Allyl-isothiocyanate Content and Physiological Responses of Wasabia japonica Matusum as Affected by Different EC Levels in Hydroponics

This study aimed to determine the effect of EC (electrical conductivity) levels of nutrient solution in hydroponic culture on allyl-isothiocyanate (AITC) content within plant tissues, Vitamin C content and physiological responses in wasabi plant (Wasabia japonica M. 'Darma'). The 'Darma' was grown for 5 weeks with a deep flow technique (DFT) system controlled at 5 different EC levels, including 0.5, 1, 2, 3, and $5dS{\cdot}m^{-1}$. In result, the highest total content of AITC showed at EC level 5 and $3dS{\cdot}m^{-1}$ for 1 or 5- week, respectively. The total content of AITC increased about 1.2-1.4 times when the plants were grown in the EC levels between 0.5 and $2dS{\cdot}m^{-1}$, whereas the content decreased about 6 and 56 % in the EC level 3 and $5dS{\cdot}m^{-1}$, respectively. The content of AITC was relatively higher in petiole tissue, about 53 %, taken from 1 week-grown plants when the EC was controlled between 0.5 and $2dS{\cdot}m^{-1}$. Root tissue also had relatively higher content of AITC, about 45.1 %, when the EC was controlled at 3 and $5dS{\cdot}m^{-1}$. However, a 5-fold decrease in the AITC content was found in blade tissue and a 6.8-fold decrease in root when the EC was controlled at $5dS{\cdot}m^{-1}$ for 5 weeks. There was no significant difference in the vitamin C content in 1-week grown leaf tissues under the different EC level treatments; but, the content increased about 27% in 5-week grown plants at the EC level between 0.5 and $2dS{\cdot}m^{-1}$, compared to the 1 week-grown leaf tissue. Electrolyte leakage of leaf tissue taken from 3-week grown plant was 3-fold higher at the EC level $5dS{\cdot}m^{-1}$, compared to the EC level between 0.5 and $2dS{\cdot}m^{-1}$. Chlorophyll content, photosynthesis rate and transpiration rate were decreased when the EC was controlled at higher than $2dS{\cdot}m^{-1}$. Leaf water content, specific leaf area and growth were decreased when the EC was controlled at $5dS{\cdot}m^{-1}$ for 5 weeks. All the integrated results in this study suggest that the EC level of nutrient solution should be maintained at lower than $3dS{\cdot}m^{-1}$ in order to improve nutritional value and quantity required for hydroponically grown wasabi as functional vegetable.

고추냉이 수경재배시 배양액의 EC 수준이 Allyl-isothiocyanate 함량과 생리적 반응에 미치는 영향

본 연구는 고추냉이 '달마' 품종을 배양액의 EC 수준을 달리하여 수경재배하였을 때, 기능성 성분인 AITC의 조직별 함량, 비타민 C 함량 및 생리적 반응들에 미치는 영향을 구명하고자 하였다. 배양액의 EC는 Yamasaki 배양액 EC $0.5dS{\cdot}m^{-1}$를 기준으로 1N-NaCl로 조절한 5수준(EC 0.5, 1, 2, 3, $5dS{\cdot}m^{-1}$)으로 5주간 담액 수경재배하였다. 고추냉이의 총 AITC 함량은 처리 1주에는 EC $5dS{\cdot}m^{-1}$에서, 처리 5주에는 EC $3dS{\cdot}m^{-1}$에서 가장 높았다. 처리 5주 후 고추냉이 AITC 함량은 처리 1주에 비하여 EC 0.5-$2dS{\cdot}m^{-1}$에서 1.2-1.4배 증가하였으나, EC $3dS{\cdot}m^{-1}$에서는 6%, EC $5dS{\cdot}m^{-1}$에서는 56% 감소하였다. AITC의 상대적 비율이 EC 0.5-$2dS{\cdot}m^{-1}$에서는 처리 1주와 처리 5주 모두 엽신과 뿌리에 비해 엽병(평균 53.4%, 49.5-61.1%)에서 높았다. 그러나 EC 3과 EC $5dS{\cdot}m^{-1}$에서 뿌리의 AITC 상대적 비율이 처리 1주에는 평균 45.1%(43.7-46.1%)로 엽신과 엽병에 비해 높은 반면 처리 5주에는 평균 16.6%(16.0-17.1%)로 낮아져, 엽신에서는 5배, 뿌리에서는 6.8배의 AITC 함량이 감소하였다. 처리 1주 비타민 C 함량은 83.7-$107mg{\cdot}100g^{-1}FW$로 처리에 따른 차이가 없었으나, 처리 5주 후, EC 0.5-$2dS{\cdot}m^{-1}$에서는 117.8-$137.5mg{\cdot}100g^{-1}FW$로 27% 증가하였다. 고추냉이 잎 전해질 유출은 EC $5dS{\cdot}m^{-1}$에서 EC 0.5-$2dS{\cdot}m^{-1}$에 비해 3배 증가하였다. 그러나 엽록소 함량, 광합성 및 증산율은 EC $2dS{\cdot}m^{-1}$ 이상에서, 수분함량과 비엽면적은 EC $5dS{\cdot}m^{-1}$에서 감소하였다. 처리 5주 후 고추냉이 생육은 EC 3과 $5dS{\cdot}m^{-1}$에서 엽수와 지상부 생체중이 감소하였다. 이상의 결과, 기능성 채소로서 고추냉이 수경재배시 품질과 생육을 유지하기 위한 적정 배양액의 EC는 $3dS{\cdot}m^{-1}$ 이하가 적합하리라 판단된다.