推 mibhxnxu:感謝呀！大大！因為天氣冷，我睡過頭翹課了。......XD 12/04 23:54
Phylum sphenophyta (horsetails)
Single herbaceous genus: equisetum
15 species, the oldest surviving genus of plants of earth
Reproduction: homosporous
Strobilus
Sporangiophores
Ealters- arise from the outer layer of the spore wall
Gpt.: green, free living, bisexual or male
Sperm: multiflagellated and require water
Life cycle
Ch18
seed plants are vascular plants that produce seeds.
Contributing to the success of seed plants as terrestrial organisms are three
important reproductive adaptations:
Continued reduction of the gametophyte
The advent of the seed
The evolution of pollen
The haploid generation may provide a mechanism for “screening” new alleles,
including mutations.
The gametophyte nourishes the sporophyte embryo, at least during its early
development.
All seed plants are heterosporous, producing two different types of sporangia
that produce two types of spores.
Layers of sporophyte tissues, integument, envelop and protect the
megasporangium
A ovule consists of integuments, megaspore, and megasporangium.
A female gametophyte develops inside a megaspore and produces one or more eggs…
The whole ovule develops into a seed.
The microspores, released from the microsporangium, develop into pollen grains.
These are covered with a tough coat containing sporopollenin.
The sperm in most gymnosperms and all angiosperms lack flagella.
Gymnos = naked
Sperma = seed
Seeds are superioir to spores:
The most massive organism: giant sequoia
The tallest tree: coastal red woods
The oldest living tree: bristlecone pine
Megaphylls
Phylum progymnospermophyta
Progymnosperms: seedless vascular plants
Produced spores
Secondary growth, vascular cambia
Seed plants evolved from the progymnosperms
The most familiar gymnosperms are the conifers, the cone-bearing plants such
as pines.
Have second growth, usually forms woody trees or shrubs but some species are
more vine like
Most gymnosperms lack vessels in their xylem.
Phloem: sieve cells, fibers, ray parenchyma, axial parenchyma
Levels: thich cuticle, sunken stomata, fibrous epidermis, mesophyll no
intercellular spaces
Microsporangiate strobili
Seed plant do not form antheridia.
Pollen grain – pollination
Pollen tube
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星不晴
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