저온에서 완두유묘 줄기의 유리 IAA 수준과 그 전구체인 트립토판 수준이 저하하므로, IAA수준의 조절 메커니즘을 규명하기 위하여 IAA분해효소계에 미치는 저온의 영향을 조사하였다. $25^{circ}C$에서 키운 백색 관두유표를 $5^{circ}C$의 저온으로 옮기면 IAA oxidase와 peroxidase의 수준은 증가하였으며 catalase의 수준은 저하되었고 과산화수소는 축적되어, 전체적으로 IAA분해계가 저온에서 강화되었다. 저온에 놓였던 유묘를 상온으로 옮기면 IAA 분해계는 다시 대조구 수준으로 회복하였다.
Previous work has shown that the levels of free and total IAA and tryptophan decrease on exposing etiolated pea (Pisum sativum L. var. Sparkle) seedlings grown at $25^{circ}C$ to $5^{circ}C$ for 3 days, suggesting that low temperature down-regulates the level of endogenous IAA, in part, by reducing tryptophan biosynthesis. To understand, in this study, the effect of low temperature on the regulation of IAA degradation system in etiolated pea seedlings, enzyme levels of IAA degradation system and hydrogen peroxide content were analyzed during and after chilling($5^{circ}C$) 6-day-old pea seedlings grown at $25^{circ}C$. The levels of IAA oxidase and peroxidase increased during chilling and gradually restored to the level of control on termination of chilling. Catalase levels decreased upon chilling and increased to the level of control on termination of chilling. $H_2O_2$ was accumulated during chilling up to the level of $5.5;{mu}mol/g$ fresh weight while at $25^{circ}C$ maintained a relatively constant $H_2O_2$ level of $4;{mu}mol/g$ FW. All together, it appears that low temperature, in part, by increasing enzyme levels of IAA degradation system and accumulating $H_2O_2$, down-regulates endogenous level of IAA in etiolated pea shoots.
