와막자사발을이용해분말화시켰으며, 분말시료 100mg에 80% MeOH 2mL을넣고 1시간동안초음파처리 (sonication) 를한뒤, 12,000rpm에서 15분간원심분리한상등액을 0.45µm의 syringe filter로필터링하여분석시료로사용하였다. Chlorogenic acid, quercetin 두물질에대한정량분석을위하여 HPLC(1260 Infinity Ⅱ, Agilent Technologies Co. Ltd., USA) 를이용하였으며, 컬럼은 optimapak C18 column ( mm, 5µm) 을사용하였고컬럼온도는 30 C, 유량은 1.0mL min -1, 검출파장은 280nm로설정하였다. 이동상용매로는 0.15% 아세트산을포함한 solvent A와 80% MeOH 의 solvent B를이용하였다. Chlorogenic acid와 quercetin 표준물질 (Sigma-Aldrich Co., USA) 을 99.9% MeOH에 1000, 500, 250, 200, 100, 50µg ml -1 농도로희석한후검량선을작성하여정량분석에사용하였다. 5. DPPH 라디컬소거능분석상추의항산화도를알아보기위해 DPPH 라디컬소거능을측정하였다. 측정은생리활성물질분석시제조한상춧잎추출시료를사용하였으며, 1.5mL 튜브에 1mM의 DPPH 용액 500µL와 100배희석한상춧잎추출시료 500µL를실온에서 30분간반응시킨후 UV/Vis 분광광도계 (OPTIZEN POP BIO, Mecasys Co. Ltd., Daejeon, Korea) 를이용하여 517nm 에서흡광도를측정하였다. 측정값은 [1-시료첨가구의흡광도 / 시료무첨가구의흡광도 ] 100의계산식을이용하여 DPPH 라디컬소거능을계산하였다. 6. 통계분석모든분석결과는처리구별평균간비교를위하여 SPSS 프로그램 (SPSS Statistic 26, IBM Co. Ltd., USA) 을사용하여 one-way ANOVA 분석을수행하였으며평균간유의차검증을위하여 Duncan의다중검정법으로유의수준 p 0.05 에서분석하였다. 결과및고찰 1. 탄산정처리에따른 CO 2 농도및양액 ph 변화탄산정처리에의한챔버안 CO 2 농도를측정한결과, 탄산정처리직후챔버내대기이산화탄소농도는대조구의경우 375µL L -1 로가장낮았으며, 0.5배처리구는 437µL L -1, 1배처리구는 444µL L -1, 2배처리구는 442µL L -1 까지증가하는모습을나타내다가이후 2시간에걸쳐점차감소하는경향을나타내었다 (Fig. 1). 처리 4시간이후야간암조건에들어서자식물의호흡에의한이산화탄소배출량이증가함에따라야간챔버내이산화탄소농도가증가하는경향을나타내었는데야간최대이산화탄소농도는대조구, 0.5, 1.0, 2.0배의경우각각 450, 455, 464, 472µL L -1 를나타내었다 (Fig. 1). 이후부터탄산정처리의챔버내이산화탄소농도가대조구농도수준으로낮아지는것을확인할수있었다. 이처럼 CO 2 농도가높을수록야간 CO 2 배출량이증가하는이유는지상부발달정 생물환경조절학회지, 제 30 권제 1 호 2021 년 87

복권정 노승원 김영국 남창수 진채린 박종석 Fig. 1. Time course of CO 2 concentration in the atmosphere of chambers by different CO 2 tablet treatments.

도에기인한것으로 Kimball(1983) 에따르면지상부발달에따른동화산물소모증가가 CO 2 배출에영향을미친다는연구결과와일치한것으로보인다. 탄산정처리후 3일간양액내 ph 농도를측정한결과대조구의경우양액내 ph가측정첫날 ph 6.34에서측정마지막날 ph 6.49까지증가하는경향을나타냈다. 탄산정 0.

