Plants IIPlants II
The Vascular Plants
Hypericum sp.Photo by Alan Mulvey
THE SEED PLANTS I
Gymnosperms
Evolution of the Seed PlantsEvolution of the Seed Plants
Heterosporous Seed: (embryo & stored food) Evolution of pollen
Megagametophyte develops within ovule* Microgametophyte develops within pollen grain*Pollen grains evolved by reduction of male gametophyte
& protection by pollen wallsBoth the male & female gametophytes were retained
within the sporophytes
Evolution of the seedEvolution of the seed
One cell megaspore is retained within megasporangium It is protected by integument It develops into mature megagametophyte within the embryo sac After fertilization, it matures into the embryo (sporophyte)
Lilium: PollenLilium: Pollen
Generative cell (2 sperms)
Tube cell
Pollen wall
Pine: PollenPine: Pollen
Generative cell
Tube cell
Wings
Evolutionary transition from a Evolutionary transition from a gametophyte to sporophyte dominancegametophyte to sporophyte dominance
From Keeton, 1993
The Gymnosperms: CharacteristicsThe Gymnosperms: Characteristics
(naked seed)*Water is not required for fertilizationMainly pollinated by windReproductive changes increased protection of
gametesHave sunken stoma & thicker cuticles
Seed ConeSeed Cone
Cone Scale
Two Seeds per Scale
Pine: LeafPine: Leaf
Sunken Soma
Epidermis
Hypodermis
Characteristics Cont..Characteristics Cont..
Have secondary growth - all trees or shrubs Mostly evergreen Xylem has tracheids, lacks vessels (except
some Gnetophytes) Phloem has sieve cells, lacks sieve tube
members
ProgymnospermsProgymnosperms
An extinct group that arose in late Paleozoic Intermediate between seedless & seed
plants Progymnosperms were ancestors of seed
plants Evolved bifacial V.C. & wood (page 411)
Seed Plants I - GymnospermsSeed Plants I - Gymnosperms
Conifers – Coniferophyta Cycads – Cycadophyta Maidenhair tree – Ginkgophyta Gnetophytes – Gnetophyta
Conifers: Phylum ConiferophytaConifers: Phylum Coniferophyta
evolved 290 MYO Constitute the largest group of gymnosperms (50 genera,
550 spp.) Include the tallest & largest trees ever (Giant redwood) Conifers (pine, fir, spruce) have great commercial value
in temperate zones Leaves are either
needles, long or short, as in pines, fir, sprucesmall flat, scale-like as in junipers, cypresses
Mostly evergreen, monoecious
White Pine: White Pine: Pinus strobusPinus strobus
White Pine
White Pine : Twig &Needles : Twig &Needles
White PineWhite Pine
Pollen Cones Seed Cone
Longleaf Pine: Longleaf Pine: Pinus palustrisPinus palustris
Loblolly Pine: Loblolly Pine: P. taedaP. taeda
Loblolly Pine: Loblolly Pine: Pollen ConesPollen Cones
Slash Pine: Slash Pine: P. elliottiiP. elliottii
Turpentine Production
Bald Cyprus Knees: Bald Cyprus Knees: Taxodium distichumTaxodium distichum
Knees
Bald CyprusBald Cyprus
Bald CyprusBald Cyprus
Bald Cyprus: Crown & Seed ConesBald Cyprus: Crown & Seed Cones
Coast Red Wood: Coast Red Wood: Sequoia Sequoia sempervirenssempervirens
Fossil
Sequoia: Coast Red Sequoia: Coast Red WoodWood
Giant Red Wood Giant Red Wood SequoiaSequoia
http://www.habitas.org.uk/gardenflora/sequoiadendron.htm
Giant Red WoodGiant Red Wood
Seed Cones Pollen Cones
http://www.conifers.org/cu/se2/
Balsam Fir: Balsam Fir: Abies balsameaAbies balsamea
Balsam FirBalsam Fir
Seed Cone Leaves
Larch: Larch: Larix deciduaLarix decidua
LarchLarch
Developing cones
Common Juniper: Common Juniper: Juniperus communisJuniperus communis
Tree
Leaves
Juniperus virginiana Juniperus virginiana (Eastern Red Cedar)(Eastern Red Cedar)
Cones
Hemlock:Hemlock: Tsuga canadensisTsuga canadensis
Hemlock: Leaf & ConeHemlock: Leaf & Cone
White Spruce: White Spruce: Picea glaucaPicea glauca
Pollen conesYoung seed cones
Pollinated seed cones
White White SpruceSpruce
Pacific yew: Pacific yew: Taxus brevifoliaTaxus brevifolia
http://www.fw.vt.edu/dendro/dendrology/syllabus/tbrevifolia.htm
Maidenhair tree Maidenhair tree Phylum Ginkgophyta:Phylum Ginkgophyta:
One extant species, Ginkgo biloba (notched leaf)* Reproduction is dioecious Ginkgo is resistant to air pollution (city parks) Pickled seeds are eaten in Asia Ginkgo is now cultivated, could be in the wild
(Asia)
Ginkgo Ginkgo bilobabiloba
Leaves are broad with dichotomous venation
The Ginkgo tree has properties which make it resistant to nuclear radiation. This tree survived the Hiroshima bombings.
