Cytological Observations and In Vitro Germination of Nipa (Nypa fruticans Wurmb., Arecaceae) Pollen

Abstract

The staminate rachillae from laterals of nipa (Nypa fruticans Wurmb.) at different stages of inflorescence development were sampled for cytological observations using squash technique, with 2% acetocarmine as the stain. Results showed that the dividing microsporocytes exhibited a tetrad in tetragonal shape enclosed in thick callose walls at the end of meiosis II. The microspore products consisted not only of uninucleate but also of binucleate and trinucleate pollen during anthesis. Meiotic stages were interpreted as highly normal, which suggests high pollen viability. In vitro germination observed every 4-h intervals for 24 h showed that sucrose level at 15% attained significantly highest germination at 53%. The germinated pollen developed a knob protrusion instead of an elongated pollen tube. There was a significant difference in pollen knob length at 15% sucrose measuring 9.6 µm, the longest observed, compared to the control. With significant interaction between sucrose and boron levels, 10% and 15% sucrose levels achieved higher in vitro germination when combined with 0.01% and 0.005% boron, respectively. Indeed, sucrose and boric acid consisting of the liquid medium can initiate nipa pollen germination, confirming earlier results with lower concentrations.