The observation of ultra-structure during the petal senescence of Dracocephalum argunense Fisch. ex Link

Dracocephalum argunense is a local wild flower in Heilongjiang, China, which has been successfully domesticated. The value of D. argunense in landscaping has been severely affected due to its flowering time of only 2-3 days. The petal senescence is related to the programmed cell death. It is important to elucidate phenomenon and mechanisms of the petal senescence process. Therefore, in the present study, the ultrastructure of the petal cells during the process of flowering was first investigated. The results showed that the programmed cell death appeared during the process of the petal senescence of D. argunense. There were many big phagocytic vesicles produced by vacuoles in the cells acted as lysosome that led to the selfdisintegration of the petal cells and thus fulfilled the process of cell death. It was suggested that the petal senescence of D. argunense is the type of vacuole related programmed cell death.