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Chapter 22 Seed Plants Without Flowers (Concepts (Major character suites…
Chapter 22 Seed Plants Without Flowers
Trimerophytes - ancestors of ferns and seed plants
Evolution of vascular cambium with radial longitudinal division
Progymnosperms - true woody trees with wood similar to conifers, no seeds
Evolution of early seeds - megaspores reduced to one, integument made from fused telomes, micropyle on the tegument, early pollen chamber
Early seed plants
Conifers - always trees of moderate to gigantic size, leaves always simple needles or scales, have transfusion parenchyma and tracheids, mostly perennial, lack vessel elements and sieve tubes, have both simple cones and seed cones, microspores develop into pollen grains in simple cones and are released into wind, germinate with a pollen tube to fertilize, megaspores develop from ovules into seeds in seed cones after pollination
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Cycadophyta - mostly 1 to 2 m tall but up to 18 m, trunk has bark and persistent leaf bases, prominent pith surrounded by little amounts of soft wood, dioecious with pollen and seed cones on different plants, pollen germinates into flagellated sperm cells and pollen tubes, seed cones differ from seed fern-like less derived types to more cone-like structures, ovules are like those of seed ferns
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Cycadeoidophyta - almost identical to cycads, but had both microsporophylls and microsporophylls in each cone, microsporophylls were located below the megasporophylls and swept around to envelop them
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Ginkgophyta - one extant species, large tree with broad leaves bearing dichotomously branched veins, dioecious, microsporophylls occur in small clusters, ovules paired at the end of small stalks
Gnetophyta - mostly vines or small shrubs with broad leaves, have vessel elements, pollen and seed cones are both compound and seed cones have an extra integument around the ovule
Aneurophytales - shrub-size to large trees, protostele xylem, webbing too little to be true leaves, reproduction through spores
Seed evolution
Pteridospermophyta - called seed ferns, any woody plant with fern-like foliage that carried seeds on its leaves
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Archaeopteridales - up to 8.4 m tall, siphonostele like modern conifers, planated branch system with simple leaves, heterosporous reproduction with released spores
Concepts
Major character suites
Production of a small amount of soft, spongy, parenchymatous wood (manoxylic); large compound leaves, radially symmetrical seeds
Produces hard, strong wood with little parenchyma (pycnoxylic); small, simple leaves and flattened seeds
Evolutionary advantage of the seed over a free-living gametophyte because of enhanced survivorship
