Answer to Question #111278 in Biology for Yogita sharma

Question

List the characteristics of the pollen grains that are useful as taxonomic
evidences. Explain in detail.

Answer 1

The characteristics of the pollen grains that are useful for the identification of the taxonomic features include:

• size, shape, and symmetry. The pollen in modern flowering plants varies between 2.4 μm and 200 μm. The shapes of the pollan grains include circular, triangular, spheroidal, oblate, pro-late, etc. Grains may be symmetrical (radially, bilaterally symmetrical) or asymmetrical.
• number and arrangement of pollen units. The pollen grains may be organized into tetrads, dyads, and polyads. The arrangement of pollen units can be categorized as tetrahedral, tetragonal, rhomboidal, linear, etc.
• number, shape, and position of apertures. These are thin-walled in the outer pollen wall where the pollen tube emerges. The types of apertures include sulcus (elongated ectoaperture), ulcus (rounded aperture), colpus (long furrow-like aperture), etc. According to the position of the aperture, grains are classified as proximal, zonal, and global.
• exine stratification. Exin is the outer layer covering the pollen. They can be distinguished by the presence and form of lectum, etc.