Effects of Salt Stress on Photosynthesis, Free Proline Content and Ion Content in Tobacco.

염스트레스가 담배식물의 광합성, proline 및 이온함량에 미치는 영향

This experiment was conducted to investigate effects of NaCl concentration on photosynthetic rate, free proline content and ion content in tobacco. As NaCl concentration was increased growth was retarded. The decrease growth characteristics(shoot/root ratio was 2.0) at 90mM NaCl indicated that this concentration could be a limiting level. As NaCl concentration was increased photosynthetic rate, transpiration rate, and water use efficiency were decreased. Photosynthetic rate was highly decreased at 60mM NaCl. There was no significant difference between transpiration rate and water use efficiency. Leaf water potential was decreased as NaCl concentration was increased, in that twice lower at 30mM than that of control and drop largely at 120mM NaCl. Free proline content was increased as NaCl increased until 120mM NaCl and drop at 150mM NaCl. The $Ca^{2+}$, $Mg^{2+}$, and $K^+$ contents were increased until NaCl concentration was 120mM. The $Na^{2+}$ content was slowly increased as NaCl concentration increased until 120mM NaCl, and largely increased at 150mM NaCl. There was no significant difference between $Cl^-$ and NaCl treatments except 30 mM NaCl in which $Cl^-$ content was higher than that of control. As NaCl concentration was increased $K^+/Na^+$ ratio was decreased. The negative correlation between $K^+$ and $Na^+$, and positive correlation between $K^+/Na^+$ and protein content were found.

본 실험은 담배의 염스트레스에 대한 생장특성 및 생리적반응을 구명하기 위하여 NaCl을 농도별로 처리하여 시험한 결과를 요약하면 다음과 같다. NaCl농도가 높아질수록 생장은 크게 억제되었으며, 90mM의 지상부/지하부율이 약 2.0이하에서 생육형질이 크게 감소하여 생리적인 제한농도로 나타났다. 광합성량, 증산량 및 수분이용효율은 NaCl농도가 높아질수록 감소하였으며, 광합성량은 60mM에서 대조구의 50%의 감소로 염해에 민감하게 반응하였으며, 증산량과 수분이용효율은 처리농도간에 큰 차이는 없었다. 잎수분포텐셀은 염농도의 증가에 따라 낮아졌으며 30mM에서 대조구의 2배로 낮아졌으며 처리농도간에는 120mM에서 크게 감소하였다. Proline함량은 NaCl농도가 높아짐에 따라 120mM가지는 일정하게 증가하다가 150mM에서 감소하였다. NaCl농도에 따라 $Ca^{2+}$, $Mg^{2+}$, $K^+$의 함량은 90mM까지는 증가하였고, 120mM이상에서는 감소하였다. $K^+$은 염농도의 증가에 따라 완만히 증가하다가 150mM이상에서 급격히 증가하였다. $Cl^-$은 염농도의 증가에 따라 30mM의 일시적 증가외는 처리간의 차이는 없이 감소하는 경향이었다. $K^+/Na^+$율은 염농도가 높아질수록 감소하였으며 90mM의 1.0이하에서 세포내의 항상성이 유지되는 농도로 나타났다. $K^+$와 $Na^+$함량과는 부의 상관을, $K^+/Na^+$율과 단백질함량과는 정의 상관을 나타냈다.