Post on 18-Dec-2015
transcript
Kingdom Plantae
Bryophyta: Nonvascular PlantsLycophyta, Sphenophyta, Pterophyta:
Seedless Vascular PlantsGymnosperms: Coniferophyta
Setting the Stage for Plants
• Earth’s atmosphere was originally oxygen free
• Ultraviolet radiation bombarded the surface
• Photosynthetic cells produced oxygen and allowed formation of a protective ozone layer
Invading the Land
• Cyanobacteria were probably the first to
spread into and up freshwater streams
• Later, green algae and fungi made the
journey together
• Every plant is descended from species of
green algae
The Plant Kingdom
• Nearly all are multicelled
• Vast majority are photoautotrophs
– Energy from sun
– Carbon dioxide from air
– Minerals dissolved in water
Evolutionary Tree for Plants
greenalgae
zygophytes, related groups
charophytes bryophytes lycophytes horsetails cycads conifersflowering
plants
seed plants
euphyllophytes
vascular plants
embryophytes (land plants)
(closely related groups)
ferns ginkgos gnetophytes
Figure 23.3Page 387
Nonvascular Plants
• Bryophytes
• Fewer than 19,000 species
• Three groups
Liverworts
Hornworts
Mosses
Vascular Plants
• Majority of plants
• Have internal tissues that carry water
and solutes
• Two groups
– Seedless vascular plants
– Seed-bearing vascular plants
Seedless Vascular Plants
• Arose during the Devonian
• Produce spores but no seeds
• Four main groups
Whisk ferns
Lycophytes
Horsetails
Ferns
Seed-Bearing Vascular Plants
• Gymnosperms arose first– Cycads– Ginkgos– Gnetophytes– Conifers
• Angiosperms arose later– Monocots– Dicots
Evolutionary Trend
zygote
SPOROPHYTE (2n)
GAMETOPHYTE (n)
GREEN ALGA BRYOPHYTE FERN GYMNOSPERM ANGIOSPERM
Traits of Seed-Bearing Plants
• Pollen grains– Arise from megaspores– Develop into male gametophytes– Can be transported without water
• Seeds– Embryo sporophyte inside nutritive tissues
and a protective coat– Can withstand hostile conditions
Bryophytes
• Small, nonvascular, nonwooody
• Gametophyte dominates life cycle; has leaflike, stemlike, and rootlike parts
• Usually live in wet habitats
• Flagellated sperm require water to reach eggs
Moss Life Cycle
Zygote grows, develops into a sporophyte while still attached to gametophyte.
Fertilization
zygote
sperm-producing structure
egg-producing structure
Diploid Stage
Haploid Stage
mature sporophyte
Meiosis
Spores germinate.
male gametophyte
female gametophyteFigure 23.5
Page 388
Phylum Bryophyta“Mosses”
The gametophyte of mosses consists of a leafy shoot that is anchored to the substrate by branched multicellular rhizoids.
http://www.science.siu.edu/landplants/Bryophyta/MossDesc.html
Leaf arrangement is normally spiralled.
The initial stage of gametophyte development, resulting from germination of the spore,
is a filamentous branched structure known as the protonema.
Antheridia are equally elongated with a long narrow stalk
General morphology are seen in Sphagnum
Habit shot of female shoots with terminal sporophytes and male shoots with clusters of orange antheridia surrounded by leaves. Copyright by Alan Heilman (Univ. Tenn.).
Marchantia: A Liverwort
• Reproduces asexually by gemmae
• Gametophytes are
male or female
Female gametophyte
Do not post on Internet
Figure 23.7 Page 389
Seedless Vascular Plants
Lycophytes (Lycophyta)
Whisk ferns (Psilophyta)
Horsetails (Sphenophyta)
Ferns (Pterophyta)
Ferns (Pterophyta)
• 12,000 species, mostly tropical
• Most common sporophyte structure– Perennial underground stem (rhizome)– Roots and fronds arise from rhizome– Young fronds are coiled “fiddleheads”– Mature fronds divided into leaflets– Spores form on lower surface of some
fronds
Fern Life Cycle
Spores are released
Sporophyte still attached to gametophyte
zygote
fertilizationDiploid StageHaploid Stage
egg
sperm
mature gametophyte
Spores develop
meiosis
Spore germinates
rhizomesorus
On the back (abaxial) side of the frond occur the spore-producing structures called sori (singular sorus).
On the underside (ventral) of the prothallus, archegonia are frequently clustered around the apical notch as evidenced by the protruding archegonial necks seen in this SEM photo (by Joan Nester-Hudson).
At the moment of fertilization, the nuclei of sperm and egg fuse and a diploid zygote is formed. This begins the sporophytic generation again. The zygote divides mitotically to form and embryo and eventually a tiny sporophytic plant. These can often be seen still attached to the notch area of the prothallus.
The sporophyte is relatively simple with dichotomously to pseudomonopodally branched green stems and spirally arranged microphylls (simple leaves with single veins).
Typically, the shoot system is separated into upright aerial shoots and morphologically distinct creeping rhizomes from which adventitious roots arise.
Sporangia are positioned on the adaxial side of specialized leaves that in turn are arranged in zones along the stem or in a terminal series, known as strobili
The sporophyte of Equisetum is differentiated into an underground rhizome that bears adventitious roots and an upright, photosynthetic stem with whorls of microphylls. The stem is jointed, i.e., the nodes are clearly defined by whorls of leaves.
Longitudinal section through a microsporangiate cone of pine consisting of microsporophylls spirally arranged around the central axis bearing microsporophylls.