Selaginella Reproduction Flashcards
Step 1
What do Microsporophylls produce?
Microsporophylls of a particular strobilus produce microsporangia that develop & produce a large number of ordinary-sized microspores by meiotic division.
Step 2 (Hint: Megasporophylls)
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Megasporophylls in megasporangia … only one sporocyte completes meiotic process & forms one single tetrad which develops into megaspores.
Which plants are Heterosporous?
Selaginella
It has dimorphism of spores (microspores & megaspores).
Which plants are Homosporous?
Psilotum, Lycopodium, mosses, liverworts & hornworts.
Step 3
What do Microspores develop into & how?
Microspores develop into male gametophytes internally by NUCLEAR & CELL divisions.
What does the Male gametophyte consist of?
Spermatogenous tissue & sterile cell surrounded by a jacket of sterile cells.
128-to-256 sperms are produced.
Step 4
What do Megaspores develop into & how?
1) Megaspores develop into female gametophytes by FREE NUCLEAR DIVISION (formation of many nuclei before cytokinesis).
2) Cytokinesis produces a female gametophyte with several archegonia organized on the surface.
3) Rhizoids develop from the female gametophyte.
Briefly describe the Archegonia.
Have short necks (two tiers of four cells).
What do male & female gametophytes have in common?
Both lack chlorophyll & are saprophytic.
Step 5
What occurs after fertilization?
1) After fertilization of egg by biflagellate sperm, zygote develops.
2) As zygote grows, it develops primary root (radicle) & two primary leaves (cotyledons).
What are the similarities between Selaginella & the reproductive process in seed plants?
1) Localization of sporangium-bearing appendages in strobili.
2) Heterospory
3) Endosporic & intrasporangial development of gametophytes.
4) Unisexual gametophytes