감소폭은탄산정처리량이클수록크게나타났으며처리후 2일, 3일차에측정한양액내 ph 값으로보아 ph가처리전수준으로회복하는모습을나타내었다 (Fig. 2).

본연구에는 CO 2 에의한양액의 ph가작물의생육에부정적인영향을미치지않는수준에서유지되었으며양액에용해되어있던 CO 2 가지속해서대기중으로발산하며작물의생육을증가시키는작용을한것으로판단된다. Fig. 2. ph change of the nutrient solution in the hydroponic systems.

4 복권정 노승원 김영국 남창수 진채린 박종석 Fig. 1. Time course of CO 2 concentration in the atmosphere of chambers by different CO 2 tablet treatments. The CO 2 concentration measured every 30 minutes for 24 hours after treatment. The white and gray zones represent day and night time, respectively. 도에기인한것으로 Kimball(1983) 에따르면지상부발달에따른동화산물소모증가가 CO 2 배출에영향을미친다는연구결과와일치한것으로보인다. 탄산정처리후 3일간양액내 ph 농도를측정한결과대조구의경우양액내 ph가측정첫날 ph 6.34에서측정마지막날 ph 6.49까지증가하는경향을나타냈다. 탄산정 0.5배, 1 배, 2배처리구의경우탄산정처리전각각 ph 6.38, ph 6.37, ph 6.35로모두비슷한수준의값을나타내었지만, 탄산정처리 1일후탄산정처리구의모든양액내 ph가 0.12에서 0.32 만큼감소하는모습을나타냈다. 감소폭은탄산정처리량이클수록크게나타났으며처리후 2일, 3일차에측정한양액내 ph 값으로보아 ph가처리전수준으로회복하는모습을나타내었다 (Fig. 2). Lee 등 (2013) 은 ph가급격하게높아진정수장의원수에 CO 2 주입을통해정상범위의 ph로조절시켰는데이는물에용해된 CO 2 는 H 2CO 3 로만존재하는것이아니고물과맞닿고있는대기중의 CO 2 와평행을이루고있어서 CO 2 가과도하게용해될때 H + 가증가하게되어 ph가낮아지기때문이라설명하고있다. 본연구에는 CO 2 에의한양액의 ph가작물의생육에부정적인영향을미치지않는수준에서유지되었으며양액에용해되어있던 CO 2 가지속해서대기중으로발산하며작물의생육을증가시키는작용을한것으로판단된다. Fig. 2. ph change of the nutrient solution in the hydroponic systems. ph change measured daily for 3 days after treatment. 2. 생육분석 수확후상추의외관을관찰한결과형태학적으로탄산정처리에의한시각적차이는발견되지않았다. 하지만지하부의 Fig. 3. Photos of the lettuces grown in different CO 2 tablet treatments for 3 weeks after transplanting. (A, B, C, D mean Control, 0.5x 1.0x 2.0x treatment) 88 Journal of Bio-Environment Control, Vol. 30, No. 1, 2021

