청색파장(靑色波長)영역이 결여된 태양광이 작물(作物)의 생산성(生産性) 및 내냉성(耐冷性)의 향상에 미치는 효과 II. 미토콘드리아막(膜)의 인지질불포화도(燐脂質不飽和度)의 증가

Effect of Blue Color-deficient Sunlight on the Productivity and Cold Tolerance of Crop Plants II. On the unsaturation of mitochondrial phospholipid

청색광(靑色光)파장영역이 결여된 태양광하에서 재배된 작물(광질(光質)처리구)의 잎에서 분리한 인지질(燐脂質)과 미토콘드리아막(膜)에서 분리한 인지질의 지방산조성(組成)의 특성을 지방산 부포화도(不飽和度)(지질분자당(當) 이중결합(二重結合)수)로서 조사하고 백색자연광(白色自然光)하의 작물(대조구(對照區))의 그것과 비교하였다. 공시(供試)된 작물(오이, 호박, 고추, 토마토)에서 공(共)히 광질처리구의 미토콘드리아가 대조구보다 최저 8%(토마토) 최고 49%(오이)의 지방산불포화도증가율($4%{\sim}8%$, 광질(光質)처리구/대조구(對照區))를 훨씬 상회하였다. 이러한 관찰사실은 청색광(靑色光)이 세포생체막(生體膜)의 화학적(化學的) 특성(特性)에 미치는 효과는, 지질지방산의 불포화도에 관한한, 주(主)로 미토콘드리아막(膜)에서 일어났음을 시사한다. 미토콘드리아막의 지방산불포화도가 세포생체막 전체의 평균지방산불포화도보다 현저히 낮은 것을 확인하고, 이것은 미토콘드리아막(膜)에서 전자전달과정(電子傳達過程)의 부반응(副反應)과 청색광에 의한 photosensitized reaction에 의해 각각 생성되는 산화력이 강한 산소화학종(化學種)(특히 oxygen super radical;$O_2-$)에 의한 불포화지방산의 산화적(酸化的) 파괴의 결과라고 해석하였다. 따라서 청색광의 제거는 최소한 photosensitized reaction에 의한 $O_2-$의 생성만은 줄일수 있으므로, 상기 광질처기구에서 나타난 지방산분석결과는 지용성 항산화제(抗酸化劑)(${\alpha}-tocopherol$) 수준의 증가($6{\sim}13%$, 광질처리구/대조구)는 청색광이 유발하는 photodynamic action의 존재를 간접적으로 시사하는 자료가 되었다.

The fatty acid compositions of phospholipids extracted from leaves and leaf mitochondria, which were sampled from several horicultural plants grown under blue color-deficient sunlight (BCDS), were determined and compared with those from plants grown under natural white colored sunlight(WCS). It was found that the mitochondria isolated from plants grown under BCDS contained phospholipid whose degree of unsaturation in unit of number of double bonds per lipid molecule was remarkably higher than that from plants grown under WCS, the relative increment being $8{\sim}49%$. This was significantly larger than the relative increment, $4{\sim}8%$ for total phospholipid extracted from whole leaves grown under BCDS campared to WCS. This observation demonstrated that the blue light effect of sunlight on the chemical property of cellular membranes, as long as it was concerned with fatty acid composition, arose mainly at the mitochondrial membrane. Also observing that the degree of unsaturation of mitochondrial phospholipid was much lower than that of total phospholipid, it was interpreted that this was the consequence of rather active oxidative destruction of lipid-fatty acid components occuring in mitochondrial membrane by the reactive oxygen species, especially superoxide($O_2-$), which was known to be produced in mitochondrial inner membrane through the side reactions of the respiratory electron transport chain and also probably through the photosensitized reaction involving oxygen induced by blue colored light. Thus, it may be tentatively concluded that the extent of photosensitization in mitochondrial membrane could be considerably reduced under BCDS resulting in lowering of the $O_2-$ level in the respirating organelle The possible involvement of photodynamic action in membrane oxidation was also indicated by the fact that the typical fat-soluble antioxidant, ${\alpha}-tocopherol$, was found to be contained on a higher level in leaves under BCDS than those under WCS.