| Abstract: | A uniform batch of tulip bulbs were kept in the dark eitherat 2 °C or 18 °C. Sample bulbs were withdrawn at intervalsfrom both treatments and mitochondria were isolated from thescale tissue. Arrhenius plots of succinate and NADH oxidationby the mitochondria were made. Within the range 036 °C,mitochondria from uncooled bulbs showed a single transitionpoint at about 16 °C, as did mitochondria from freshly formeddaughter bulbs. In contrast, mitochondria from bulbs kept for 8 weeks or longerat 2 °C showed strong indications of two discontinuitiesin the Arrhenius diagrams within a similar temperature range,one about 10 °C below the other. The results suggest thattulip bulbs are chilling-sensitive, and that alterations inthe activation energies of certain oxidative enzymes in responseto accumulated cold treatment are necessary for metabolism tobe directed towards the growth of normal flowers. |
