Generative Cell Division and Sperm Cell Association in the Pollen Grain of Sambucus nigra

Generative cell division in tricellular pollen grains of Sambucusnigra L. (Caprifoliaceae) has been examined with light and electronmicroscopy. During division the generative cell is located inthe centre of the pollen grain, near to the nucleus of a surroundingvegetative cell. Conventional mitosis of the generative cellis followed by cytokinesis through centrifugal cell plate formation.Two sister sperm cells remain in spatial contact with each otherand are surrounded, as formerly their progenitor cell was, bythe vegetative cell. From the changes of shape of the generativecell during division and of the sperm cells it may be assumedthat the space between these cells and the vegetative one containsa labile, non-rigid, wall material. No plastids have been observedin the generative cell and its mitochondria appear to be unequallydistributed between the two future sperm cells during division. Sambucus nigra L., generative cell division, pollen, sperm cell association