Kingdom Plantae
1.
2.
3.
4.
5.
Alternation of generations.
Haploid gametophyte that produces gametes by mitosis
Diploid sporophytes that produce spores by meiosis
mostly autotrophic
Fertilization by sperm or pollen nucleus produces a
diploid embryo, which is kept within female sex organ on
parent plant.
6. First known from the mid-Ordovician, some 476 million
years ago.
Land Plants
There are four main groups of land plants:
1. Bryophytes, including mosses, liverworts
and hornworts.
2. Pteridophytes, including ferns and seedless
vascular plants.
3. Gymnosperms or conifers.
4. Angiosperms or flowering plants.
CLASSIFICATION OF SEEDLESS VASCULAR PLANTS
• There are two phyla of pteridophytes found in the modern
flora: Licophyta and Pterophyta.
• 1. Phylum Lycophyta.
• There are about 15 genera of lycophytes and
approximately 1000 living species.
• This phylum includes the Lycopods (club mosses),
Selaginella (spike moss) and Isoetes (quillwort).
• This evolutionary line extends back into the Devonian
(409-363 mya) but were most prevalent in the wet swamps
of the Carboniferous period (363-290 mya).
Lycophyta
•
The Lycophyta eventually split up into two
evolutionary lines.
1. The first were very large woody trees that did
not survive in the drier climate at the end of and
after the Carboniferous age. In the
Carboniferous some lycophytes were forestforming trees more than 35 meters tall.
2. The second and the surviving group of
Lycopods are the small and herbaceous trees.
CHARACTERISTICS OF THE
LYCOPHYTA
•
Lycophyta are characterized by
1. microphyllous leaves,
2. a special spore producing body called a
strobilus,
3. the presence of true vascular stems, roots
and leaves.
Importance of the Lycophyta
• Lycophyta remains became the largest
coal deposits of all geologic time.
Some important terms:
• The sporophytes of lycophytes consist of
true roots, stems and leaves.
• Sporophylls are specialized leaves that
bear sporangia and are organized into a
structure called the strobilus (pl. strobili).
• Some Selaginella are heterosporous;
Lycopodium is homosporous.
SELAGINELLA
• There are about 700 species of Selaginella,
showing a wide range of characters.
• There are about 38 species in North America.
• Selaginellas are mostly tropical and subtropical.
• The genus is overdue for a revision which might
include subdivision into several genera.
SELAGINELLA
• The gametophyte that arises from the microspore is called a
microgametophyte.
• The microgametophyte never leaves the wall of the microspore; it is
endosporic. It is not photosynthetic but heterotrophic; its supply of
nutrients is limited to what is contained in the original microspore.
• Its development is limited to the formation of an antheridium (sterile
jacket) containing up to 32 sperm. Thus, the microgametophyte can
be thought of as a male structure.
• The microspore wall and sterile jacket rupture in free water to
release the sperm to swim to the egg.
Megagametophyte
• The gametophyte that arises from the megaspore is
called a megagametophyte.
• It too is endosporic and heterotrophic. Its large volume
means that it can contain considerable
reserves....usually oils.
• After cracking the megaspore wall, the megaspore
divides into several sterile cells that hold the nutrients,
some rhizoid cells that protrude from the cracks, and a
few archegonia with eggs.