in nonvascular plants ,gametophyte is dominant,sporophyte is visible

1
in nonvascular plants , gametophyte is
dominant, sporophyte is visible in
seedless vascular plants, sporophyte is
dominant, gametophyte is visible

in seed plants gymnosperms and
angiosperms, sporophyte is increasingly
dominant, gametophyte is enclosed in the
sporophyte
2
homosporous plants one kind of
sporangia one kind of
spore one kind of
gametophyte each gametophyte can
produce both eggs and sperm
3
Seed Plants are heterosporous plants have two
kinds of sporangia
megasporangia megaspores
megagametophytes
microsporangia microspores
microgametophytes
megagametophytes produce eggs microgametophytes
produce sperm
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Megasporangia, megagametophytes, and
eggs megasporangia are located within larger
ovules - each ovule consists of
integuments, a nucellus (the
megasporangium), and a funiculus
micropyle
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megasporogenesis - one or more cells in the
nucellus (megasporocytes) undergo meiosis
produces megaspores enclosed in the ovule
megasporocyte
megaspores (diploid) (haploid)
nucellus (diploid)
integument (diploid)
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- megaspore germinates in the nucellus, produces
a megagametophyte (multicellular,
haploid) - megagametophyte will produce
at least one egg (haploid) (the
process megagametogenesis)
gametophyte generation is entirely enclosed in
sporophyte generation
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Microsporangia, microgametophytes, and
sperm microsporangia consist of sporogenous
tissue (microsporocytes) and a microsporangium
wall
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microsporogenesis microsporocytes (2n)
microspores (1n) meiosis
sporangium
sporangium
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microgametogenesis microspore (1n)
microgametophyte germination
(mitosis)
- the microgametophyte is very small and
enclosed in cell wall of a single microspore
a pollen grain
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cells of the sporangium wall have diploid nuclei
MICROSPORANGIUM
microsporocytes (cells of the sporogenous tissue)
have diploid nuclei
microspores each have a haploid nucleus
each pollen grain is made up of a few cells, each
with a haploid nucleus
- each pollen grain (microgametophyte) produces
at least two sperm and carries them to an
ovule for fertilization
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microsporangium opens to release pollen grains
dehiscence pollen grains are dispersed,
landing near an ovule pollination pollen
grain germinates, producing a pollen tube
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- pollen tube grows to the egg cell sperm
travel through pollen tube, are released near
egg
POLLEN TUBE ELIMINATES THE NEED TO SWIM
THROUGH EXTERNAL WATER
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embryo is enclosed in the ovule
integument (2n)
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- hardening of the integuments produces a
seed - hardened integuments seed coat -
interior contains the embryo (offspring
sporophyte), and nutrition (stored in
nucellus or other tissue)
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seeds provide many adaptive advantages to
plants 1) protection 2) carries
nutrients 3) offspring dispersal