XVI International Botanical Congess
In ovules of P. densiflora, nucellus cells that lie along the route of pollen tube growth toward the female gametophyte become deformed and die. In this study, following pollination, nuclei of the nucellus cells around the pollen tube were stained by the TUNEL method. No TUNEL-positive cells were found in the ovule prior to pollination. The plasma membrane of dying nucellus cells became separated from the cell wall and the protoplast shrunk. In the shrunken protoplast, vacuoles were collapsed and degradation of chromatin, plastids and mitochondria was noted. Agarose gel analysis of DNA isolation from the ovule revealed DNA ladders. These results suggest that the Pinus nucellus cell die by programmed cell death associated with pollen tube growth.