BIOL 2P93 Lecture Notes - Lecture 17: Leptosporangiate Fern, Embryophyte, Ligule
24 Jan 2016
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Male gametophytes (microgametophytes): develop w/in microspore + lack chlorophyll. Mature = consist of single prothalial/vegetative cell + an antheridium biflagellated sperm. Female gametophyte: (megagametophyte): megaspore wall ruptures + gametophyte protrudes through outside = portion which archegonia develop. Fertilization after microspores + megaspores shed near one another from strobilus= sperm have short swim to reach eggs (still need water). W/ lycopodiaceae, during embryonic development, suspensor is formed. = thrusts developing embryo deep w/in nutrient rich tissue of female gametophyte. Developing sporophyte slowly emerges from gametophyte + becomes independent. Step 1: remember that selaginella sp. is heterosporous = micro + megasporangia together in same strobilus on diploid mature sporophyte. : presence of ligule (small scale-like outgrowth) near base of upper surface sporophyll. Step 2: sporophyte makes many small microspores + fewer, but larger megaspores = shed by strobilus in close to each other. During development of haploid female gametophyte (megagametophyte), megaspore wall ruptures + gametophyte protrudes to outside = makes archegonia.
