Question

Describe the structure of mature sporangium in pteridophytes.

Answer 1

Structure of mature sporangium in pteridophytes:

1. The sporophyte is generally herbaceous and is differentiated into true roots (adventitious), stem and leaves. The leaves may be small microphyllous or large macrophyllous (fronds).
2. The mature sporangium is the capsule structure in which the reproductive spores are produced and stored.
3. Vegetative reproduction takes place by vegetative buds that develop on the rhizome or by fragmentation of rhizome.
4. Asexual reproduction takes place by means of spores produced inside the sporangia.
5. The sporangia are borne on lower surface or in axils of fertile leaves called sporophylls.
6. In the ferns, the sporangia are clustered into dense aggregations called ‘sori’, which appear as round dots on the under side of the fronds.
7. Plants may be Homosporous i.e., they produce only one type of spores or may be Heterosporous i.e., produce two different types of spores- smaller microspores and larger megaspores.
8. The inner archesporial cells which are tetrahedral in nature divide to form an outer tapetal initial and an inner primary sporogenous cell. The tapetal initial forms a two-layered tapetum by one periclinal and a few anticlinal divisions.
9. The primary sporogenous cells are known to divide and form twelve spore mother cells.
10. A sporophyte (diploid) phase produces haploid spores by meiosis. These spores germinate to produce haploid Gametophyte