5 경우대조구와비교하여탄산정처리농도가높아질수록뿌리의길이가짧아지고진한갈색을띠는모습을나타내었다 (Fig. 3). 생육분석결과뿌리의형태적인변화가지상부의생육에부정적인영향을주지않은것으로보인다. Table 2는탄산정처리에의한상추의생육분석결과이다. 엽수와엽장의경우탄산정처리에따른유의적차이가나타나지않았으며, 엽폭의경우탄산정처리 1배, 2배처리에서각각 17.8, 17.9cm로대조구와비교하여유의하게증가하였다. 상추개체별총엽면적역시대조구와비교하여 0.5배, 1배, 2 배처리구모두각각 15.0, 16.8, 20.2% 씩유의적으로증가하였다. 하지만엽록소지표를나타내는 SPAD 값은 2배처리구에서높은평균값을나타내었지만대조구와비교하여유의적인차이가나타나지않았다. 지상부생체중과건물중의경우 0.5배처리에서각각 63.9g과 3.08g으로가장높은값을나타냈으며모든탄산정처리의지상부생육이대조구와비교하여유의적으로증가되었다. 상추의지하부생육조사결과근장의경우대조구와비교하여탄산정처리농도가높을수록근장이유의적으로감소했으나 (Fig. 3) 지하부건물중의경우근장과반대되는경향으로탄산정처리농도가높아질수록증가하였다 (Table 2). 양액에탄산정을용해시키면 H 2CO 3 의형태로존재하며 ph가약간하강하여 6.1 정도를유지하였다. 상추는 ph 5.0에서 7.0까지생육에큰장애가발생하지않는다고보고되었으며 (Park 등, 1999), 식물은종에따라서스트레스에대한저항성이다르므로 (Lichtenthaler, 1996) 토양의 CO 2 가과도하게높아지는환경에서식물종에따라그반응역시다양하게나타난다. Patil(2012) 은외떡잎식물이쌍떡잎식물보다토양 CO 2 증가에대한저항성이더클것이라고보고하였으며, 실제토양 CO 2 가증가하였을때쌍떡잎식물인알팔파의생육저해가외떡잎식물인옥수수보다더크게나타났다 (Wu 등, 2014). 본실험의상추의경우쌍떡잎식물에속 하며뿌리신장은대조구보다저해되었지만, 생육에는차이가나타나지않았다. 백합나무에서 CO 2 농도가증가함에따라곁가지의발생이증가 (Lee 등, 2013) 한것으로보아, 기포형태의탄산이뿌리에자극을주어뿌리의길이생장은억제됐지만 2차또는 3차지근이발달하여전체뿌리의생육은증가한것으로판단된다. 식물은 CO 2 포화점까지 CO 2 농도가증가함에따라광합성량역시증가하게된다. 광합성량의증가는식물의엽면적및생육의증가등다양한식물생리반응으로나타나게된다 (Nederhoff 등, 1992). 또한, 이산화탄소처리는잎의표피조직세포의신장을촉진하고, 작물과품종에따라정도의차이는있지만, 식물의엽면적및엽수를증가시키기때문에식물의생장에효과가있다고보고되었다 (Taylor 등, 2001). 따라서생육조사결과, 양액에용해시킨탄산정이이산화탄소로기화되면서공기중의 CO 2 농도가증가하였고, 이러한영향이지상부상추의생리, 생장반응에영향을미치는것으로확인되었다. 3. 생리활성물질정량분석결과탄산정처리에따른상추내생리활성물질분석결과 chlorogenic acid와 quercetin이검출되었다. 단위건물중당 chlorogenic acid 함량은탄산정처리구에서대조구보다더높게나타났다. 1배처리구에서단위건물중당 3.24mg g -1 로대조구보다 114% 증가하여가장높은값을나타냈으며 0.5배처리구에서는 2.42mg g -1, 2배처리구에서는 2.21mg g -1 로대조구대비각각 60.3, 47.4% 증가한결과를나타내었다. Quercetin 함량은대조구에서 mg g -1 로가장높았으며 1.0배처리구에서대조구보다 54% 감소한 0.169mg g -1 으로가장낮은값을나타냈다 (Fig. 4A). 단위건물중당생리활성물질함량을실제건물중에곱하여식물 1개체당생리활성물 Table 2. Influences of carbonated water on lettuce growth parameters at harvest (21 days after transplanting). Tratment Number of leafs Leaf length (cm) Leaf width (cm) Above-ground Leaf area (m 2 ) SPAD Fresh weight (g) Dry weight (g) Root length (cm) Under-ground Fresh weight (g) Dry weight (g) Control z 9.7 a y 16.1 a 16.9 b 887 b 14.4 a 51.9 b 2.52 b 28.4 a 10.5 a 0.44 a 0.5x 10.0 a 16.7 a 16.8 b 1021 a 15.2 a 63.8 a 3.08 a 25.1 ab 11.4 a 0.44 a 1.0x 10.0 a 17.0 a 17.8 a 1036 a 13.6 a 60.7 a 2.93 a 20.6 bc 11.2 a 0.52 a 2.0x 9.5 a 17.0 a 17.8 a 1067 a 17.3 a 61.7 a 2.92 a 16.2 c 9.9 a 0.53 a ANOVA test x NS NS * * NS * * ** NS NS z Control, no treatment. y Mean separation within columns and different letter means significant difference by Duncan s multiple range test at p x NS, *, **, ***, Nonsignificant or significant at p 0.05, 0.01, or 0.001, respectively. 생물환경조절학회지, 제 30 권제 1 호 2021 년 89

