Evolution of Cycads, Gymnosperms and Ferns. Div: Progymnospermophyta Gymnosperm anatomy - secondary...
-
date post
21-Dec-2015 -
Category
Documents
-
view
220 -
download
1
Transcript of Evolution of Cycads, Gymnosperms and Ferns. Div: Progymnospermophyta Gymnosperm anatomy - secondary...
Evolution of Cycads, Gymnosperms and Ferns
Div: Progymnospermophyta
• Gymnosperm anatomy - secondary xylem tracheids, circular bordered pits - and fern-like fronds & reproductive dispersal by spores. (no seeds)
• Arose in Upper Devonian 350 mya --> Pennsylvanian 290 mya
• All extinct
• Probably the immediate ancestor of all seed plants.
• Archaeopteris
Div: Pteridospermophyta “Seed Ferns”
• Gymnosperm anatomy and gymnosperm seed type with fern-like fronds. (seeds on fronds)
• Arose during Carboniferous Period 345 mya --> Permian 250 mya.
• All extinct
• Probably the immediate ancestor of the cycads.
Div: Pteridospermophyta “Seed Ferns”
• Ovules (megasporangium with embryo after fertilization) develop into “seeds” covered with two cells layers from integument or seed coat.
• Naked Seed, “Gymnosperm”
• Monoecious
Div: Cycadophyta “Cycads”
• Resemble “palm trees”.
• Cycad foliage does not bear ovules or seeds - these are in special seed cones (strobili); pollen (with sperms) produced in pollen cones.
• Arose during Permian Period 280 mya --> extant
• A dominant form of vegetation during the Jurassic and Triassic Periods --> 135 mya.
Div: Cycadophyta “Cycads”
• All are dioecious: Micro and Megasporangia (strobili) on separate plants.
• Cycas
Div: Cycadophyta “Cycads”• Reproductive cycle in cycads wind pollination; pollen droplet
• 4 - 6 months between• pollination &• fertilization
• interval between pollination and fertilization: 4 - 6 months.
Div: Cycadophyta “Cycads”
• Two motile sperms produced by each pollen tube --> archegonial chamber.
• Cycads & Ginkgos are
• only seed plants with
• motile sperm
Div: Cycadophyta “Cycads”
• No fixed period of dormancy in cycads.
Evolution of Seed Plants
• Derived Trait
Evolution of Seed PlantsGymnosperms
• Pollen - Encased male microgametophyte (n) that produces
• sperms (n).
• (Frees plant from the need for water in the pollination
• process.)
• prothallus cell(s), tube cell(s), generative cell
• ---> sperms
• Ovule - The female megagametophyte (n) with eggs (n) surrounded
• by the old megasporangium (2n) with two layers from the
• old sporophyte (2n) that will form the integument (2n).
• (Frees plant from the need for water in fertilization.)
• Cones - An axis bearing a tight cluster of scales or leaves for
• reproduction. Scales either bear microsporangia or
• meagasporangia in separate cones. (Pollen & Seed Cones)
• Seed - ?
Evolution of Seed PlantsGymnosperms
• Seed - The matured ovule with an embryo in a resting state.– Integument - (2n) May be fleshy
– Female Gametophyte - (n) nuritive; includes nucellus
– Embryo - (2n) forms from zygote after fertilization.
Evolution of Seed PlantsGymnosperms
Div: Ginkgophyta“Ginkgos, Maidenhair Trees, Yin hing (silver apricot)”
• Arose during the Permian 250 mya.
• Richly branched woody plant with simple leaves.
• Ginkgo biloba living fossil
Div: Ginkgophyta
• 1. Large stems; small simple leaves; deciduous.
• 2. Dioecious (female more shrubby)
Div: Ginkgophyta
• 1. Large stems; small simple leaves; deciduous.
• 2. Dioecious (female more shrubby)
• 3. Has bud scales; dimorphism in branches. (long and spur shoots).
