Abstract
The transition temperature of respiratory activity of mitochondria isolated from panicles of rice plant was measured with 41 varieties bred in Korea, which had been agronomically classified into five groups based on their relative cold-tolerance; S (strong cold-tolerance), S-M (moderate to strong cold-tolerance), M (moderate cold-tolerance), M-W (moderate to weak cold-tolerance) and W (weak cold-tolerance). The temperature was found to be $11.5{\sim}13.5^{\circ}C$ for group S, $13.5{\sim}16^{\circ}C$ for group S-M, $16{\sim}17^{\circ}C$ for group M, $17{\sim}18^{\circ}C$ for group M-W, and ${\geq}18^{\circ}C$ for group W respectively with a few exceptions of minor deviation, demonstrating a close correlation between the transition temperature and the chilling susceptivity of a variety. This observation supports the suggestion that the transition temperature of respiratory activity of panicles be adopted as a reliable index for grading a rice variety as to its overall cold tolerance. Also studied is on the methodology for measurement of the transition temperature in the aspect of analytical biochemistry. In addition to the usual polarographic method, a spectrophotometric method which is based on the enzymatic assay of membrane-bound cytochrome C oxidase was examined. This enzyme was found previousely and confirmed again in the present work to be a key factor governing the respiratory trantion at least in plant mitochondria. The optical method was turned out to be very successful, although it was a little more complicate and time-consuming than the electrochemical method.
생육기간동안 냉수처리하는 포장시험(작물시험장 시험사업)을 통해 재배학적방법으로 상대적 내냉성정도가 판정되어 있는 벼 41품종을 재배하여 그 유수로부터 분리한 미토콘드리아의 호흡활성전이 온도를 측정하였다. 강내냉성으로 분류된 품종들은 $11.5{\sim}13.5^{\circ}C$의 상대적으로 낮은 활성전이온도를 보였으며 내냉성이 약한 품종들일수록 그 온도가 높아졌다. 작물시험장의 내냉성 판정등급(강, 중강, 중, 중약 및 약)에 따라 그룹별로 해당품종들의 호흡활성 전이온도를 배열하면 그 순서는 그룹별로 내냉성이 약해지는 순서와 일치하였다. 이 결과는 유수미토콘드리아의 호흡활성 전이온도가 전반적 내냉성(overall cold-tolerance) 판정의 객관적 지표가 된다는 사실을 강하게 시사하고 있다. 호흡활성 전이온도의 간편한 측정을 위한 방법론을 분석생화학적 측면에서 검토하였다. 본연구에서 주로 이용한 polarographic method 이외에도 막에 결합된 cytochrome C oxidase가 호흡활성 및 그 전이온도를 결정한다는 발견에 입각하여 이 효소의 온도에 따른 활성변화를 spectrophotometric method로 측정하므로서 미토콘드리아 호흡계 전체의 활성전이온도를 측정할 수 있음도 확인하였다.