The effects of cadmium ions (Cd2+) on the Chl a fluorescence of Ricciocarpos natans were investigated in order to determine whether Chl fluorescence can be used as a biomarker to estimate the physiological responses of plants to cadmium stress. In all plants treated with Cd2+, the image of Fv/Fm, which represents the maximum photochemical efficiency of PSⅡ, changed as the Cd2+ concentration increased, when treated for 48 h or more. Changes of ΦPSⅡ and QP images were recognized even at 10 μM Cd2+. The Chl a O-J-I-P fluorescence transient was also affected even at 10 μM Cd2+. The fluorescence yield decreased considerably in steps J, I and P in plants treated with Cd2+, although a typical polyphasic rise was observed in non-treated plants. The Chl fluorescence parameters, Fm, Fv/Fo, Sm, SFIabs, PIabs and ETo/CS, decreased as the Cd2+ concentration increased, while the Mo and Kn parameters increased. Peroxidase activity decreased significantly and catalase activity increased as the Cd2+ concentration increased. Because of its sensitivity to Cd2+ Ricciocarpos natans is useful in experiments investigating the responses of plants to cadmium exposure. Several parameters (Fm, Fv/Fo, Sm, SFIabs, PIabs, ETo/CS, Mo and Kn) can be applied to determine quantitatively the physiological states of plants under cadmium stress.

Abstract
 1. 서 론
 2. 재료 및 방법
  2.1. 식물재료 및 배양
  2.2. 광합성효율 분석
  2.3. 항산화효소 활성 분석
 3. 결과 및 고찰
  3.1. 카드뮴 스트레스에 의한 형광이미지의 변화
  3.2. 항산화효소 활성의 패턴
  3.3. O-J-I-P 곡선 및 형광변수의 변화
 4. 결 론
 참 고 문 헌

• 오순자(농촌진흥청 국립원예특작과학원 온난화대응농업센터) | Soonja Oh (Agricultural Research Center for Climate Change, National Institute of Horticultural and Herbal Science, RDA)
• 고석찬(제주대학교 생물학과) | Seok Chan Koh (Department of Biology, Jeju National University) Corresponding author