Different letters at the top of bars indicate significant differences between the CO 2 tablet treatments (p 0.05). 질함량을분석한결과 chlorogenic acid와 quercetin 모두건물중당생리활성물질함량과동일한경향성을나타냈다.

6 복권정 노승원 김영국 남창수 진채린 박종석 Fig. 4. Contents of chlorogenic acid and quercetin in the lettuce treated with different CO 2 tablet concentration. In the graph, the X axis means the CO 2 tablet concentration. The bars represent the means and the error bars indicate standard error (n=3). Different letters at the top of bars indicate significant differences between the CO 2 tablet treatments (p 0.05). 질함량을분석한결과 chlorogenic acid와 quercetin 모두건물중당생리활성물질함량과동일한경향성을나타냈다. 1배처리구에서 chlorogenic acid의함량이가장높았으며 9.47 mg plant -1 으로대조구 3.81mg plant -1 보다 249% 높게나타났다. 하지만 1배처리구에서 quercetin 함량이가장낮았으며 0.373mg plant -1 으로대조구 0.593mg plant -1 보다 37% 낮게나타났다. 상추는중간정도의가벼운환경스트레스조건에의해식물체내페놀화합물축적및항산화도가향상될수있다는많은연구결과가보고되었다 (Sgherri 등, 2017; Samuolienė 등, 2012). 탄산정처리는상추의생리활성물질을증가시키는데이러한가벼운환경스트레스로작용한것으로보이며, 이는실제탄소- 영양소균형가설 (Bidart-Bouzat와 Imeh-Nathaniel, 2008) 에기초하여광합성이과도해질경우더많은비율의탄수화물이 2차대사산물합성을유도한다 (Becker와 Kläring, 2016; Pérez-López 등, 2013) 는이전연구결과와도유사하였다. HPLC를이용하여상추 6품종에대한주요항산화폴리페놀화합물을분석한이전연구결과 chlorogenic acid, caffeic acid, dicaffeoyl tartaric acid, quercetin 3-O-glucuronide 등의물질이검출됨을확인하였으며 (Nicolle 등, 2004), Oh 등 (2009) 은 Baronet 라는품종의상추에온도및광도조절을통한가벼운환경스트레스처리를통해 chlorogenic acid와 quercetin의함량이모두대조구와비교하여증가하는것을확인하였다. 하지만본연구에서는두물질의함량이탄산정농도에대해반대되는경향성을나타내어향후상추의품종에따른생리활성물질함량에대한추가적인연구가필요하다. 4. DPPH 라디컬소거능분석결과상추잎의추출액을이용하여 DPPH 라디컬소거능을분석한결과대조구와 0.5배처리구에서각각 49.2, 49.3% 로 1배 Fig. 5. DPPH radical scavenging activity in the lettuce leafs treated with different CO 2 tablet concentration. In the graph, the X axis means the CO 2 tablet concentration. The bars represent the means and the error bars indicate standard error (n=3). Different letters at the top of bars indicate significant differences between the CO 2 tablet treatments (p 0.05). 처리구 42.4% 와 2배처리구 40.2% 에비교하였을때유의적으로높은값을나타내었다 (Fig. 5). DPPH 라디컬소거능은항산화활성을나타내는지표로측정시작물의종류나샘플의상태, 추출용매의종류에따라측정결과가매우다양하게나올수있다 (Proteggente 등, 2002; Suh 등, 2013; Kim 등, 2009). 적치마상추와청치마상추의안토시아닌과카로티노이드에의한항산화활성을측정한결과이들물질의농도와항산화활성이양의상관관계를나타내었지만, 물질에따라활성도가크게차이가나는결과를나타내기도하였다 (Park 등, 2015). 이들은식물의항산화활성에관여하는물질에는비타민 C와같은다른수용성항산화물질이관여하는것으로추정하였는데, 본연구의 DPPH 연구결과역시본연구에서분석한 chlorogenic acid, quercetin 외의항산화관련물질이많이관여한것으로사료된다. 90 Journal of Bio-Environment Control, Vol. 30, No. 1, 2021

