Download The Plants

THE PLANTS
General Characteristics
Nonvascular Plants
What Are Plants?
 Traditionally: All
the photosynthetic organisms
plus Fungi
 Fungi have been removed to a separate kingdom
 Prokaryotic photosynthetic “Blue-Green Algae”
removed to Bacteria (Cyanobacteria)
 Other “Algae” removed to the Protista
 Plants probably evolved from certain Charophytes
“Green Algae”
Characteristic Features of Plants
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Multicellular, with distinct tissues and organs
Chlorophylls a & b; carotenoids
Gametangia with outer non-reproductive cells that
protect developing gametes
Developing embryo enclosed in a female reproductive
structure
Alternation of generations
Form phragmoplast and cell plate during cell division
Starch is the primary food reserves in the chloroplast
Cellulose is the principal component of the cell wall
Sporic Meiosis
Plants alternation
of generations
+ Gamete
Spores
- + - +
Meiosis
This cell
undergo meiosis
1n
2n
- Gamete
Fertilization
Zygote
Sporophyte
(Diploid individual)
Bryophytes: Nonvascular Plants
 Early land plants, require water for fertilization
 Two characteristics distinguish them from vascular plants
a. Lack specialized vascular tissues but:
 Mosses have hydroids (water) and leptoids (sugar)
 Most Bryophytes have rhizoids (anchor)
b. The nature of alternation of generation
 Gametophytes are nutritionally independent
 Sporophytes are permanently attached to gametophytes
 Thus the gametophyte is the noticeable and dominant
generation
Bryophytes: Habitats
 Often
abundant in relatively moist habitats
 A number of mosses are able to survive
severe temp. (also on bare rocks)
 Some mosses & liverworts are
predominantly aquatic
 Bryophytes are sensitive to air pollution
specially SO2 (indicators)
Liverworts: Phylum Hepatophyta
 Thought that
they cure liver diseases (Doctrine
of Signature)*
 Less conspicuous plants
 Their rhizoids are single celled unlike mosses
 Have
numerous pores (associated with air
gaps) which function as stoma
 Gametophytes are Thallose
or Leafy
Liverwort
Thallose Liverworts (nonleafy)
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The thallus is many layers thick, perennial*
Mostly unisexual e.g. Marchantia
Male gametophytes produce antheridia on disk
headed stalks *
Female gametophytes produce archegonia on
umbrella headed stalks *
Sexual reproduction requires water
Asexual reproduction by means of Gemma cups
Thallose
Liverwort
Return
♀
♂
Marchantia
Gemmae in a Liverwort
Life cycle of Marchanta
Leafy Liverworts
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The majority of liverworts (4000 species) are leafy
Abundant in the tropics and subtropics
Leaf as in mosses is one cell thick
Leaves are arranged in two rows with a third of
reduced leaves*
Monoecious (terminal archegonium & lateral
antheridium)
Archegonium & the developing sporophyte are
covered by perianth
Leafy
Liverworts
By A. Nelson
Nowellia curvifolia
Gametophte
Young sporophyte
N. Curyifolia
sporophyte
Gametophyte
Leafy
Liverworts
Lophocolea heterophylla
Sporophyte
young sporophyte
Mosses: Division Bryophyta *
True mosses are small inconspicuous plants
Gametophytes are represented by
Leaves which are one cell thick
Have multicellular rhizoids, Stoma are present
Have hydroids that resemble xylem tracheids
Have leptoids that resemble sieve elements
Sporophytes are photosynthetic
Two patterns of growth: Feathery & Cushiony
Mosses
Atrichum undulatum
“Roof Moss”
Mosses morphology
Sporophyte with
capsule
Gametophyte
Feathery Mosses
Feathery:
Much branched, creeping
 Sporophytes are born laterally
Feathery
Mosses
Cushiony mosses
Atrichum undulatum
 Gametophytes are
 Bear
erect and little branched
a terminal sporophyte
Gemmae in a Moss
Gemmae
•Detach from parent
gametophyte and grow into
new gametophyte.
•An example of vegetative
reproduction
Tetraphis pellucida
Life Cycle of a Moss
Ecology of Sphagnum
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Leaves consist of large dead cells with pores, readily
become filled with water
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Water holding capacity of the moss is 20 times its dry
weight (5 times cotton)
 They form extensive peat bogs in temperate regions
 Peat bogs cover 1% of world's land surface (~1/2 USA)
 Contribute to acidity of their own habitat (pH 4)
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Peat is formed from accumulation of the moss and
associated grasses and sedges
 In Ireland and other northern regions it is used as fuel