www.ginkgo.co.nz/images/ large/ginkgotree.jpg
Ginkgo bilobaGinkgo biloba
Male conesMale cones
Sperms are flagellated, Sperms are flagellated, borne in cone-like structureborne in cone-like structure
Ginkgo Brach & FruitGinkgo Brach & Fruit
Ginkgo Seed Cones
The fleshy part which covers the seed is the integument (offensive odor)No cones but ovules are borne in pairs and stalked
Cycads: Phylum CycadophytaCycads: Phylum Cycadophyta
About 250 MYO, common during the Mesozoic (age of cycads & Dinosaurs)*
Constitute 11 genera (140 spp) Tropical or subtropical Zamia, the only cycad in the States, is native to Florida Most cycads are large palm-like plants Highly toxic (produce neurotoxins & carcinogenic compounds) Sperms are motile, but they are pollinated by beetles Dioecious
Cycad:
Encephalartos humlis
Zamia floridanaZamia floridana
http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/cycadpg?taxname=Zamia+pumila
Male/female cones
Zamia: ConesZamia: Cones
Male
Female
Cycad: Cycad: Encephalartos altensteiniiEncephalartos altensteinii
http://www.calflora.net/southafrica/pageseventeen.html
Cycad: Cycad: Encephalartos feroxEncephalartos ferox
Native to Africa
Encephalartos feroxEncephalartos ferox
Gnetophytes: Phylum GnetophytaGnetophytes: Phylum Gnetophyta
Comprise 3 genera (70 spp) The most derived group of gymnosperms Similarities to angiosperms: Produce vessels (in xylem) Their strobili are similar to angiosperms’ inflorescence Double fertilization in Ephedra & Gnetum Produce nectar & insects play a role in pollination Leaves are borne in opposite pairs
The genus The genus GnetumGnetum
Has 30 spp (trees & woody vines)* Native to SE Asia, tropical Africa, Amazon
basin Have broad leathery leaves similar to dicot.
Gnetum gnemonGnetum gnemon
Gnetum: LeafGnetum: Leaf
Gnetum: Gnetum: Pollen ConesPollen Cones
Gnetum: Seed ConesGnetum: Seed Cones
The genusThe genus Ephedra Ephedra
Has 35 spp Tough shrubs inhabit deserts in N Mexico
and SE USA* Leaves reduced and scale-like Dioecious or monoecious
EphedraEphedra
- Cures respiratory problems
- Used in weight loss prog.
- A stimulant
Ephedra: Pollen Cones
Welwitschia mirabilisWelwitschia mirabilis
The most bizarre vascular plant* Native only to deserts of South Africa,
Angola, & Namibia Dioecious
WelwitschiaWelwitschia
- Most of the plant is buried in the sand- Aboveground discoid wide stem (1.5 m wide) produces 2 long
leaves
DISK
Welwitschia HabitatWelwitschia Habitat
http://www.csdl.tamu.edu/FLORA/imaxxwlw.htm
Population
Welwitschia HabitatWelwitschia Habitat
Welwitschia ConesWelwitschia Cones
WelwitschiaWelwitschia
Male cones
Female cones