7 결론 본연구의결과담액수경재배시고형탄산정 0.5배처리시상추의엽폭과엽면적, 생체중과건물중이대조구와비교하여유의적으로증가하는것을확인하였다. 1배와 2배처리구역시대조구와비교하여생육이증가하였지만엽폭을제외하고 0.5배처리와유의적인차이를나타내지않았다. 뿌리의생체중과건물중은탄산정처리와대조구간유의적인차이가발견되지않았지만, 뿌리길이의경우탄산정처리농도가증가함에따라급격히감소하는모습을나타냈다. 이는탄산정처리를통한추가적인이산화탄소공급이전체적인식물의생육증대에긍정적인역할을하지만탄산정처리로인해발생된양액내발포탄산가스의직접적인자극이식물뿌리의형태형성에영향을주는것으로보인다. 따라서향후이러한물리적자극이식물근권부에미치는영향에대한추가적인연구가필요해보인다. 상추의생리활성물질의함량은물질의종류에따라축적되는함량이상이하게나타났으며, 실제항산화활성을나타내는 DPPH 라디컬소거능분석결과탄산정 1 배처리와 2배처리는대조구보다항산화활성능이감소하는것으로나타났는데, 향후상추의항산화활성에직접적으로관여하는생리활성물질에대한추가적인연구가필요하다고판단된다. 적요 수경재배시양액내탄산정처리를통한상추의생육및생리활성물질변화를조사하기위해네덜란드에서시판되는고형탄산정을사용하였다. 실험은무처리를대조구로하여 0.5 배, 1배, 2배처리구로구성하였다. 실험결과, 탄산정처리후챔버내대기 CO 2 농도는처리직후 2배처리구에서 472.2µL L -1 로가장높은수치를보였으며, 양액내 ph는 2배처리구는 ph 6.03로가장많이감소하였다. 이후시간이경과함에따라 CO 2 농도와 ph는처리전수준으로회복하는모습을나타냈다. 상추의엽폭과엽면적은탄산정 2배처리시 17.1cm, 1067cm 2 로가장큰값을나타내었으며지상부생체중, 건물중은 0.5배처리구에서 63.87g, 3.08g으로가장높게나타났다. 상추의근장은대조구에서 28.4cm로가장길었으나처리구들간에지하부의생체중, 건물중은유의적인차이를나타내지않았다. 외관상탄산정처리에의해상추의근장이짧아지고곁뿌리가많이발생한것이관찰되었다. 또한뿌리가갈색으로약간변하는결과가있었지만, 지상부생육에는부정적인영향을미치지않은것으로나타났다. 탄산정처리에의한상추의생리활성물질을분석한결과 chlorogenic acid와 quercetin 두가지물질이검출되었으며이를정량분석한결과 1배처리구에서 chlrogenic acid는대조구보다 249% 증가하였지만 quercetin은 37% 감소한결과를나타냈다. 항산화활성을나타내는 DPPH 라디컬소거능을비교한결과대조구와 0.5배처리가 1배, 2배처리보다유의적으로높은값을나타냈다. 이를통해탄산정처리가수경재배상추의생육과생리활성물질을증대에효과가있음을제시한다. 추가주제어 : chlorogenic acid, DPPH, quercetin, 담액수경, 액체크로마토그래피, 항산화활성 사사 이논문은 2020년도정부 ( 과학기술정보통신부 ) 의재원으로정보통신기획평가원의지원을받아수행된연구임 [No , 인공지능융합연구센터지원 ( 충남대학교 )]. Literature Cited Ainsworth E.A. and A. Rogers The response of photosynthesis and stomatal conductance to rising [CO 2]: mechanisms and environmental interactions. Plant, Cell & Environment 30: Akula R. and G.A. Ravishankar Influence of abiotic stress signals on secondary metabolites in plants. Plant Signaling& Behavior 6: Alexandrov G. and T. Oikawa TsuBiMo: a biosphere model of the CO 2-fertilization effect. Climate Research 19: Becker C. and H.P. Kläring CO 2 enrichment can produce high red leaf lettuce yield while increasing most flavonoid glycoside and some caffeic acid derivative concentrations. Food chemistry 199: Bidart-Bouzat M.G. and A. Imeh-Nathaniel Global change effects on plant chemical defenses against insect herbivores. Journal of Integrative Plant Biology 50: Choi I.L., J.S. Yoon, H.S. Yoon, K.Y. Choi, I.S. Kim, and H.M. Kang Effects of carbon dioxide fertilization on the quality and storability of strawberry Maehyang. Protected Horticulture and Plant Factory 26: (in Korean). Choi K.Y., E.Y. Yang, D.K. Park, Y.C. Kim, T.C. Seo, H.K. Yun, and H.D. Seo Development of nutrient solution for hydroponics of Cruciferae leaf vegetables based on nutrient-water absorption rate and the cation ratio. J. Bio- Environ. Con. 14: (in Korean). Huang J.G., Y. Bergeron, B. Denneler, F. Berninger, and J. Tardif Response of ferest trees to increased atmospheric CO 2. Critical Reviews in Plant Sciences 26: 생물환경조절학회지, 제 30 권제 1 호 2021 년 91

