Relation Between Environmental Factors and the LOX Activities Upon Potato Tuber Formation and Flower-bud Formation in Morning Glory

Life cycles of plants including tuberization and flowering are strongly related to environmental factors such as photoperiod and temperature. Theobroxide induces potato tuber formation and flower bud formation of morning glory under non-inductive conditions and stimulates the activity of lipoxygenase (LOX). In this study, to understand the LOX activity more systematically, the relationships between LOX activity and light and temperature, which effects potato tuber and flower-bud formation, have been investigated. The results showed that LOX activity in morning glory was greatly enhanced up to 30 min and then declined after switching from the light to the dark condition, while the activity did not vary when switching from the dark to the light condition. In addition, the temperature profile of measured LOX activity in the potato and morning glory plants was nearly consistent with the time taken to form potato tubers and flower buds in morning glory, respectively, at different growing temperatures. These results strongly suggest that LOX activity is directly connected with light and temperature to regulate the formation of tubers and flower-buds.