Winter's bark pollen. Coloured scanning electron micrograph of winter's bark Drimys winteri pollen. The pollen is found in associations of 4 grains,known as tetrads. The outer wall (exine) of the grain comprises rod- like processes (bacula),fused at their tips,forming a network of ridges (muri) and surrounding a circular germinal pore. When the pollen,containing male gametes,lands on the stigma of a flower,it germinates. A pollen tube grows out of a pore,down the stigma,to the ovary. Male nuclei pass down the tube and fertilize the ovules to form seeds. Winter's bark is a flowering shrub native to South America. Magnification: x1380 when printed 10cm high | |
Lizenzart: | Lizenzpflichtig |
Credit: | Science Photo Library / Litchfield, R.E. |
Bildgröße: | 4150 px × 5114 px |
Modell-Rechte: | nicht erforderlich |
Eigentums-Rechte: | nicht erforderlich |
Restrictions: | - |