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9 Elevated CO 2 and salinity are responsible for phenolicsenrichment in two differently pigmented lettuces. Plant Physiology and Biochemistry 115: Suh J.H., O.J. Paek, Y.W. Kang, J.E. Ahn, J.S. Yun, K.S. Oh, Y.S. An, and S.H. Park Study on the antioxidant activity in the various vegetables. Journal of Food Hygiene and Safety 28: (in Korean). Taylor G., R. Ceulemans, R. Ferris, S.D.L. Gardner, and B.Y. Shao Increased leaf area expansion of hybrid poplar in elevated CO 2. From controlled environments to open-top chambers and to FACE. Environmental Pollution 115: Um Y.C., S.S. Oh, J.G. Lee, S.Y. Kim, and Y.A. Jang The development of container-type plant factory and growth of leafy vegetables as affected by different light sources. J. Bio-Environ. Con. 19: (in Korean). Wu Y., X. Ma, Y.E. Li, and Y.F. Wan The impacts of introduced CO 2 flux on maize/alfalfa and soil. International Journal of Greenhouse Gas Control 23: 생물환경조절학회지, 제 30 권제 1 호 2021 년 93

Journal of Life Science 2011, Vol. 21. No μ μ

Journal of Life Science 2011 Vol. 21. No. 8. 1120~1126 ISSN : 1225-9918 DOI : http://dx.doi.org/10.5352/jls.2011.21.8.1120 μ μ μ α β Journal of Life Science 2011, Vol. 21. No. 8 1121 μ μ 1122 생명과학회지 2011,