In V itro Pollen Germ ina tion and Pollen Tube Growth of P inus thunbe rgii

The organization of pollen and pollen tubes of Pinus thunbergiiwas studied by using a confocal laser scanning microscope after fluorescence labeling. A Pinus thunberg ii pollen was 4-celled pollen with two degenerated p rothallial cells, one generative cell and one tube cell. In culture, pollen germination occurred after app roximately 12h of hydration. During tube growth, the tube cell nucleusmoved into the elongating tube, but the generative cells remained within the pollen grain. There are two distinct zones in elongating pollen tubes. One began in the pollen andextended towards the pollen tube tip, containing abounding amylop lasts. The other zone was the clear zone lackingamylop lasts at the elongating pollen tube tip. The cytop lasmic-streaming type in the tube cellwas a regular fountainlike pattern, with organellesmoving towards the tip in the center of the tube and away from the tip along the cellcortex. Fluorescence microscopy indicated that the pollen tube wall contained cellulose microfibrils and, callose wasp resent in the younger pollen tubes, but disappeared from the older tubes. No callose p lug was detected within thepollen tube. The pollen tube generally developed two to six branches. The sucrose concentration in culture mediumaffected the formation of tube branching and the growth rate of tubes to a great extent. The p resent study suggestedthat the development and cellular organization of gymnosperms pollen tubeswere considerably different from those ofangiosperm pollen tubes.