Abstract:

The developmental morphology of the obturator and micropyle and the pathway of the pollen tubes in the ovarian locule in Phellodendron amurense Rupr. have been investigated by scanning electron microscopy and light microscopy. The obturator of the ovule is of funicular origin. As the ovule is fully developed, the obturator becomes considerably large and closely covers the micropyle. When the pistillate flower reaches the receptive phase, the morphology of the obturator is greatly modified, and its cells on the surface are radially expanded and appear to be columnar, semi-papillar or papillar. Following fertilization the obturator reduces in size and degenerates. The pollen tubes need not necessarily traverse the obturator. Whether the pollen tubes pass the obturator or not depends on the sites at which they enter the ovarian locule. This observation does not support the idea that the obturator mainly serves the function of mechanical guidance for the growth of pollen tubes. Our investigations indicate that the structure of the micropyle changes with the different stages of the reproductive process, and becomes asymmetrical during pollination. The development of the obturator and the micropyle correlates with that of the female gametophyte in P. amurense.

Key words: developmental morphology, micropyle, obturator, Phellodendron amurense, pollen tube pathway