• 4. Stomates on abaxial (bottom) of leaf; two vascular bundles and 2 leaf traces per leaf.
•
Div: Ginkgophyta
• 1. Large stems; small simple leaves; deciduous.
• 2. Dioecious (female more shrubby)
• 3. Has bud scales; dimorphism in branches. (long and spur shoots).
• 4. Stomates on abaxial (bottom) of leaf; two vascular bundles and 2 leaf traces per leaf.
• 5. Initiation of cambium after primary growth; growth rings.
• 6. Cork cambium or phellogen develops in outer cortex --> phellem (cork cells, bark)
•
Div: GinkgophytaReproduction: Dioecious
• Microsporangia (2n) - strobili
• 1 yr. --> microsporocyte (2n) --> meiosis --> microspores (n) Spring --> pollen (male gametophyte)
• Pollination (pollen droplet mucilaginous) -->
• Megasporangia - ovules
• 1 yr. Development of megasporocyte (2n) --> meiosis --> megaspore (n) --> female gametophyte ( with egg - n) as pollen tube grows - after 5 mos.
• (Aug-Oct) fertilization - development of seed - 2nd yr.
•
Div: GinkgophytaReproduction: Fertilization the 2nd Year
• generative cell --> 2 flagellated sperms (just prior to fertilization) --> swim to end of pollen tube
• egg from archegonium swells and forces apart neck cells --> exposed to pollen tube and sperm for fertilization.
• Micropyle
•
Div: GinkgophytaReproduction: Development
• seed
•
Div: GinkgophytaReproduction: Development
• Outer fleshy layer of the integument emits foul order!
• However, inner part of the seed is edible!
•
•
Div: Coniferophyta“Pines”, “Spruces” and “Firs”
• Evolved during the Carboniferous Period 325 mya
Div: Coniferophyta“Pines, Spruces and Firs”
Div: Coniferophyta“Pines, Spruces and Firs”
Div: Coniferophyta“Pines”, “Spruces” and “Firs”
• Evolved during the Carboniferous Period 325 mya
• 1. Leaves simple; often needle-like or scale-like.
• 2. Xylem compact, composed mostly of tracheids (seasonal growth - rings).
• 3. Pith and cortex restricted - xylem composes most of the stem.
Div: Coniferophyta“Pines”, “Spruces” and “Firs”
• 1. Leaves simple; often needle-like or scale-like.
• 2. Xylem compact, composed mostly of tracheids (seasonal growth - rings).
• 3. Pith and cortex restricted - xylem composes most of the stem.
Div: Coniferophyta“Pines”, “Spruces” and “Firs”
• 1. Leaves simple; often needle-like or scale-like.
• 2. Xylem compact, composed mostly of tracheids (seasonal growth - rings).
• 3. Pith and cortex restricted - xylem composes most of the stem.
• 4. Stem may be differentiated into long and spur shoots.
Div: Coniferophyta“Pines”, “Spruces” and “Firs”
Div: Coniferophyta“Pines”, “Spruces” and “Firs”
• 1. Leaves simple; often needle-like or scale-like.
• 2. Xylem compact, composed mostly of tracheids (seasonal growth - rings).
• 3. Pith and cortex restricted - xylem composes most of the stem.
• 4. Stem may be differentiated into long and spur shoots.
• 5. Leaf traces one or few per leaf.
• 6. Typically evergreen; loose leaves gradually.
• 7. Protostelic taproot.
Div: Coniferophyta“Pines”, “Spruces” and “Firs”
Div: Coniferophyta
• Pollen or Staminate Cone
• Seed or Ovulate Cone
Div: Coniferophyta
• Pine Pollen
Div: Coniferophyta• Ovulate Pine Cones:
Div: Coniferophyta
• Mature Pine Ovule with Two Archegonia:
Div: Coniferophyta• Ovules at Fertilization and with Embryo:
Div: Coniferophyta
• Pine Seedling:
Div: Coniferophyta