Pteridophytes MCQ - Practice Questions with Answers

• Pteridophytes are first vascular and successful terrestrial plants with true roots, stem and leaves but no flowers, fruits and seeds.
• These plants are mostly found in cool, damp, shady places. Some may also be found in sandy-soil conditions. 
• The dominant stage in the life cycle of pteridophytes is sporophyte. It possesses roots, stem and leaves.
• The sporophyte of pteridophytes possesses vascular tissue i.e. xylem and phloem.
• In xylem, true vessels are absent but tracheids are found.
• In phloem, companion cells and sieve tubes are absent, however, sieve cells are present.
• The leaves in pteridophytes can be of two types i.e. they can be small, microphyllous without leaf gaps as in Selaginella and Lycopodium or they can be large macrophyllus as in Ferns like Dryopteris.

 
Reproduction in Pteridophytes:
 

• The sporangia are formed singly in the axil of sporophylls which aggregate to form cones as in Selaginella and Equisetum or developed on the abaxial surface of leaves in groups called sori as in ferns like Dryopteris.
• Sporangium may develop from a single cell (Leptosporangiate development) or from a group of cells (Eusporangiate development).
• The spore mother cells in sporangia give rise to spores by undergoing meiosis.
•  Pteridophytes can be homosporous or heterosporous. Homosporous pteridophytes produce similar kind of spores. Heterosporous pteridophytes produce two kinds of spores i.e. microspores and megaspores. Microspores develop into male gametophyte and megaspores develop into the female gametophyte.
• Spores after germination give rise to a microscopic, usually photosynthetic, independent gametophytes known as Prothalli. 
• Prothallus can be monoecious or dioecious in homosporous species but always dioecious in heterosporous species. 
• Gametophytes have stalkless (sessile), jacketed multicellular sex organs. The male organ is antheridium and female organ is archegonium.
• Antheridia give rise to biflagellate (Selaginella, Lycopodium) or multi flagellated (Dryopteris) male gametes.
• Archegonium possesses jacket at the neck with four rows of jacket cells. Only one egg cell is present in the archegonium.
• Fertilisation is by Zooidogamous Oogamy.
• In some pteridophytes, the female gametophyte is retained in the megasporangium of the sporophyte. Fertilization and embryo development takes place in the sporangium itself. This event is considered as a precursor for seed habit.
• The embryo develops into the sporophyte. 

 Apospory:
 

• In most life histories, a 2n sporophyte typically alternates with a 1n gametophyte, but there are significant deviations such as apospory and apogamy. 
• Apospory is the development of 2n gametophytes, without meiosis and spores, from vegetative, or nonreproductive, cells of the sporophyte. 
• The aposporous gametophyte thus formed is infertile under natural conditions. 

Apogamy:
 

• Apogamy refers to the development of 1n sporophytes without the formation of gametes and syngamy from vegetative cells of the gametophyte. 
• The 1n apogamous sporophyte is infertile under natural conditions because of disruption of cytological events.